Biomimetic Graphene Actuators Enabled by Multiresponse Graphene Oxide Paper with Pretailored Reduction Gradient

Abstract

The strong interaction between water molecules and graphene oxide (GO) enables moisture‐responsive graphene actuators, revealing great potential for soft robots. However, current strategies for developing smart graphene actuators fail to tailor their material property gradient in a controlled manner, and the driving manner is usually limited to single stimulus actuation. Here, a facile preparation of humidity/thermal/light multiresponsive graphene actuators by sequential vacuum filtration of GO and reduced GO (RGO) aqueous solutions is reported. The photoreduction degree of RGO layer is tuned precisely beforehand by changing ultraviolet (UV) light irradiation time, and thus a pretailored reduction gradient along the normal direction of the GO/RGO bilayer paper would form in a highly controlled manner. Taking advantage of the competitive water adsorption between the GO and RGO layers, as well as the thermal‐, light‐promoted desorption, the GO/RGO bilayers deform in response to moisture, light, and temperature changes; and the deformation degree can be modulated by controlling the gradient of oxygen‐containing groups (OCGs). As a proof of principle, a humidity‐responsive graphene mimosa and a humidity/thermal/light multiresponsive graphene actuators are fabricated. The GO/RGO bilayer paper with pretailored reduction gradient holds great promise for easy fabrication of biomimetic actuators that enable performing predictable deformation.

Moisture-Responsive Graphene Actuators Prepared by Two-Beam Laser Interference of Graphene Oxide Paper

“…Graphene oxides (GOs), as derivatives of graphene materials (Zhu et al, 2010), possess immense potential for a broad range of graphene-device applications owning to several advantages, such as solubility, batch preparation, ease of fabrication of large films, eco-friendliness, and stable physicochemical properties (Becerril et al, 2008; Eda et al, 2008; Kudin et al, 2008). As the surface contains numerous hydrophilic oxygen-containing groups (OCGs), desiccative GO films are extremely sensitive to ambient humidity (Han D. et al, 2018). In spite of surface defects of GO, suitable chemical, thermal and photoreduction method have been successfully developed to realize some sort of OCGs removal, which leads to the formation of RGO structure with different components from GO (Stankovich et al, 2007; Li et al, 2011).…”

Light-Responsive Actuators Based on Graphene

“…It is worth mentioning that GO demonstrates a more apparent negative CTE, deriving from the adsorption/desorption of water molecules associated with temperature changes (Zhu et al, 2012). Numerous actuators have been made based on the photothermal desorption effect (Mu et al, 2015; Chen L. et al, 2017; Han D. D. et al, 2018). The excellent electronic conductivity and thermal conductivity (up to 5,000 W·m −1 ·K −1 ) (Balandin et al, 2008) can further facilitate the actuation process, exhibiting fast and large bending performance.…”

“…et al (2017) with permission of American Chemical Society. Reproduced from Han D. D. et al (2018) with permission of WILEY-VCH. Reproduced from Tang et al (2017) with permission of WILEY-VCH.…”

Unravelling humidity-gated, temperature responsive bilayer actuators

“…[19][20][21][22][23] These often multi-layer materials are commonly employed to obtain macroscopic bending, twisting or even rolling. [24][25][26][27][28][29][30] Yet, selecting the proper operating conditions is key to obtaining precise mechanical motions as temperature closely correlates to environmental relative humidity. This constraint is oftentimes circumvented by examining actuation under isothermal or constant humidity conditions.…”