A Multi‐Responsive MXene‐Based Actuator with Integrated Sensing Function

Abstract

Soft actuators have demonstrated promising applications in artificial muscles, bionic robotics, smart apparatus, and beyond. Nevertheless, most of the current soft actuators only present actuating features without any real‐time sensory feedbacks, which may prohibit the timely correction of actuation error leading to the damage of the systems and target objects especially in some interactive applications. Here, a multi‐responsive actuator with self‐sensing function is enabled by a bilayer structure composing of MXene coated‐paper and polyethylene. This actuator can be triggered by multi‐stimuli and performs large deformation with low power consumption but high response speed because of the remarkable photothermal and hygroscopic performance of MXene. Meanwhile, this actuator can detect its own deformation with an amplified sensing signal on the basis of the synergetic strain‐ and stimulus‐resistance response of the MXene coated‐paper. It is demonstrated that this actuator can not only serve as a multi‐responsive switch to monitor the environmental temperature and humidity, but also as a smart gripper. This multi‐responsive actuator with self‐sensing function provides a potential application in the field of soft robotics, intelligent switch, and bionic prosthesis.

Thermal Properties of MXenes and Relevant Applications

“…[173] When the system was exposed to the NIR irradiation (808 nm), a prominent temperature increase was observed (Figure 14(c)) due to the photothermal conversion capability of MXene sheets. [173] More importantly, the temperature improvement not only led to a volumetric reduction of MCP layer by removing the adsorbed water molecules in the cellulose paper and the interlayer space of MXenes but also expanded the PE layer further than MCP film due to the higher thermal expansion coefficient (~10 À 4 (PE) versus ~10 À 6 K À 1 (MCP)), [175] and both effects forced the bilayer system to bend towards the MCP side (as shown in the inset in Figure 14(c)). [173] As mentioned above, MXenes are able to effectively convert electricity into heat by Joule heating, and the deformation of an MXene-based bilayer can thus be triggered by the corresponding temperature variation.…”

“…[173] More importantly, the temperature improvement not only led to a volumetric reduction of MCP layer by removing the adsorbed water molecules in the cellulose paper and the interlayer space of MXenes but also expanded the PE layer further than MCP film due to the higher thermal expansion coefficient (~10 À 4 (PE) versus ~10 À 6 K À 1 (MCP)), [175] and both effects forced the bilayer system to bend towards the MCP side (as shown in the inset in Figure 14(c)). [173] As mentioned above, MXenes are able to effectively convert electricity into heat by Joule heating, and the deformation of an MXene-based bilayer can thus be triggered by the corresponding temperature variation. For instance, a bilayer structure consisting of Ti 3 C 2 T x and low-density polyethylene (with mismatched thermal expansion coefficient, Ti 3 C 2 T x /LDPE) was prepared by spraying MXene dispersion on the polymer substrate, followed by a specific thermal treatment to create an original curled shape.…”

“…[173] Reprinted with permission from ref. [173] Copyright 2022 Wiley-VCH Verlag GmbH & Co. KGaA. (d) The deformation of the bilayer system (Ti 3 C 2 T x /LDPE) triggered by an external electrical voltage from 0 to 1.7 V. [174] Reproduced with permission from ref.…”

“…Triggers/Drivers Ion transport p [170][171][172]206] Actuators p p p p [173][174]207] Motion of liquid droplets p [208] Self-healing polymerization p [209] Responsive hydrogels p [210] Thermoacoustic devices p [91] All optical modulation devices p p [128,211] Modulators for neuronal electrical activity p [212] Heat management Heaters p p [213] Heat dissipation p p [176][177] Heat insulation p p [178][179] Structure patterning at high temperatures p p [214] Multispectral camouflage devices p p [86,215] reactivity at elevated temperatures up to 2000 °C as well as the temperature-dependent properties) and thermophysical properties (i.e., heat conduction capability, coefficient of thermal expansion, thermoelectric properties, Joule heating and photothermal conversion effect). Though MXenes have shown great potential to be applied in a range of fields based on the unique thermal properties (including biological agents, environmental protection, energy conversion/storage devices, sensors/detectors, triggers for chemical reactions or physical changes, and heat management strategies), this research area is still in its infancy.…”

“…(c) Temperature and the corresponding curvature of the bilayer system (MCP/PE) correlated with the power density of the incident light. The inset displays the reversible deformation of the system triggered by the light source [173]. Reprinted with permission from ref [173].…”