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Publications (10 of 241) Show all publications
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
Andersson, M., Rodriguez-Meizoso, I., Turner, C., Hjort, K. & Klintberg, L. (2018). Dynamic pH determination at high pressure of aqueous additive mixtures in contact with dense CO2. Journal of Supercritical Fluids, 136, 95-101
Open this publication in new window or tab >>Dynamic pH determination at high pressure of aqueous additive mixtures in contact with dense CO2
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2018 (English)In: Journal of Supercritical Fluids, ISSN 0896-8446, E-ISSN 1872-8162, Vol. 136, p. 95-101Article in journal (Refereed) Published
Abstract [en]

A system consisting of a high-pressure tolerant microfluidic glass chip, high-speed absorbance imaging, and image processing has been developed to study rapid dynamic events like pH change in a multiphase flow. The system gives both kinetic and quantitative equilibrated information. By tracking the interactions of aqueous additive mixtures and liquid CO2, at 80 bar and 24 °C, under flow, measurement at a given P, T condition is done in 0.25 s. The acidification rate to steady state was found to be mass transport limited, occurring in less than 1 s. For 30 mM of the additives ammonium acetate and ammonium formate, equilibrium pH of 4.5 and 4.1, respectively, was seen. These additives are of key importance in common mobile phases used in SFC.

Keywords
Supercritical fluid chromatography, High-pressure microfluidics, Additive salts, Dense CO, Multiphase flow, Image analysis
National Category
Chemical Engineering Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-353940 (URN)10.1016/j.supflu.2018.02.012 (DOI)000430767400011 ()
Funder
Knut and Alice Wallenberg Foundation
Available from: 2018-06-18 Created: 2018-06-18 Last updated: 2018-08-02Bibliographically approved
Sahlberg, A., Nilsson, F., Berglund, A., Nguyen, H., Hjort, K. & Jeong, S. H. (2018). High-Resolution Liquid Alloy Patterning for Small Stretchable Strain Sensor Arrays. Advanced materials technologologies, 3(4), Article ID 1700330.
Open this publication in new window or tab >>High-Resolution Liquid Alloy Patterning for Small Stretchable Strain Sensor Arrays
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2018 (English)In: Advanced materials technologologies, ISSN 2365-709X, Vol. 3, no 4, article id 1700330Article in journal (Refereed) Published
Abstract [en]

Soft material applied technology has in recent years become more advanced, enabling for, e.g., soft robotics, skin electronics, and wearable systems. Yet, the processing technology of soft materials has not been sufficiently developed to create high performance in soft and stretchable systems, as compared to the processing technology of conventional electronics or electromechanical systems. Liquid alloys have shown excellent properties for soft and stretchable electrical interconnectors and conductors, which is a basic building block to produce electric or electromechanical systems. In order to overcome the limited resolution of previously developed liquid alloy patterning methods for large-area printed circuits, this work explores the possibility of employing shrinking substrates. By utilizing the characteristics of liquid alloys and elastomers the pattern resolution is improved through a stretch-shrink patterning (SSP) process. The process provides highly conductive liquid conductors of high resolution and can be combined with existing printing techniques for liquid alloys. The SSP process increases design flexibility of soft and stretchable systems that use liquid alloys and enables designs with finer and denser patterns, and cost-effective production for small scale systems.

Keywords
elastomers, high-resolution patterning, liquid alloys, shrink substrates, stretchable strain sensors
National Category
Other Materials Engineering
Identifiers
urn:nbn:se:uu:diva-353211 (URN)10.1002/admt.201700330 (DOI)000430164100012 ()
Available from: 2018-06-13 Created: 2018-06-13 Last updated: 2018-06-14Bibliographically approved
Jiao, M., Nguyen Viet, C., Duy, N. V., Nguyen Duc, H., Hieu, N. V., Hjort, K. & Nguyen, H. (2018). Influence of annealing temperature on theperformance and stability of on-chip hydrothermally grown ZnO nanorod gassensor toward NO2. Academia Journal of Scientific Research, 6(5), 180-189
Open this publication in new window or tab >>Influence of annealing temperature on theperformance and stability of on-chip hydrothermally grown ZnO nanorod gassensor toward NO2
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2018 (English)In: Academia Journal of Scientific Research, ISSN 2315-7712, Vol. 6, no 5, p. 180-189Article in journal (Refereed) Published
Abstract [en]

