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Publications (10 of 233) Show all publications
Hjort, K., Rask-Andersen, H. & Li, H. (2018). Softer, thinner and more compliant implants. In: : . Paper presented at 8th IEEE Int. Nanoelectronics Conf, INEC2018. .
Open this publication in new window or tab >>Softer, thinner and more compliant implants
2018 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

Tissue irritation is caused by two main reasons – chemical and mechanical. In recent years, material chemical biocompatibility has been much improved but most implants used in soft tissue still have low compliance. This is especially severe in the brain, where the tissue often has a compliance of a soft hydrogel and ordinary silicone materials like PDMS have an elastic modulus up to 1,000 times higher, i.e. like a wooden stick irritating your skin. Starting from the remaining challenges of the highly successful Cochlear Implants and recent work on stretchable electronics this review conclude on the merits with soft stretchable printed circuitboards, with components of fluids, gels, and sprinkled with a smart dust of small chips.

Keyword
stretchable electronics, Cochlear implant, PCB, liquid alloy
National Category
Other Medical Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Microsystems Technology; Oto-Rhino-Laryngology
Identifiers
urn:nbn:se:uu:diva-338013 (URN)
Conference
8th IEEE Int. Nanoelectronics Conf, INEC2018
Projects
Mjukare, tunnare och mer följsamma cocleaimplantat
Funder
Swedish Research Council, 2017-03801
Available from: 2018-01-06 Created: 2018-01-06 Last updated: 2018-01-08Bibliographically approved
Jiao, M., Nguyen, v. D., Nguyen, V. C., Nguyen, D. H., Nguyen, V. H., Hjort, K. & Nguyen, H. (2017). Comparison of NO2 Gas-Sensing Properties of Three Different ZnO Nanostructures Synthesized by On-Chip Low-Temperature Hydrothermal Growth. Journal of Electronic Materials.
Open this publication in new window or tab >>Comparison of NO2 Gas-Sensing Properties of Three Different ZnO Nanostructures Synthesized by On-Chip Low-Temperature Hydrothermal Growth
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2017 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186XArticle in journal (Refereed) Epub ahead of print
Abstract [en]

Three different ZnO nanostructures, dense nanorods, dense nanowires, and sparse nanowires, were synthesized between Pt electrodes by on-chip hydrothermal growth at 90°C and below. The three nanostructures were characterized by scanning electron microscopy and x-ray diffraction to identify their morphologies and crystal structures. The three ZnO nanostructures were confirmed to have the same crystal type, but their dimensions and densities differed. The NO2 gas-sensing performance of the three ZnO nanostructures was investigated at different operation temperatures. ZnO nanorods had the lowest response to NO2 along with the longest response/recovery time, whereas sparse ZnO nanowires had the highest response to NO2 and the shortest response/recovery time. Sparse ZnO nanowires also performed best at 300°C and still work well and fast at 200°C. The current–voltage curves of the three ZnO nanostructures were obtained at various temperatures, and the results clearly showed that sparse ZnO nanowires did not have the linear characteristics of the others. Analysis of this phenomenon in connection with the highly sensitive behavior of sparse ZnO nanowires is also presented.

National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-320153 (URN)10.1007/s11664-017-5829-6 (DOI)
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2017-11-09Bibliographically approved
Andersson, M., Stocklassa, J., Klintberg, L. & Hjort, K. (2017). Control Systems For Gas-Expanded Liquids In Microreactors. In: : . Paper presented at Flow17 Conference, France, Paris, 3-5 July 2017. .
Open this publication in new window or tab >>Control Systems For Gas-Expanded Liquids In Microreactors
2017 (English)Conference paper, Published paper (Refereed)
National Category
Chemical Process Engineering
Identifiers
urn:nbn:se:uu:diva-333204 (URN)
Conference
Flow17 Conference, France, Paris, 3-5 July 2017
Available from: 2017-11-08 Created: 2017-11-08 Last updated: 2017-12-29Bibliographically approved
Ohlin, M., Andersson, M., Klintberg, L., Hjort, K. & Tenje, M. (2017). In situ temperature monitoring during acoustophoresis using integrated thin film Pt temperature sensors. In: : . Paper presented at Acoustofluidics 2017, San Diego, USA, August 28-29 2017. .
Open this publication in new window or tab >>In situ temperature monitoring during acoustophoresis using integrated thin film Pt temperature sensors
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2017 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Engineering and Technology Medical Laboratory and Measurements Technologies
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-335786 (URN)
Conference
Acoustofluidics 2017, San Diego, USA, August 28-29 2017
Funder
Swedish Research CouncilThe Crafoord FoundationKnut and Alice Wallenberg Foundation
Available from: 2017-12-11 Created: 2017-12-11 Last updated: 2017-12-29Bibliographically approved
Ohlin, M., Andersson, M., Klintberg, L., Hjort, K. & Tenje, M. (2017). Internal temperature sensing in an acoustophoretic glass chip. In: : . Paper presented at 28th Micromechanics and Microsystems Europe workshop (MME 2017), Uppsala, Sweden, August 23-25 2017. .
Open this publication in new window or tab >>Internal temperature sensing in an acoustophoretic glass chip
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2017 (English)Conference paper, Poster (with or without abstract) (Refereed)
National Category
Engineering and Technology Medical Laboratory and Measurements Technologies
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-335727 (URN)
Conference
28th Micromechanics and Microsystems Europe workshop (MME 2017), Uppsala, Sweden, August 23-25 2017
Available from: 2017-12-07 Created: 2017-12-07 Last updated: 2017-12-29Bibliographically approved
Jiao, M., Nguyen, V. D., Nguyen, V. C., Nguyen, D. H., Nguyen, V. H., Hjort, K. & Nguyen, H. (2017). On-chip growth of patterned ZnO nanorod sensors with PdO decoration for enhancement of hydrogen-sensing performance. International journal of hydrogen energy, 42(25), 16294-16304.
Open this publication in new window or tab >>On-chip growth of patterned ZnO nanorod sensors with PdO decoration for enhancement of hydrogen-sensing performance
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2017 (English)In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 42, no 25, 16294-16304 p.Article in journal (Refereed) Published
Abstract [en]

