Flexible Torsional Photoactuators Based on MXene–Carbon Nanotube–Paraffin Wax Films

Abstract

A flexible actuator, which can convert external stimuli to mechanical motion, is an essential component of every soft robot and determines its performance. As a novel two-dimensional material, MXene has been used to fabricate flexible actuators due to its excellent physical properties. Although MXene-based actuators exhibit excellent actuation performance, their bending deformation is solely due to the in-plane isotropy of the MXene film, and an MXene torsional actuator has not been reported. This study presents a flexible torsional actuator based on an MXene−carbon nanotube (CNT)−paraffin wax (PW) film. In this actuator, the MXene thin film acts as a light absorption layer with wavelength selectivity, superaligned CNT provides structural anisotropy for the composite film, and PW acts as the active layer. The chirality and helical structure of the actuator could be tuned by the orientation of the CNT film. Such an actuator delivers excellent actuation performance, including high work density (∼1.2 J/cm 3 ), low triggering power (77 mW/cm 2 ), high rotational speed (320°/s), long lifetime (30,000 cycles), and wavelength selectivity. Inspired by vines, we used the torsional actuator as a spiral grabber, which lifted an object that weighs 20 times more than the actuator. The high-performance torsional actuator would be potentially used as a noncontact sensor, rotary motor, and grabbing tool in the soft robot system.

The modeling method and simulation study on the biaxially anisotropic polymer films

“…Ansys, Comsol and Abaqus are three kinds of widely used commercial FEA tools/software in the fields of engineering and academic research. Many researchers employed Ansys [20][21][22], Comsol [23][24][25][26][27] and Abaqus [28][29][30][31][32][33][34][35][36][37] to study the properties of novel materials and simulate morphing behaviors of various actuators. However, the biaxially anisotropic Young's modulus and CTE of the BAPs cannot be well described in all these FEA software by defining material properties.…”

Stimuli responsive actuators: recent advances

“…Besides, inspired by the helical structure of DNA, Ding et al designed a MXene/carbon nanotube (CNT) torsional light responsive actuator. 72 This actuator demonstrated exceptional performance under near-infrared (NIR) light stimulation, including a high working density (1.2 J cm −3 ), a low trigger power (77 mW cm −2 ), a high speed (320° s −1 ), and a long lifetime (30 000 cycles), and its bending angle could reach up to 640°. In addition, this MXene-based torsional actuator served as a spiral capture device capable of capturing objects weighing 20 times its own weight.…”

Responsive soft actuators with MXene nanomaterials

“…[107] On this basis, Ding et al designed a flexible torsional actuator using an MXene-carbon nanotube (CNT)paraffin wax (PW) film, wherein the MXene thin film serves as a wavelength-selective light absorption layer, superaligned CNT imparts structural anisotropy to the composite film, and PW functions as the active layer. [108] The orientation of the CNT film can be adjusted to modify the chirality and helical structure of the actuator.…”