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High-Pressure Microfluidics
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Microsystems Technology.
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, some fundamentals and possible applications of high-pressure microfluidics have been explored. Furthermore, handling fluids at high pressures has been addressed, specifically by creating and characterizing strong microvalves and pumps.

A variety of microstructuring techniques was used to realize these microfluidic devices, e.g., etching, lithography, and bonding. To be able to handle high pressures, the valves and pumps need to be strong. This necessitates a strong actuator material. In this thesis, the material of choice is paraffin wax.

A new way of latching paraffin-actuated microvalves into either closed or open position has been developed, using the low thermal conductivity of paraffin to create large thermal gradients within a microactuator. This allows for long open and closed times without power consumption.

In addition, three types of paraffin-actuated pumps are presented: A peristaltic high-pressure pump with integrated temperature control, a microdispensing pump with high repeatability, and a pump system with two pumps working with an offset to reduce flow irregularities. Furthermore, the fundamental behavior of paraffin as a microactuator material has been explored by finite element modeling.

One possibility that arises with high-pressure microfluidics, is the utilization of supercritical fluids for different applications. The unique combination of material properties found in supercritical fluids yields them interesting applications in, e.g., extraction and cleaning. In an attempt to understand the microfluidic behavior of supercritical carbon dioxide, the two-phase flow, with liquid water as the second phase, in a microchannel has been studied and mapped with respect to both flow regime and droplet behavior at a bi-furcating outlet.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2013. , 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1085
Keyword [en]
phase change, actuator, valve, pump, supercritical fluid
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
URN: urn:nbn:se:uu:diva-208915ISBN: 978-91-554-8773-7 (print)OAI: oai:DiVA.org:uu-208915DiVA: diva2:655470
Public defence
2013-11-29, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, 751 21, Uppsala, 09:30 (English)
Opponent
Supervisors
Funder
Swedish Research Council
Available from: 2013-11-07 Created: 2013-10-10 Last updated: 2014-01-23
List of papers
1. A Latchable Valve for High-Pressure Microfluidics
Open this publication in new window or tab >>A Latchable Valve for High-Pressure Microfluidics
2010 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 19, no 2, 396-401 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, the strongest yet latchable valve in subcubic-centimeter size for microfluidic applications is presented. The device has an integrated actuator cavity consisting of three segments filled with paraffin, each operated by a separate heater. At one of the segments, a membrane valve head is deflected by the expansion of the resistively melted paraffin to close against its valve seat. Different heating sequences provide a latched closed or opened valve. The maximum pressure before any leakage occurred was 2.5 MPa. The leak pressure is found to be progressively dependent on the clamping pressure applied. The valve has an opening and closing time of 7 and 1 s, respectively. At an applied pressure of 0.3 MPa, the closed valve needs to be reactivated every 100 min to remain leakage free, leading to an average power consumption of 4.5 mW.

Keyword
Fluid flow control, microactuators, steel, valves
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-126963 (URN)10.1109/JMEMS.2010.2041749 (DOI)000276257700019 ()
Available from: 2010-07-01 Created: 2010-07-01 Last updated: 2016-04-19Bibliographically approved
2. High-pressure stainless steel active membrane microvalves
Open this publication in new window or tab >>High-pressure stainless steel active membrane microvalves
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2011 (English)In: Journal of Micromechanics and Microengineering, ISSN 0960-1317, E-ISSN 1361-6439, Vol. 21, no 7, 075010- p.Article in journal (Refereed) Published
Abstract [en]

In this work, high-pressure membrane microvalves have been designed, manufactured andevaluated. The valves were able to withstand back-pressures of 200 bar with a response timeof less than 0.6 s. These stainless steel valves, manufactured with back-end batch production,utilize the large volume expansion coupled to the solid–liquid phase transition in paraffin wax.When membrane materials were evaluated, parylene coated stainless steel was found to be thebest choice as compared to polydimethylsiloxane and polyimide. Also, the influence of theorifice placement and diameter is included in this work. If the orifice is placed too close to therim of the membrane, the valve can stay sealed even after turning the power off, and the valvewill not open until the pressure in the system is released. The developed steel valves, evaluatedfor both water and air, provide excellent properties in terms of mechanical stability, ease offabrication, and low cost. Possible applications include sampling at high pressures, chemicalmicroreactors, high performance liquid chromatography, pneumatics, and hydraulics.