In this study, we used a low-temperature hydrothermal technique to fabricate arrays of sensors with ZnO nanorods grown on-chip. The sensors on the glass substrate then were sputter decorated with Pd at thicknesses of 2, 4, and 8 nm and annealed at 650 °C in air for an hour. Scanning electron microscopy, high resolution transmission microscopy, X-ray diffraction, and surface analysis by X-ray photoelectron spectroscopy characterization demonstrated that decoration of homogenous PdO nanoparticles on the surface of ZnO nanorods had been achieved. The sensors were tested against three reducing gases, namely hydrogen, ethanol, and ammonia, at 350, 400, and 450 °C. The ZnO nanorods decorated with PdO particles from the 2 and 4 nm layers showed the highest responses to H2 at 450 and 350 °C, respectively. These samples also generally exhibited better selectivity for hydrogen than for ethanol and ammonia at the same concentrations and at all tested temperatures. However, the ZnO nanorods decorated with PdO particles from the 8 nm layer showed a reverse sensing behaviour compared with the first two. The sensing mechanism behind these phenomena is discussed in the light of the spillover effect of hydrogen in contact with the PdO particles as well as the negative competition of the PdO thin film formed between the sensor electrodes during sputter decoration, Pd-Zn heterojunction that forms at high temperature and thus influences the conductivity of the ZnO nanorods.

Keyword
Hydrogen-sensing at high temperature; On-chip hydrothermal growth; ZnO nanorods; Sputter-decoration; PdO nanoparticles
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-320156 (URN)10.1016/j.ijhydene.2017.05.135 (DOI)000405251500028 ()
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2017-10-10Bibliographically approved
Jeong, S. H., Cruz, J., Chen, S., Gravier, L., Liu, J., Wu, Z., . . . Zhang, Z.-B. (2017). Stretchable thermoelectric generators metallized with liquid alloy. ACS Applied Materials and Interfaces, 9(18), 15791-15797.
Open this publication in new window or tab >>Stretchable thermoelectric generators metallized with liquid alloy
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2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 18, 15791-15797 p.Article in journal (Refereed) Published
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.

National Category
Energy Engineering Textile, Rubber and Polymeric Materials Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:uu:diva-281213 (URN)10.1021/acsami.7b04752 (DOI)000401307100064 ()28453282 (PubMedID)
Funder
Swedish Foundation for Strategic Research , EM11-0002, SE13-0061Swedish Research Council, 621-2014-5596
Available from: 2016-03-21 Created: 2016-03-21 Last updated: 2017-07-04Bibliographically approved
Andersson, M., Ek, J., Hedman, L., Johansson, F., Sehlstedt, V., Stocklassa, J., . . . Klintberg, L. (2017). Thin film metal sensors in fusion bonded glass chips for high-pressure microfluidics. Journal of Micromechanics and Microengineering, 27(1), Article ID 015018.
Open this publication in new window or tab >>Thin film metal sensors in fusion bonded glass chips for high-pressure microfluidics
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2017 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 27, no 1, 015018Article in journal (Refereed) Published
Abstract [en]

High-pressure microfluidics offers fast analyses of thermodynamic parameters for compressed process solvents. However, microfluidic platforms handling highly compressible supercritical CO2 are difficult to control, and on-chip sensing would offer added control of the devices. Therefore, there is a need to integrate sensors into highly pressure tolerant glass chips. In this paper, thin film Pt sensors were embedded in shallow etched trenches in a glass wafer that was bonded with another glass wafer having microfluidic channels. The devices having sensors integrated into the flow channels sustained pressures up to 220 bar, typical for the operation of supercritical CO2. No leakage from the devices could be found. Integrated temperature sensors were capable of measuring local decompression cooling effects and integrated calorimetric sensors measured flow velocities over the range 0.5-13.8 mm/s. By this, a better control of high-pressure microfluidic platforms has been achieved.

