Bioinspired Freeze‐Tolerant Soft Materials: Design, Properties, and Applications

Abstract

In nature, many biological organisms have developed the exceptional antifreezing ability to survive in extremely cold environments. Inspired by the freeze resistance of these organisms, researchers have devoted extensive efforts to develop advanced freeze‐tolerant soft materials and explore their potential applications in diverse areas such as electronic skin, soft robotics, flexible energy, and biological science. Herein, a comprehensive overview on the recent advancement of freeze‐tolerant soft materials and their emerging applications from the perspective of bioinspiration and advanced material engineering is provided. First, the mechanisms underlying the freeze tolerance of cold‐enduring biological organisms are introduced. Then, engineering strategies for developing antifreezing soft materials are summarized. Thereafter, recent advances in freeze‐tolerant soft materials for different technological applications such as smart sensors and actuators, energy harvesting and storage, and cryogenic medical applications are presented. Finally, future challenges and opportunities for the rapid development of bioinspired freeze‐tolerant soft materials are discussed.

Ultrahigh conductivity and antifreezing zwitterionic sulfobetaine hydrogel electrolyte for low-temperature resistance flexible supercapacitors

“…4f shows the ionic conductivities of PHEAA /LiCl (6) and PSH 4-6/LiCl(6) hydrogel electrolytes at different temperatures. According to the zwitterionic groups of SBMA, 28,31,60 hydrophilic amide groups and hydroxyl groups of HEAA, 37 and Li + , they can interact with water molecules and can then hinder the formation of ice crystals. At −40 °C, the ionic conductivity of PSH 4-6/LiCl(6) reached up to 2.21 S m −1 , which was much higher than the 0.08 S m −1 for PHEAA /LiCl (6) and also surpassed that of previously reported values, such as 1.26 S m −1 for SBMA-HEA/LiCl and 0.28 S m −1 for PVA/P(SBMA-AM)/CaCl 2 at −40 °C; 32,61 detailed comparisons with more examples are shown in Table S3.…”

Bioinspired MXene-Based Soft Actuators Exhibiting Angle-Independent Structural Color

“…As proof-of-concept illustrations, angle-independent structurally colored soft actuators were used to demonstrate a blue gripper such as bird's claw that can capture the target, artificial green tendrils that can twine around the tree branches, and artificial multicolored butterflies that can flutter the wings, as well as biomimetic blooming flowers and inchworm-inspired soft walkers, upon cyclic exposure to acetone vapor. This research is expected to shed new light on the design and synthesis of advanced photonic nanostructures with angle-independent structural color and provide useful insights for the development of biomimetic multifunctional soft actuators toward somatosensory soft robotics, next-generation intelligent machines and thermal regulation materials [58][59][60][61][62][63].…”

Ionic skin: from imitating natural skin to beyond

“…Therefore, reducing the freezing point of water and inhibiting the large-scale growth of ice crystals is the universal strategies to improve the freezing resistance of this type of ionic skin. 74 The formation and growth of ice nuclei are mediated by high density hydrogen bonds between water molecules. Breaking the hydrogen bond between water molecules is the essential reason to produce the reduced the freezing point.…”