S.Pruksawan, X.Ao, Y. S. Y.Lee, et al. “Reversibly Anisotropic Soft Actuator via a Molecularly Aligned Chitosan-Templated Ionic Network.” Advanced Functional Materials (2026): e75305. https://doi.org/10.1002/adfm.75305
Abstract:
Natural actuation systems achieve adaptive motion by activating internal stress and stiffness only when required, rather than maintaining permanent structural anisotropy. In contrast, most artificial soft actuators rely on embedded fibers or layered architectures that lock anisotropy and generate motion primarily through passive swelling constraints. Here, a reversibly ion-activated soft actuator that dynamically switches between isotropic and anisotropic mechanical states is reported. The system consists of shear-aligned stiff chitosan (∼2.4 wt.%) chains dispersed in a poly(acrylic acid) hydrogel, where molecular alignment acts as a latent template that is mechanically inactive in the absence of ions. Upon cation exposure, the aligned chitosan directs the formation of dense ionic bridges orthogonal to the alignment, producing inverse anisotropy with higher strength perpendicular to the alignment (6.0 MPa) than parallel direction (3.0 MPa). This ion-templated reinforcement drives robust actuation perpendicular to the alignment (67°) while suppressing deformation along the alignment direction (3°), arising from active ionic interactions rather than passive swelling. Ion removal restores mechanical isotropy, enabling repeatable and cyclable transitions. Integration with extrusion-based 4D bioprinting further enables programmable, cross-axis shape transformations guided by finite-element simulations, offering a versatile platform for bio-inspired soft actuators.
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Funding Info:
This research / project is supported by the A*STAR - Manufacturing, Trade and Connectivity (MTC) Individual Research Grant
Grant Reference no. : M23M6c0110
This research / project is supported by the A*STAR - A*STAR Career Development Fund
Grant Reference no. : C233312015
This research / project is supported by the A*STAR - Singapore RIE2025 Manufacturing, Trade and Connectivity (MTC) Programmatic Fund
Grant Reference no. : M24N3b0028
Description:
This is the peer reviewed version of the following article: S.Pruksawan, X.Ao, Y. S. Y.Lee, et al. “Reversibly Anisotropic Soft Actuator via a Molecularly Aligned Chitosan-Templated Ionic Network.” Advanced Functional Materials (2026): e75305. https://doi.org/10.1002/adfm.75305, which has been published in final form at https://doi.org/10.1002/adfm.75305. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. This article may not be enhanced, enriched or otherwise transformed into a derivative work, without express permission from Wiley or by statutory rights under applicable legislation. Copyright notices must not be removed, obscured or modified. The article must be linked to Wiley’s version of record on Wiley Online Library and any embedding, framing or otherwise making available the article or pages thereof by third parties from platforms, services and websites other than Wiley Online Library must be prohibited.