Keyword
stainless steel, high pressure microvalve, paraffin
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-131007 (URN)10.1088/0960-1317/21/7/075010 (DOI)000291935000024 ()
Available from: 2010-09-20 Created: 2010-09-20 Last updated: 2017-05-16Bibliographically approved
3. A latchable high-pressure thermohydraulic valve actuator
Open this publication in new window or tab >>A latchable high-pressure thermohydraulic valve actuator
2012 (English)In: Sensors and Actuators A-Physical, ISSN 0924-4247, E-ISSN 1873-3069, Vol. 188, 292-297 p.Article in journal (Refereed) Published
Abstract [en]

This work presents a latchable thermohydraulic microactuator for use in high-pressure valves, e.g. for oceanic sampling in missions of long duration. Mounted on a miniature submersible, it can be used in confined spaces to explore previously unreachable environments. However, the device can be used in any high-pressure application where long duration open and/or closed valve states are required, and power consumption is an issue. The actuator is fabricated using standard batch-processes as photochemical machining, wet etching and photolithography. The actuation and latching mechanisms are both thermohydraulic, using solid-to-liquid phase transition of paraffin for actuation and of a low melting point alloy for latching. Focus of this work is on the endurance of the actuator to facilitate a bistable valve. The actuator managed to keep a deflected position for almost 50 hours to the load equivalent to 1.8 MPa applied pressure, after which the experiment was aborted. No pressure dependence was discovered in the latching losses, i.e. the difference in deflection before and after the actuator is powered off. Furthermore, the effect of intermixing of paraffin and the low melting point alloy was evaluated.

Place, publisher, year, edition, pages
Elsevier, 2012
Keyword
Fluid control, Bistable, Steel, Actuator, Paraffin, Low melting point alloy
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-171755 (URN)10.1016/j.sna.2011.11.027 (DOI)000312692500039 ()
Conference
The 16th International Conference on Solid-State Sensors, Actuators and Microsystems, 5-9 June, 2011, Beijing, CHINA
Available from: 2012-03-27 Created: 2012-03-27 Last updated: 2017-12-07Bibliographically approved
4. Acoustically enriching, large-depth aquatic sampler
Open this publication in new window or tab >>Acoustically enriching, large-depth aquatic sampler
Show others...
2012 (English)In: Lab on a Chip, ISSN 1473-0197, E-ISSN 1473-0189, Vol. 12, no 9, 1619-1628 p.Article in journal (Refereed) Published
Abstract [en]

In marine biology, it is useful to collect water samples when exploring the distribution and diversity of microbial communities in underwater environments. In order to provide, e.g., a miniaturized submersible explorer with the capability of collecting microorganisms, a compact sample enrichment system has been developed. The sampler is 30 mm long, 15 mm wide, and just a few millimetres thick. Integrated in a multilayer steel, polyimide and glass construction is a microfluidic channel with piezoelectric transducers, where microorganism and particle samples are collected and enriched, using acoustic radiation forces for gentle and labelless trapping. High-pressure, latchable valves, using paraffin as the actuation material, at each end of the microfluidic channel keep the collected sample pristine. A funnel structure raised above the surface of the device directs water into the microfluidic channel as the vehicle propels itself or when there is a flow across its hull. The valves proved leak proof to a pressure of 2.1 MPa for 19 hours and momentary pressures of 12.5 MPa, corresponding to an ocean depth of more than 1200 metres. By reactivating the latching mechanism, small leakages through the valves could be remedied, which could thus increase the leak-less operational time. Fluorescent particles, 1.9 µm in diameter, were successfully trapped in the microfluidic channel at flow rates up to 15 ml min-1, corresponding to an 18.5 cm s-1 external flow rate of the sampler. In addition, liquid-suspended GFP-marked yeast cells were successfully trapped.

Keyword
Acoustic, microorganism, enriching, trap, valve, paraffin, sampler, marine, actuator
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-171734 (URN)10.1039/C2LC00025C (DOI)000302368200009 ()
Projects
Deeper Access, Deeper Understanding (DADU)
Available from: 2012-03-26 Created: 2012-03-26 Last updated: 2017-12-07Bibliographically approved
5. Modeling and Analysis of a Phase Change Material Thermohydraulic Membrane Microactuator
Open this publication in new window or tab >>Modeling and Analysis of a Phase Change Material Thermohydraulic Membrane Microactuator
2013 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 22, no 1, 186-194 p.Article in journal (Refereed) Published
Abstract [en]

