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Publications (10 of 253) Show all publications
Perez, M. D., Jeong, S. H., Raman, S., Nowinski, D., Wu, Z., Redzwan, S., . . . Augustine, R. (2020). Head-compliant microstrip split ring resonator for non-invasive healing monitoring after craniosynostosis-based surgery. HEALTHCARE TECHNOLOGY LETTERS, 7(1), 29-34
Open this publication in new window or tab >>Head-compliant microstrip split ring resonator for non-invasive healing monitoring after craniosynostosis-based surgery
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2020 (English)In: HEALTHCARE TECHNOLOGY LETTERS, ISSN 2053-3713, Vol. 7, no 1, p. 29-34Article in journal (Refereed) Published
Abstract [en]

A soft and highly directive, proximity-coupled split-ring resonator fabricated with a liquid alloy, copper and polydimethylsiloxane (PDMS) is presented. The same was designed for sensing osteogenesis of calvarial bone. As dielectric properties of bone grafts in ossifying calvarial defects should change during the osteogenesis process, devices like this could monitor the gradual transformation of the defect into bone by differentiating changes in the dielectric properties as shifts in the resonance frequency. Computational Software Technology (CST) Microwave Studio (R)-based simulation results on computational head models were in good agreement with laboratory results on head phantom models, which also included the comparison with an in-vivo measurement on the human head. A discussion based on an inductive reasoning regarding dynamics' considerations is provided as well. Since the skin elasticity of newborn children is high, stretching and crumpling could be significant. In addition, due to typical head curvatures in newborn children, bending should not be a significant issue, and can provide higher energy focus in the defect area and improve conformability. The present concept could support the development of soft, cheap and portable follow-up monitoring systems to use in outpatient hospital and home care settings for post-operative monitoring of bone healing after reconstructive surgical procedures.

Place, publisher, year, edition, pages
INST ENGINEERING TECHNOLOGY-IET, 2020
Keywords
bone, phantoms, surgery, skin, elasticity, bending, biomechanics, paediatrics, split ring resonators, microstrip resonators, patient monitoring, liquid alloys, microwave resonators, biomedical equipment, bone grafts, calvarial defects, osteogenesis process, dielectric properties, resonance frequency, computational head models, head phantom models, human head, newborn children, defect area, monitoring systems, post-operative monitoring, bone healing, head-compliant microstrip split ring resonator, noninvasive healing monitoring, craniosynostosis-based surgery, soft proximity-coupled split-ring resonator, highly directive proximity-coupled split-ring resonator, copper, polydimethylsiloxane, liquid alloy, calvarial bone osteogenesis, computational software technology microwave studio-based simulation, head curvatures, skin elasticity, reconstructive surgical procedures
National Category
Orthopaedics Medical Materials
Identifiers
urn:nbn:se:uu:diva-408515 (URN)10.1049/htl.2018.5083 (DOI)000520504200002 ()32190338 (PubMedID)
Funder
Vinnova, 2015-04159Swedish Research Council, 2017-04644EU, Horizon 2020, 824984-SINTEC
Available from: 2020-04-08 Created: 2020-04-08 Last updated: 2020-04-08Bibliographically approved
Andersson, M., Wilson, A., Hjort, K. & Klintberg, L. (2019). A microfluidic relative permittivity sensor for feedback control of carbon dioxide expanded liquid flows. Sensors and Actuators A-Physical, 285, 165-172
Open this publication in new window or tab >>A microfluidic relative permittivity sensor for feedback control of carbon dioxide expanded liquid flows
2019 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 285, p. 165-172Article in journal (Refereed) Published
Abstract [en]

Binary CO2-alcohol mixtures, such as CO2-expanded liquids (CXLs), are promising green solvents for reaching higher performance in flow chemistry and separation processing. However, their compressibility and high working pressure makes handling challenging. These mixtures allow for a tuneable polarity but, to do so, requires precise flow control. Here, a high-pressure tolerant microfluidic system containing a relative permittivity sensor and a mixing chip is used to actively regulate the relative permittivity of these fluids and indirectly—composition. The sensor is a fluid-filled plate capacitor created using embedded 3D-structured thin films and has a linearity of 0.9999, a sensitivity of 4.88 pF per unit of relative permittivity, and a precision within 0.6% for a sampling volume of 0.3 μL. Composition and relative permittivity of CO2-ethanol mixtures were measured at 82 bar and 21 °C during flow. By flow and dielectric models, this relationship was found to be described by the pure components and a quadratic mixing rule with an interaction parameter, kij, of -0.63 ± 0.02. Microflows with a relative permittivity of 1.7–21.4 were generated, and using the models, this was found to correspond to compositions of 6–90 mol % ethanol in CO2. With the sensor, a closed loop control system was realised and CO2-ethanol flows were tuned to setpoints of the relative permittivity in 30 s.

