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Thermally controlled microfluidic back pressure regulator
Uppsala Univ, Ctr Nat Hazard & Disaster Sci CNDS, Microsyst Technol Div, Box 35, S-75103 Uppsala, Sweden..
Uppsala Univ, Ctr Nat Hazard & Disaster Sci CNDS, Microsyst Technol Div, Box 35, S-75103 Uppsala, Sweden..
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology. Uppsala Univ, Ctr Nat Hazard & Disaster Sci CNDS, Microsyst Technol Div, Box 35, S-75103 Uppsala, Sweden..ORCID iD: 0000-0003-2744-1634
2022 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 12, no 1, article id 569Article in journal (Refereed) Published
Abstract [en]

By using the temperature dependence of viscosity, we introduce a novel type of microfluidic lab-on-a-chip back pressure regulator (BPR) that can be integrated into a micro-total-analysis-system. A BPR is an important component used to gain pressure control and maintain elevated pressures in e.g. chemical extractions, synthesis, and analyses. Such applications have been limited in microfluidics, since the back pressure regularly has been attained by passive restrictors or external large-scale BPRs. Herein, an active microfluidic BPR is presented, consisting of a glass chip with integrated thin-film heaters and thermal sensors. It has no moving parts but a fluid restrictor where the flow resistance is controlled by the change of viscosity with temperature. Performance was evaluated by regulating the upstream pressure of methanol or water using a PID controller. The developed BPR has the smallest reported dead volume of 3 nL and the thermal actuation has time constants of a few seconds. The pressure regulation were reproducible with a precision in the millibar range, limited by the pressure sensor. The time constant of the pressure changes was evaluated and its dependence of the total upstream volume and the compressibility of the liquids is introduced.

Place, publisher, year, edition, pages
NATURE PORTFOLIO , 2022. Vol. 12, no 1, article id 569
Keywords [en]
SUPERCRITICAL-FLUID: CHROMATOGRAPHY; LIQUID-CHROMATOGRAPHY: FLOWSYSTEM: HPLC; SEPARATION
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
URN: urn:nbn:se:uu:diva-466637DOI: 10.1038/s41598-021-04320-6ISI: 000742155800057PubMedID: 35022424OAI: oai:DiVA.org:uu-466637DiVA, id: diva2:1633556
Available from: 2022-01-31 Created: 2022-01-31 Last updated: 2024-02-18Bibliographically approved
In thesis
1. Miniaturized fluid system for high-pressure analytics
Open this publication in new window or tab >>Miniaturized fluid system for high-pressure analytics
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

High-pressure chemistry can be used to determine the contents of blood or water samples and to discover new chemistries. However, working with chemistry at pressures of many tens, or even hundreds, of bars often requires expensive and stationary equipment, such as autoclaves or chromatographic systems like high-performance liquid chromatography (HPLC).

Since the introduction of microfluidics in the '90s, researchers have attempted to develop microfluidic chips as microreactors to speed up synthesis with faster mass and heat transfer. Other researchers have made efforts to create microfluidic chip-based HPLC to reduce the cost, increase the separation quality, speed up the analysis, and even enable portable systems for on-site medical or environmental analysis. Still, fully integrated systems have not yet been realized due to a lack of fluidic control components.

This thesis presents novel methods for on-chip regulation and monitoring of pressure, flow, and temperature. Papers I and II specifically suggest a method for regulating backpressure and stabilizing pressure and flows using thermally controlled restrictors. Furthermore, a collaboration was made where a pressure-regulating chip was connected to an on-chip HPLC. The purpose of this was to activate sample plugs and therefore reduce the requirement for expensive surrounding equipment and enable portability, Paper III. Paper IV explores the use of a pressurized capsule to generate high-pressure flows that are coupled to a pressure-regulating chip to stabilize and regulate the pressure. Finally, an approach for integrating pressure sensors into high-pressure tolerant microchannels has been proposed, Paper V.

The work conducted has provided new insights into fluid dynamics. The regulating method employed in Paper I-IV utilizes a restrictor that alters the pressure drop as temperature changes, hence changing the viscosity of the fluid. Although this technology has been known since before, new understandings have emerged regarding how the compressibility of incompressible fluids must be considered at higher pressures. Additionally, the concept of buffer capacitance is presented, which is central when working with high-pressure microfluidics.

Through this thesis, discoveries of high-pressure microfluidics have been accomplished, which enable micro-total-analysis systems that could serve as portable HPLC equipment.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2024. p. 60
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 2366
Keywords
High-pressure, Microfluidics, Thermal regulation, Fluid mechanics, In-situ sensors, High-pressure analytics
National Category
Fluid Mechanics and Acoustics Materials Engineering
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-523408 (URN)978-91-513-2038-0 (ISBN)
Public defence
2024-04-05, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2024-03-13 Created: 2024-02-18 Last updated: 2024-03-13

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Svensson, KarolinaHjort, Klas

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