Presented in this paper is a finite-element-method-based model for phase change material actuators, modeling the active material as a fluid as opposed to a solid. This enables the model to better conform to localized loads and offering the opportunity to follow material movement in enclosed volumes. Modeling, simulation, and analysis of an electrothermally activated paraffin microactuator have been conducted. The paraffin microactuator used for the analysis in this study exploits the large volumetric expansion of paraffin upon melting, which, combined with its low compressibility in the liquid state, allows for high hydraulic pressures to be generated. The purpose of this study is to supply a geometry-independent model of such a microactuator through the implementation of a fluid model rather than a solid one, which has been utilized in previous studies. Numerical simulations are conducted at different frequencies of the heating source and for different geometries of the microactuator. The results are compared with the empirical data obtained on a close to identical paraffin microactuator, which clearly show the advantages of a fluid model instead of a solid-state approximation.

National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-186116 (URN)10.1109/JMEMS.2012.2222866 (DOI)000314726900026 ()
Funder
Swedish Research Council
Available from: 2012-11-28 Created: 2012-11-28 Last updated: 2017-12-07Bibliographically approved
6. High-Pressure Peristaltic Membrane Micropump With Temperature Control
Open this publication in new window or tab >>High-Pressure Peristaltic Membrane Micropump With Temperature Control
Show others...
2010 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 19, no 6, 1462-1469 p.Article in journal (Refereed) Published
Abstract [en]

A high-pressure peristaltic membrane micropump, which is capable of pumping against a back pressure of 150 bar, has been evaluated. The main focus was to maintain the flow characteristics also at high back pressures. The pump was manufactured by fusion bonding of parylene-coated stainless-steel stencils. A large-volume expansion connected to the solid-to-liquid phase transition in paraffin was used to move 10 µm stainless-steel membranes. The pump was evaluated by using two different driving schemes, a four-phase cycle and a six-phase cycle. With the six-phase cycle, a constant flow rate of 0.4 µL min-1 was achieved over an interval ranging from atmospheric pressure to 130 bar. At lower back pressures, the more energy efficient four-phase cycle achieved slightly higher flow rates than the six-phase cycle. However, it required higher driving voltage at high back pressures. Since the pump is thermally activated, a temperature sensor was integrated to control the melting and solidification of paraffin, implying capability of increasing the performance of the pump. With a thickness of only 1 mm as well as a simple and robust design, the micropump is well suited for integration in analytical systems. The high pressures managed are in the region needed for, e.g., high-performance liquid chromatography systems.

Keyword
High back pressure, integrated temperature sensor, paraffin actuator, peristaltic micropump, pressure-independent flow, stainless-steel membrane
National Category
Materials Engineering
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-139213 (URN)10.1109/JMEMS.2010.2076784 (DOI)000284875400020 ()
Available from: 2010-12-22 Created: 2010-12-22 Last updated: 2016-04-19Bibliographically approved
7. Microdispenser with continuous flow and selectable target volume for microfluidic high-pressure applications
Open this publication in new window or tab >>Microdispenser with continuous flow and selectable target volume for microfluidic high-pressure applications
2014 (English)In: Journal of microelectromechanical systems, ISSN 1057-7157, E-ISSN 1941-0158, Vol. 23, no 2, 452-458 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a reusable microdispenser intended for continuous flow dispensing of variable and controlled volumes of liquid against high back-pressures. The microdispenser consists of two active valves and a dispenser chamber, all actuated by the volume change associated with the solid-to-liquid phase transition of paraffin wax. It is fabricated using stainless steel sheets, a flexible printed circuit board, and a polyimide membrane. All are covered with Parylene C for insulation and fusion bonding at assembly. A finite element method (FEM) model of the paraffin actuator is used to predict the resulting flow characteristics. The results show dispensing of well-defined volumes of 350 and 540 nL, with a good repeatability between dispensing sequences, as well as reproducibility between devices. In addition, the flow characteristics show no back-pressure dependence of the dispensed flow in the interval 0.5--2.0 MPa. The FEM model can be used to predict the flow characteristics qualitatively

Keyword
High pressure, liquid chromatography, MEMS, microdispenser, micropump, phase change material
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-208855 (URN)10.1109/JMEMS.2013.2279976 (DOI)000334526200022 ()
Funder
Swedish Research CouncilVINNOVA, 29461-1ÅForsk (Ångpanneföreningen's Foundation for Research and Development)
Available from: 2013-10-09 Created: 2013-10-09 Last updated: 2017-12-06Bibliographically approved
8. On-chip pump system for high-pressure microfluidic applications
Open this publication in new window or tab >>On-chip pump system for high-pressure microfluidic applications
Show others...
2013 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

