Fabrication of Non-spherical Particles and Self-wrinkling of the Surfaces by Non-uniform Crosslinking of the Polymer at a Water/Oil Interface*

Fabrication of non-spherical shapes or wrinkles on the curved surfaces may help us to understand an aspect of morphological development found in nature such as pollens, fruits, and vegetables. Popular methods to fabricate microparticles of various geometries rely on molding or 2D lithography, which have challenges in creating 3D shapes. Moreover, in order to create wrinkles on them, additional processes are required to form an outer layer of different material properties and impose stress. We present a simple system of UV-curable hydrogel droplets dispersed in oil, of which initial spherical shapes by a water-oil interfacial tension are subjected to non-uniform UV crosslinking resulting in shape deformations. We also find that the presence of crosslinking gradient in the cured droplets induces surface wrinkles by self-swelling, and we can control the pattern of wrinkles with the shapes of particles or by spatially varying UV exposure. Further research will develop applications such as fabrication of nanochannels and patterns on 3D objects to impart multifunctionality.