Recent Advances in Stimuli‐Responsive Shape‐Morphing Hydrogels

Abstract

Inspired by shape-morphing organisms in nature, researchers have developed various hydrogels with stimuli-responsive swelling, shrinking, bending, folding, origami, rolling, twisting, or locomotion. These smart hydrogels are usually created by patterning or 4D printing. The shape morphing of hydrogels allows the fabrication of helixing, twisting, and rolling microstructures, all of which are hard to reproduce directly by ordinary techniques. More importantly, under external stimuli (e.g., solvent, humidity, temperature, light, pH, and electric/magnetic fields), many hydrogels exhibit recoverable shape morphing and thus find promising applications in grippers, sensors, valves, soft robotics, etc. Since shape morphing determines the functions of hydrogels in a great number of cases, herein, recent advances of stimuli-responsive hydrogels are summarized, with their types, shape-morphing mechanisms, fabrication methods, shape-morphing modes, and extensive applications covered. The conclusion and perspectives are also presented to guide the design and fabrication of functional hydrogels.

Progress of layered double hydroxide-based materials for supercapacitors

“…The device reached a voltage window of 2 V at temperatures ranging from À15 1C to 100 1C and had good cycling stability. 50 Due to the difference in the energy storage mechanism, supercapacitors can be divided into double layer supercapacitors, 51,52 Faraday pseudo supercapacitors and hybrid supercapacitors. 53,54 Fig.…”

“…Due to the difference in the energy storage mechanism, supercapacitors can be divided into double layer supercapacitors, 51,52 Faraday pseudo supercapacitors and hybrid supercapacitors. 53,54 Fig.…”

Hofmeister Effect Assisted Dual‐Dynamic‐Bond Cross‐Linked Organohydrogels with Enhanced Ionic Conductivity and Balanced Mechanical Properties for Flexible Sensors

“…ICHs usually consist of three basic components: water, polymers, and ionic conductors. [ 4,5 ] Water is highly embedded and provides ion transport paths for soluble salt ions. Polymers are chemically or physically connected to construct 3D networks that provide structural support.…”

Synthesis and Characterization of Temperature‐/pH‐Responsive Hydrogels for Drug Delivery

“…Hydrogels are polymers with a three-dimensional network structure formed by covalent bonds, hydrogen bonds, van der Waals force, or ionic bonds. [1][2][3][4][5][6][7] With the advantages of adhesion, biocompatibility, and degradability, hydrogels are biomaterials with excellent performance and have important applications in tissue engineering, [8][9][10] wound dressing, [11][12][13][14] drug delivery, [15][16][17][18][19] and so on. Hydrogels can be divided into intelligent hydrogels and non-intelligent hydrogels.…”