Highly Efficient Actuator of Graphene/Polydopamine Uniform Composite Thin Film Driven by Moisture Gradients

Abstract

upon a change in relative humidity of the surrounding air. [ 13 ] Sun et al. have demonstrated the fabrication of an energetic walking device driven by a powerful humidity responsive bilayer actuator comprising an action layer of cross-linked poly(allylamine hydrochloride)/poly(acrylic acid) (PAH/PAA) fi lms and a supporting layer of UV-cured Norland Optical Adhesive (NOA)-63. [ 8 ] Considering that graphene has many extraordinary characteristics, such as high thermal conductivity and excellent mechanical properties, it has also served as the smart water responsive actuators. [ 20 ] Ruoff et al. presented a macroscopic actuator based on graphene oxide/carbon nanotubes (GO/CNTs) bilayer fi lm to show obvious actuation that depends on variation of humidity onto water responsive materials of GO. [ 21 ] We have reported previously the asymmetric graphene/ graphene oxide (G/GO) fi ber structures obtained by positioned laser reduction of GO fi bers display well-controlled motion in a predetermined manner once exposed to moisture. [ 22 ] To realize the desired performance in a predefi ned fashion, bilayer materials or structures with different swelling behavior was necessary to mimic the strain transition among different material layers. However, as a moving component, bilayer actuators may also suffer from poor interlayer adhesion during frequent bending and complex fabrication process, etc. Moreover, concerns with respect to toughness, elasticity, and chemical/ physical stabilities also constitute a main barrier for the development of smart actuators. In this regard, from a manufacturing point of view, rational design and fabrication of actuators by refi ned control of the lateral microstructures of a solo material or even a single piece of thin fi lm might be a solution to the above-mentioned problems, but obviously, still remains big challenging. To overcome this limitation and further take advantage of the bilayer design of actuators, we present an alternative strategy in this article that a moisture gradients responsive reduced graphene oxide/polydopamine (RGO-PDA) thin fi lm, the uniform materials can serve as highly effi cient actuator driven by water absorption induced in situ formation of the bilayer structures in swelling difference. During the trigger of RGO-PDA fi lm by water with a gradient from one side, humidity-responsible hydrophilic PDA can absorb water on the surface layers of the RGO-PDA fi lm and act as soft "muscle" to active the swelling locomotion. The existing of rigid RGO sheets with relatively hydrophobic nature inside the fi lm hinders or delays the diffusion of water across the fi lm and construct the "skeleton" of the actuator which hold the PDA "muscle" to transfer the energy of water gradients to a mechanical motion.As energy transducers, actuators can provide controllable mechanical response into 2D or 3D motions upon the trigger by external stimuli, such as electric fi elds, [1][2][3][4] heat, [ 5,6 ] light, [ 7,8 ] and moisture. [ 9,10 ] Therefore, the fabrication of various actuators...

Flexible Actuators for Soft Robotics

“…The mechanism of humidity actuation is attributed to the in‐and‐out migration of water molecules. In pioneering works, many efforts have been made to fabricate humidity‐responsive actuators based on various materials, including cellulose nanofiber, PPy, graphene, polydopamine, and so on. Recently, Arazoe et al .…”

Research Progress of Solvent-based Smart Actuator Materials

“…(A) Schematic illustration of the mechanical locomotion mechanism of the uniform RGO-PDA thin film actuator. Upon the trigger by moisture from bottom side, hydrophilic PDA inside the bottom layer of RGO-PDA uniform thin film absorbed water to expand due to the formation a stronger intermolecular hydrogen bonds interaction between water molecular and PDA [32] . (B) Solvent-sensitive PC actuators.…”

Enhancement of Lightweight Composite Parts with Robust Cellular Structures by Combining Fused Deposition Modeling and Electromagnetic Induction Heating

“…Polymer matrix composites (PMCs) are the materials consisting of polymer matrix combined with reinforcing dispersed phases, such as nano‐ or micro‐particles, fibers, and other nanomaterials, etc., which are designed to transfer loads between reinforcing dispersed phases through the matrix. Some of the advantages of PMCs include good stiffness, toughness, and strength .…”