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In-line small high-pressure sensors in anodically bonded microfluidic restrictors
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science and Engineering, Microsystems Technology.ORCID iD: 0000-0003-2744-1634
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. Vol. 356, article id 114345
Keywords [en]
High-pressure microfluidics, Diaphragm pressure sensor, Piezoresestivity, Micro total analysis system, Process control
National Category
Energy Engineering
Identifiers
URN: urn:nbn:se:uu:diva-506963DOI: 10.1016/j.sna.2023.114345ISI: 001002776000001OAI: oai:DiVA.org:uu-506963DiVA, id: diva2:1779285
Funder
The Kamprad Family Foundation, 20170169Available from: 2023-07-04 Created: 2023-07-04 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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Södergren, SimonSvensson, KarolinaHjort, Klas

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