Inhomogeneous swelling behavior of temperature sensitive PNIPAM hydrogels in micro-valves: analytical and numerical study

In this work, inhomogeneous swelling of the temperature-sensitive PNIPAM hydrogel is investigated with application to micro-valves. In this regard, a modified model is considered, and an analytical solution of the inhomogeneous swelling of a hydrogel jacket coated on a rigid pillar is performed, which is valuable for the conceptual design of the micro-valve. Then, finite element implementation of the modified model is carried out, and its validity is verified by both the analytical and experimental results. Thereafter, thermo-mechanical behavior of the micro-valve is investigated considering the coupling between the inhomogeneous swelling of the jacket and contact problems due to the temperature changes. Finally, a comprehensive study on the effects of the geometrical and material parameters in the micro-valve design is performed, and the results are presented.