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Publications (10 of 284) Show all publications
Svensson, K., Södergren, S. & Hjort, K. (2024). Portable high-pressure pump system for HPLC combining pressurized gas and on-chip pressure regulation. Sensors and Actuators A-Physical, 371, Article ID 115286.
Open this publication in new window or tab >>Portable high-pressure pump system for HPLC combining pressurized gas and on-chip pressure regulation
2024 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 371, article id 115286Article in journal (Refereed) Published
Abstract [en]

High-pressure pumps for microfluidic systems typically require high powerand have large sizes, which hinder portability of otherwise miniaturized HPLC systems. To solve this, a battery-powered, pneumatic system for pressure-driven chromatography is presented. The system utilizes the stored energy in pressurized gas without consuming any of the gas. As the chromatography liquid flows, the gas in the pressure container expands and its pressure reduces. To compensate for this, a solution is presented with an on-chip microfluidic pressure regulator. The chip contains a microfluidic restrictor where fluid is heated by Joule heating to decrease viscosity, and thus reduce the pressure drop over the restrictor. An 18 V battery driven system with 50 ml N2 at 51 bar could provide a water flow rate of 55 µl/min at 32 bar for 67 min with a mean power consumption of 0.2 W. With the regulating microfluidic chip, the pressure stability was 2 mbar, i.e., on pair with high-quality high-pressure syringe pumps. The required gas volume, and hence the total size, is scalable with the desired liquid volume, which makes it suitable for miniaturized systems.

Place, publisher, year, edition, pages
Elsevier, 2024
National Category
Other Materials Engineering Fluid Mechanics and Acoustics
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-523406 (URN)10.1016/j.sna.2024.115286 (DOI)001218330300001 ()
Available from: 2024-02-18 Created: 2024-02-18 Last updated: 2024-06-24Bibliographically approved
Verdel, N., Drobnič, M., Maslik, J., Gumiero, A., Hjort, K., Holmberg, H.-C. & Supej, M. (2024). Reliability and Validity of Running Step Rate Derived From a Novel Wearable Smart Patch. IEEE Sensors Journal, 24(9), 14343-14351
Open this publication in new window or tab >>Reliability and Validity of Running Step Rate Derived From a Novel Wearable Smart Patch
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2024 (English)In: IEEE Sensors Journal, ISSN 1530-437X, E-ISSN 1558-1748, Vol. 24, no 9, p. 14343-14351Article in journal (Refereed) Published
Abstract [en]

A novel, wearable, stretchable Smart Patch can monitor various aspects of physical activity, including the dynamics of running. However, like any new device developed for such applications, it must first be tested for validity and reliability. Here, we compare the step rate while running on a treadmill measured by this smart patch with the corresponding values obtained with the "gold standard" OptoGait, as well as with other devices commonly used to assess running dynamics, that is, the MEMS accelerometer and commercially available and widely used Garmin Running Dynamic Pod. The 14 healthy, physically active volunteers completed two identical sessions with a 5-min rest between. Each session involved two 1-min runs at 11 and 14 km/h separated by a 1-min rest. The major finding was that the Smart Patch demonstrated fair to good test-retest reliability. The best test-retest reliability for the Running Pod was observed in connection with running at 11 km/h and both velocities combined (good and excellent, respectively) and for the OptoGait when running at 14 km/h (good). The best concurrent validity was achieved with the Smart Patch, as reflected in the highest Pearson correlation coefficient for this device when running at 11 or 14 km/h, as well as for both velocities combined. In conclusion, this study demonstrates that the novel wearable Smart Patch shows promising reliability and excellent concurrent validity in measuring step rate during treadmill running, making it a viable tool for both research and practical applications in sports and exercise science.

