Characterization of pneumatically activated microvalves by measuring electrical conductance
Introduction
Pneumatic microvalves can be easily produced on chip based on multi-layer soft lithography techniques [1], [2]. With elastic polymer such as polydimethylsiloxane (PDMS), two microchannels can be made in a cross-configuration separated with a thin film of PDMS. Applying a pressure in one of the channels, the PDMS film is deformed so that the cross-section of the adjacent channel is changed, resulting an effective actuation or valving. Several other functionalities including peristaltic pumping and solution mixing can also be obtained based on the same principle of PDMS thin film actuation [1]. This has lead to a successful integration of more than 1000 microfluidic elements on a chip in the same way of microelectronic integrated circuits [3]. Similarly, advanced microfluidic devices can then be fabricated for chemical and biological applications [4], [5], [6]. In all cases, accurate determination of the mechanical properties of pneumatic activated membranes is important for the optimization of microfluidic elements. In this work, we study the response of the PDMS microvalves by measuring the conductance of an electrolyte solution through the microvalve section controlled pneumatically [7], [8]. By changing systematically the pressure applied in the flow and control channels, we were able to determine the optimal condition for actuation which should be useful for the improvement of performances of several types of microfluidic components.
Section snippets
Experimental
Multi-layer soft lithography has been used for the rapid prototyping. Fig. 1 shows a schematic presentation and a microphotograph of a microfluidic device used in this work. It consists of a two layer PDMS microchannel structure bonded on a glass substrate. Both the flow and the control channels are designed to have an initial channel width of 100 μm and a height of 10 μm. To obtain these channels, molds were fabricated by optical lithography with SJR 5740 (from Shipley) and SU8 2010 (from
Results and discussion
Firstly, we study the dependence of the mechanical properties of microvalves on the pressure in both control and flow channel in a static mode. In Fig. 2 is shown the current measured between the two electrodes as a function of the control pressure for several values of the pressure presented in the flow channel. As can be seen, higher the pressure in the flow channel, higher the pressure is required in the control valve for a perfect closing. For zero pressure applied in the control channel,
Conclusion
We have performed a systematic investigation on the pressure actuation of PDMS thin film in microfluidic configurations. The conductance measurement appears to be suitable for the characterization of dynamic response of pneumatically actuated microfluidic elements. We found that the surface adhesion at low actuation frequencies influences the PDMS membrane opening time. Clearly, the response of the PDMS membrane is delayed respect to the switch off of the applied control pressure and once the
References (8)
- et al.
Microelectron. Eng.
(2004) - et al.
Science
(2000) - et al.
J. Appl. Phys.
(2004) - et al.
Science
(2002)
Cited by (10)
Fabrication and detection of microvalves for SPR array sensing
2012, Microelectronic EngineeringCitation Excerpt :These two methods provide intuitive information but cannot be quantified. Galas et al. adopted quantified conductance method to investigate single microvalve open/close process [16]. However, the electrodes in their setup were deposited in a microchannel through a complicated process and may induce measurement error; in addition, how to characterize multiple microvalves simultaneously is also an issue.
Microfluidic devices with integrated active valves based on thermoplastic elastomers
2006, Microelectronic EngineeringDesign of micro-displacement amplifier for the micro-channel cooling system in the micro-pump
2020, Forschung im Ingenieurwesen/Engineering ResearchResearch on precise pneumatic-electric displacement sensor with large measurement range
2017, Proceedings of SPIE - The International Society for Optical EngineeringFabrication of microscale materials with programmable composition gradients
2016, Lab on a ChipA microfluidic synchronizer for fission yeast cells
2013, Lab on a Chip