Hydrophobic surface patterning with soft, wax-infused micro-stamps

In this paper, we demonstrate an easy-to-use and inexpensive stamping method that can be used to generate hydrophobic paraffin surface patterns on a variety of materials and surface geometries, including flat and curved surfaces. In this method, a waxy Parafilm sheet is placed on the back of a polydimethylsiloxane (PDMS) stamp containing microscale surface features; when heated above the melting temperature, the paraffin liquefies and diffuses into the stamp, which functions as a paraffin reservoir. The directional diffusion of the paraffin allows only a thin layer of liquid to be present at the micropatterned stamp surface. Hence, when it is put into contact with a target surface, it transfers a paraffin pattern with submicron lateral resolution and sub-100 nm thickness. By using XPS analysis to track paraffin diffusion process within the PDMS stamp, the diffusion coefficient in PDMS is estimated to be 5.3 x 10-11 m2/s at 65°C. In addition to improved patterning, the paraffin-saturated PDMS stamp removes the need for re-inking for consecutive patterning. In general, our process allows for rapid deposition of complex, multi-layer paraffin patterns on a variety of surfaces.