The controlled formation of ordered, sinusoidal structures by plasma oxidation of an elastomeric polymer

This letter describes a technique for generating waves on polydimethylsiloxane (PDMS) patterned in bas-relief. The PDMS is heated, and its surface oxidized in an oxygen plasma; this oxidation forms a thin, stiff silicate layer on the surface. When the PDMS cools, it contracts and places the silicate layer under compressive stress. This stress is relieved by buckling to form patterns of waves with wavelengths from 0.5 to 10 mu m. The waves are locally ordered near a step or edge in the PDMS. The wavelength, amplitude, and pattern of the waves can be controlled by controlling the temperature of the PDMS and the duration of the oxidation. The mechanism for the formation and order of the waves is described. (C) 1999 American Institute of Physics. [S0003-6951(99)01943-9].