Fabrication of elastomeric high-aspect-ratio microstructures using polydimethylsiloxane (PDMS) double casting technique

A new polydimethylsiloxane (PDMS) double casting technique is presented for the fabrication of high-aspect-ratio flexible microstructures. Experimental results showed that microstructures with aspect-ratio as high as 20 can be consistently replicated with high fidelity. Microstructures on the master mold were first replicated onto a PDMS negative mold using conventional soft lithography process. The resulting negative mold was then used to cast secondly PDMS replicas. A corona discharge treatment assisted surface modification process was developed for PDMS to PDMS casting. The whole process requires no expensive equipment and can be easily carried out in most labs. With this technique, molding replicas with same structures as the master mold can be obtained, in comparison to the conventional molding process in which an opposite of the master mold is obtained. This technique may greatly simplify the design and fabrication of master molds, provide more flexibility to widely used soft lithography process, and also reduce the damage to the master by using PDMS negative mold as the working mold.