Functionalization Of Nanocomposite Hydrogels And Preparation Of Bio-inspired Hydrogel Arm Actuated By Near Infrared

Several functional hydrogels were studied in the present work. Firstly, thermo-moldable property of nanocomposite hydrogels(NC gels) were achieved by changing the treating conditions, which provided a new method to broad the application of NC gels. Secondly, a tough NC gel with excellent malleability or bio-adhesive capacity were obtained by introducing functional additive. Thirdly, a novel NIR controlled bio-inspired arm which could accomplish the entire “extend-grab-withdraw” action by one hydrogel actuator quickly and efficiently was prepared. The main contents and results are as follows:1. An interesting and versatile thermo-moldable property of poly(N,N-dimethylacrylamide)(PDMAA)-clay NC gel was discovered. The NC gel can be thermo-pressed and molded to a desired shape at 80 oC and the shape can be fixed by cooling to 20 oC. Mechanical test and synchrotron radiation small angle X-ray scattering(SAXS) demonstrated that the molded NC gel still exhibited high strength with elastic network structure. Viscoelastic measurements showed that with increasing temperature, the equilibrium shear modulus Ge decreased, and the creep and permanent deformation increased obviously, suggesting a decrease in the cross-linking density. Ge recovered as cooled down to room temperature, reflecting the recovery of the cross-linking density. This thermo-moldable property was attributed to the reversible cross-linking in such NC gels by changing temperature. This work provides a facile method to deform or pattern the tough NC gels after synthesis.2. The tough NC gel with excellent bio-adhesive capacity were obtained by introducing alpha-Cyclodextrin(α-CD). Adhesive hydrogels with Super-Elongation(elongation up to 3500%) were obtained by introducing polyvinyl alcohol(PVA) into PDMAA hydrogel; A bio-adhesive hybrid hydrogel with infrared(IR) irradiation triggered detaching property based on thermo-sensitive poly(N-isopropyl-acrylamide)(PNIPAm) and graphene oxide(GO). Mechanical test, creep test, Swelling behavior, and actuating process demonstrated that introduction of a large amount of hydroxyl groups provided by α-CD could enhance the interaction between hydrogel and substrate through hydrogen bonding; Super-Elongation of NC gel was achieved because PVA shielded part of crosslinking points during synthesize process. The fast and efficient photo-thermal transition of GO, This kind of hydrogel is sticky enough to adhere on skins during use and can be easily detached by IR irradiation triggering when necessary.3. A new type of rapid NIR triggering bio-inspired smart hydrogel arm based on multicomponent polymer-clay-GO hybrid hydrogels with excellent mechanical strength was synthesized. The hydrogel arm could realize the action of “extend-grab-withdraw” like human arms under NIR irradiation by combining the fast and efficient photo-thermal transition of GO with different thermo-response hydrogels. The extension and shrink motions were simulated by heating PDMAA gel and PNIPAm gel with NIR irradiation respectively, the capture part was achieved by bio-adhesive hybrid hydrogel. Mechanical test, creep test and repeating actuation demonstrated that the hydrogel arm exhibits excellent mechanical properties, convenient operation, fast NIR response and preferable repeatability for at least six times. Based on the concept in this study, combining different responsive hydrogels under the same stimulus, numerous bio-inspired hydrogel actuators in addition to smart arms could be designed conveniently.