Humidity‐Driven Mechanical and Electrical Response of Graphene/Cloisite Hybrid Films

Abstract

Humidity-driven and electrically responsive graphene/cloisite hybrid films are obtained by casting water dispersions of graphene oxide and cloisite Na + . Coupling hydrophilicity and a high water vapor barrier in a homogenous film enables to realize humidity-driven actuators which exploit the water gradient generated across the film section under asymmetric exposure to humidity. The hybrid films are self-standing, flexible, and exhibit fast humidity-triggered bidirectional bending up to 75°, which is tuned by varying the relative amount of the two components. Up to 60% of the bending angle can be preserved at the steady state, providing a large and reliable response to humidity. Moreover, thermal treatment results in the reduction of graphene oxide, endowing the films with humidity-dependent electrical conductivity, which increases from 1.5 × 10 −6 S at 20% relative humidity (RH) up to 2.7 × 10 −5 S at 90% RH. The films are used to realize a humiditysensitive electrical switching system in which the reversible actuation is due to water desorption induced by the Joule effect. Due to their ease of preparation and tunable properties, this new class of graphene-based materials is suitable for the realization of humidity-driven and electrically responsive actuators and sensors. development of new humidity-driven mechanically and electrically responsive actuators and sensors.

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

“…S7). Given its lamellar structure and excellent swelling rate resulting from water absorption, the pollen paper appeared to exhibit a degree of mechanical responsiveness to humidity somewhat similar to that of many synthetic materials studied previously (14,18,22,25).…”

“…Inspiration drawn from such naturally occurring biological systems has led to the development of a wide range of artificial soft actuators that can reversibly alter morphological or mechanical characteristics in response to external stimuli (9)(10)(11). Owing to their dynamic responsiveness, these actuators have a wide range of potential applications, including soft robots (12)(13)(14)(15)(16)(17), artificial muscles (18)(19)(20)(21), sensors (22,23), and electric generators (24,25).…”

Highly Conductive MXene Film Actuator Based on Moisture Gradients

“…of transforming other forms of energy into mechanical deformation after exposure to various external stimuli, showing considerable potential in the fields of intelligent robots, [1] artificial muscles, [2] sensors, [3] and medical devices. [4] Note that the actuator drivers excited by the moisture composed of water have received increasing attention in recent years, [5] because water is a rich renewable resource and a pure natural green energy source. In general, the main route for achieving humidity-driven motion by a reversible actuator is to design double-layered/or multilayered structures with different expansion properties.…”

Soft bimorph actuator with real-time multiplex motion perception

“…During this effort, a number of intriguing and potential applications have been reported, such as artificial muscles, bionic robotics, skin-like sensors, smart textiles, multifunctional fibres, and bio-medicine. [1][2][3][4][5][6][7][8][9][10][11][12] These soft actuators are usually capable of selfdeformation under external stimuli such as electrics, [13][14][15] light, [16][17][18] heat, [19][20][21] moisture, [22][23][24] and magnetics. [25][26][27] To obtain both short-term soft actuators and long-term AI robotics, accurate realtime motion perception under external stimuli is essential in actuators, robotics and intelligent autonomous systems.…”