Photothermal Nanotrigger Enables Rapid Gelation and Spatially-Programmable Printability Under Broad-Spectrum Light.

Controllable and versatile manufacturing of nanocomposite hydrogels is highly desirable for attaining preferential performance and pushing their applications. However, the conventional thermal-initiated method suffers from sluggish and uncontrollable bulky gelation, whereas the photo-initiated method is controllable yet is limited by a special wavelength of light and is ineffective for hydrogel precursors containing light-absorbing conductive/magnetic nanomaterials. Herein, these limitations are fundamentally overcome, and a new concept of photothermal nanotrigger (PTNT) is discovered that leverages the classic photothermal effect of light-absorbing nanomaterials to transform uncontrollable thermal initiation into a new photo-controlled initiation. The design of PTNT is universal and can be extended for arbitrary photothermal nanomaterials from 2D nanosheets to 1D nanotubes and 0D nanoparticles, exhibiting high gelation efficiency and superior compatibility to broad-spectrum light from visible to ultraviolet and near-infrared. Intriguingly, the PTNT approach can be imparted with excellent spatially-programmable printability by introducing viscous and low thermally-conductive glycerol to confine the photothermal-generated heat and eliminate the diffusion of the formed free radicals to the unexposed region, enabling the manufacturing of high-resolution and heterogenous architecture. Moreover, in addition to the basic initiation function, the PTNT can parasitize the hydrogel network to find many additional applications in the fields of flexible electronics, light/magnetic-manipulated soft robotics, and beyond.