This paper presents a micropump system with four integrated paraffin actuated pumps: Two mobile phase pumps and two sample injector pumps. The mobile phase pumps are evaluated by their ability to deliver a stable, low-ripple flow to be used in chip-based high performance liquid chromatography. It is shown that the two mobile phase pumps can be driven in combined operation with an induced offset to significantly lower flow fluctuations.

Keyword
High Pressure, Paraffin, Phase Change Material, Microelectromechanical Systems
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-204725 (URN)
Conference
µTAS 2013
Funder
Swedish Research Council
Available from: 2013-08-09 Created: 2013-08-09 Last updated: 2015-09-07
9. Fluid behavior of supercritical carbon dioxide with water in a double-Y-channel microfluidic chip
Open this publication in new window or tab >>Fluid behavior of supercritical carbon dioxide with water in a double-Y-channel microfluidic chip
Show others...
2014 (English)In: Microfluidics and Nanofluidics, ISSN 1613-4982, E-ISSN 1613-4990, Vol. 17, no 6, 1105-1112 p.Article in journal (Refereed) Published
Abstract [en]

The use of supercritical carbon dioxide (scCO2) as an apolar solvent has been known for decades. It offers a greener approach than, e.g., hexane or chloroform, when such solvents are needed. The use of scCO2 in microsystems, however, has only recently started to attract attention. In microfluidics, the flow characteristics need to be known to be able to successfully design such components and systems. As supercritical fluids exhibit the exciting combination of low viscosity, high density, and high diffusion rates, the fluidic behavior is not directly transferrable from aqueous systems. In this paper, three flow regimes in the scCO2–liquid water two-phase microfluidic system have been mapped. The effect of both total flow rate and relative flow rate on the flow regime is evaluated. Furthermore, the droplet dynamics at the bifurcating exit channel are analyzed at different flow rates. Due to the low viscosity of scCO2, segmented flows were observed even at fairly high flow rates. Furthermore, the carbon dioxide droplet behavior exhibited a clear dependence on both flow rate and droplet length.

Keyword
Two-phase flow, segmented flow, parallel flow, wavy flow droplet dynamics
National Category
Fluid Mechanics and Acoustics
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-207265 (URN)10.1007/s10404-014-1399-6 (DOI)000345389900014 ()
Funder
Swedish Research Council
Available from: 2013-10-10 Created: 2013-09-11 Last updated: 2017-12-06Bibliographically approved
10. Review on miniaturized paraffin phase change actuators, valves, and pumps
Open this publication in new window or tab >>Review on miniaturized paraffin phase change actuators, valves, and pumps
Show others...
2014 (English)In: Microfluidics and Nanofluidics, ISSN 1613-4982, E-ISSN 1613-4990, Vol. 17, no 1, 53-71 p.Article, review/survey (Refereed) Published
Abstract [en]

During the last fifteen years, miniaturised paraffin actuation has evolved through the need of a simple actuation principle, still able to deliver large strokes and high actuation forces at small scales. This is achieved by the large and rather incompressible volume expansion associated with the solid-to-liquid phase transition of paraffin. The common approach has been to encapsulate the paraffin by a stiff surrounding that directs the volume expansion towards a flexible membrane, which deflects in a directed stroke. However, a number of alternative methods have also been used in the literature. The most common applications to this date have been switches, positioning actuators, and microfluidic valves and pumps. This review will treat the historical background, as well as the fundamentals in paraffin actuation, including material properties of paraffin. Besides reviewing the three major groups of paraffin actuator applications; actuators, valves, and pumps, the modelling done on paraffin actuation will be explored. Furthermore, a section focusing on fabrication of paraffin microactuators is also included. The review ends with conclusions and outlook of the field, identifying unexplored potential of paraffin actuation.

National Category
Applied Mechanics
Research subject
Engineering Science with specialization in Microsystems Technology
Identifiers
urn:nbn:se:uu:diva-208904 (URN)10.1007/s10404-013-1289-3 (DOI)000338835300002 ()
Available from: 2013-11-30 Created: 2013-10-10 Last updated: 2017-12-06Bibliographically approved

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