| Summary: | Herein, a methodology for the directed self‐assembly of untethered microactuators and soft robotic microdevices from nanoscale building blocks is presented. The building block is a multifunctional stimuli‐responsive nanoactuator that consists of a magnetized gold nanorod encapsulated by a thermoresponsive hydrogel. The metallic core serves as a photonic nanoheater that transduces thermal energy from near‐infrared (NIR) light and a magnetic nanomotor that generates motion while driven by magnetic fields. Rapid control of temperature enables collective manipulation of nanoactuators through thermocapillary flows. In addition, catalytic activity of the nanorod instantiates a chemical reaction that covalently binds amine groups displayed on the surface of the surrounding soft gel capsule. A combination of optical and magnetic excitation realizes both reversible and permanent in situ assembly of microactuators within seconds that can perform both spatiotemporally controlled muscle‐like contraction (up to 30% strain) and motion. It is demonstrated that by linking nanoactuators with rationally designed compliant microstructures, more complex devices such as micromanipulators can be both fabricated and operated remotely. Colloidal assembly of microactuators ensures homogenous distribution of materials and functionality, thus preserving high performance provided by nanotechnology at multiple scales.
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