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  • 1.
    Ahlberg, Patrik
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Seung, Hee Jeong
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Jiao, Mingzhi
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Graphene as a Diffusion Barrier in Galinstan-Solid Metal Contacts2014In: IEEE Transactions on Electron Devices, ISSN 0018-9383, E-ISSN 1557-9646, Vol. 61, no 8, p. 2996-3000Article in journal (Refereed)
    Abstract [en]

    This paper presents the use of graphene as a diffusion barrier to a eutectic Ga-In-Sn alloy, i.e., galinstan, for electrical contacts in electronics. Galinstan is known to be incompatible with many conventional metals used for electrical contacts. When galinstan is in direct contact with Al thin films, Al is readily dissolved leading to the formation of Al oxides present on the surface of the galinstan droplets. This reaction is monitored ex situ using several material analysis methods as well as in situ using a simple circuit to follow the time-dependent resistance variation. In the presence of a multilayer graphene diffusion barrier, the Al-galinstan reaction is effectively prevented for galinstan deposited by means of drop casting. When deposited by spray coating, the high-impact momentum of the galinstan droplets causes damage to the multilayer graphene and the Al-galinstan reaction is observed at some defective spots. Nonetheless, the graphene barrier is likely to block the formation of Al oxides at the Al/galinstan interface leading to a stable electrical current in the test circuit.

  • 2.
    Chang, Bo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zhou, Quan
    Aalto University, Finland.
    Ras, Robin
    Aalto University, Finland.
    Shah, Ali
    Aalto University, Finland.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sliding droplets on hydrophilic/superhydrophobic patterned surfaces for liquid deposition2016In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 108, no 15, article id 154102Article in journal (Refereed)
    Abstract [en]

    A facile gravity-induced sliding droplets method is reported for deposition of nanoliter sized droplets on hydrophilic/superhydrophobic patterned surface. The deposition process is parallel where multiple different liquids can be deposited simultaneously. The process is also high-throughput, having a great potential to be scaled up by increasing the size of the substrate.

  • 3.
    Chang, Bo
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Aalto Univ, Sch Sci, Dept Appl Phys, FI-00076 Aalto, Finland.
    Zhou, Quan
    Aalto Univ, Dept Elect Engn & Automat, FI-00076 Aalto, Finland.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Peoples R China.
    Ras, Robin
    Aalto Univ, Sch Sci, Dept Appl Phys, FI-00076 Aalto, Finland.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Capillary Self-Alignment of Microchips on Soft Substrates2016In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 7, no 3, article id 41Article in journal (Refereed)
    Abstract [en]

    Soft micro devices and stretchable electronics have attracted great interest for their potential applications in sensory skins and wearable bio-integrated devices. One of the most important steps in building printed circuits is the alignment of assembled micro objects. Previously, the capillary self-alignment of microchips driven by surface tension effects has been shown to be able to achieve high-throughput and high-precision in the integration of micro parts on rigid hydrophilic/superhydrophobic patterned surfaces. In this paper, the self-alignment of microchips on a patterned soft and stretchable substrate, which consists of hydrophilic pads surrounded by a superhydrophobic polydimethylsiloxane (PDMS) background, is demonstrated for the first time. A simple process has been developed for making superhydrophobic soft surface by replicating nanostructures of black silicon onto a PDMS surface. Different kinds of PDMS have been investigated, and the parameters for fabricating superhydrophobic PDMS have been optimized. A self-alignment strategy has been proposed that can result in reliable self-alignment on a soft PDMS substrate. Our results show that capillary self-alignment has great potential for building soft printed circuits.

  • 4.
    Cheng, Shi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Liquid metal stretchable unbalanced loop antenna2009In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 94, no 14, p. 144103-Article in journal (Refereed)
    Abstract [en]

    We present a 2.4 GHz unbalanced loop antenna that can be stretched along multiple dimensions simultaneously. It was realized by incorporating room temperature liquid metal alloy into microstructured channels in an elastic material. The demonstrated prototype exhibits a stretchability of up to 40% along two orthogonal orientations as well as foldability and twistability. Port impedance and radiation characteristics of the nonstretched and stretched antenna were studied numerically and experimentally. Measured results indicate a radiation efficiency of more than 80%.

  • 5.
    Cheng, Shi
    et al.
    Advanced Technology, Laird Technologies, Kista.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A Microfluidic, Reversibly Stretchable, Large-Area Wireless Strain Sensor2011In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 12, p. 2282-2290Article in journal (Refereed)
    Abstract [en]

    This article describes the implementation and characterization of a new self-contained large-area wireless strain sensor, operating around 1.5 GHz, based on the concept of multi-layer microfluidic stretchable radiofrequency electronics (mu FSRFEs). Compared to existing solutions, the presented integrated strain sensor is capable of remotely detecting repeated high tensile dynamic strains of up to 15% over very large surfaces or movable parts, and gets rid of all hardwiring to external storage or data processing equipment. Unlike conventional electronic devices, the major part of the sensor is a mechanically reconfigurable and reversibly deformable patch antenna, which consists of two layers of liquid metal alloy filled microfluidic channels in a silicone elastomer. A simplified radiofrequency (RF) transmitter composed of miniaturized rigid active integrated circuits (ICs) associated with discrete passive components was assembled on a flexible printed circuit board (FPCB) and then heterogeneously integrated to the antenna. The elastic patch antenna can withstand repeated mechanical stretches while still maintaining its electrical function to some extent, and return to its original state after removal of the stress. Additionally, its electrical characteristics at frequency of operation are highly sensitive to mechanical strains. Consequently, not only is this antenna a radiator for transmitting and receiving RF signals like any other conventional antennas, but also acts as a reversible large-area strain sensor in the integrated device. Good electrical performance of the standalone antenna and the RF transmitter sub-module was respectively verified by experiments. Furthermore, a personal computer (PC)-assisted RF receiver for receiving and processing the measured data was also designed, implemented, and evaluated. In the real-life demonstration, the integrated strain sensor successfully monitored periodically repeated human body motion, and wirelessly transmitted the measured data to the custom-designed receiver at a distance of 5m in real-time.