Place, publisher, year, edition, pages
Institute of Electrical and Electronics Engineers (IEEE), 2024
Keywords
Sensors, Accelerometers, Reliability, Intelligent sensors, Sports, Skin, Micromechanical devices, Garmin running pod, MEMS accelerometers, OptoGait, running, smart patch, treadmill, validity
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:uu:diva-532265 (URN)10.1109/JSEN.2024.3370304 (DOI)001219652600070 ()
Funder
EU, Horizon 2020, 824984
Available from: 2024-06-19 Created: 2024-06-19 Last updated: 2024-06-19Bibliographically approved
Svensson, K., Weise, C., Westphal, H., Södergren, S., Belder, D. & Hjort, K. (2023). Coupling microchip pressure regulators with chipHPLC as a step toward fully portable analysis system. Sensors and actuators. B, Chemical, 385, Article ID 133732.
Open this publication in new window or tab >>Coupling microchip pressure regulators with chipHPLC as a step toward fully portable analysis system
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2023 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, Vol. 385, article id 133732Article in journal (Refereed) Published
Abstract [en]

Herein the coupling of a miniaturized, nanoliter scaled, pressure regulator (chipPR), and a chipHPLC device is introduced. The active temperature based flow control of the chipPR is able to generate rapid pressure changes and therefore enables on-chip pinched injection and flow gradients with reduced instrumental effort and minimal dead volumes. The functionality of the chipPR empowered chipHLPC device was demonstrated with high-speed HPLC-separations applying fluorescence and electrospray mass spectrometry (ESI-MS) detection. The system shows excellent long-term stability of chromatography integrity (retention times with RSD of 0.44-0.91%) due to the integration of a PID feedback regulation. This first chip-based HPLC device equipped with chipPRs enables precise flow control with significantly reduced technical effort compared to the state-of-the-art.

Place, publisher, year, edition, pages
Elsevier, 2023
Keywords
Lab-on-a-chip, ChipHPLC, Thermal actuation, Microfluidics, Pressure regulation
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering Analytical Chemistry
Identifiers
urn:nbn:se:uu:diva-502526 (URN)10.1016/j.snb.2023.133732 (DOI)000977773900001 ()
Funder
The Kamprad Family Foundation, 20170169
Available from: 2023-05-26 Created: 2023-05-26 Last updated: 2024-04-25Bibliographically approved
Akbari, S., Voigt, T. & Hjort, K. (2023). Demo: Sensor Node Communication Through Conductive Mesh Placed on Cotton Knit Fabric. In: : . Paper presented at International Conference on Embedded Wireless Systems and Networks (EWSN), Rende, Italy, 25-27 September, 2023.
Open this publication in new window or tab >>Demo: Sensor Node Communication Through Conductive Mesh Placed on Cotton Knit Fabric
2023 (English)Conference paper, Poster (with or without abstract) (Other academic)
Keywords
Power-line communications (PLC), channel capacitance, embedded sensors in fabrics, conductive mesh
National Category
Computer Systems
Identifiers
urn:nbn:se:uu:diva-518288 (URN)
Conference
International Conference on Embedded Wireless Systems and Networks (EWSN), Rende, Italy, 25-27 September, 2023
Funder
Swedish Foundation for Strategic Research
Available from: 2023-12-18 Created: 2023-12-18 Last updated: 2023-12-19
Akbari, S., Bergman, J., Voigt, T., Fredriksson, J. & Hjort, K. (2023). Feasibility of Communication Between Sensor Nodes On-board Spacecraft Using Multi Layer Insulation. In: : . Paper presented at International Conference on Embedded Wireless Systems and Networks (EWSN), Rende, Italy, 25-27 September, 2023.
Open this publication in new window or tab >>Feasibility of Communication Between Sensor Nodes On-board Spacecraft Using Multi Layer Insulation
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2023 (English)Conference paper, Published paper (Refereed)
Keywords
Multi-layer insulation, in-spacecraft communication, embedded sensing, power-line communications (PLC)
National Category
Computer Systems
Identifiers
urn:nbn:se:uu:diva-518301 (URN)
Conference
International Conference on Embedded Wireless Systems and Networks (EWSN), Rende, Italy, 25-27 September, 2023
Available from: 2023-12-18 Created: 2023-12-18 Last updated: 2023-12-19
Södergren, S., Svensson, K. & Hjort, K. (2023). In-line small high-pressure sensors in anodically bonded microfluidic restrictors. Sensors and Actuators A-Physical, 356, Article ID 114345.
Open this publication in new window or tab >>In-line small high-pressure sensors in anodically bonded microfluidic restrictors
2023 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 356, article id 114345Article in journal (Refereed) Published
Abstract [en]

