Pre‐Stretched Double Network Polymer Films Based on Agarose and Polyacrylamide with Sensitive Humidity‐Responsive Deformation, Shape Memory, and Self‐Healing Properties

Abstract

A series of pre‐stretched double network (DN) polymer films based on agarose and polyacrylamide (Agar/PAM) are prepared. These films show the rapid and large deformation in response to humidity due to the release of contraction stress. The pre‐stretched dry film can curl toward the humidity direction into a scroll‐like structure in an extremely short time. The deformation direction can be also well controlled by the stretching direction. The released contraction stress increases with the increase of tensile strain. The DN Agar/PAM hydrogel film shows good water‐induced shape memory effect. It can be stretched to form various temporary shapes such as circle, square, and spiral. The shape fixing and recovery ratios are both close to 100%. The released large contraction stress accelerates the shape recovery process. The recovery time increases with the increase of film thickness. The DN dry film shows the good water‐induced self‐healing ability. The healed film maintains about 88% tensile strength (103 MPa) of the original film. Due to these good properties, the pre‐stretched DN dry films can be fabricated into a soft robot jack which can easily lift up to ≈20 times its own weight within 8 s.

Development and challenges of smart actuators based on water-responsive materials

“…Furthermore, natural pollen, corn xerogel, and agar have similar humidity-driven effects and are used to produce soft actuators. [60][61][62][63] Additionally, due to the advantages of material breathability and good heat dissipation properties, WR plant materials also performed well in the field of smart textiles. For example, Hu et al reported a self-balanced torsional actuator based on WR twisted bamboo yarns.…”

“…Furthermore, natural pollen, corn xerogel, and agar have similar humidity-driven effects and are used to produce soft actuators. 60–63…”

Reversible Patterning Cross-Linked, Humidity-Responsive Polymer Films with Programmatically and Accurately Controlled Deformation

“…It is well-known that polyethylene glycol (PEG) and poly­(acrylic acid) (PAA) are hydrophilic polymers. PEG- and PAA-based films show good humidity responsiveness. − Coumarins are a kind of traditional perfume materials extracted from many plants. So far, more than 1000 coumarin derivatives have been studied.…”

Cellulose membranes as moisture-driven actuators with predetermined deformations and high load uptake

“…The rational design and realization of smart materials are one of the fast-growing fields in materials science and engineering [1][2][3][4][5][6][7][8]. The functional materials with a controllable and intelligent response to external stimuli are of particular appeal and practical import, especially when the responsiveness is inherently incorporated in the materials [9][10][11][12][13][14].…”

“…This sort of actuators avoids the use of large optical, electric and magnetic fields that not only require sophisticated devices to generate but also may cause local heating to undermine the durability of materials. The humidity-driven actuators have been fabricated with various natural or artificial materials, including copy paper, π-stacked carbon nitride polymer, xerogel film, NaAlg-epoxidized natural rubber, cellulose nanomaterials, carbon nanotubes/shape memory polyurethane, paper derived from nature pollen, nafion-polypropylene-PDMS/graphite and agarose/polyacrylamide [5,[15][16][17][21][22][23][24][25].…”