  • 6.
    Cheng, Shi
    et al.
    Radio Hardware Division at Ericsson.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microfluidic electronics2012In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 12, no 16, p. 2782-2791Article in journal (Refereed)
    Abstract [en]

    Microfluidics, a field that has been well-established for several decades, has seen extensive applications in the areas of biology, chemistry, and medicine. However, it might be very hard to imagine how such soft microfluidic devices would be used in other areas, such as electronics, in which stiff, solid metals, insulators, and semiconductors have previously dominated. Very recently, things have radically changed. Taking advantage of native properties of microfluidics, advances in microfluidics-based electronics have shown great potential in numerous new appealing applications, e. g. bio-inspired devices, body-worn healthcare and medical sensing systems, and ergonomic units, in which conventional rigid, bulky electronics are facing insurmountable obstacles to fulfil the demand on comfortable user experience. Not only would the birth of microfluidic electronics contribute to both the microfluidics and electronics fields, but it may also shape the future of our daily life. Nevertheless, microfluidic electronics are still at a very early stage, and significant efforts in research and development are needed to advance this emerging field. The intention of this article is to review recent research outcomes in the field of microfluidic electronics, and address current technical challenges and issues. The outlook of future development in microfluidic electronic devices and systems, as well as new fabrication techniques, is also discussed. Moreover, the authors would like to inspire both the microfluidics and electronics communities to further exploit this newly-established field.

  • 7.
    Cheng, Shi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microfluidic Reversibly Stretchable Large-Area Wireless Strain Sensor2011In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 12, p. 2282-2290Article in journal (Refereed)
  • 8.
    Cheng, Shi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microfluidic stretchable RF electronics2010In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 10, no 23, p. 3227-3234Article in journal (Refereed)
    Abstract [en]

    Stretchable electronics is a revolutionary technology that will potentially create a world of radically different electronic devices and systems that open up an entirely new spectrum of possibilities. This article proposes a microfluidic based solution for stretchable radio frequency (RF) electronics, using hybrid integration of active circuits assembled on flex foils and liquid alloy passive structures embedded in elastic substrates, e. g. polydimethylsiloxane (PDMS). This concept was employed to implement a 900 MHz stretchable RF radiation sensor, consisting of a large area elastic antenna and a cluster of conventional rigid components for RF power detection. The integrated radiation sensor except the power supply was fully embedded in a thin elastomeric substrate. Good electrical performance of the standalone stretchable antenna as well as the RF power detection sub-module was verified by experiments. The sensor successfully detected the RF radiation over 5 m distance in the system demonstration. Experiments on two-dimensional (2D) stretching up to 15%, folding and twisting of the demonstrated sensor were also carried out. Despite the integrated device was severely deformed, no failure in RF radiation sensing was observed in the tests. This technique illuminates a promising route of realizing stretchable and foldable large area integrated RF electronics that are of great interest to a variety of applications like wearable computing, health monitoring, medical diagnostics, and curvilinear electronics.

  • 9.
    Cheng, Shi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hallbjörner, Paul
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Foldable and stretchable liquid metal planar inverted cone antenna2009In: IEEE Transactions on Antennas and Propagation, ISSN 0018-926X, E-ISSN 1558-2221, Vol. 57, no 12, p. 3765-3771Article in journal (Refereed)
    Abstract [en]

    A mechanically flexible planar inverted cone antenna (PICA) for   ultrawideband (UWB) applications is presented. It can be both folded   and stretched significantly without permanent damage or loss of   electrical functionality. The antenna is manufactured with a process in   which conductors are realized by injecting room temperature liquid   metal alloy into micro-structured channels in an elastic dielectric   material. The elastic dielectric material together with the liquid   metal enables bending with a very small radius, twisting, and   stretching along any direction. Port impedance and radiation   characteristics of the non-stretched and stretched antenna are studied   in simulations and experiments. The presented antenna has a return loss   better than 10 dB within 3-11 GHz and a radiation efficiency of > 70%   over 3-10 GHz, also when stretched. Tests verify that stretching up to   40% is possible with maintained electrical performance. The presented   antenna is useful for example for body-worn antennas and in   applications in harsh environments where mechanical flexibility helps   improve durability.

  • 10.
    Cheng, Shi
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microwave and Terahertz Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A highly stretchable microfluidic meandered monopole antenna2009In: 13th International Conference on Miniaturized Systems for Chemistry and Life Sciences µTAS 2009, 2009, p. 1946-1948Conference paper (Refereed)
  • 11.
    Cruz, Javier
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hooshmand Zadeh, S
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan, China.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Inertial focusing of microparticles and its limitations2016Conference paper (Refereed)
    Abstract [en]

    Microfluidic devices are useful tools for healthcare, biological and chemical analysis and m aterials synthesis amongst fields that can benefit from the unique physics of these systems. In this paper we studied inertial focusing as a tool for hydrodynamic sorting of particles by size. Theory and experimental results are provided as a background for a discussion on how to extend the technology to submicron particles. Different geometries and dimensions of microchannels were designed and simulation data was compared to the experimental results.

  • 12.
    Cruz, Javier
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zadeh, S. Hooshmand
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Graells, Tiscar
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences. Univ Autonoma Barcelona, Dept Genet & Microbiol, Barcelona, Spain..
    Andersson, Martin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Malmström, Jonas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences.
    Wu, Zhigang G.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan, Peoples R China..
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    High pressure inertial focusing for separating and concentrating bacteria at high throughput2017In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 27, no 8, article id 084001Article in journal (Refereed)
    Abstract [en]

    Inertial focusing is a promising microfluidic technology for concentration and separation of particles by size. However, there is a strong correlation of increased pressure with decreased particle size. Theory and experimental results for larger particles were used to scale down the phenomenon and find the conditions that focus 1 mu m particles. High pressure experiments in robust glass chips were used to demonstrate the alignment. We show how the technique works for 1 mu m spherical polystyrene particles and for Escherichia coli, not being harmful for the bacteria at 50 mu l min(-1). The potential to focus bacteria, simplicity of use and high throughput make this technology interesting for healthcare applications, where concentration and purification of a sample may be required as an initial step.

