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Publications (10 of 245) Show all publications
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
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
Cruz, F. J. & Hjort, K. (2018). High pressure inertial focusing: integration in parallel and series. In: : . Paper presented at The Micronano System Workshop (MSW 2018), Aalto University, Espoo, Finland, May 13th-18th, 2018.
Open this publication in new window or tab >>High pressure inertial focusing: integration in parallel and series
2018 (English)Conference paper, Oral presentation only (Other academic)
Keywords
Microfluidics, Inertial focusing
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:uu:diva-368494 (URN)
Conference
The Micronano System Workshop (MSW 2018), Aalto University, Espoo, Finland, May 13th-18th, 2018
Funder
EU, Horizon 2020, 644669
Available from: 2018-12-05 Created: 2018-12-05 Last updated: 2018-12-10Bibliographically approved
Svensson, K., Södergren, S., Andersson, M., Klintberg, L. & Hjort, K. (2018). High-pressure microfluidic electrochemical and image analysis dual detection for HPLC. In: : . Paper presented at Micromechanics and Microsystems Europe Workshop (MME 2018), Aug. 26-29, Smolenice, Slovakia (pp. 113-119).
Open this publication in new window or tab >>High-pressure microfluidic electrochemical and image analysis dual detection for HPLC
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2018 (English)Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

High-performance liquid chromatography (HPLC) is often set as the lab-based golden standard. For point-of-care and point-of-site applications, making HPLC portable, easy to use and low cost, is very desirable. To reach lower costs, one important task is the development of suitable detectors. Because of the potential for low cost and high performance, a dual-detection microfluidic chip with an electrochemical detector (ECD) and optical access for image analysis was evaluated at high pressure, downstream an HPLC column. For the image analysis, a camera and near-UV-light was used to extract absorption data. To validate the response, a spectrometer was coupled downstream the chip. The results of the three different detectors were comparable, with the camera providing similar absorbance-time chromatograms as the spectrometer. However, the ECD registered only peaks from one of two analytes. To conclude, this experimental setup has potential to provide better understanding of the capability for microfluidic HPLC systems.

National Category
Engineering and Technology Other Chemical Engineering
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-367300 (URN)
Conference
Micromechanics and Microsystems Europe Workshop (MME 2018), Aug. 26-29, Smolenice, Slovakia
Funder
The Kamprad Family Foundation, 20170169
Available from: 2018-11-29 Created: 2018-11-29 Last updated: 2018-12-10Bibliographically 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. (2018). Microsystems for the good life. In: Int. Summit Forum on Micro and Nano Manipul. and Manufact.: MNMM 2018. Paper presented at Int. Summit Forum on Micro and Nano Manipul. and Manufact. (pp. 5-5).
Open this publication in new window or tab >>Microsystems for the good life
2018 (English)In: Int. Summit Forum on Micro and Nano Manipul. and Manufact.: MNMM 2018, 2018, p. 5-5Conference paper, Oral presentation with published abstract (Other academic)
Abstract [en]

The Microsystems Technology Division of Uppsala University is committed to make microsystems for the good life. I will present our research on novel materials and technologies for miniaturized systems that are for the good of society and can provide fundamental answers in science.

National Category
Other Engineering and Technologies
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-367187 (URN)
Conference
Int. Summit Forum on Micro and Nano Manipul. and Manufact.
Available from: 2018-11-28 Created: 2018-11-28 Last updated: 2018-11-30
Li, S., Zeng, S., Chen, L., Zhang, Z., Hjort, K. & Zhang, S.-L. (2018). Nanoarrays on Passivated Aluminum Surface for Site-Specific Immobilization of Biomolecules. ACS Applied Bio Materials, 1(1), 125-135
Open this publication in new window or tab >>Nanoarrays on Passivated Aluminum Surface for Site-Specific Immobilization of Biomolecules
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2018 (English)In: ACS Applied Bio Materials, Vol. 1, no 1, p. 125-135Article in journal (Refereed) Published
Abstract [en]

The rapid development of biosensing platforms for highly sensitive and specific detection raises the desire of precise localization of biomolecules onto various material surfaces. Aluminum has been strategically employed in the biosensor system due to its compatibility with CMOS technology and its optical and electrical properties such as prominent propagation of surface plasmons. Herein, we present an adaptable method for preparation of carbon nanoarrays on aluminum surface passivated with poly(vinylphosphonic acid) (PVPA). The carbon nanoarrays were defined by means of electron beam induced deposition (EBID) and they were employed to realize site-specific immobilization of target biomolecules. To demonstrate the concept, selective streptavidin/neutravidin immobilization on the carbon nanoarrays was achieved through protein physisorption with a significantly high contrast of the carbon domains over the surrounding PVPA-modified aluminum surface. By adjusting the fabrication parameters, local protein densities could be varied on similarly sized nanodomains in a parallel process. Moreover, localization of single 40 nm biotinylated beads was achieved by loading them on the neutravidin-decorated nanoarrays. As a further demonstration, DNA polymerase with a streptavidin tag was bound to the biotin-beads that were immobilized on the nanoarrays and in situ rolling circle amplification (RCA) was subsequently performed. The observation of organized DNA arrays synthesized by RCA verified the nanoscale localization of the enzyme with retained biological activity. Hence, the presented approach could provide a flexible and universal avenue to precise localizing various biomolecules on aluminum surface for potential biosensor and bioelectronic applications.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:uu:diva-364770 (URN)10.1021/acsabm.8b00037 (DOI)
Note

00000

Available from: 2018-11-02 Created: 2018-11-02 Last updated: 2018-11-28
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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2744-1634

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