Waveguide Microactuators Self-Rolled Around an Optical Fiber Taper.

Precisely capturing and manipulating microscale objects, such as individual cells and microorganisms, is fundamental to advancements in biomedical research and microrobotics. Photoactuators based on optical fibers serving as flexible, unobstructed waveguides are well-suited for these operations, particularly in confined locations where free-space illumination is impractical. However, integrating optical fibers with microscale actuators poses significant challenges due to size mismatch, resulting in slow responses inadequate for handling motile micro-objects. This study designs microactuators based on hydrogel/Au bilayer heterostructures that self-roll around a tapered optical fiber. This self-rolling mechanism enables the use of thin hydrogel layers only a few micrometers thick, which rapidly absorb and release water molecules during a phase transition. The resulting microactuators exhibit low bending stiffness and extremely fast responses, achieving large bending angles exceeding 800° within 0.55 s. Using this technique, this study successfully captures rapidly swimming Chlamydomonas and Paramecium, and demonstrates programmable non-reciprocal motion for effective non-contact manipulation of yeast cells. This approach provides a versatile platform for microscale manipulations and holds promise for advanced biomedical applications.