Janus microfiber-based photothermal microgripper integrated on an optical fiber tip for precise micromanipulation

Light-driven microactuators show great promise in micromanipulation, but conventional free-space illumination approaches are often limited by thermal crosstalk and spatial restrictions. To address these issues, we herein present a photothermal microgripper directly integrated onto an optical fiber tip, comprising two symmetrically arranged composite microfibers. Each microfiber contains both a carbon-loaded polyethylene (CPE) core and a transparent polymethyl methacrylate (PMMA) core. Upon optical excitation via the fiber, the CPE core absorbs light and experiences pronounced thermal expansion, whereas the PMMA core remains largely inert. This differential expansion gives rise to substantial interfacial stress, which drives a predictable outward bending of the two fingers. Characterization shows that the microgripper achieves a rapid response time of less than 1 s. By modulating the laser power from 0 to 100 mW, the tip opening distance expands monotonically from 211.1 to 561.1 μm, providing a wide tuning range. The practical versatility of this platform is demonstrated through the precise picking and transferring of micro-objects, as exemplified by strawberry seeds. This compact, low-power architecture offers a promising solution for remote micromanipulation and biomedical engineering.