Mechanowetting:numerical and theoretical analysis of droplet dynamics on deforming surfaces

Surface tension is a well-known and widespread natural phenomenon. It can be exploited to control how fluids behave on surfaces to generate, for example, self-cleaning surfaces, but it also plays an important role in modern technology, such as microfluidic chips used in biomedical analysis. Such microfluidic chips entail an extensive network of small channels and surfaces, and require only small amounts of fluids, enabling incredibly fast and accurate (medical) analyses. To get the right fluids in the right amounts at the right place at the right time on such chips is a big technological challenge, and different techniques can be used. This dissertation presents mechanowetting, a new surface-tension driven methodology that can be used to move and mix small droplets on deformable surfaces. When a droplet is deposited on a surface and that surface can be locally deformed in a controlled manner, the deformations generate a net, surface-tension driven force, pushing the droplet in the desired direction. The mechanisms behind mechanowetting were captured theoretically and computationally, and applications of mechanowetting were demonstrated using simulations and experiments. It is anticipated that the presented findings will lead to new externally-controlled, surface-deforming actuation methods as well as new applications in future microfluidic chips.