Photodirected Morphing Structures of Nanocomposite Shape Memory Hydrogel with High Stiffness and Toughness

Abstract

Shape memory hydrogels have drawn increasing attention in recent years. Practical applications require these hydrogels to have good mechanical properties as well as contactless stimulations to trigger the shape deformations. Here we report a stiff and tough shape memory hydrogel that can transform to various configurations sequentially by phototriggered site-specific deformations. Response of the shape memory hydrogel to near-infrared (NIR) light irradiation was achieved by incorporating gold nanorods (AuNRs) into the glassy gel matrix of poly­(methacrylic acid-co-methacrylamide) without compromising the excellent mechanical properties. Owing to the photothermal effect of the AuNRs, the localized temperature rise led to a dramatic decrease in Young’s modulus (from 200 to 2 MPa) of the prestretched hydrogel and bending deformation with a programmable direction and amplitude. More complex three-dimensional configurations can be obtained by multidirectional prestretching and shape memorizing the individual parts of the nanocomposite hydrogel. Furthermore, the AuNRs embedded in the gel were aligned along the prestretching direction, leading to anisotropic plasmon resonance. These photomediated programmable deformations of tough shape memory hydrogels should find applications in the biomedical and engineering fields.

Unconstrained 3D Shape Programming with Light‐Induced Stress Gradient

“…Compared with other morphing shape-memory materials, [59] the folding direction of this strategy is dominated by stress gradient but not the photothermal effect. Therefore, it can only be regulated by the stress relaxing process, and is unrelated to Since the laser has strong spatiotemporal controllability, the folding deformation can be conducted sequentially.…”

Recent progress in the shape deformation of polymeric hydrogels from memory to actuation

“…Recently, Wu and coworkers prepared a photo-responsive shape memory hydrogel that exhibits programmable deformation behavior under NIR irradiation. 58 Gold nanorods (AuNRs) were incorporated into a poly(methacrylic acid- co -methacrylamide) hydrogel (P(MAAm- co -MAAc)) after being stabilized by methoxy polyethylene glycol thiol (MPEG-SH) ( Fig. 4a ).…”

A Dual Physical Cross‐Linking Strategy to Construct Tough Hydrogels with High Strength, Excellent Fatigue Resistance, and Stretching‐Induced Strengthening Effect

“…High strength and toughness are highly desirable to meet the demand associated with practical application of hydrogels. [ 10–12 ]…”

“…High strength and toughness are highly desirable to meet the demand associated with practical application of hydrogels. [10][11][12] Hence, in recent years, many efforts have been committed to promote the strength and toughness of hydrogels, for instance, nanocomposite hydrogels, [13,14] topological hydrogels, [15,16] hydrogen bonding-enhanced hydrogels, [17,18] macromolecular microsphere composite hydrogels, [19,20] and double-network (DN) hydrogels. [21,22] Among these, DN hydrogels have drawn intensive attention due to their fascinating energy dissipation mechanism.…”