Nanorod-based gas sensors synthesized at low temperature should generally be stabilized by anneling before usage. However, the influence of annealing on the sensing performance and stability of these nanorods is rarely reported. In this study, we first fabricated gas sensors based on ZnO nanorods grown on-chip on glass substrate using hydrothermal method. Subsequently, these sensors were annealed at either 400 °C, 500 °C, or 600 °C in air for 4 h. The gas-sensing performance of the ZnO nanorods toward NO2 was tested before and after annealing. The sensitivity of the gas sensors to NO2 decreased, but the stability increased with the increase in annealing temperature. Photoluminescence spectroscopy and X-ray diffraction were used to investigate the material structure of ZnO nanorods. Results revealed that the oxygen-atom-related defects in the ZnO lattice in the region close to the surface influenced by annealing process were the most significant factors on the sensing properties and stability of ZnO nanorods.

Keywords
Annealing, defects in nanorods, gas sensor, hydrothermal, zinc oxide.
National Category
Other Natural Sciences Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-363650 (URN)10.15413/ajsr.2018.0104 (DOI)
Available from: 2018-10-18 Created: 2018-10-18 Last updated: 2018-10-19Bibliographically approved
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 (Refereed)
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.

Keywords
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: 2018-10-19Bibliographically 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: 2018-06-07Bibliographically approved
Cruz, J., Zadeh, S. H., Graells, T., Andersson, M., Malmström, J., Wu, Z. G. & Hjort, K. (2017). High pressure inertial focusing for separating and concentrating bacteria at high throughput. Journal of Micromechanics and Microengineering, 27(8), Article ID 084001.
Open this publication in new window or tab >>High pressure inertial focusing for separating and concentrating bacteria at high throughput
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2017 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 27, no 8, article id 084001Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
bacteria separation, particle separation, inertial focusing, high pressure, glass chips, PDMS, microfluidic channel
National Category
Condensed Matter Physics Other Materials Engineering Analytical Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-329919 (URN)10.1088/1361-6439/aa6b14 (DOI)000404540500001 ()
Funder
EU, Horizon 2020, 644669
Available from: 2018-02-22 Created: 2018-02-22 Last updated: 2018-04-23Bibliographically approved
Cruz, F. J. & Hjort, K. (2017). High pressure inertial focusing for separation and concentration of bacteria at high throughput. Paper presented at 28th Micromechanics and Microsystems Europe Workshop (MME), AUG 23-25, 2017, Uppsala, SWEDEN. Journal of Physics, Conference Series, Article ID UNSP 012001.
Open this publication in new window or tab >>High pressure inertial focusing for separation and concentration of bacteria at high throughput
2017 (English)In: Journal of Physics, Conference Series, ISSN 1742-6588, E-ISSN 1742-6596, article id UNSP 012001Article in journal, Meeting abstract (Refereed) Published
Abstract [en]

Inertial focusing is a phenomenon where particles migrate across streamlines in microchannels and focus at well-defined, size dependent equilibrium points of the cross section. It can be taken into advantage for focusing, separation and concentration of particles at high through-put and high efficiency. As particles decrease in size, smaller channels and higher pressures are needed. Hence, new designs are needed to decrease the pressure drop. In this work a novel design was adapted to focus and separate 1 mu m from 3 mu m spherical polystyrene particles. Also 0.5 mu m spherical polystyrene particles were separated, although in a band instead of a single line. The ability to separate, concentrate and focus bacteria, its simplicity of use and high throughput make this technology a candidate for daily routines in laboratories and hospitals.

Place, publisher, year, edition, pages
IOP PUBLISHING LTD, 2017
Keywords
Particle separation, Bacteria separation, Inertial focusing, Microfluidic channel, High pressure
National Category
Condensed Matter Physics Other Materials Engineering Analytical Chemistry Physical Chemistry
Identifiers
urn:nbn:se:uu:diva-347122 (URN)10.1088/1742-6596/922/1/012001 (DOI)000419231200001 ()
Conference
28th Micromechanics and Microsystems Europe Workshop (MME), AUG 23-25, 2017, Uppsala, SWEDEN
Funder
EU, Horizon 2020, 644669
Available from: 2018-04-06 Created: 2018-04-06 Last updated: 2018-04-06Bibliographically 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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2744-1634

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