Stimuli-responsive gel based microfluidic switch

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Elastic instabilities such as buckling, wrinkling and creasing of surfaces, and snapping transitions have historically represented mechanical failure in thin films. However, this does not have to be the case and elastic instabilities, particularly on soft polymer surfaces, can provide reversible control, sensing or actuation in response to well-defined signals or changes in their environment. In previous work, I have shown that surface instabilities can be electrically triggered on a gel surface supported by specifically designed underlying electrodes. The demonstrated actuation required a low voltage of 2 - 4 V. (Adv Mater. Vol 25, 2013) and a rapid actuation was also obtained with response times less than 1 second. This project uses the above insights together with my established understanding and experience in surface instability (mechanics) and materials science to produce a robust electric voltage controlled switch to regulate the liquid flow in a micro-channel. Practically, the project will focus on understanding a hydrogel based micro-system that will allow quantitative determination of the following: i) the conditions under which buckling occurs and how the onset of buckling depends on the materials properties of the soft surface, the environmental parameters (Ionic values, temperature, pH values) and the electrode geometries; ii) how the morphology of buckling relates to the materials properties of the soft surface, the initial swelling state prior to the actuation, and the electrode geometries; iii) how to trim the buckled shape of the gel layer to effectively control the fluid flow in a micro-environment. Using the understanding from these experiments, a responsive gel based switch will be developed to dynamically regulate the liquid flow in a micro-channel. The work of this project is cross disciplinary and includes mechanics, materials science and micro-engineering. A range of materials innovations will be used from lithographically produced structural electrodes to gel chemistry. The passive valve technology with an 'on-demand' actuation described in this project is situated in a broad scientific context (chemistry, applied physics, chemical-physics, micro-engineering, chemical engineering, and electro-chemistry). The project will provide the understanding needed to allow future development of novel micro-fluidic devices with high integratibility and automation of liquid flow.