  • 13.
    Hjort, Klas
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Huazhong University of Science and Technology.
    Microfluidic mixing and separation2016In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 26, no 1, article id 010402Article in journal (Refereed)
  • 14.
    Hou, Zining
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    An, Yu
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Karin
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sandegren, Linus
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Medical Biochemistry and Microbiology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Time lapse investigation of antibiotic susceptibility using a microfluidic linear gradient 3D culture device2014In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 14, no 17, p. 3409-3418Article in journal (Refereed)
    Abstract [en]

    This study reports a novel approach to quantitatively investigate the antibacterial effect of antibiotics on bacteria using a three-dimensional microfluidic culture device. In particular, our approach is suitable for studying the pharmacodynamics effects of antibiotics on bacterial cells temporally and with a continuous range of concentrations in a single experiment. The responses of bacterial cells to a linear concentration gradient of antibiotics were observed using time-lapse photography, by encapsulating bacterial cells in an agarose-based gel located in a commercially available microfluidics chamber. This approach generates dynamic information with high resolution, in a single operation, e. g., growth curves and antibiotic pharmacodynamics, in a well-controlled environment. No pre-labelling of the cells is needed and therefore any bacterial sample can be tested in this setup. It also provides static information comparable to that of standard techniques for measuring minimum inhibitory concentration (MIC). Five antibiotics with different mechanisms were analysed against wild-type Escherichia coli, Staphylococcus aureus and Salmonella Typhimurium. The entire process, including data analysis, took 2.5-4 h and from the same analysis, high-resolution growth curves were obtained. As a proof of principle, a pharmacodynamic model of streptomycin against Salmonella Typhimurium was built based on the maximal effect model, which agreed well with the experimental results. Our approach has the potential to be a simple and flexible solution to study responding behaviours of microbial cells under different selection pressures both temporally and in a range of concentrations.

  • 15.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Chen, Si
    Chalmers, Dept Microtechnol & Nanosci MC2, SE-41296 Gothenburg, Sweden..
    Huo, Jinxing
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Gamstedt, Erik Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Liu, Johan
    Chalmers, Dept Microtechnol & Nanosci MC2, SE-41296 Gothenburg, Sweden..
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Mechanically Stretchable and Electrically Insulating Thermal Elastomer Composite by Liquid Alloy Droplet Embedment2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, article id 18257Article in journal (Refereed)
    Abstract [en]

    Stretchable electronics and soft robotics have shown unsurpassed features, inheriting remarkable functions from stretchable and soft materials. Electrically conductive and mechanically stretchable materials based on composites have been widely studied for stretchable electronics as electrical conductors using various combinations of materials. However, thermally tunable and stretchable materials, which have high potential in soft and stretchable thermal devices as interface or packaging materials, have not been sufficiently studied. Here, a mechanically stretchable and electrically insulating thermal elastomer composite is demonstrated, which can be easily processed for device fabrication. A liquid alloy is embedded as liquid droplet fillers in an elastomer matrix to achieve softness and stretchability. This new elastomer composite is expected useful to enhance thermal response or efficiency of soft and stretchable thermal devices or systems. The thermal elastomer composites demonstrate advantages such as thermal interface and packaging layers with thermal shrink films in transient and steady-state cases and a stretchable temperature sensor.

  • 16.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Chen, Si
    Chalmers University of Technology.
    Huo, Jinxing
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Gravier, Laurent
    University of Applied Sciences and Arts Western Switzerland.
    Gamstedt, Erik Kristofer
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Mechanics.
    Liu, Johan
    Chalmers University of Technology.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan, Peoples R China.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Thermal Elastomer Composites for Soft Transducers2015Conference paper (Refereed)
    Abstract [en]

    There is a need for thermal elastomer composites (TEC) which are stretchable, electrically insulating and easily processablefor soft and stretchable sensor or actuator systems as a thermal conductor or heat spreader at an interface or in a package.A novel TEC was made by embedding a gallium based liquid alloy (Galinstan) as a droplet in polydimethylsiloxane (PDMS,Elastosil RT 601) matrix with a high speed mechanical mixing process.

  • 17.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Cruz, Javier
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Chen, Si
    Chalmers, Dept Microtechnol & Nanosci MC2, Kemivagen 9, SE-41296 Gothenburg, Sweden.
    Gravier, Laurent
    Univ Appl Sci & Arts Western Switzerland, Inst Micro & Nano Tech, CH-1401 Yverdon, Switzerland.
    Liu, Johan
    Chalmers, Dept Microtechnol & Nanosci MC2, Kemivagen 9, SE-41296 Gothenburg, Sweden.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Peoples R China.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Zhi-Bin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Stretchable thermoelectric generators metallized with liquid alloy2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 18, p. 15791-15797Article in journal (Refereed)
    Abstract [en]

    Conventional thermoelectric generators (TEGs) are normally hard, rigid, and flat. However, most objects have curvy surfaces, which require soft and even stretchable TEGs for maximizing efficiency of thermal energy harvesting. Here, soft and stretchable TEGs using conventional rigid Bi2Te3 pellets metallized with a liquid alloy is reported. The fabrication is implemented by means of a tailored layer-by-layer fabrication process. The STEGs exhibit an output power density of 40.6 mu W/cm(2) at room temperature. The STEGs are operational after being mechanically stretched-and-released more than 1000 times, thanks to the compliant contact between the liquid alloy interconnects and the rigid pellets. The demonstrated interconnect scheme will provide a new route to the development of soft and stretchable energy-harvesting avenues for a variety of emerging electronic applications.