Keywords
Relative permittivity, Process control, CO2-expanded liquids, Binary fluid mixtures, High-pressure microfluidics
National Category
Chemical Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-353945 (URN)10.1016/j.sna.2018.11.015 (DOI)000456902600021 ()
Funder
Knut and Alice Wallenberg Foundation
Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2019-02-25Bibliographically approved
Wang, B., Wu, K., Hjort, K., Guo, C. & Wu, Z. (2019). High-Performance Liquid Alloy Patterning of Epidermal Strain Sensors for Local Fine Skin Movement Monitoring. SOFT ROBOTICS, 6(3), 414-421
Open this publication in new window or tab >>High-Performance Liquid Alloy Patterning of Epidermal Strain Sensors for Local Fine Skin Movement Monitoring
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2019 (English)In: SOFT ROBOTICS, ISSN 2169-5172, Vol. 6, no 3, p. 414-421Article in journal (Refereed) Published
Abstract [en]

Nowadays, stretchable/epidermal electronics based on liquid alloys has attracted more and more attention, and various processing techniques have subsequently been developed to demonstrate diverse applications never seen before. However, to fully exploit its potential advantages, epidermal electronics is still searching for a technique meeting all demands on resolution, pattern complexity, and operational flexibility. In this study, we propose a technique that allows for complex and high-density patterns on thin stretchable substrates by combining ultraviolet laser patterning of a modified water-soluble mask, atomized spray deposition of liquid alloys on a flexible temporary substrate, lift-off by water dissolving, and finally, component integration and encapsulation. With this new technique, it was possible to make epidermal precision strain sensors with liquid alloy patterns of high density, which were capable of monitoring fine local skin movements such as the detailed process of wrinkle formation as well as the overall motion of the body part. In addition, this process is highly efficient and well controllable, with high potential for possible industrial automation and massive production.

Place, publisher, year, edition, pages
MARY ANN LIEBERT, INC, 2019
Keywords
laser patterning soluble mask, liquid alloy patterning, epidermal strain sensor, two-dimensional strain sensor, local strain sensor, skin movement
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-395561 (URN)10.1089/soro.2018.0008 (DOI)000462512600001 ()30917090 (PubMedID)
Available from: 2019-10-21 Created: 2019-10-21 Last updated: 2019-10-30Bibliographically approved
Cruz, J., Graells, T., Wallden, M. & Hjort, K. (2019). Inertial focusing with sub-micron resolution for separation of bacteria. Lab on a Chip, 19(7), 1257-1266
Open this publication in new window or tab >>Inertial focusing with sub-micron resolution for separation of bacteria
2019 (English)In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 19, no 7, p. 1257-1266Article in journal (Refereed) Published
Abstract [en]

In this paper, we study inertial focusing in curved channels and demonstrate the alignment of particles with diameters between 0.5 and 2.0 m, a range of biological relevance since it comprises a multitude of bacteria and organelles of eukaryotic cells. The devices offer very sensitive control over the equilibrium positions and allow two modes of operation. In the first, particles having a large variation in size are focused and concentrated together. In the second, the distribution spreads in a range of sizes achieving separation with sub-micron resolution. These systems were validated with three bacteria species (Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae) showing good alignment while maintaining the viability in all cases. The experiments also revealed that the particles follow a helicoidal trajectory to reach the equilibrium positions, similar to the fluid streamlines simulated in COMSOL, implying that these positions occupy different heights in the cross section. When the equilibrium positions move to the inner wall as the flow rate increases, they are at a similar distance from the centre than in straight channels (approximate to 0.6R), but when the equilibrium positions move to the outer wall as the flow rate increases, they are closer to the centre and the particles pass close to the inner wall to elevate their position before reaching them. These observations were used along with COMSOL simulations to explain the mechanism behind the local force balance and the migration of particles, which we believe contributes to further understanding of the phenomenon. Hopefully, this will make designing more intuitive and reduce the high pressure demands, enabling manipulation of particles much smaller than a micrometer.

