Direct-Ink-Write 3D Printing of Hydrogels into Biomimetic Soft Robots

Abstract

Hydrogels are promising starting materials for biomimetic soft robots as they are intrinsically soft and hold properties analogous to nature’s organic parts. However, the restrictive mold-casting and post-assembly fabrication alongside mechanical fragility impedes the development of hydrogel-based soft robots. Herein, we harness biocompatible alginate as a rheological modifier to manufacture 3D freeform architectures of both chemically and physically cross-linked hydrogels using the direct-ink-write (DIW) printing. The intrinsically hydrophilic polymer network of alginate allows the preservation of the targeted functions of the host hydrogels, accompanied by enhanced mechanical toughness. The integration of free structures and available functionalities from diversified hydrogel family renders an enriched design platform for bioinspired fluidic and stimulus-activated robotic prototypes from an artificial mobile tentacle, a bioengineered robotic heart with beating–transporting functions, and an artificial tendril with phototropic motion. The design strategy expands the capabilities of hydrogels in realizing geometrical versatility, mechanical tunability, and actuation complexity for biocompatible soft robots.

Extrusion 3D Printing of Polymeric Materials with Advanced Properties

“…Various elaborate shape changing behaviors including elongation, contraction, or twisting motions which mimic complex architectures found in biological systems, were achieved through programming of the lead angle Ho and co‐workers have constructed 3D artificial tentacle with four‐channel hydraulic connections through printing with a rationally designed hydrogel. [ 251 ] Full circle rotation movement was observed when water flow was controlled through four different channels. Furthermore, 3D robotic heart capable of beating and transporting biomaterials was also fabricated.…”

Scalable thermoelectric fibers for multifunctional textile-electronics

“…The p-type and n-type composite gel in the two separate polytetrafluoroethylene (PTFE) tubes move back and forth to closely align and extrude into a core tube. Both the loss modulus G" and storage modulus G' of the formulated hydrocolloids are prepared to be very low with G' < G", enabling the gel deformable under applied pressure 33 . The rheological properties of hydrogel after freezing gelation show much higher G' and G" of around three orders of magnitude increase.…”

Scalable thermoelectric fibers for multifunctional textile-electronics

“…Both the loss modulus G" and storage modulus G' of the formulated hydrocolloids are prepared to be very low with G' < G", enabling the gel deformable under applied pressure. 33 The rheological properties of hydrogel after freezing gelation show much higher G' and G" of around three orders of magnitude increase. The G' of the gel is higher than the G" below the critical shear stress point, meaning that the gel will maintain its shape as long as the shear stress is lower than the critical value.…”