Quantum‐Confined‐Superfluidics‐Enabled Moisture Actuation Based on Unilaterally Structured Graphene Oxide Papers

Abstract

The mechanical stimulation on Mimosa give rise to the fast flow of water through aquaporins leading to the falling down of the petiole, avoiding the damage. [6][7][8] The "quantum tunneling fluidics effect," recently defined as "quantum confined superfluidics (QSF)" by Jiang and coworkers, [9] has also inspired the rapid development of artificial QSF systems, for instance, funnel-shaped nanochannels, [10] smart DNA hydrogels integrated nanochannels, [11] and azobenzene-derivatives-modified polymer nanochannels, [12] toward various bionic applications that involve ultrafast ion and mass transport.Recently, 2D materials, e.g., graphene, [13,14] graphene oxides (GO), [15][16][17] and MoS 2 , [18] have been considered extremely promising candidates for developing layered QSF system due to their tunable interlayer-spacing and nanoporous structures. For instance, GO that possesses plenty of hydrophilic oxygen groups on their plane shows strong interaction with water molecules, e.g., forming hydrogen bonds. [19][20][21] Since the interlayer spacing of GO is generally between 6-12 Å, [16,22,23] which further depends on the water contents, GO films can be considered as a natural QSF system for ultrafast water transmission. It has been reported that the diffusion of water molecules between adjacent GO sheets is ultrafast since the process features ultralow friction and large slip lengths. [24] Based on the QSF effect, Geim's group found that GO membrane allow ultrafast permeation of water, which is at least 10 10 times faster than He. [15] Subsequently, the same group demonstrated the tunable sieving of ions using GO membrane by controlling their interlayer spacing via humidity change. [16] In addition to the application in molecular/ion separation, the QSF effect of GO can also provide new design principle for other graphene-based devices such as desalination membranes, sensors, actuators, energy generation, and storage devices. [25][26][27][28][29] Taking actuators as an example, GO films enable rapid adsorption and ultrafast transmission of water molecules, which provides a feasibility of fabricating moisture responsive actuators by coupling another moisture-inert material layer. [30][31][32] Under moisture actuation, the selective adsorption of water molecules would directly generate a strain mismatch at the bilayer interface, leading to predictable deformation. However, in most cases, this kind of The strong interaction between graphene oxides (GO) and water molecules has trigged enormous research interest in developing GO-based separation films, sensors, and actuators. However, sophisticated control over the ultrafast water transmission among the GO sheets and the consequent deformation of the entire GO film is still challenging. Inspired from the natural "quantum-tunneling-fluidics-effect," here quantum-confined-superfluidicsenabled moisture actuation of GO paper by introducing periodic gratings unilaterally is reported. The folded GO nanosheets that act as quantumconfined-superfluidics channels can significantly pr...

Actuation and locomotion driven by moisture in paper made with natural pollen

“…Significant progress has been made in the development of actuator materials. Consider, for example, the case of smart actuators wherein most of the key components are derived from graphenebased materials or synthetic polymers (26)(27)(28)(29)(30). Given the common limitations associated with these materials in terms of their relatively high cost, strict reaction control, and issues with environmental sustainability, the quest for more cost-effective materials from natural and renewable sources has accelerated (31)(32)(33)(34).…”

Bioinspired Surfaces With Switchable Wettability

“…The surface wettability of plants exhibits unique advantages (Wu et al, 2009 , 2010 , 2011a , b ; Jiang et al, 2011 ), which enhances the environmental adaptability and improves survival chances. (Zhang et al, 2012a , 2019b , 2020 ; Yong et al, 2017 ) For example, water droplets roll freely on the surface of lotus leaves, which shows self-cleaning characteristics ( Figure 1a ; Zhang et al, 2012c ). Rose petals demonstrate water droplets pinning effect, which is helpful for keeping rose petals hydrated ( Figure 1b ; Zhang et al, 2012b ) Water droplets on the surface of reed leaves prefer to flow along the direction of the parallel leaf veins ( Figure 1c ; Wang et al, 2015 ) This anisotropic rolling characteristic plays an important role in collecting dewdrops on the roots and improves the environmental adaptability in dry and hot climates (Jiang et al, 2016 ).…”

Electro-responsive actuators based on graphene

“… 64 , 65 Consequently, graphene and related materials have emerged as appealing candidates in developing different kinds of electronic devices, 66 , 68 , 67 including generators, 69 , 70 , 71 supercapacitors, 72 , 73 , 74 , 75 , 76 photodetectors, 77 , 78 , 79 sensors, 80 , 81 , 82 and actuators. 83 , 84 , 85 , 86 , 87 Especially, after more than 15 years of intense research, graphene can be readily prepared by various approaches, such as chemical vapor deposition (CVD), reduction of graphene oxide (GO), and laser-induced graphene (LIG). 88 , 89 , 90 , 91 , 92 Nowadays, due to the advances in preparation methods, graphene and its derivatives have been successfully employed in various stimuli-responsive actuators, revealing the great potential for adaptive optics, bionic robots, motion perception, and soft MEMS.…”