Intelligent Hydrogel Actuators With Controllable Deformations and Movements

Qian Zhao,Luquan Ren,Zhenglei Yu,Yunhong Liang,Lei Ren

doi:10.3389/fmats.2021.661104

Abstract

Near infrared laser- (NIR-) driven intelligent hydrogel actuator systems including printable N-isopropylacrylamide- (NIPAm-) nanosized synthetic hectorite clay-nanofibrillated cellulose (NFC) hydrogels and NIPAm-4-hydroxybutyl acrylate- (4HBA-) NFC hydrogels with a high response rate were prepared via three-dimensional (3D) printing and hydrothermal synthesis, respectively. The addition of NFC was beneficial to the improvement in rheology. The 3D printed intelligent hydrogel actuators with a structure pattern of Model I and Model II exhibited the saddle and inverted saddle deformations, respectively, to prove the validity of 3D printing. In order to improve the response rate and enrich movement patterns, the hydrothermal synthesized intelligent hydrogel actuators were prepared on the base of the 3D printed intelligent hydrogel compositions. The addition of NFC maintained the controllable NIR response. Based on a wedge-shaped design, the hydrothermal synthesized intelligent hydrogel pushed the resin ball with weight of 130 mg forward 8 mm in 39 s. By changing the torque values of a hydrogel in a different direction, the actuator realized controllable continuous rollover movement. Attributed to the longilineal shape, the intelligent hydrogel actuator reached an effective displacement of 20 mm in 10 s via a forward movement. The characteristics and structure design of a hydrogel material significantly realized multiple controllable functional four-dimensional (4D) printed deformations and movements. The combination of advantages of the 3D printed and hydrothermal synthesized intelligent hydrogels provided a new direction of development and abundant material candidates for the practical applications of 4D printing in soft robot, information sensing, and health engineering.

Highlights

With the development of materials and equipment manufacturing technology, intelligent materials and corresponding advanced preparation methods promote the integrative development of materials, mechanics, and information (Zhang et al, 2014; Hakan et al, 2016; Wang et al, 2018)
As a novel kind of reinforcement, nanofibrillated cellulose (NFC) increased the crosslinking degree of intelligent hydrogels, which realized 3D printing of hydrogel reaction mixtures via the free radical polymerization under vacuum based on the improvement in the rheology property and increased Young’s modulus of the hydrothermal synthesized hydrogels via a hydroxide radical on the dehydration synthesis between a monomer and crosslinking agent
The designed structure patterns affected Near infrared laser- (NIR-)driven deformation characteristics, which realized controllable deformations of saddle and inverted saddle based on the Model I and Model II, respectively

Summary

INTRODUCTION

With the development of materials and equipment manufacturing technology, intelligent materials and corresponding advanced preparation methods promote the integrative development of materials, mechanics, and information (Zhang et al, 2014; Hakan et al, 2016; Wang et al, 2018). Attributed to the crosslinking patterns and a relatively low swelling/deswelling rate, the existing NIR-driven intelligent hydrogels including 3D printed hydrogels exhibit a relatively low response rate, which restricts functional movement abilities. The NFC-reinforced hydrothermal synthesized intelligent hydrogels, in combination with entirety infiltration of GO, were prepared to further extend the corresponding functional movement patterns. NIR Response Measurement of Hydrothermal Synthesized Intelligent Hydrogel Actuator After the infiltration of GO, the wedge-shaped NFC2 intelligent hydrogel with dimensions of 12 mm × 3 mm × 4 mm (length × width × maximal thickness) was used to push the resin ball (Φ6 mm) with weight of 130 mg on a glass surface. After infiltration of GO, the bottom part of the NFC0 hydrogel with dimensions of 23 mm × 2 mm × 2 mm (length × width × thickness) was cutting off to exhibit the forward movement under the stimulation of NIR with power of 7.1 W

RESULTS AND DISCUSSION

CONCLUSION

DATA AVAILABILITY STATEMENT