High-pressure microflow chemistry is advancing due to its potential advantages of being rapid, inexpensive, and accessible. However, as microfluidic devices gain popularity in areas such as synthesis and analysis, there is still a lack of control over thermodynamic parameters during high-pressure processes. This is an effect of existing external sensors causing an excessive increase in the system's internal and dead volumes. To avoid this, more sensors need to be integrated into high-pressure-resistant microfluidic channels. Herein, a proposed approach for integrating an in-line pressure-flow-temperature sensor is provided, where the flow is calculated from the pressure drop over a restrictor. An anodically bonded Si-glass microfluidic chip was constructed with wet-etched glass channels, boron-doped piezoresistors, and dry-etched diaphragms. The pressure sensors showed a precision of +/- 0.07% of full scale (70 bar) and the chip can withstand more than 210 bar. The internal volume was 25 nL and the diaphragms measured 72 x 108 mu m. With this work, improved control of high-pressure microfluidics has been accomplished.

Place, publisher, year, edition, pages
ELSEVIER SCIENCE SA, 2023
Keywords
High-pressure microfluidics, Diaphragm pressure sensor, Piezoresestivity, Micro total analysis system, Process control
National Category
Energy Engineering
Identifiers
urn:nbn:se:uu:diva-506963 (URN)10.1016/j.sna.2023.114345 (DOI)001002776000001 ()
Funder
The Kamprad Family Foundation, 20170169
Available from: 2023-07-04 Created: 2023-07-04 Last updated: 2024-02-18Bibliographically approved
Hjort, K., Mårtensson, G. & Vicini, I. (2023). SINTEC Final Workshop “Smart Bioelectronic and Wearable Systems”. In: Klas Hjort, Gustaf Mårtensson, Isella Vicini (Ed.), Smart Bioelectronic and Wearable Systems: SINTEC Final Workshop. Paper presented at Smart Bioelectronic and Wearable Systems: SINTEC Final Workshop, April 26-28, 2023, Uppsala, Sweden (pp. 5-5). Uppsala: Uppsala universitet
Open this publication in new window or tab >>SINTEC Final Workshop “Smart Bioelectronic and Wearable Systems”
2023 (English)In: Smart Bioelectronic and Wearable Systems: SINTEC Final Workshop / [ed] Klas Hjort, Gustaf Mårtensson, Isella Vicini, Uppsala: Uppsala universitet, 2023, p. 5-5Conference paper, Published paper (Other academic)
Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2023
Keywords
Smart patches, bioelectronic, wearable, ultra-flexible, stretchable, soft electronics, conformal electronics
National Category
Medical Engineering Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-501952 (URN)
Conference
Smart Bioelectronic and Wearable Systems: SINTEC Final Workshop, April 26-28, 2023, Uppsala, Sweden
Projects
SINTEC
Funder
EU, Horizon 2020, 824984
Available from: 2023-05-17 Created: 2023-05-17 Last updated: 2023-05-17Bibliographically approved
Hjort, K., Vicini, I. & Mårtensson, G. (Eds.). (2023). Smart Bioelectronic and Wearable Systems: SINTEC Final Workshop: Proceedings. Paper presented at SINTEC Final Workshop “Smart Bioelectronic and Wearable Systems”, Uppsala, April 26-28, 2023. Uppsala: Uppsala universitet
Open this publication in new window or tab >>Smart Bioelectronic and Wearable Systems: SINTEC Final Workshop: Proceedings
2023 (English)Conference proceedings (editor) (Other academic)
Abstract [en]

The aim of the SINTEC Final Workshop “Smart Bioelectronic and Wearable Systems” is to highlight European research focused on the ultra-flexible, stretchable, soft and conformal technologies, and networking with companies and European funded projects to discover future opportunities in the stretchable electronics market.

Topics include: Bioelectronics, Stretchable and conformal electronics, Wearable sensors and actuators, Smart patches and clothings, Wearables for sports and healthcare application, Intra-body communication, and Network solutions for wearable health and sport monitoring.

