Coupled diffusion–deformation behavior of stimuli-responsive thin polymer films

Pratoori, Raghunandan; Meena, Rajesh Kumar; Ghosh, Pijush K.; Annabattula, Ratna Kumar

doi:10.1016/j.mechmat.2020.103648

Cited by 7 publications

(2 citation statements)

References 58 publications

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“…However, there is a limitation to such systems, i.e., the film can only be exposed to solvent from one side, and after some time, the film again relaxes to a state closer to the original configuration before actuation. Such a behavior is observed because actuation in such systems is driven by the solvent/moisture-induced concentration gradient from the outside environment to film, which is nullified when the film is exposed to solvent from all sides. − To create a responsive film that functions effectively under different environmental conditions, one or more passive layers can be added to the polymer structure. This leads to the contraction or swelling of one layer more relative to the other, resulting in the bending or curving of the film. , However, the addition of multiple layers can introduce complexities to the system and reduce the structure’s functionality in terms of actuation rate and bending angle .…”

Section: Introductionmentioning

confidence: 99%

Solvent-Responsive Functionally Graded Hydrogel Thin Films for Programmed Actuation

Debta,

Kumbhar,

Ghosh

et al. 2024

ACS Appl. Eng. Mater.

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Shape-shifting solvent-responsive hydrogels have emerged as a crucial material platform for the design of soft robots, sensors, and actuators. Generally, to achieve actuation under different environments, using a layered structure with heterogeneous properties is a prevalent approach. However, the nonuniform force distribution at the interface between the layers can induce material delamination, thus greatly compromising the system’s stability and applicability. Here, we present the fabrication, design, and analysis of a reversible and structurally stable single-component functionally graded (FG) hydrogel thin film. The gradation is in terms of the modulus and diffusion coefficient. The FG film exhibits a fast actuation rate and is capable of actuating in both immersed and nonimmersed aqueous environments. The fabricated FG film can eliminate the requirement for a layered structure yet retain all its functionalities. A coupled diffusion–deformation framework using the finite element (FE) method is employed to comprehend the mechanism and understand the factors governing the actuation of a FG film. The displacement profiles obtained from the simulations are successfully compared with the experiments for a FG–chitosan–water system. The rate of concentration change in different layers of the FG film is shown to play a pivotal role in steering the direction of actuation as well as the reversibility of folding under different conditions. The differential strain obtained from the length change between the different layers of the FG films is identified as a contributing factor for different actuation rates. Additionally, the simulation curvatures from different scenarios elucidate the influence of cross-linking gradation, water diffusion, and thickness on the folding of a FG film. As a prospective application, we demonstrate the design of different underwater grippers using geometrically engineered symmetric and asymmetric FG films.

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Section: Introductionmentioning

confidence: 99%

Solvent-Responsive Functionally Graded Hydrogel Thin Films for Programmed Actuation

Debta,

Kumbhar,

Ghosh

et al. 2024

ACS Appl. Eng. Mater.

Self Cite

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show abstract

“…Such behaviour of hydrogels has been widely explored and their fast actuation characteristics in the presence of external triggers such as solvent are reported. 4,5 The actuation characteristics are correlated with the thermo-mechanical properties of such hydrogels. The increase in the tensile strength of a temperature responsive gel made of a functionalized copolymer crosslinked with EDA is reported.…”

Section: Introductionmentioning

confidence: 99%