  • 18.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Cruz, Javier
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zhang, Zhibin
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Zhang, Shi-Li
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Soft Bendable Thermoelectric Generator for Uneven Surface Implementation2015In: 26th Micromechanics and Microsystems Europe Workshop, 2015, p. A8-Conference paper (Other academic)
  • 19.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hagman, Anton
    KTH, Hållfasthetslära, Stockholm.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Jobs, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Sundqvist, Johan
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Liquid alloy printing of microfluidic stretchable electronics2012In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 22, no 12, p. 4657-4664Article in journal (Refereed)
    Abstract [en]

    Recently, microfluidic stretchable electronics has attracted great interest from academia since conductive liquids allow for larger cross-sections when stretched and hence low resistance at longer lengths. However, as a serial process it has suffered from low throughput, and a parallel processing technology is needed for more complex systems and production at low costs. In this work, we demonstrate such a technology to implement microfluidic electronics by stencil printing of a liquid alloy onto a semi-cured polydimethylsiloxane (PDMS) substrate, assembly of rigid active components, encapsulation by pouring uncured PDMS on-top and subsequent curing. The printing showed resolution of 200 mm and linear resistance increase of the liquid conductors when elongated up to 60%. No significant change of resistance was shown for a circuit with one LED after 1000 times of cycling between a 0% and an elongation of 60% every 2 s. A radio frequency identity (RFID) tag was demonstrated using the developed technology, showing that good performance could be maintained well into the radio frequency (RF) range.

  • 20.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A fast liquid alloy patterning technique for microfluidic stretchable electronics2014In: A fast liquid alloy patterning technique for microfluidic stretchable electronics, 2014, p. 48-50Conference paper (Refereed)
    Abstract [en]

    By tape-transferring cut patterns in vinyl onto a PDMS substrate and then using it as stencil masks, liquid alloy is printed with arbitrary patterns onto the substrate for stretchable electronics. This brings new possibilities in printing patterns such as loop and ring structures, which are impossible to achieve with a conventional metal stencil that will lose the isolated parts.

  • 21.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Adhesive transfer soft lithography: low-cost and flexible rapid prototyping of microfluidic devices, Micro and Nanosystems2014In: micro and nanosystems, ISSN 1876-4037, Vol. 6, p. 42-49Article in journal (Refereed)
    Abstract [en]

    A simple and low-cost approach was proposed for prototyping PDMS based microfluidic devices by transferringadhesive film microstructures onto a flexible substrate as a mould for PDMS replicas. The microstructures were engravedon an adhesive coated film using a commercial cutting plotter and then transferred (or laminated) onto a flexiblesubstrate, allowing for engraved isolated patterns. The proposed technique was demonstrated by a hydrodynamic focusingmicrofluidic device, having splitting and re-combining sheath channels. The whole processing could be finished within 1h in a normal laboratory environment. This approach offers an easy, flexible and rapid prototyping of microfluidic andlab-on-a-chip devices to users without expertise in microfabrication. In addition, by minimizing the use of chemicals, theprocess becomes more environmentally friendly than conventional photolithography based micro-fabrication techniques.

  • 22.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Tape transfer atomization patterning of liquid alloys for microfluidic stretchable wireless power transfer2015In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 5, p. 8419-Article in journal (Refereed)
    Abstract [en]

    Stretchable electronics offers unsurpassed mechanical compliance on complex or soft surfaces like the human skin and organs. To fully exploit this great advantage, an autonomous system with a self-powered energy source has been sought for. Here, we present a new technology to pattern liquid alloys on soft substrates, targeting at fabrication of a hybrid-integrated power source in microfluidic stretchable electronics. By atomized spraying of a liquid alloy onto a soft surface with a tape transferred adhesive mask, a universal fabrication process is provided for high quality patterns of liquid conductors in a meter scale. With the developed multilayer fabrication technique, a microfluidic stretchable wireless power transfer device with an integrated LED was demonstrated, which could survive cycling between 0% and 25% strain over 1,000 times.

  • 23.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Tape Transfer Printing of a Liquid Metal Alloy for Stretchable RF Electronics2014In: Sensors, ISSN 1424-8220, E-ISSN 1424-8220, Vol. 14, no 9, p. 16311-16321Article in journal (Refereed)
    Abstract [en]

    In order to make conductors with large cross sections for low impedance radio frequency (RF) electronics, while still retaining high stretchability, liquid-alloy-based microfluidic stretchable electronics offers stretchable electronic systems the unique opportunity to combine various sensors on our bodies or organs with high-quality wireless communication with the external world (devices/systems), without sacrificing enhanced user comfort. This microfluidic approach, based on printed circuit board technology, allows large area processing of large cross section conductors and robust contacts, which can handle a lot of stretching between the embedded rigid active components and the surrounding system. Although it provides such benefits, further development is needed to realize its potential as a high throughput, cost-effective process technology. In this paper, tape transfer printing is proposed to supply a rapid prototyping batch process at low cost, albeit at a low resolution of 150 mu m. In particular, isolated patterns can be obtained in a simple one-step process. Finally, a stretchable radio frequency identification (RFID) tag is demonstrated. The measured results show the robustness of the hybrid integrated system when the tag is stretched at 50% for 3000 cycles.

  • 24.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Shou, Zhang
    Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Peoples R China.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hilborn, Jöns
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Chemistry - Ångström, Polymer Chemistry.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Mfg Equipment & Technol, Wuhan 430074, Peoples R China.
    PDMS-Based Elastomer Tuned Soft, Stretchable, and Sticky for epidermal electronics2016In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 28, no 28, p. 5830-5836Article in journal (Refereed)
    Abstract [en]

    Targeting good user experiences, softness and stretchability are essential features for epidermal devices in body signal monitoring and body area stimulation. A highly soft, stretchable and sticky polydimethylsiloxane based elastomer (S3-PDMS) is achieved by a simple process with a widely used siloxane precursors, the properties of which are tuned by adding small fractions of an amine-based polymer, ethoxylated polyethylenimine (EPEI). This allows formation of a thick unobstrusive patch and may ease implementation of epidermal electronics in wearable healthcare applications. 

