The soft lithographic fabrication of high-aspect-ratio polydimethylsiloxane (PDMS)
microstructures is quite challenging because of the strong interfacial adhesion between them
and masters during demolding. This paper presents a simple method for fabricating
high-aspect-ratio PDMS microstructures by reducing the interfacial adhesion through the
cooling process. The effect of cooling process on the topography, elastic property, and adhesion
property of Sylgard 184 PDMS is studied. It is found that wrinkles are formed on the surface of
PDMS and that the Young’s modulus of PDMS is increased by the air cooling process.
Consequently, the air-cooled PDMS has lower adhesion than the traditional oven-cooled PDMS.
This result could be explained by the adhesion parameter theory: both the high amplitude of the
wrinkles formed on the surface of PDMS and the high Young’s modulus of PDMS increase
separation forces and reduce adhesive forces in the interface. Application of this method is
demonstrated by fabricating PDMS microchannels from a silicon master which has
microstructures with different aspect ratios. Compared with PDMS microchannels obtained by
the oven cooling process, PDMS microchannels with a depth of 200 µm and an aspect ratio of
10 are successfully fabricated by the air cooling process.