No abstract

4D printing has emerged as an important technique for fabricating 3D objects from programmable materials capable of time‐dependent reshaping. In the present investigation, novel 4D thermoinks composed of laponite (LAP), an interpenetrating network of poly(N‐isopropylacrylamide) (PNIPAAm), and alginate (ALG) are developed for direct printing of shape‐morphing structures. This approach consists of the design and fabrication of 3D honeycomb‐patterned hydrogel discs self‐rolling into tubular constructs under the stimulus of temperature. The shape morphing behavior of hydrogels is due to shear‐induced anisotropy generated via 3D printing. The compositionally tunable hydrogel discs can be programmed to exhibit different actuation behaviors at different temperatures. Upon immersion in 12 °C water, singly crosslinked sheets roll up into a tubular construct. When transferred to 42 °C water, the tubes first rapidly unfold and then slightly curve up in the opposite direction. Through a dual photocrosslinking of PNIPAAm, it is possible to inverse temperature‐dependent shape morphing and induce self‐folding at higher and unrolling at lower temperatures. The extensive self‐assembling motion is essential to developing thermal actuators with broad applications in, e.g., soft robotics and active implantology, whereas controllable self‐rolling of planar hydrogels is of the highest interest to biomedical engineering as it allows for effective fabrication of hollow tubes.

Thermoresponsive hydrogel-based wound dressings with an incorporated antimicrobial agent can be fabricated employing 3D printing technology. A novel printable ink containing poly(N-isopropylacrylamide) (PNIPAAm) precursors, sodium alginate (ALG), methylcellulose (MC) that is laden with a mixture of octenidine dihydrochloride and 2-phenoxyethanol (Octenisept®, OCT) possess accurate printability and shape fidelity. This study also provides the protocol of ink’s use for the 3D printing of hydrogel scaffolds. The hydrogel’s physicochemical properties and drug release profiles from the hydrogel specimens to the external solution have been determined at two temperatures (20 and 37 °C). The release test showed a sustained OCT delivery into ultrapure water and the PBS solution. The temperature-responsive hydrogel exhibited antimicrobial activity against Staphylococcus aureus, Candida albicans, and Pseudomonas aeruginosa and demonstrated non-cytotoxicity towards fibroblasts. The thermoresponsive behavior along with biocompatibility, antimicrobial activity, and controlled drug release make this hydrogel a promising class of materials for wound dressing applications.