  • 25.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University.
    Shou, ZhangHuazhong University of Science and Technology.Hjort, KlasUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.Wu, ZhigangUppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sticky elstomer composites for microfluidic stretchable sensor patches2015Conference proceedings (editor) (Refereed)
    Abstract [en]

    Epidermal electronics and soft robotics are harnessing the advantages of the adaptable and compliantsoft contacts of soft materials. Soft materials can conformally match the morphology of the contact surfaces, which isthe vital point in the implementation of epidermal sensors or soft actuators (S. Xu et al., Soft Microfluidic Assemblies ofSensors, Circuits, and Radios for the Skin, Science, 2014, 344, 70-74). Unfortunately, this conformality can suffer fromdelamination or air trapping at the interface during contact movement. Here, adhesion of soft material surfaces is thecritical parameter. For example, an epidermal sensor on human internal organs and skin, or soft-robotic fingers forgrabbing or climbing needs proper adhesion to its targeted contact surface. Mechanical softness of elastomermaterials provides a good ensemble with surface adhesion because the conformal contact of the soft materials assiststhe adhesion on the target surfaces. Alas, when the soft device is thicker, with its inherent adhesion its compliancemay not suffice but an adhesive layer is needed to ensure good contact.Sticky surfaces of soft materials will significantly help to improve adhesion on target surfaces by preventing sliding.Therefore, more reliable immobilization and manipulation of contacted objects can be secured. Physical and chemicaladhesion forces of the soft material surfaces can be utilized for this purpose. We have developed a sticky elastomercomposite based on PDMS, which has a tape-like adhesive surface after curing. This sticky elastomer composite isstretchable and compliant. The processability of it is compatible with PDMS processes for microfluidic stretchabledevices. It can be easily shaped with laminating, spinning and casting before curing. And, it is reusable several timeswithout leaving residues on the adhered surfaces after detaching and its adhesive strength is tunable with differentmixing ratios with the additive.The sticky elastomer composite showed high enough adhesion to secure attachment on human skin and to lift smallobjects with different surface roughness. Here, soft fingers lifting masses which have different surface morphologieswere tested to verify the compatibility of adhesion force on various surface conditions for soft-robotic manipulationapplication. To show the easy and robust implementation, the sticky elastomer composite is demonstrated with astretchable sensor patch that can be secured to human skin, using much of our recently developed pamphlet ofprocessing technologies (Z.G. Wu, K. Hjort, S.H. Jeong, Microfluidic Stretchable Radio Frequency Devices,Proceedings of the IEEE, 2015, 99, 1-15). Such sensor patches may be suitable as wireless sensor nodes inepidermal body area networks for fitness and healthcare monitoring.

  • 26.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huazhong Univ Sci & Technol, State Key Lab Digital Equipment & Mfg, Wuhan, Peoples R China.
    Stretchable wireless power transfer with a liquid alloy coil2015In: Micro Electro Mechanical Systems (MEMS), 2015 28th IEEE International Conference on, 2015, p. 1137-1140Conference paper (Refereed)
    Abstract [en]

    An integrated stretchable wireless power transfer device was demonstrated by packaging rigid electronic chips onto a liquid alloy coil patterned on a half-cured polydimethylsiloxane (PDMS) surface. To obtain low enough resistance, the long liquid alloy coil with a large cross section was made with a tape transfer masking followed by spray deposition of the liquid alloy. The measured results indicated the wireless power transfer efficiency reached 10% at 140 kHz and good performance under 25% overall strain. Different sizes of liquid alloy coils and a soft magnetic composite core were tested to improve the efficiency of the system.

  • 27.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Batch produced microfluidic stretchable printed circuits for wireless systems2014In: Batch produced microfluidic stretchable printed circuits for wireless systems, 2014, p. 27-30Conference paper (Refereed)
    Abstract [en]

    The liquid alloy which is Ga-In-Sn based alloy is the most promising stretchable conductor material for soft electronics. Patterning ofliquid alloys will be the key processing step to fabricate devices and we have here applied a screen printing technique withtape transfer masking to enable batch processing for a large areas at low cost. The elastomer surface should be controlled forthe printing and encapsulation of liquid alloys. Liquid-alloy-based RF electronics shows potential in interfacing man to machinein applications such as body area network or soft robotics.

  • 28.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Huangzhou University of Science and Technology, Wuhan, China.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Plåster med sträckbara trådlösa givare för medicinsk teknik2015In: Abstracts Medicinteknikdagarna 2015 / [ed] Fredrik Nikolajeff, 2015, p. 59-Conference paper (Refereed)
    Abstract [sv]

    Målet med denna presentation är att visa på olika möjligheter för sträckbara trådlösa givare för medicinsk teknik. Vi söker läkare och företag som är intresserade av detta.

    Elektronikbranschen förutspår en massiv ökning av trådlösa sensorsystem inom en snar framtid och ett ”Sakernas Internet”. En av de stora utvecklingsområdena här är  bärbara tillbehör; trådlösa sensornoder i kroppsnära nätverk som kommunicerar med en smartphone. Men det finns en generation efter detta och många förutspår att det kommer att vara nätverk med trådlösa givare och kommunikationsnoder som är i direktkontakt med kroppen, på huden eller som implantat. Det är här töjbar elektronik kommer att sätta sin prägel då dess mjuka, följsamma och sträckbara folier med givare och elektronik erbjuder en oöverträffad mekanisk koppling till vår hud och våra organ.

    Den mest uppmärksammade tekniken är den s.k. elastiska elektroniken, vilken utgår från ultratunna, och därmed flexibla, integrerade kretsar som överförs till elastiska substrat. Det möjliggör väldigt tunna system som kan ha samma höga upplösning och täthet av komponenter som annan mikroelektronik1. Detta passar väl till mindre strukturer men har flera svagheter vid tillverkning av system där större och tjockare komponenter krävs. Här har vi i stället utvecklat sträckbara kretskort med en flytande metall som ledare och kontakter. De främsta fördelarna med flytande ledare är att en vätska följer med alla formändringar utan motstånd och att små styva komponenter kan modulärt monteras och kontakteras till ledaren utan att kontakter bryts när den utsätts för en större töjning – istället kommer komponentens kontakt att glida på vätskan2. Vi har redan visat att vi idag kan producera avancerade kretsar med flera lager av ledare och monterade små komponenter för olika trådlösa system med töjningsgivare, RFID, trådlös energiöverföring, termoelektriska komponenter, mm.