Place, publisher, year, edition, pages
Uppsala: Uppsala universitet, 2023. p. 57
Keywords
Smart patches, bioelectronic, wearable, ultra-flexible, stretchable, soft electronics, conformal electronics
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-501835 (URN)
Conference
SINTEC Final Workshop “Smart Bioelectronic and Wearable Systems”, Uppsala, April 26-28, 2023
Projects
SINTEC
Funder
EU, Horizon 2020, 824984
Available from: 2023-05-17 Created: 2023-05-17 Last updated: 2023-05-17Bibliographically approved
Wang, B., Maslik, J., Hellman, O., Gumiero, A. & Hjort, K. (2023). Supercooled Liquid Ga Stretchable Electronics. Advanced Functional Materials, 33(29)
Open this publication in new window or tab >>Supercooled Liquid Ga Stretchable Electronics
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2023 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 33, no 29Article in journal (Refereed) Published
Abstract [en]

By controlling the properties of its medium, supercooled liquid Ga (SLGa) based stretchable remains stretchable at -22 degrees C, i.e., 52 degrees C below its thermo-dynamic melting point of Ga. Thus far, our oldest deposited SLGa circuit and film have remained liquids for 2 years at room temperature. The study investi-gates the crystallization of SLGa triggered by the surface energy of nucleation agents, temperature, circuit cross-section, and mechanical impact. Based on these parameters, a method is presented to integrate electronic components with SLGa circuits without compromising its supercooling effect. Further, the large stiffness variation induced by phase transition is demonstrated in dif-ferent applications. For the desired stiffness variation, the crystallization rate can be controlled by varying the temperature and cross-section area. Finally, spray-printing an ink of microscale SLGa microscale particles can confor-mally pattern Ga on a rough surface, e.g., to fabricate a stretchable array of SLGa microelectrodes. A smart patch with stretchable SLGa electrode arrays records human electrocardiogram signals in cold water and does not stain the skin after use. Its low and stable impedance in water will enable novel applications in wearable electronics.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2023
Keywords
microelectrode arrays, microscale depositions, smart ECG patches, stiffness variations, stretchable electronics, supercooled liquid gallium
National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-511073 (URN)10.1002/adfm.202300036 (DOI)000973456200001 ()
Funder
Swedish Research Council, 2017-03801Forte, Swedish Research Council for Health, Working Life and Welfare, 2017-03801Swedish Research Council Formas, 2017-03801
Available from: 2023-09-07 Created: 2023-09-07 Last updated: 2023-09-07Bibliographically approved
Verdel, N., Hjort, K., Sperlich, B., Holmberg, H.-C. & Supej, M. (2023). Use of smart patches by athletes: A concise SWOT analysis. Frontiers in Physiology, 14, Article ID 1055173.
Open this publication in new window or tab >>Use of smart patches by athletes: A concise SWOT analysis
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2023 (English)In: Frontiers in Physiology, E-ISSN 1664-042X, Vol. 14, article id 1055173Article in journal, Editorial material (Other academic) Published
Place, publisher, year, edition, pages
Frontiers Media S.A., 2023
Keywords
sensor, sport, internet of thing (IoT), wearable, strechable, flexible, electronis, IMU
National Category
Sport and Fitness Sciences
Identifiers
urn:nbn:se:uu:diva-504019 (URN)10.3389/fphys.2023.1055173 (DOI)000980485100001 ()37035682 (PubMedID)
Funder
EU, Horizon 2020, 824984
Available from: 2023-06-16 Created: 2023-06-16 Last updated: 2024-01-17Bibliographically approved
Projects
Microfluidic Hydraulics [2008-03870_VR]; Uppsala UniversitySupercritical microfluidics [2011-05037_VR]; Uppsala UniversityInnovative Deep Exploration [2014-01772_ VINNOVA]; Uppsala UniversityInnovative deep exploration 1phc [2015-01301_ VINNOVA]; Uppsala UniversitySmarter Smelting [2016-01807_ VINNOVA]; Uppsala UniversitySmarter melt - Innovative building set for sensors in steel production [2017-01859_ VINNOVA]; Uppsala UniversitySofter, thinner and more compliant cochlear implants [2017-03801_VR]; Uppsala University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2744-1634

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