Tunable wrinkle structure formed on surface of polydimethylsiloxane microspheres

Abstract

Soft materials with controlled surface patterns are useful for a range of applications, including microdevices, sensors and adhesives. In this work, the spontaneously wrinkled morphologies on the surfaces of crosslinked polydimethylsiloxane (PDMS) microspheres were observed. These wrinkled microspheres may have great potentials for construction of high-performance functional materials. They were fabricated in curable PDMS/water emulsions stabilized by surfactants. After curing and drying, the PDMS droplets in the emulsions formed microspheres with different surface wrinkling morphologies, including dimples and labyrinth patterns. The buckling patterns could be well tuned by the surfactant concentration, curing temperature, evaporation and compositions of PDMS phase. A power-law dependence of the wrinkling wavelength on microsphere radius was also observed. Furthermore, the wrinkling morphologies showed good reversibility by simply drying after wetting with water. It is speculated that the evaporation of dissolved water in the PDMS phase triggers interfacial instabilities and result in the wrinkled morphologies. This work gives new insights into the surface wrinkling behavior of soft microspheres, and provides a simple, efficient and environmentally friendly route to fabricate microspheres with complex surface patterns.