    I denna presentation visar vi hur kan tillverka intelligenta och trådlösa sträckbara plåster med olika givare för att läsa av värmeflödet från en kropp. Vi tror dock att det är lätt för oss att göra andra typer av givare eller montera små chip av kommersiella givare och transdermala elektroder för andra medicinska tillämpningar. Vi behöver dock samverka med läkare och medicinsktekniska företag för att välja och pröva de bäst lämpade givarna.

  • 29.
    Jeong, Seung Hee
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Zhang, S.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sticky elastomer composite for microfluidic stretchable sensor patches2015In: 2015 MRS Fall Meeting, 2015, p. B12.04-Conference paper (Other academic)
  • 30.
    Jobs, Magnus
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A Tunable Spherical Cap Microfluidic Electrically Small Antenna2013In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 9, no 19, p. 3230-3234Article in journal (Refereed)
    Abstract [en]

    We present a novel microfluidic three-dimensional elec- trically small antenna (ESA). It is easy to construct simply by pneumatically inflating a planar stretchable liquid alloy microfluidic antenna into a spherical cap. Its center frequency is tuned when it is inflated; demonstrating combined high efficiency and a wide tunable frequency range around its hemispherical shape.

  • 31. Liu, Zhenhua
    et al.
    Xu, Wenchao
    Hou, Zining
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A Rapid Prototyping Technique for Microfluidics with High Robustness and Flexibility2016In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 7, no 11, article id 201Article in journal (Refereed)
    Abstract [en]

    In microfluidic device prototyping, master fabrication by traditional photolithography is expensive and time-consuming, especially when the design requires being repeatedly modified to achieve a satisfactory performance. By introducing a high-performance/cost-ratio laser to the traditional soft lithography, this paper describes a flexible and rapid prototyping technique for microfluidics. An ultraviolet (UV) laser directly writes on the photoresist without a photomask, which is suitable for master fabrication. By eliminating the constraints of fixed patterns in the traditional photomask when the masters are made, this prototyping technique gives designers/researchers the convenience to revise or modify their designs iteratively. A device fabricated by this method is tested for particle separation and demonstrates good properties. This technique provides a flexible and rapid solution to fabricating microfluidic devices for non-professionals at relatively low cost.

  • 32.
    Ogden, Sam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Bodén, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Do-Quang, Minh
    KTH.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Amberg, Gustav
    KTH.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Fluid behavior of supercritical carbon dioxide with water in a double-Y-channel microfluidic chip2014In: Microfluidics and Nanofluidics, ISSN 1613-4982, E-ISSN 1613-4990, Vol. 17, no 6, p. 1105-1112Article in journal (Refereed)
    Abstract [en]

    The use of supercritical carbon dioxide (scCO2) as an apolar solvent has been known for decades. It offers a greener approach than, e.g., hexane or chloroform, when such solvents are needed. The use of scCO2 in microsystems, however, has only recently started to attract attention. In microfluidics, the flow characteristics need to be known to be able to successfully design such components and systems. As supercritical fluids exhibit the exciting combination of low viscosity, high density, and high diffusion rates, the fluidic behavior is not directly transferrable from aqueous systems. In this paper, three flow regimes in the scCO2–liquid water two-phase microfluidic system have been mapped. The effect of both total flow rate and relative flow rate on the flow regime is evaluated. Furthermore, the droplet dynamics at the bifurcating exit channel are analyzed at different flow rates. Due to the low viscosity of scCO2, segmented flows were observed even at fairly high flow rates. Furthermore, the carbon dioxide droplet behavior exhibited a clear dependence on both flow rate and droplet length.

  • 33.
    Ogden, Sam
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Bodén, Roger
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Do-Quang, Minh
    KTH.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Fluid mechanics of supercritical carbon dioxide with water in a double-y-channel microfluidic chip2013In: Micromechanics and microsystems europe, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, three flow regimes in thesupercritical carbon dioxide-water two-phase microfluidicsystem are mapped. The effect of both totalflow rate and relative flow rate on the flow regime isevaluated. Furthermore, the droplet dynamics at thebifurcating exit channel is analysed at different flowrates. The influence of the capillary number ondroplet splitting at the exit is also evaluated.

  • 34.
    Qiu, Wenjun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sun, Xiaojiao
    Uppsala University, Disciplinary Domain of Science and Technology, Chemistry, Department of Biochemistry and Organic Chemistry, Organic Chemistry II.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Investigation of the interaction between embedded amphiphilic molecules and PDMS matrix in aqueous environment and their impact on surface2013In: MME 2013 24th Micromechanics and Microsystems Europe Conference, 2013Conference paper (Refereed)
    Abstract [en]

    In this paper, we are the first to investigate systematically how the embedded molecules interact with PDMS matrix in aqueous environments and their impacts on the surface performance by varying various processing conditions such as water exposure time, curing master materials and embedded amphiphilic molecules. The results indicate that the interaction is strongly influenced by various processing conditions in a complicated way and the dominant forces are quite different in various conditions. Among them, water exposure time plays a clearly important role during the process.

