Photocatalytic Micro/Nanomotors Functioning in the Near-Infrared Window for Biomedical Applications

Near-infrared (NIR) light-driven photocatalytic micro- and nanomotors are emerging as a new class of self-propelled micro/nanodevices for minimally invasive biomedical applications. By operating within the biological transparency window, they enable autonomous motion and light-induced redox reactions under biocompatible illumination conditions. Yet, the low photon energy of NIR light imposes fundamental constraints on photocatalytic efficiency and propulsion, requiring innovative materials design. This review systematically discusses recent progress in materials strategies for achieving NIR responsiveness, including heterostructure formation, upconversion coupling, defect modulation, and photosensitization via dyes or plasmonic nanostructures. The relationships between material composition, optical absorption, charge separation, and motion behavior are analyzed, with emphasis on photocatalytic propulsion. Particular attention is given to their potential application in photodynamic therapy, neural stimulation, and redox-based treatments, while discussing remaining challenges related to fuel-free propulsion, ionic tolerance, and immune system evasion. Finally, key design principles and future research directions are outlined, positioning NIR-responsive photocatalytic micro/nanomotors as a versatile platform for minimally invasive therapeutic treatments and remote-controlled catalysis.