Microcontact Printing and Ice Molding for the Creation of 3D Micropatterned Surfaces

While many natural features are rounded, few techniques exist to create microstructures with rounded features. Here, we describe an approach which uses microcontact printing to pattern molds around water and ice for the creation of 3D rounded microscale features. Microcontact printing is a technique that uses polymer stamps to create patterns of self-assembled monolayers (SAMs) in order to selectively modify the chemical properties of a surface. This process was used to deposit patterns of hexadecanethiol (HDT) on a gold-coated silicon wafer using a microstructured stamp. Mercaptoundecanoic acid (MUA) was used to backfill the remaining surface area, creating a surface with distinctly hydrophobic (HDT) and hydrophilic (MUA) regions. When these surfaces were exposed to water, the liquid localized on the hydrophilic regions of the pattern and could be frozen in place, forming arrays of curved, 3D structures. These patterned ice molds were then cast in polydimethylsiloxane (PDMS), forming polymer replicas of the three dimensional surfaces.