  • 35.
    Qiu, Wenjun
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Sun, Xiaojiao
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Chaoqun
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    A Contact Angle Study of the Interaction between Embedded Amphiphilic Molecules and the PDMS Matrix in an Aqueous Environment2014In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 5, no 3, p. 515-527Article in journal (Refereed)
    Abstract [en]

    Poly(dimethylsiloxane) (PDMS) surface modification via gradient-induced transport of embedded amphiphilic molecules is a novel, easy, flexible, and environmentally friendly approach for reducing protein adsorption on PDMS in microfluidic applications. To better understand the processing and the potential use in the viability-sensitive applications such as manipulation and culturing of primary neural cells, we systematically investigate how embedded molecules interact with a PDMS matrix and its surface in aqueous environments by studying the wetting angle over time under various processing conditions, including water exposure time, water exposure temperature, curing master materials, in addition to comparing different embedded amphiphilic molecules. The results indicate that the water exposure time clearly plays an important role in the surface properties. Our interpretation is that molecular rearrangement of the surface-embedded molecules improves surface coverage in the short term; while over a longer period, the transport of molecules embedded in the bulk enhance its coverage. However, this improvement finally terminates when molecules transported from the bulk to the surface are not sufficient to replace the molecules leaching into the water.

  • 36.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microfluidic cell separation,2009Conference paper (Other academic)
  • 37.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microfluidic devices using flexible organic electronic materials2015In: Handbook of Flexible Organic Electronics: Materials, Manufacturing and Applications / [ed] S LOGOTHETIDIS, London: Woodhead Publishing Limited, 2015, p. 397-412Chapter in book (Refereed)
    Abstract [en]

    Being deformed without any discontinuities, microfluidics-based electronic devices demonstrate great mechanical flexibility. This chapter systematically reviews the development of microfluidics-based electronic devices with examples. In addition, discussions and perspectives on future development are included.

  • 38.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Passive and Active Micromixers2009In: Handbook of Micro Reactors: Vol.1: Fundamentals, Operations and Catalysts / [ed] V. Hessel, J.C. Schouten, A. Renken, and J.-I. Yoshida,, Weinheim: Wiley-VCH Verlagsgesellschaft, 2009, 1Chapter in book (Refereed)
  • 39.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Surface modification of PDMS in Microfluidic Devices2014In: Concise Encycloppedia of High Performance Silicones / [ed] Atul Tiwari and Mark D Soucek, Salem, Massachusetts: John Wiley & Sons, 2014Chapter in book (Refereed)
    Abstract [en]

    Being one of the most used materials for fabrication of microfluidic devices, Polydimethylsiloxane (PDMS) attracts great attention for years since G M Whitesides’ group introduced soft lithography - a rapid prototyping of microfluidic systems with PDMS, into the scientific community in the early 1990s. Its advantages in both physical and chemical properties promote a lots of micro/nano applications. Great efforts have been put to enhance its ability as well as minimize its drawbacks. In this chapter, kinds of common used methods in PDMS surface modification with their characterization methods and their recent development are introduced and discussed.

  • 40.
    Wu, Zhigang
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Tape Transfer Printing for Microfluidic based Stretchable Electronics2015In: ASME IMECE: Material processing of Flexible Electronics, Devices and Sensors, Zhigang WU , 2015Conference paper (Refereed)
    Abstract [en]

    Stretchable electronics offers unsurpassed mechanical compliance on complex or soft surfaces like the human skin and organs. With uncompromised stretchablility, microfluidic processing offers high possibility to make high performance stretchable electronics. Hence, it is very important to find a good solution to make such kind of stretchable electronics.

     

    Here, with a newly introduced tape transfer printing technique, we present here a new direction to pattern liquid alloys on elastic substrates. By rolling printing or atomized spraying of a liquid alloy onto a soft surface with a tape transferred adhesive mask, a universal fabrication process is provided for high quality patterns of liquid conductors in a meter scale. With this tape transfer printing technique, we can print any pattern on the elastic substrate, which can be done the traditional stencil printing. With the developed technology, we present here an integrated radio frequency identify tag, which showed the robustness of the packaged hybrid integrated system when stretched at 50% in 3,000 cycles. Further developed with a multilayer fabrication technique, a microfluidic stretchable wireless power transfer device with an integrated LED was demonstrated, which could survive cycling between 0% and 25% strain over 1,000 times.

     

    Briefly, the process of tape transfer printing of a liquid alloy is summarized here:

    1. 1.     PDMS substrate was prepared on a rigid support and half-cured on a hot plate.
    2. 2.     A mask for patterning liquid alloy was designed and cut by a cut plotter.
    3. 3.     Then gently, the tape mask on the transfer tape was transferred to the as-prepared half-cured PDMS substrate through the laminated transfer tape after removing the unnecessary patterns.
    4. 4.     The liquid alloy was printed with a sponge head roller by rolling it over several times or atomizing printing with an airbrush scanning.
    5. 5.     The printed liquid alloy patterns were ready, by slowly peeling the tape mask off from the substrate.
    6. 6.     With optional integrating rigid components with so-called localized stiff cells, the liquid alloy circuits were encapsulated with a secondary PDMS layer. This processing can be stacked further for a multilayer fabrication.

    This technique is able to pattern high quality, uniform and clear patterns of 500 μm wide lines with lengths near a meter. A microfluidic RFID and wireless power transfer device were successfully demonstrated with excellent mechanical stretchability as well as good performance.

    In conclusion, our work demonstrated a versatile liquid alloy patterning technique on soft substrates based on tape transferred adhesive masking, and deposition of a liquid alloy. Further improvement and optimization of this process technique could offer higher resolution and repeatability, and create new opportunities to introduce advanced functions in conformal devices, intelligent systems on the skin or what could be implanted for man-machine communication.

  • 41.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Fast microfluidic particle filtering by dean spreading2008In: International Conference on Miniaturized Systems for Chemistry and Life Sciences μTAS2008, 2008, p. 1441-1443Conference paper (Refereed)
  • 42.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microfluidic hydrodynamic cell separation2007Conference paper (Refereed)
  • 43.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Microfluidic Hydrodynamic Cell Separation: A Review2009In: Micro and Nanosystems, ISSN 1876-4037, Vol. 1, no 3, p. 181-192Article in journal (Refereed)
    Abstract [en]

    Microfluidic continuous cell separation based on hydrodynamic interaction in a microfluidic channel has attracted attention because of its robustness, high throughput and cell viability. This paper systematically gives an overview on recent advances in hydrodynamic particle and cell separation in microfluidic devices. It presents the basic ideas and fluid mechanics for the hydrodynamic interaction of a particle in a microfluidic system. Secondly, different kinds of devices are introduced with detailed descriptions of their mechanisms, designs and performances. Finally, the review addresses some practical issues of microfluidic sorting devices for use in biological or medical studies.

