Highly efficient humidity-dependent motions in plants, such as the opening of seed pods or pine cones, has inspired the fabrication of various humidity-driven artificial actuators. However, humidity is difficult to precisely control in manipulating actuator motion. Light-driven actuators, on the other hand, would be much easier to use, because light can be controlled remotely and precisely.
Now, researchers at Jilin University, China have reported the fabrication of low-power near-infrared (NIR) light-driven bilayer actuators capable of fast, highly efficient, and reversible bending/unbending motions toward periodic NIR light irradiation. The bilayer actuator, which comprises a NIR-absorbing and humidity-sensitive layer of polydopamine-modified reduced graphene oxide (PDA-RGO) and a non-water-absorbing layer of UV-cured Norland Optical Adhesive (NOA)-63, can bend/unbend quickly toward humidity changes because of the different swelling and shrinkage of the two layers. When exposed to a NIR light, RGO sheets absorb NIR light and induce water desorption, which transfers the humidity-responsive PDA-RGO into NIR light-responsive for fabricating highly efficient NIR light-driven bilayer actuators.
