Controlled Fabrication of 3D Chiral Microwrinkles via Asymmetrical and Biaxial Bucklings

Abstract

Nano- and microsized chiral materials are receiving significant attention because of their unique characteristics, which include chiroptical activities and enantioselective interactions with living materials. However, the realization of chiral morphologies in such small-scale materials has been an issue because of the complicated fabrication methods and limited material selection. In this study, a facile and reproducible method is developed for fabricating 3D chiral microwrinkles with twisted shapes by asymmetric and biaxial buckling. Soft polydimethylsiloxane (PDMS) substrates are asymmetrically stretched with angled biaxial strains and exposed to UV/ozone to prepare hard silica layers on top of the PDMS substrates to induce microwrinkles. The chiral shapes are controlled by changing the angle (theta) between the two strain axes and the UV/ozone exposure times (t(1), t(2)) in each stage of buckling. The 3D chiral microwrinkles are shaped like "fusilli pasta" and occupy an area of 1.5 cm x 1.5 cm. The patterned area can be easily scaled, and no innate chiral biomaterial is necessary. This method could be widely extended to the fabrication of diverse types of chiral materials for advanced optical and bio-applications.