  • 44.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Microfluidics for hydrodynamics2008In: Micro System Workshop MSW08, 2008, p. 54-Conference paper (Refereed)
  • 45.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Surface modification of PDMS by gradient-induced migration of embedded Pluronic2009In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 9, no 11, p. 1500-1503Article in journal (Refereed)
    Abstract [en]

    We present a simple, flexible, and environmentally friendly approach to modify the PDMS surface by gradient-induced migration of embedded amphiphilic copolymer Pluronic F127 and the hydrophobic interaction between the migrated embedded Pluronic and substrate molecules near the surface. The modified surface is hydrophilic and reduces the nonspecific adsorption of protein significantly.

  • 46.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Jeong, Seung Hee
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology. Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Microfluidic Stretchable Radio-Frequency Devices2015In: Proceedings of the IEEE, ISSN 0018-9219, E-ISSN 1558-2256, Vol. 103, no 7, p. 1211-1225Article in journal (Refereed)
    Abstract [en]

    Recently, the shrinking of the personal computer market has given a clear signal that it is time to divert our focus from the strategy of miniaturization of transistors to a different strategy with emerging technologies. As a new form of electronics, stretchable electronics has significantly advanced in the past few years by micro/nanofabrication of thin films of traditional stiff and hard materials such as silicon, metals, and ceramics, and especially subsequent transfer process on an elastic substrate. However, such a thin structure often suffers from high resistance that leads to low performance when long structures are required. This is particularly true for antennas in radio-frequency (RF) electronics. By introducing microfluidics into RF electronics, we found out that it was an excellent way to make high-performance stretchable RF electronics. Apart from antennas, the microfluidic approach was also adopted and further developed to various devices with integrated wireless communication. This fusion of microfluidics with RF electronics brings not only a lot of opportunities for researchers as a radically new research field, but also potentially commercial benefits for industry. As a new emerging field, a huge effort, ranging from fundamental science to technology development, is required to realize it. This paper illustrates the fundamentals in processing and relevant applications, and highlights recent advances in microfluidic RF electronics. The authors would like to inspire the electronics community to further exploit the advantages of this approach and accelerate innovations in this field.

  • 47.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Micro Structural Technology.
    Wicher, Grzegorz
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
    Svenningsen, Åsa Fex
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
    Microfluidic high viability neural cell separation using viscoelastically tuned hydrodynamic spreading2008In: Biomedical microdevices (Print), ISSN 1387-2176, E-ISSN 1572-8781, Vol. 10, no 5, p. 631-638Article in journal (Refereed)
    Abstract [en]

    A high viability microfluidic cell separation technique of high throughput was demonstrated based on size difference continuous mode hydrodynamic spreading with viscoelastic tuning. Using water with fluorescent dye as sample fluid and in parallel introducing as elution a viscoelastic biocompatible polymer solution of alginic sodium, the spreading behavior was investigated at different polymer concentrations and flow rates. Particle separation was studied in the same detail for 9.9 mu m and 1.9 mu m latex beads. Using buffered aqueous solutions and further surface treatments to protect from cell adhesion, separation between neuron cells and glial cells from rat's spine cord was demonstrated and compared to the separation of latex particles of 20 and 4.6 mu m sizes. High relative viability (above 90%) of neural cells was demonstrated compared the reference cells of the same batch.

  • 48.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Jobs, Magnus
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Rydberg, Anders
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Hemispherical coil electrically small antenna made by stretchable conductors printing and plastic thermoforming2015In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 25, no 2, article id 027004Article in journal (Refereed)
    Abstract [en]

    A production scalable technique is presented to make hemispherical coil antennas by using a stretchable printed silver paste conductor and plastic thermoforming. To ease the fabrication process an unbalanced feed-structure was designed for solderless mounting on conductive materials. The manufactured antenna had a resonance frequency of 2.467 GHz with a reflection coefficient of -33.8 dB. The measured and simulated radiation patterns corresponded to that of monopole structure and the measured efficiency was 40%.

  • 49.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Qun Liu, Ai
    Nanyang Technological University, Singapore.
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Microfluidic continuous particle/cell separation via electroosmotic-flow-tuned hydrodynamic spreading2007In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 17, no 10, p. 1992-1999Article in journal (Refereed)
    Abstract [en]

    Among the microfluidic separation methods, hydrodynamic spreading is a simple and high-throughput continuous separation technique based on the difference in size. However, it is difficult to adjust tiny pressure differences accurately in microfluidic devices. In this study, a combination of electroosmotic flow (EOF) and hydrodynamic flow spreading was employed to tune the size separation of particles. A stream with different kinds of particle suspensions was driven co-fluently with a particle-free carrier stream under both mechanical external and electroosmotic pressure in a microchannel. The EOF-tuned hydrodynamic spreading behaviour was investigated experimentally and modelled through an electric equivalent model and numerical simulation. When the magnitudes of the mechanically and electroosmotically induced pressures were similar, the EOF tuning on the pressure-driven flow became significant. Hence, the hydrodynamic spreading could be easily adjusted by a tuned power supply. The separation was studied in more detail with 1.9 and 9.9 µm fluorescent polystyrene particles. Moreover, separation of E. coli and yeast cells was accomplished. In conclusion, this technique has the advantages of good stability of mechanical-pressure-driven flow and precise tuning of the EOF, and provides a robust method for size-based separation of particles and cells.

  • 50.
    Wu, Zhigang
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Wicher, Grzegorz
    Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Neuroscience.
    Fex Svenningsen, Åsa
    Hjort, Klas
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
    Separation of neural cells using two-step separation by combination of soft inertial microfluidics and pinched flow fractionation2010Conference paper (Refereed)
12 1 - 50 of 57
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