Aqueous phase separation induced self-assembly towards all-water robotics

Abstract

Soft robots, made from soft solid materials, such as elastomers, easily bend and flex, but deformability constraints, severely limit navigation through and within narrow, confined spaces. Further, the solid components in soft robots are not amenable to surface reactions, unlike the natural systems mimicked. Functionalization of current soft robots require complex integration of bulky external components. Using aqueous two-phase systems we print water-in-water constructs that, by aqueous phase-separation-induced self-assembly, produces ultra-soft liquid robots, termed aquabots, comprised of hierarchical structures that span in length scale from the nanoscopic to microsciopic, that are beyond the resolution limits of printing and overcome the deformability barrier. The exterior of the compartmentalized membranes, akin to biological systems, is easily functionalized, e.g., by binding enzymes, catalytic nanoparticles and magnetic nanoparticles that impart sensitive magnetic responsiveness. These ultra-soft aquabots can adapt their shape for gripping and transporting objects, and be used for targeted photocatalysis, delivery and release in confined, and tortuous spaces. Especially, the responsive-hydrogel-membrane all-water robots can shrink their size upon temperature or light stimulus to pass through the spaces that are much smaller that the robot size. These biocompatible, multi-compartmental, and multi-functional aquabots open numerous opportunities for medical micromanipulation, targeted cargo delivery, tissue engineering and biomimetics.