BS in Materials Engineering
Materials Engineering Department
Gecko tape was processed through nanomolding involving two types of templates. One template was a Millapore Isopore polycarbonate membrane filter and the other template was an n-type silicon wafer processed to include four different pore diameters. These pore diameters were 20, 40, 80, and 160 microns. AutoCAD was used to design to a mask to be used later during photolithography. Two n-type wafers were sputtered with aluminum, underwent photolithography, and then etched using reactive ion etching. A template was placed into a Petri dish and Sylgard 184 polydimethylsiloxane (PDMS) was poured on the template. Once the PDMS cured, the 1 mm slab of PDMS gecko tape was sliced into 20 mm x 20 mm samples. Micrographs of the gecko tape processed using the Isopore filters revealed hairs that were 5 µm in diameter and 20 µm in height. The hairs were also dispersed, and sporadically oriented; some hairs being erected but most were lying down. Using a thinner Isopore filter will produce PDMS gecko tape with micro-hairs that will stand straight up. About 99% of the micro-hairs of the gecko tape processed using the silicon wafer templates failed to peel out of the pores. The possible causes for the failed peel out were thermal mechanical lock between the PDMS micro-hairs and silicon pores, incorrect application of mold release agent, and the mold release agent, Jerseycote, did not provide an adequate release layer. Improvements on fabricating gecko tape using silicon wafers include freezing PDMS before peeling it off, spin coating the mold release agent, and using SU-8 negative resist to fabricate the pores.