Keyword
supercritical carbon dioxide, high pressure microfluidics, integrated electrodes, temperature sensing, flow sensing, glass
National Category
Other Engineering and Technologies not elsewhere specified
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-310063 (URN)10.1088/0960-1317/27/1/015018 (DOI)000388703300003 ()
Funder
Swedish Research Council, 2011-5037VINNOVAKnut and Alice Wallenberg Foundation
Note

Part financed through Swedish Agency for the Innovation System, Vinnova, through the Centre for Natural Disaster Science (CNDS)

Available from: 2016-12-09 Created: 2016-12-09 Last updated: 2017-11-29Bibliographically approved
Chang, B., Zhou, Q., Wu, Z., Ras, R. & Hjort, K. (2016). Capillary Self-Alignment of Microchips on Soft Substrates. Micromachines, 7(3), Article ID 41.
Open this publication in new window or tab >>Capillary Self-Alignment of Microchips on Soft Substrates
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2016 (English)In: Micromachines, ISSN 2072-666X, E-ISSN 2072-666X, Vol. 7, no 3, 41Article in journal (Refereed) Published
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.

National Category
Manufacturing, Surface and Joining Technology
Identifiers
urn:nbn:se:uu:diva-279824 (URN)10.3390/mi7030041 (DOI)000373053100012 ()
Available from: 2016-03-04 Created: 2016-03-04 Last updated: 2017-11-30Bibliographically approved
Jiao, M., Nguyen, D. H., Nguyen, V. D., Nguyen, V. H., Hjort, K. & Nguyen, H. (2016). Controlled Synthesis and Understanding of GrowthMechanism: Parameters for Atmospheric PressureHydrothermal Synthesis of Ultrathin SecondaryZnO Nanowires. Journal of Scientific Research and Reports, 9(5), 1-10.
Open this publication in new window or tab >>Controlled Synthesis and Understanding of GrowthMechanism: Parameters for Atmospheric PressureHydrothermal Synthesis of Ultrathin SecondaryZnO Nanowires
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2016 (English)In: Journal of Scientific Research and Reports, ISSN 2320-0227, E-ISSN 2320-0227, Vol. 9, no 5, 1-10 p.Article in journal (Refereed) Published
Abstract [en]

Synthesis of ultrathin ZnO nanowires gains great attention from research community because oftheir large potential in applications involving optoelectronics and sensors. In this study, a lowpressure and low-temperature hydrothermal synthesis of ultrathin ZnO nanowires is studied tounderstand the growth mechanisms better. To achieve this aim, an about 10 nm thin Zn seed layerwas sputter-deposited on a silicon (100) wafer for the hydrothermal growth of ZnO nanowires in anequimolar aqueous solution of Zn(NO3)2 and hexamethylenetetramine. X-ray diffraction analysis confirmed that the Zn layer was self-oxidized into ZnO in air soon after deposition and thenfunctioned as the seed for the preferred growth of c-oriented ZnO nanorods. Different growthconditions were investigated to identify how concentration, temperature, and time influence the finalmorphology of the synthesized ZnO nanostructures. It was found that under the atmosphericpressure, concentration and temperature have to be higher than 0.0025 M and 50°C, respectively,for the ZnO nanorods to nucleate and grow densely. Low concentration gives sparse and randomlyoriented nanorods, whereas high concentration gives dense and vertical nanorods. Ultrathin ZnOsecondary nanowires with an average diameter of less than 20 nm were successfully synthesizedin a solution with concentration of 0.005 M at 90°C for about 16 h. By analyzing the scanningelectron microscopy images of the ZnO nanostructures obtained at different growth conditions, amechanism is proposed for the growth of the ultrathin secondary ZnO nanowires. This findingprovides a cost-effective and straightforward pathway to prepare ultrathin ZnO nanowires.

Keyword
ZnO nanowires, growth parameters, growth mechanism
National Category
Nano Technology
Identifiers
urn:nbn:se:uu:diva-286795 (URN)
Available from: 2016-04-21 Created: 2016-04-21 Last updated: 2017-11-30Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2744-1634

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