Fluid Manipulation Using Thermoexpandable Polymer Based on Ploydimethylsiloxane and Expancel

Nowadays, manipulation of liquids in miniaturised environments finds applications in many fields in biology and medicine such as diagnostics, toxicity analysis, drug delivery and so on. In those domains, the use of disposable devices has the great advantage of removing any surface contamination which could results in device malfunction. In this context, the present work revolves around the use of a thermoexpandable material, composed of expandable beads in an elastomeric matrix, used as actuator for liquids. This material is expandable only once, providing a good actuation for disposable devices. It also allows to keep the material inflated without additional energy input. This thesis has three main goals: understanding the expansion properties of this material through characterisation and modelling, proposing implementation of the heating source, and investigating possible applications. Characterisation of the material reviews its capability to create movement. The two main parameters characterised are the volumetric expansion of the material and the pressure it can provide. To better understand those behaviours, a morphological study of Expancel® beads is also undertaken. Expansion of the composite is then theoretically modelled to provide a tool for future designs. The following part of this thesis focuses on solutions to implement the material for liquid actuation. Before this investigation, the main solution used to heat the material was the resistive heating of copper tracks on a circuit board. Here, alternative solutions are provided such as the use of clean room facilities, screen-printing and polymeric conductors. The pros and cons of the proposed solutions are stated in a way to allow the reader to choose the best option for his application. Finally, some applications of this actuation system are implemented and tested to highlight the limitations and advantages of this technology when put into application.

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