Programmable Reversible Shape Transformation of Hydrogels Based on Transient Structural Anisotropy

Liu, Kangkang; Zhang, Yue; Cao, Heqing; Liu, Haonan; Geng, Yuhui; Yuan, Wenhua; Zhou, Jian; Wu, Zi Liang; Shan, Guorong; Bao, Yongzhong; Zhao, Qian; Xie, Tao; Pan, Pengju

doi:10.1002/adma.202001693

Cited by 92 publications

(75 citation statements)

References 36 publications

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“…The adjacent hydrophobic and hydrophilic regions introduce stiffness inhomogeneities into the composite network. [ 18 ] In consequence, at the macroscale, the release of water occurs unevenly inducing the asymmetric stress responsible for shape morphing. Because the immersion temperature of 42 °C is well beyond LCSTs of S1 and S2 and their microstructure is less dense than that of S3, dewetting and contraction are rapid.…”

Section: Resultsmentioning

confidence: 99%

“…Bending and folding motions of thermally sensitive polymers usually result from their anisotropic nature and the presence of zones of different swelling behaviors within their structure. [ 16–18 ] Shape transformation occurs when swelling‐induced nonuniform in‐plane stresses are relieved as an out‐of‐plane motion. The majority of recently designed thermally actuated constructs have a bilayer structure composed of a support inactive layer and a swellable thermoresponsive layer.…”

Section: Introductionmentioning

confidence: 99%

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Development of Thermoinks for 4D Direct Printing of Temperature‐Induced Self‐Rolling Hydrogel Actuators

Podstawczyk

Nizioł

Szymczyk‐Ziółkowska

et al. 2021

Adv Funct Materials

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Development of Thermoinks for 4D Direct Printing of Temperature‐Induced Self‐Rolling Hydrogel Actuators

Podstawczyk

Nizioł

Szymczyk‐Ziółkowska

et al. 2021

Adv Funct Materials

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“…b) Comparison of mechanical properties of photochromic hydrogels doped with different photochromic molecules, e.g., lanthanide ions, [ 32,33 ] polymetallic oxides, [ 34,35 ] diarylvinyl, [ 36 ] azobenzene, [ 37 ] and spiropyran. [ 38–41 ]…”

Section: Resultsmentioning

confidence: 99%

High‐Performance Photochromic Hydrogels for Rewritable Information Record

Long

Jin

et al. 2021

Macromol. Rapid Commun.

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Rewritable information record materials usually demand not only reversibly stimuli‐responsive ability, but also strong mechanical properties. To achieve one photochromic hydrogel with super‐strong mechanical strength, hydrophobic molecule spiropyran (SP) has been introduced into a copolymer based on ion‐hybrid crosslink. The hydrogels exhibit both photoinduced reversible color changes and excellent mechanical properties, i.e., the tensile stress of 3.22 MPa, work of tension of 12.8 MJ m−3, and modulus of elasticity of 8.6 MPa. Moreover, the SP‐based Ca2+ crosslinked hydrogels can be enhanced further when exposed to UV‐light via ionic interaction coordination between Ca2+, merocyanine (MC) with polar copolymer chain. In particular, hydrogels have excellent reversible conversion behavior, which can be used to realize repeatable writing of optical information. Thus, the novel design is demonstrated to support future applications in writing repeatable optical information, optical displays, information storage, artificial intelligence systems, and flexible wearable devices.

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“…The LCST of the PNIPAM hydrogel can be tuned by copolymerization with a second monomer and is generally decreased by the incorporation of hydrophobic comonomers or increased with hydrophilic comonomers. [27,28] Furthermore, the VPTT increases with an increase in the amount of hydrophilic monomer. [29] GelMA is a biocompatible hydrogel that is hydrophilic; [30][31][32] therefore, the VPTT of the P/G hydrogel gradually increases with the increase in GelMA concentration.…”

Section: Thermoresponsive Poly(n-isopropylacrylamide)/gelatin Methacrylate Hydrogelmentioning

confidence: 98%

Fabrication of Thermoresponsive Hydrogel Scaffolds with Engineered Microscale Vasculatures

Wang

et al. 2021

Adv Funct Materials

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Precise fabrication of microscale vasculatures (MSVs) has long been an unresolved challenge in tissue engineering. Currently, light-assisted printing is the most common approach. However, this approach is often associated with an intricate fabrication process, high cost, and a requirement for specific photoresponsive materials. Here, thermoresponsive hydrogels are employed to induce volume shrinkage at 37 °C, which allows for MSV engineering without complex protocols. The thermoresponsive hydrogel consists of thermosensitive poly(N-isopropylacrylamide) and biocompatible gelatin methacrylate (GelMA). In cell culture, the thermoresponsive hydrogel exhibits an apparent volume shrinkage and effectively triggers the creation of MSVs with smaller size. The results show that a higher concentration of GelMA blocks the shrinkage, and the thermoresponsive hydrogel demonstrates different behaviors in water and air at 37 °C. The MSVs can be effectively fabricated using the sacrificial alginate fibers, and the minimum MSV diameter achieved is 50 µm. Human umbilical vein endothelial cells form endothelial monolayers in the MSVs. Osteosarcoma cells maintain high viability in the thermoresponsive hydrogel, and the in vivo experiment shows that the MSVs provide a site for the perfusion of host vessels. This technique may help in the development of a facile method for fabricating MSVs and demonstrates strong potential for clinical application in tissue regeneration.

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Programmable Reversible Shape Transformation of Hydrogels Based on Transient Structural Anisotropy

Cited by 92 publications

References 36 publications

Development of Thermoinks for 4D Direct Printing of Temperature‐Induced Self‐Rolling Hydrogel Actuators

Development of Thermoinks for 4D Direct Printing of Temperature‐Induced Self‐Rolling Hydrogel Actuators

High‐Performance Photochromic Hydrogels for Rewritable Information Record

Fabrication of Thermoresponsive Hydrogel Scaffolds with Engineered Microscale Vasculatures

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