Biomimetic thermoresponsive superstructures by colloidal soft-and-hard co-assembly

Soft-and-hard hybrid structures are ubiquitous in biological systems and have inspired the design of man-made mechanical devices, actuators, and robots. The realization of these structures, however, has been challenging at microscale, where material integration and actuation become exceedingly less practical. Here, through simple colloidal assembly, we create microscale superstructures consisting of soft and hard materials, which, serving as microactuators, have thermoresponsive shape-transforming properties. In this case, anisotropic metal-organic framework (MOF) particles as the hard components are integrated with liquid droplets, forming spine-mimicking colloidal chains via valence-limited assembly. The chains, with alternating soft and hard segments, are referred to as MicroSpine and can reversibly change shape, switching between straight and curved states through a thermoresponsive swelling/deswelling mechanism. By solidification of the liquid parts within a chain with prescribed patterns, we design various chain morphologies, such as colloidal arms, with controlled actuating behaviors. The chains are further used to build colloidal capsules, which encapsulate and release guests by the temperature-programmed actuation.

Automated summary

Soft-and-hard hybrid structures have been challenging to realize at microscale due to material integration and actuation difficulties. In this research, microscale superstructures consisting of soft and hard materials were created through simple colloidal assembly. The resulting structures, referred to as MicroSpine, demonstrated thermoresponsive shape-transforming properties and served as microactuators. By solidifying the liquid parts within the chains with prescribed patterns, various chain morphologies were designed to achieve controlled actuating behaviors. The chains were further used to construct colloidal capsules for temperature-programmed encapsulation and release of guests.