Fiber-tip photothermal microparticle controller based on asymmetric thermal effect

Miniaturization and multi-functionalization integration of microparticle manipulation devices remain the two major challenges in micro–nano control. Here, we demonstrate a fiber-tip photothermal microparticle controller based on asymmetric thermal effect. The fiber-tip controller is composed of an optical fiber microcavity structure and a GO+AuNBPs/PDMS composite film. The optical fiber microcavity is used to limit the spread of incident light to enhance the interaction between the optical field and the composite film and to provide real-time spectral monitoring of the thermal and deformation states of the composite film. The photothermal conversion efficiency has been enhanced significantly due to the special structure of composite film. Theory and experiments indicate that the target microparticle exhibits stable periodic oscillations and self-rotations manipulated by the controller. The oscillation frequency increased as the power of driven laser. As the power of driven laser increased exceeds 18.6 mW, the composite film undergoes irreversible deformation, which further enhances the asymmetry of the surrounding thermal field. The target microparticle would maintain stable self-rotation in asymmetric thermal field. The proposed fiber-tip controller enables the precise capture of microparticle in liquid environments, providing a reliable tool for the manipulation and selection of microparticle at a microscale.