Friction-directed self-assembly of Janus lithographic microgels into anisotropic 2D structures

We present a method for creating ordered 2D structures with material anisotropy from self-assembling micro-sized hydrogel particles (microgels). Microgel platelets of polygonal shapes (hexagon, square, and rhombus), obtained by a continuous scalable lithographic process, are suspended in an aqueous environment and sediment on an inclined plane. As a consequence of gravitational pull, they slide over the plane. Each half of the microgel is composed of a different type of hydrogel [poly(N-isopropylacrylamide) (PNIPAM), and poly(ethylene glycol) diacrylate (PEGDA), respectively] which exhibit different frictional coefficients when sheared over a substrate. Hence the microgels self-orientate as they slide, and the side with the lower frictional coefficient positions in the direction of sliding. The self-oriented microgels concentrate at the bottom of the tilted plane. Here they form densely packed structures with translational as well as orientational order.

Automated summary

This method involves using different types of microgel platelets to self-assemble into ordered 2D structures with material anisotropy on an inclined plane. Through gravitational pull, the microgel platelets self-orient and form densely packed structures at the bottom of the tilted plane.