Abstract
Photoactuators have attracted significant interest for soft robot and gripper applications, yet most of them rely on free-space illumination, which requires a line-of-site low-loss optical path. While waveguide photoactuators can overcome this limitation, their actuating performances are fundamentally restricted by the nature of standard optical fibres. Herein, we demonstrated miniature photoactuators by embedding optical fibre taper in a polydimethylsiloxane/Au nanorod-graphene oxide photothermal film. The special geometric features of the taper endow the designed photoactuator with microscale active layer thickness, high energy density and optical coupling efficiency. Hence, our photoactuator show large bending angles (>270°), fast response (1.8 s for 180° bending), and low energy consumption (<0.55 mW/°), significantly exceeding the performance of state-of-the-art waveguide photoactuators. As a proof-of-concept study, one-arm and two-arm photoactuator-based soft grippers are demonstrated for capturing/moving small objects, which is challenging for free-space light-driven photoactuators.
Highlights
Photoactuators have attracted significant interest for soft robot and gripper applications, yet most of them rely on free-space illumination, which requires a line-of-site low-loss optical path
The elastomeric composite sheet is made of a polydimethylsiloxane (PDMS) film, which is doped with Au nanorods (AuNRs) as the photothermal agent, and a graphene oxide (GO) film
When a control light is launched into the elastomeric composite via the Optical fibre tapers (OFTs), photothermal heating induced by the AuNR will cause a significant expansion of the PDMS/AuNR layer due to the high coefficient of thermal expansion (CTE) of PDMS37,38
Summary
Photoactuators have attracted significant interest for soft robot and gripper applications, yet most of them rely on free-space illumination, which requires a line-of-site low-loss optical path. These reports shed light on the development of waveguide photoactuators, all of them suffered from limited bending amplitude and long response time This could be ascribed to three possible reasons: (1) large thickness of the active layer due to the relatively large size of the commercially available optical fibre (typically >100 μm in diameter); (2) low energy density due to the non-focused light beam; (3) low optical coupling efficiency due to the size mismatch between the optical waveguide and the photo-responsive material. To address these issues, a thinner optical fibre with enhanced optical intensity is highly desired for high-performance photoactuators with large deformation and fast response. The energy density of light guided by OFT is much higher than that of commercially available optical fibres, resulting in a higher photothermal conversion efficiency
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