Tough Al-alginate/Poly(N-isopropylacrylamide) Hydrogel with Tunable LCST for Soft Robotics

Abstract

Tough Al-alginate/poly(N-isopropylacrylamide) (PNIPAM) hydrogel has been synthesized by introducing an interpenetrating network with hybrid physically cross-linked alginate and chemically cross-linked PNIPAM. Varying the concentration of AlCl3 regulates the mechanical properties of the tough hydrogel and tunes its lower critical solution temperature (LCST) as well. The tough Al-alginate/PNIPAM exhibits 6.3 ± 0.3 MPa of compressive stress and 9.95 of uniaxial stretch. Tunability of LCST is also achieved in a wide range within 22.5-32 °C. A bending beam actuator and a four-arm gripper made of bilayer (Na-alginate/PNIPAM)/(Al-alginate/PNIPAM) hydrogel as prototype of all-hydrogel soft robotics are demonstrated. A finite element (FE) simulation model is developed to simulate the deformation of the soft robotics. The FE simulation not only reproduces the deformation process of performed experiments but also predicts more complicated devices that can be explored in the future. This work broadens the application of temperature-responsive PNIPAM-based hydrogels.

Sensitively Humidity‐Driven Actuator Based on Photopolymerizable PEG‐DA Films

“…[33] Cellulose-type film showed significant moisture response, especially the film of cellulose stearoyl esters shows reversibly moistureresponsive shape transition, [34] and nanofibrillated cellulose film is responsive to small humidity of human hand. [37][38][39][40][41][42] Hydrogels are 3D hydrophilic polymeric networks, which swell but do not dissolve when contact with water, allowing one to achieve the desired degrees of polymer hydration and volume changes in response to a change in surrounding moisture. [36] There is ever greater interest of using hydrogels for the construction of functional materials in recent years.…”

“…[32] Very recently, Zhang et al fabricated a polymer film actuator composed of hygroscopic agarose and azobenzene-containing photoactive poly(ethylene glycol), which is capable of self-actuation in response to humidity gradient and of photogated control by light. [37][38][39][40][41][42] Hydrogels are 3D hydrophilic polymeric networks, which swell but do not dissolve when contact with water, allowing one to achieve the desired degrees of polymer hydration and volume changes in response to a change in surrounding moisture. [35] In addition, scaling up bilayer film of Bacillus subtilis spores and polyimide tape as engines is able to drive a miniature car and to power light-emitting diodes (LEDs).…”

Novel Self‐Healing, Shape‐Memory, Tunable Double‐Layer Actuators Based on Semi‐IPN and Physical Double‐Network Hydrogels

“…The combination of various multivalent cations and sodium alginate has been used in chemical–physical DN gels, with excellent performance in strength and toughness . The thermosensitive Al‐alginate/PNIPAM hydrogel has been reported to be used as a bending beam actuator and a four‐arm gripper . In these systems, the addition of Ca 2+ and SA significantly enhanced the mechanical strength of hydrogels.…”

Thermoresponsive Three‐Stage Optical Modulation of a Self‐Healing Composite Hydrogel

“…Thermosensitive poly( N ‐isopropylacrylamide) (PNIPAM) hydrogels have drawn great attention during the past few years . Thermosensitive PNIPAM hydrogels transform from transparent to opaque when heated to their LCST, which is close to body temperature (≈32 °C).…”