The use of soft lithography to reproduce snail-like movement by creating pressure gradients in thin films

Abstract

By imitating nature, man finds ways to expand his capacities. To achieve this aim, he often takes natures designs, simplifies them to their most basic principles and then works in a retrograde fashion to add back the complexity originally stripped away to make the first discoveries. This thesis is based on previous work done on modeling snail movement on a macroscopic scale using a motor driven wave propagation machine. This project scaled down the mechanism to a size more commonly found in nature. This downscaling required a new method for producing waves. Peristaltic pumping achieved through the use of soft-lithography and pneumatics was the method chosen. This combination of ideas proved challenging for several reasons. First, the pumping method had previously only been used with one channel per pneumatic input, whereas the snail required each input to feed a multitude of branching channels creating a more complicated fluid dynamics problem. Second, the snail waves were downscaled from a continuous sinusoid to the three phase stepping mechanism of the peristaltic pump. Each three-phase cycle was considered equivalent to one wavelength. Thus, after creating a design that could move, the ratio between the traveling wavelength speed and subsequent net movement were compared to the aforementioned mathematical model. The model's ratio was 0.56 net/wave velocity. The actual ratio was .05 net/wave velocity. The difference by an order of magnitude could be attributed to the discontinuity of the pumping mechanism as opposed to the continuous nature of an actual traveling wave.