Transparent actuator made by highly-oriented carbon nanotube film for bio-inspired optical systems.

Transparent actuators can be used in variable-focus lens, tactical displays and so on. However, previous transparent actuators made with dielectric elastomer mostly required high driving voltages (>1000 V) for actuation. In this work, we propose a new kind of low-voltage-driven transparent actuator, which is made with polymer and single-layer highly-oriented carbon nanotube (HOCNT) film composites, fully utilizing the favorable conductivity and high transparency of HOCNT film. The HOCNT-based transparent actuator shows a transmittance as high as 70%. When applying a voltage of 100 V, the transparent actuator bends visibly with a displacement of 14 mm. The actuation mechanism is a large volume change between polymers when they are Joule-heated by the electrical current. In addition, a solid-state lens based on the transparent actuator is fabricated, which demonstrates an obvious magnification effect with electrical-driven actuation. Finally, a bio-inspired optical system based on the solid-state lens is also constructed, which can mimic the focusing behavior of the human eyeball. The transparent actuator proposed in this work would have potential applications in optical devices, artificial muscles and soft robotics.