Boosting the Photothermal Conversion Efficiency of MXene Film by Porous Wood for Light-driven Soft Actuators

ABSTRACT

Ti3C2Tx (a typical MXene) has been widely used in light-driven actuators due to its outstanding photothermal conversion capability. However, the response speed of these actuators is always slow because the effective irradiated area is limited to their surface. Herein, we propose a wood-based composite material which is made by coating Ti3C2Tx on delignified wood (DW). The high porosity of DW leads to high loading of Ti3C2Tx and provides large irradiated areas, thus enhancing photothermal conversion efficiency. The delignification on wood can expose cellulose with highly hydrophilic surface for rapid diffusion of Ti3C2Tx suspension, and the hydroxy in cellulose can act as binding sites to form stable combination with Ti3C2Tx. Taking advantage of the good compressibility of DW, a simple densification is conducted on TDW (Ti3C2Tx/DW) to greatly shorten the distance between adjacent oxygen-enriched Ti3C2Tx nanosheets, enhancing the conjugation among nanosheets, thus endowing TDW with good flexibility and high heat transfer efficiency. Moreover, we manufacture a light-driven bilayer actuator comprised of TDW as the passive layer and low-density polyethylene (LDPE) as the active layer. Our light-driven actuator exhibits a tremendous angle variation of 160° at a light intensity of 120 mW/cm2. A series of devices based on the TDW/LDPE actuator are demonstrated, including simulated gestures, a four-finger soft gripper, and a bionic flower. Moreover, we propose a light-controlled smart switch which can be used on non-contact (COVID-19) or dangerous (blasting) occasions. Additionally, we present a finite element simulation to predict the bending deformation, which guides the accurate control of the devices.