Abstract
Abstract The intelligent poly N,N-dimethylacrylamide hydrogel material system with high mechanical strength and the 3D printable property was prepared via in situ free radical polymerization under vacuum successfully. With the increase in nanofibrillated cellulose (NFC) content, stress and strain of hydrogels increased gradually. As the effective reinforcement, NFC enhanced the crosslinking density, which realized the controllable regulation of rheology behaviors including viscosity, storage modulus, and loss modulus of hydrogels. Combined with the swelling rate and the existence of the gel–sol transition point, a hydrogel with 10 mg/mL NFC was treated as the 3D printing ink of hydrogel actuators. Variation of printing parameters significantly affected self-driven deformations. The hydrogel actuators with 90°/0° and 45°/135° configurations owned bending and spiral deformations, respectively. Actuators with a larger length–width ratio owned a lower pitch value. The precise anisotropic swelling property of the printed bilayer structure was the self-driven deformation mechanism of hydrogel actuators, which provided material candidates for the preparation of soft robots and actuators.
Highlights
As a kind of typical intelligent soft materials, intelligent hydrogels owned the reversible swelling and deswelling properties under the stimulations of temperature [1,2], pH [3], light [4,5,6], magnetic field [7,8], and electric field [9,10] to realize shape and volume variation
The efficient and repeatable deformation properties expanded the potential application of intelligent hydrogels in fields of soft actuator [11,12,13,14], soft robot [15], artificial muscle [16], and so on
The effect of nanofibrillated cellulose (NFC) content on mechanical strength of intelligent hydrogels was evaluated by stress–strain analysis
Summary
As a kind of typical intelligent soft materials, intelligent hydrogels owned the reversible swelling and deswelling properties under the stimulations of temperature [1,2], pH [3], light [4,5,6], magnetic field [7,8], and electric field [9,10] to realize shape and volume variation. To realize the functional deformation properties, many kinds of methods were adopted to prepare intelligent hydrogels [17,18]. In situ free radical polymerization was the main method to realize the polymerization of intelligent hydrogels. Via the photothermal conversion function of graphene oxide, the near-infrared laser-driven bilayer intelligent hydrogels were prepared by in situ polymerization [21], exhibiting the multiple deformation patterns. The layered structure constructed by in situ free-radical polymerization and molding provided the effective anisotropic deformation mechanism for intelligent hydrogels. The disadvantage of relatively simple structure patterns restricted the potential application of intelligent hydrogels. Combined with the ultraviolet light polymerization, the 3D printed hydrogel actuators imitated the deformation patterns of tendrils and flowers to realize the anisotropic swelling deformations [22,23]. Based on changing printing parameters, This work is licensed under the Creative Commons Attribution 4.0
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