Polyurethane Shape Memory Polymer/pH-Responsive Hydrogel Hybrid for Bi-Function Synergistic Actuations

Abstract

Stimuli-responsive actuating hydrogels response to the external stimulus with complex deformation behaviors based on the programmable anisotropic structure design are one of the most important smart soft materials, which have great potential applications in artificial muscles, smart values, and mini-robots. However, the anisotropic structure of one actuating hydrogel can only be programmed one time, which can only provide single actuating performance, and subsequently, has severely limited their further applications. Herein, we have explored a novel SMP/hydrogel hybrid actuator through combining polyurethane shape memory polymer (PU SMP) layer and pH-responsive polyacrylic-acid (PAA) hydrogel layer by a napkin with UV-adhesive. Owing to both the super-hydrophilicity and super-lipophilicity of the cellulose-fiber based napkin, the SMP and the hydrogel can be bonded firmly by the UV-adhesive in the napkin. More importantly, this bilayer hybrid 2D sheet can be programmed by designing a different temporary shape in heat water which can be fixed easily in cool water to achieve various fixed shapes. This hybrid with a fixed temporary shape can achieve complex actuating performance based on the bi-functional synergy of temperature-triggered SMP and pH-responsive hydrogel. The relatively high modulus PU SMP achieved high to 87.19% and 88.92% shape-fixing ratio, respectively, correspond to bending and folding shapes. The hybrid actuator can actuate with the 25.71 °/min actuating speed. Most importantly, one SMP/hydrogel bi-layer hybrid sheet was repeatedly programmed at least nine times in our research to fix various temporary 1D, 2D and 3D shapes, including bending, folding and spiraling shapes. As a result, only one SMP/hydrogel hybrid can provide various complex stimuli-responsive actuations, including the reversable bending-straightening, spiraling-unspiraling. A few of the intelligent devices have been designed to simulate the movement of the natural organisms, such as bio-mimetic “paw”, “pangolin” and “octopus”. This work has developed a new SMP/hydrogel hybrid with excellent multi-repeatable (≥9 times) programmability for high-level complex actuations, including the 1D to 2D bending and the 2D to 3D spiraling actuations, which also provides a new strategy to design other new soft intelligent materials and systems.

Fibrous Structures: An Overview of Their Responsiveness to External Stimuli towards Intended Application

“…The most researched and attractive SMPs are polyurethanes (PU) [32,64,65,68,75]. Other SMPs commonly used include: poly(ε-caprolactone) (PCL) [71,76], which is a component of many PU materials; polyethylene terephthalate (PET) [26,76]; polylactic acid (PLA) [32] and co-polymers, such as poly(lactic-co-glycolic acid) (PLGA) [77]; polyethylene glycol (PEG) [78]; among others.…”

pH-Sensitive Hydrogel Bilayers: Investigation on Transient Swelling-Induced Bending through Analytical and FEM Approaches

“…The unique advantages of hydrogels make them highly attractive for diverse applications, particularly in medicine and tissue engineering. Hydrogel-based bilayers, with their high water content and customizable characteristics, find applications in biomedicine [3] and muscle-like actuators [4] while also demonstrating the ability to mimic biological membranes. Recent advances in synthesizing and characterizing hydrogel-based bilayers have demonstrated their potential in various applications.…”

Investigation of the influence of nano ZnO particle doping in electrode membrane on the output characteristics of biomimetic artificial muscles

“…9 BMAMs are employed to simulate muscle movements, enabling robots or other devices to perform various tasks, such as object manipulation or execution of complex actions. 10 However, traditional electroactive polymers, including polystyrene, polypropylene, and polyurethane, [11][12][13] have caused significant environmental damage both in their production processes and the handling of products made from them. Polystyrene, for example, exhibits an extremely slow degradation rate under natural conditions, with degradation times extending to hundreds of years or even longer.…”