Fabrication of three-dimensional PDMS microstructures by selective bonding and cohesive mechanical failure

This paper presents a novel patterning method of polydimethylsiloxane (PDMS) microstructures on solid surfaces by selective bonding and cohesive mechanical failure of PDMS. Generally, when the gold film is laid between PDMS and a Si substrate, Au film with PDMS structure is easily peeled off from a Si substrate because of weak adhesion between Au and the Si substrate. However, when the Au is patterned on the Si substrate locally, PDMS bonds selectively to the Si substrate where Au patterns are not covered. The selectivity of bonding is promoted by treatment with (3-mercaptopropyl)trimethoxysilane on Au patterns and Si substrates. Then, three-dimensional PDMS microstructures are fabricated by a cohesive mechanical failure of PDMS during a dry peel-off process due to enhanced adhesion of PDMS and the Si substrate.