Place, publisher, year, edition, pages
ROYAL SOC CHEMISTRY, 2019
National Category
Biochemistry and Molecular Biology
Identifiers
urn:nbn:se:uu:diva-382383 (URN)10.1039/c9lc00080a (DOI)000462723900009 ()30821308 (PubMedID)
Funder
EU, Horizon 2020, 644669
Available from: 2019-04-25 Created: 2019-04-25 Last updated: 2019-04-25Bibliographically approved
Werr, G., Khaji, Z., Ohlin, M., Andersson, M., Klintberg, L., Searle, S., . . . Tenje, M. (2019). Integrated thin film resistive sensors for in situ temperature measurements in an acoustic trap. Journal of Micromechanics and Microengineering, 29(9), Article ID 095003.
Open this publication in new window or tab >>Integrated thin film resistive sensors for in situ temperature measurements in an acoustic trap
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2019 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 29, no 9, article id 095003Article in journal (Refereed) Published
Abstract [en]

This work presents an acoustic trap with integrated thin film sensors to monitor temperature variations during operation. The acoustic trap is wet-etched in glass with a thermally bonded glass lid and the thin-film sensors are integrated during fabrication. We evaluated the performance of the integrated temperature sensors and measured a temperature sensitivity of +/- 0.01 degrees C and confirmed that the read-out of the thin film sensors was not affected neither by the ionic conductivity of the solution nor the addition of microparticles into the acoustic trap. From the experiments we observed a temperature increase of the acoustic trap during operation as a result of the dissipative heating of the the piezoelectric element used to actuate the trap. We also showed that when external convective cooling was applied to the system, the temperature increase of the acoustic trap was higher than the temperature increase of the piezoelectric element itself. This shows the importance of using integrated temperature sensors in acoustic trapping to monitor the local environmental conditions.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2019
Keywords
acoustophoresis, integrated RTD, external TC, acoustic trap, glass chip
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:uu:diva-391278 (URN)10.1088/1361-6439/ab2ac8 (DOI)000476561400001 ()
Funder
Knut and Alice Wallenberg Foundation
Available from: 2019-08-22 Created: 2019-08-22 Last updated: 2019-08-22Bibliographically approved
Werr, G., Khaji, Z., Ohlin, M., Andersson, M., Klintberg, L., Searle, S., . . . Tenje, M. (2019). Integrated thin film resistive sensors for in situ temperature measurements in an acoustic trap. In: Acoustofluidics 2019: This annual meeting will be held in Twente, The Netherlands in 2019. This focused meeting is dedicated to exploring the science, engineering, and use of micro- to nanoscale acoustofluidics.. Paper presented at Acoustofluidics 2019, 25-28 August 2019, Enschede, Netherlands (pp. 140-141).
Open this publication in new window or tab >>Integrated thin film resistive sensors for in situ temperature measurements in an acoustic trap
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2019 (English)In: Acoustofluidics 2019: This annual meeting will be held in Twente, The Netherlands in 2019. This focused meeting is dedicated to exploring the science, engineering, and use of micro- to nanoscale acoustofluidics., 2019, p. 140-141Conference paper, Poster (with or without abstract) (Other academic)
Abstract [en]

This work presents an acoustic trap with integrated thin film sensors to monitor temperature variations during operation. The acoustic trap is wet-etched in glass with a thermally bonded glass lid and the thin-film sensors are integrated during fabrication. We evaluated the performance of the integrated temperature sensors and measured a temperature sensitivity of ±0.01 °C and confirmed that the read-out of the thin film sensors was not affected neither by the ionic conducitiviy of the solution nor the addition of microparticles into the acoustic trap. From the experiments we observed a temperature increase of the acoustic trap during operation as a result of the dissipative heating of the the piezoelectric element used to actuate the trap. We also showed that when external convective cooling was applied to the system, the temperature increase of the acoustic trap was higher than the temperature incresase of the piezoelectric element itself. This shows the importance of using integrated temperature sensors in acoustic trapping to monitor the environmental conditions.

Keywords
acoustophoresis, platinum RTD, external TC, integrated temperature sensor, thin film resistive sensor, acoustic trapping
National Category
Medical Laboratory and Measurements Technologies
Identifiers
urn:nbn:se:uu:diva-398685 (URN)
Conference
Acoustofluidics 2019, 25-28 August 2019, Enschede, Netherlands
Funder
Knut and Alice Wallenberg Foundation
Available from: 2019-12-09 Created: 2019-12-09 Last updated: 2019-12-09Bibliographically approved
Liu, Z., Fornell, A., Barbe, L., Hjort, K. & Tenje, M. (2019). On-chip background dilution in droplets with high particle recovery using acoustophoresis. Biomicrofluidics, 13, Article ID 064123.
Open this publication in new window or tab >>On-chip background dilution in droplets with high particle recovery using acoustophoresis
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2019 (English)In: Biomicrofluidics, ISSN 1932-1058, E-ISSN 1932-1058, Vol. 13, article id 064123Article in journal (Refereed) Published
Abstract [en]

Droplet microfluidics has shown great potential for on-chip biological and chemical assays. However, fluid exchange in droplet microfluidics with high particle recovery is still a major bottleneck. Here, using acoustophoresis, we present for the first time a label-free method to achieve continuous background dilution in droplets containing cells with high sample recovery. The system comprises droplet generation, acoustic focusing, droplet splitting, picoinjection, and serpentine mixing on the same chip. The capacities of the picoinjection and the droplet split to dilute the background fluorescent signal in the droplets have been characterized. The sample recovery at different droplet split ratios has also been characterized. The results show a maximum of 4.3-fold background dilution with 87.7% particle recovery. We also demonstrated that the system can be used to dilute background fluorescent signal in droplets containing either polystyrene particles or endothelial cells.

