Hydrogel Microrobots Self‐Assembled into Ordered Structures with Programmable Actuation

Sub-millimeter robots—microrobots—that can autonomously perform mechanical work at the microscale would radically change new areas of human activity such as micromanipulation, microfabrication, or healthcare. Sets of identical microrobots that can connect into different, larger structures open the possibility for a “universal” microrobotic unit that fulfills a large variety of functions derived from the structure that multiple units can be assembled into. The capability of individual hydrogel microcrawlers to self-assemble under confinement into periodically ordered planar structures is demonstrated. Subsequently, these can be bound together using light to form a solid porous sheet. The lateral shape of the sheet is imprinted during the binding process. Furthermore, the sheets bend into 3D structures, where the bending direction can be programmed. The resulting structures actuate anisotropically when exposed to heat or laser illumination and can be designed for various modes of operation, such as manipulation or untethered locomotion. The formation of ordered microstructures from individual mobile robots enables easier transport and remote assembly of these structures at the place of interest without the need for direct intervention.