Programmable Light‐Activated Gradient Materials Based on Graphene–Polymer Composites

Abstract

materials exhibit a higher degree of freedom and compliance for force tunability. Subsequently, the development of adaptive programmable materials with sophisticated structures that are capable of more refined movements has become a burning pursuit for materials scientists. To date, most adaptive programmable materials are fabricated based on the unique properties inherent to a specific class of materials, such as metallic alloys, shapememory polymers, stimuli-responsive polymers, and polymer-inorganic hybrid materials. [8,10,11,[17][18][19][20][21] Amongst these materials, stimuli-responsive polymers and polymer-inorganic hybrid materials exhibit the greatest versatility considering their diverse molecular structures as well as the extensive range of possible triggers. In particular, polymer-inorganic hybrid materials not only possess the desired mechanical attributes, they also afford a richer range in compositions and structures that will facilitate an extensive range of engineering applications. [22][23][24] Thus, the polymer-inorganic hybrid materials present the most potential to be developed as adaptive programmable materials with an extensive range of flexibility and mobility.The design of programmable materials with shape-changing abilities relies on the nonlinear responsiveness of a localized region, where generally an external stimulus would cause distortion due to nonuniform volumetric changes. [10][11][12] Inspired by nature, creating materials with heterogonous compositions and structures have become an effective strategy to achieve controlled nonuniform volumetric changes. Broadly, there are three general approaches as follows. The first approach is to incorporate two or more responsive components with different swelling properties or responsiveness to different external triggers into one material system. [25] The stress difference between the different parts drives the shape change in response to a specific signal. Bilayer structure is the typical approach used to generate the nonuniform volumetric changes, in which the wrinkling or expansion of the active layer relative to the inert layer induces the bending or folding of the bilayer structure. [5,[26][27][28][29] The complexes of polymer and inorganic nanoparticles such as silica (SiO 2 ), Au nanoparticles, carbon nanotube (CNT), and graphene (graphene oxide (GO)), have been successfully used to form bilayer structures with another polymer layer to demonstrate large-scale bending motion in response to changes in Recently, adaptive programmable materials capable of changing their shape to perform complex motions in response to an external stimulus have attracted tremendous interest. The shape-changing abilities rely heavily on the non-linear response of a localized area, where generally an external stimulus would cause distortion due to non-uniform volumetric changes. Hence, creating materials with heterogeneous compositions and structures have become an effective strategy to achieve the non-uniform volumetric changes. Here, a versatile strategy ...

Soft Actuators Based On Carbon Nanomaterials

“…The prGO only underwent photothermal conversion under NIR, which made PEI desorb moisture by heating, resulting in volume change difference and bending. [63] In addition to the actuators with layered structure, Yang et al prepared NIR driven shape memory hydrogel by one-step polymerization, which only consists of one physically crosslinked network, and realized permanent crosslinking and reversible crosslinking in the same network. Under the irradiation of NIR, GO absorbed light and converted it into thermal energy, which rapidly increased the gel temperature, separated part of the polymer chain from clay and GO, reduced the crosslinking density, and restored the gel shape to its original shape.…”

“…[58,61,68,92,93,97,[100][101][102][103][104] (b) Electricity-driven; [75][76][77][78][81][82][83][87][88][89]100,101,104] (c) Humidity-driven. [92][93][94][96][97][98][102][103][104] ChemPlusChem and elaborate actuation to the diversified and complicated real ecological environment provide a lot of inspiration for the design of soft actuators, among which the emergence of multiresponsive actuators has been an important advance to the [ [61][62][63]92,93,97,102,103] Photothermal shape memory Pre-setting the shape at low temperature and restoring the shape under the photothermal heating of carbon nanomaterials.…”

Photoresponsive Actuators Built from Carbon‐Based Soft Materials

“…The sample strips with loading of 0.3 wt% rGO and 30 wt% TEMs could bear 140 times its own weight (6.16 g/0.043 g) at dimensions of 20 mm × 2 mm × 1.4 mm under IR exposure. For the preprogrammable photoactuators, Zhang and co‐workers demonstrated a programmable photoresponsive shape‐changing composite film comprising PEI‐modified GO (PEI‐prGO) and ultraviolet‐cured Norland Optical Adhesive 73 (NOA‐73) substrate (PEI‐prGO/NOA‐73) . The mismatch of light‐induced volume expansion between the two layers brought about its reversible 3D deformation.…”

“…c) Light‐driven programmable actuations of spring with different pitch‐size. Reproduced with permission . Copyright 2018, Wiley‐VCH.…”

Light-Responsive Actuators Based on Graphene

“…However, the response time is relatively long, due to the poor heat conducting property. Considering graphene has a high thermal conductivity and good photothermal conversion efficiency, hydrogel usually combined with graphene forming photo-active hydrogel actuators, such as polydopamine (PDA) (Mu et al, 2015), elastin-like polypeptides (ELPs) (Wang et al, 2013), poly-ethylenimine (PEI) (Zhang and Tan, 2018), and poly N-isopropylacrylamide (PNIPAM) (Ma et al, 2018). Compared to pure hydrogel actuators, the response time of the actuators made by composite materials are quite fast.…”