Quasi-photonic crystals-boosted highly efficient TiCT MXene photothermal materials for untethered actuators and therapeutics.

The near-perfect internal photothermal conversion efficiency of MXene has made them ideal candidates for diverse applications. However, the photothermal performance of MXene was limited by the low optical absorption, resulting in low overall conversion efficiency and inferior heating efficacy. Herein, we proposed a facile and universal method for obtaining high-efficiency photothermal systems simply by vacuum-filtrating polytetrafluoroethylene nanoparticles (PTFE NPs) on typical photothermal materials, e.g., TiCT MXene, forming lamellar thin film structure. Mechanistic studies revealed the essential role of PTFE NPs, which formed quasi-photonic crystals that effectively trap NIR light and reduce the reflection of MXene while significantly enhancing optical absorption. This resulted in remarkable 195% enhancement in overall photothermal conversion efficiency compared with pristine MXene, achieving a fast heating rate of ∼21.9°C s, high photothermal temperature of ∼70°C, and superior photothermal stability over 10,000 cycles under ultralow near-infrared (NIR) irradiation power densities (0.06-0.16 W cm). Based on this lamellar thin film, multifunctional photothermal devices were demonstrated, including programmable bioinspired devices, on-water Marangoni actuation, and photothermal therapeutics on tissue welding, etc. Furthermore, such a method was found helpful for graphene and other photothermal materials, highlighting the universality of the proposed method in developing high-performance photothermal systems with energy efficiency for practical applications.