A flexible metallic actuator using reduced graphene oxide as a multifunctional component

Abstract

Flexible actuators are widely in demand for many real-life applications. Considering that existing actuators based on polymers, low-dimensional materials and pore-rich materials are mostly limited by slow response rate, high driving voltage and poor stability, we report here a novel metal based flexible actuator which is fabricated simply through partial oxidation and nano-function of copper foil with the assistance of reduced graphene oxide. The obtained asymmetric metallic actuator is (electric-)thermally driven and exhibits fast response rate (∼2 s) and large curvature (2.4 cm) under a low voltage (∼1 V) with a sustainable operation of up to ∼50 000 cycles. The actuator can also be triggered by infrared irradiation and direct-heating under various conditions including air, water, and vacuum.

Electrothermal Actuators with Ultrafast Response Speed and Large Deformation

“…This input power density corresponds roughly to a temperature rise of 10 C according to Figure 4b, compared favorably to the force output by a metallic actuator (0.02 mN for a temperature rise of 10 C). [16] More interestingly, as shown in Figure 5d, it is found that when a block of polyester foam (thermal conductivity 0.02-0.04 W m À1 K À1 ) was placed in a hand wearing a nitrile glove, even the temperature difference between the foam and the environment (25 C) can drive the rolling up of the ETA (video 5, Supporting Information), demonstrating the extremely high temperature sensitivity of the ETA.…”

“…[4][5][6] Alternatively, electrothermal actuator (ETA) is another type of electricity-driven actuator that obviates the use of high operating voltage and electrolyte. [7][8][9][10][11][12][13][14][15][16][17][18][19] The fundamental principle of ETA is leveraging the thermal expansion gradient with electricity input. Specifically, for a bimorph ETA consisting of two layers with vastly different coefficients of thermal expansion (CTE), the device will bend to the side with the lower CTE when it is heated up.…”

“…Ultrafast response speed and ultralarge deformation cannot coexist if the value of HTC remains the same during the whole bending process. [14][15][16][17][18][19] Therefore, ETAs that simultaneously exhibit fast response speed (within 0.1 s) and large deformation (bending for at least 360 ) in a single device has never been achieved. [7][8][9][10][11][12][13][14][15][16][17][18][19] For a bimorphstructured ETA, ideally, at the initial stage of deformation, the value of HTC of the ETA should be low enough to achieve fast response speed; whereas at the end of the deformation, the value of HTC of the ETA should be high enough to achieve large deformation.…”

Carbon‐Based Photothermal Actuators

“…To design an actuator, it is essential to form inhomogeneous structures by introducing an anisotropic composition, material property gradient, or structure gradient . A metallic actuator constructed of asymmetric bilayer was prepared by Meng et al The slightly acidified GO gel was cast on a copper foil and a redox reaction occurred at the interface of GO and Cu, resulting in the formation of a Cu 2 O–RGO bilayer structure. The resultant actuator exhibited a rapid response (≈2 s) and large deflection curvature (2.4 cm −1 ) upon light irradiation ( Figure a).…”

“…a) Photographs and illustration of the actuation performed by a Cu 2 O–RGO/Cu bilayer. Reproduced with permission . Copyright 2017, the Royal Society of Chemistry.…”