National Category
Biochemistry and Molecular Biology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-398535 (URN)10.1063/1.5129256 (DOI)000505984000025 ()31832121 (PubMedID)
Funder
Swedish Research Council
Available from: 2019-12-06 Created: 2019-12-06 Last updated: 2020-03-24Bibliographically approved
Wang, B., Xin, W., Hjort, K., Guo, C. & Wu, Z. (2019). Sandwiched Polyethylene Shrink Film Masking with Tunable Resolution and Shape for Liquid Alloy Patterning. ACS APPLIED POLYMER MATERIALS, 1(2), 145-151
Open this publication in new window or tab >>Sandwiched Polyethylene Shrink Film Masking with Tunable Resolution and Shape for Liquid Alloy Patterning
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2019 (English)In: ACS APPLIED POLYMER MATERIALS, ISSN 2637-6105, Vol. 1, no 2, p. 145-151Article in journal (Refereed) Published
Abstract [en]

Among numerous patterning techniques, masked liquid alloy printing is one of the most promising techniques for scalable fabrication of liquid-alloy-based stretchable electronics. Like any other mask-based process, its resolution is often constrained by the quality of the mask, and the fabrication cost increases drastically with increased resolution. In this work, by introducing a sandwiched thermal shrink polymer film masking technique and a corresponding intermediate release agent, fine liquid alloy patterns were demonstrated by using a mechanical cutting plotter together with a common oven. The final resolution and shape of the mask could be tuned based on the anisotropy of the shrink polymer film and other operational parameters of the technique. After shrinkage, the width of the patterned liquid alloy lines and space in-between could be tuned to less than one third of the original cut pattern, to about 35 and 60 mu m, respectively, according to requirements. To better predict the final structure, several parameters were investigated experimentally and numerically. Finally, a liquid alloy strain sensor and three-dimensional conformal masking were demonstrated, showing the potential of the developed technique.

Keywords
masking, shrink film, resolution tuning, 3D conformal masking, liquid alloy patterning
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-392067 (URN)10.1021/acsapm.8b00010 (DOI)000476966600007 ()
Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-09-09Bibliographically approved
Andersson, M., Svensson, K., Klintberg, L. & Hjort, K. (2018). A microfluidic control board for high-pressure flow, composition, and relative permittivity. Analytical Chemistry, 90(21), 12601-12608
Open this publication in new window or tab >>A microfluidic control board for high-pressure flow, composition, and relative permittivity
2018 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 90, no 21, p. 12601-12608Article in journal (Refereed) Published
Abstract [en]

Flow control is central to microfluidics and chromatography. With decreasing dimensions and high pressures, precise fluid flows are often needed. In this paper, a high-pressure flow control system is presented, allowing for the miniaturization of chromatographic systems and the increased performance of microfluidic setups by controlling flow, composition and relative permittivity of two-component flows with CO2. The system consists of four chips: two flow actuator chips, one mixing chip and one relative permittivity sensor. The actuator chips, throttling the flow, required no moving parts as they instead relied on internal heaters to change the fluid resistance. This allows for flow control using miniaturized fluid delivery systems containing only a single pump or pressure source. Mobile phase gradients between 49% to 74% methanol in CO2 were demonstrated. Depending on how the actuator chips were dimensioned, the position of this range could be set for different method-specific needs. With the microfluidic control board, both flow and composition could be controlled from constant pressure sources, drift could be removed, and variations in composition could be lowered by 84%, resulting in microflows of CO2 and methanol with a variation in the composition of 0.30%.

National Category
Chemical Engineering
Identifiers
urn:nbn:se:uu:diva-353953 (URN)10.1021/acs.analchem.8b02758 (DOI)000449722500039 ()30269500 (PubMedID)
Funder
Knut and Alice Wallenberg Foundation
Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2018-12-21Bibliographically approved
Jiao, M., Nguyen, v. D., Nguyen, V. C., Nguyen, D. H., Nguyen, V. H., Hjort, K. & Nguyen, H. (2018). Comparison of NO2 Gas-Sensing Properties of Three Different ZnO Nanostructures Synthesized by On-Chip Low-Temperature Hydrothermal Growth. Journal of Electronic Materials, 47(1), 785-793
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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2018 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 47, no 1, p. 785-793Article in journal (Refereed) Published
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)000418580800093 ()
Available from: 2017-04-16 Created: 2017-04-16 Last updated: 2018-01-29Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0003-2744-1634

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