Design of an Electro-Stimulated Hydrogel Actuator System with Fast Flexible Folding Deformation under a Low Electric Field

Abstract

Soft actuators have recently been widely studied due to their significant advantages including light weight, continuous deformability, high environment adaptability, and safe human−robot interactions. In this study, we designed electrically responsive poly(sodium 4-vinylbenzenesulfonate/2hydroxyethylmethacrylate/acrylamide) (P(VBS/HEMA/AAm)) and poly(sodium 4-vinylbenzenesulfonate/2-hydroxyethyl methacrylate/acrylic acid) (P(VBS/HEMA/AAc)) hydrogels. A series of P(VBS/HEMA/AAm) and P(VBS/HEMA/AAc) hydrogels were prepared by adjusting the monomer composition and crosslinking density to systemically analyze various factors affecting the actuation of hydrogels under an electric field. All hydrogels exhibited more than 65% gel fraction and a high equilibrium water content (EWC) of more than 90%. The EWC of hydrogels gradually increased with decreasing cross-linker content and was also influenced by the monomer composition. The mechanical properties of hydrogels were proportional to the cross-linking density. Particularly, hydrogels showed bending deformation even at low voltages below 10 V, and the electrically responsive bending actuation of hydrogels can be modulated by cross-linking density, monomer composition, applied voltage, ion strength of the electrolyte solution, and geometrical parameters of the hydrogel. By controlling these factors, hydrogels showed a fast response with a bending of more than 100°within a minute. In addition, hydrogels did not show significant cytotoxicity in a biocompatibility test and exhibited more than 84% cell viability. These results indicate that P(VBS/HEMA/AAm) and P(VBS/HEMA/AAc) hydrogels with fast response properties even under a low electric field have the potential to be used in a wide range of soft actuator applications.

Antiliquid-Interfering, Antibacteria, and Adhesive Wearable Strain Sensor Based on Superhydrophobic and Conductive Composite Hydrogel

“…Figure F shows the FTIR spectra of P­(AAm- co -HEMA)-MXene-AgNPs hydrogel. The peaks at 3345 and 3190 cm –1 can be attributed to the −N–H stretching vibrations of the primary amide moiety in AAm. , The peaks at 1675 can be assigned to the carbonyl (−CO) stretching vibrations and 1607 cm –1 was for the −N–H deformation of primary amine. , To further characterize the structure of the wearable sensor, a SEM image of the cross section of the strain sensor was performed to visualize the interface of hydrogel and silicone rubber as shown in SI Figure S2, which indicates the interface of hydrogel and elastomer layers was extremely robust. Besides, the interface of hydrogel and silicone rubber was observed ulteriorly after 100 loading/unloading cycles under a 100% stretcher strain as shown in SI Figure S3.…”

Electroresponsive Hydrogel-Based Switching Components for Soft, Bioelectrical, and Fluidic Circuits

“…The main feature of smart hydrogels is their ability to respond to external stimuli, including temperature [3], pH [4], light [5], electric fields [6][7][8], and magnetic field [9,10]. The electroresponsive hydrogel has huge potential to be designed as a variety of fluidic devices as it can be controlled easily [11], and a few applications of the hydrogel are investigated and listed in Table 1.…”

Application of the multi-walled carbon nanotube and sodium alginate based sol-gel coatings to enhance the electrically actuated performance of muscle-like biomass hydrogel paper actuators

“…For instance, Cho and Ha et al (Cho et al 2022;Ha et al 2020) have provided an engineered fabrication platform of multi-responsive actuator by combining hydrogel lithography and electrospinning methods, which gives an insight into the design of soft actuator with stimulus specific, multi scale and functional properties. Shin et al (Shin et al 2021) has designed electrically responsive poly(sodium 4-vinylbenzenesulfonate / 2-hydroxyethyl methacrylate / acrylic acid) and poly(sodium 4-vinylbenzenesulfonate / 2-hydroxyethylmethacrylate / acrylamide) hydrogels, and their electrically responsive bending actuation can be adjusted by ion strength, cross-linking density, applied voltage, geometrical parameters and monomer composition. Kim et al (Kim et al 2020;Duan et al 2020) has fabricated cellulose nanocrystal-reinforced polyvinyl alcohol-cellulose physical hydrogels utilizing a simple blending technology for actuator application, and its immense output displacement was observed at low electrolyte concentration.…”