Intelligent Hydrogel Actuators With Controllable Deformations and Movements

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.

Controlled Release of Acetyl Salicylic Acid in Intelligent Hydrogel Based on Cross-linked O-Carboxymethyl Chitosan

Drug-loading hydrogels were prepared from O-carboxymethyl chitosan (O-CMCS) with a high degree of substitution and different deacetylation degree (DD) using acetylsalicylic acid as drug and glutaraldehyde as a cross-linking agent. Also, the DD’s effect on the controlled drug release performance of drug-loading particle was explored. The results showed that the hydrogels and particles were prepared from 5 g of O-CMCS solution (4.0 wt.%), 2.5 g of sodium acetylsalicylate solution (8.0 wt.%), and 1.5 mL of glutaraldehyde solution (1.0 wt.%). The interior pore size of the particle (DD = 51%) was between 50 and 100µm, and its cumulative drug release ratios in the simulated gastric and intestinal juices were of the top values. The drug release of the drug-loading particle was proved to be obviously pH sensitive and it can be applied as a colonic drug.

Magnetically actuated intelligent hydrogel-based child-parent microrobots for targeted drug delivery

Small intestine-targeted drug delivery by oral administration has aroused the growing interest of researchers.