Fast-response photothermal bilayer actuator based on poly(N-isopropylacrylamide)–graphene oxide–hydroxyethyl methacrylate/polydimethylsiloxane

Abstract

Schematic illustration of the preparation of the PNIPAM-based composite hydrogel and the driving behavior of the PGH/PDMS photothermal bilayer actuator when switching between a light/hot and cold environment.

Design and mechanism of photothermal soft actuators and their applications

“…Similarly, Li et al have designed a bilayer actuator by a photothermally sensitive hydrogel layer and PDMS layer. 61 The hydrogel was created by the thermally sensitive hydrogel PNIPAM with hydroxyethyl methacrylate (HEMA) and GO as photothermal materials. The HEMA effectively drives water molecules inside the hydrogel, which causes bending.…”

“…The photoresponsive components such as MXenes, 54,55 graphene, 56,57 carbon-based materials, 58 and graphene and their derivatives 59,60 have lower CTE and are used as a light absorption layer. Polymers such as polydimethylsiloxane (PDMS), 61,62 polyvinylidene fluoride (PVDF), 63 polyethylene (PE), 64 and polycarbonate (PC) 65 have high CTE and are used as thermal expansion layers. The high CTE layer expands asymmetrically due to heat generated by the low CTE layer upon exposure to light.…”

3D shape morphing of stimuli-responsive composite hydrogels

“…For example, several researchers have reported thermo- and photo-responsive composite hydrogels by loading GO into the PNIPAM matrix. 156,159,165,276,341 The out-of-plane deformation can be achieved by local light irradiation 7,163 assemblies of GO-PNIPAM active layer with a non-thermo-responsive passive layer 342,343 or by introducing a gradient distribution of GO within the matrix. 160,161 Other photothermal additives such as AuNP and WS 2 inorganic compounds can cooperate with PNIPAM hydrogel matrices using similar methods.…”

2D Materials Beyond Post‐AI Era: Smart Fibers, Soft Robotics, and Single Atom Catalysts

“…2D materials such as graphene and MXene with negative or relatively low coefficients of thermal expansion (CTE) (−3.26 × 10 −6 and 2.26 to 17.83 ×10 −6 K −1 , respectively) [235][236][237] can be combined with organic polymers, such as polytetrafluoroethylene (PTFE) and PDMS, with the CTE values of 3.56 × 10 −4 and 3 × 10 −4 K −1 , respectively, to trigger a programmable thermal actuation behavior. [212,238] While a heat is applied, the thermal coefficient mismatch leads to the desired actuation. [239] Hu et al reported reversible photothermal TRAs based on a bimorph structure of rGO/CNT and PDMS layer, demonstrating a large deformation angle of 479°under only 3.6 s sunlight irradiation.…”

“…[195] A bilayer actuator composed of PNIPAM hybridized with GO layer and hydroxyethyl methacrylate layer for photothermal effect and improved water transport, respectively, demonstrated reversible bending behavior upon thermal cycling. [238] Wang et al endowed the elastin-like polypeptide hydrogel actuators with grapheneenabled light-controllability, whose mechanical motions were readily tunable by the light intensity and irradiation direction (Figure 8c). [199] Thermotropic liquid crystalline elastomers (LCEs) are another platform for thermo-responsive soft actuation exhibiting a sizeable stimuli response.…”