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Abstract In response to external stimuli, such as heat, light, or magnetic fields, stimuli-responsive soft materials can change their current configuration to a new equilibrium state through non-equilibrium kinetic processes, including reaction, diffusion, and viscoelastic relaxation, which generates novel spatiotemporal shape-morphing behavior. Using a photothermal shape memory polymer (SMP) cantilever beam as a model system, this work analytically, numerically, and experimentally studies its non-equilibrium kinetic processes and spatiotemporal bending under light illumination. We establish a thermomechanical model for SMPs capturing the concurrent non-equilibrium processes of heat transfer and viscoelastic relaxation, which induces inhomogeneous temperature and strain distributions through the thickness of the beam, resulting in its bending and unbending. By varying the key dimensionless parameters, we theoretically and experimentally observe different types of bending dynamics. Moreover, our theory takes into consideration changes in the angles of incidence caused by extensive beam bending, and demonstrates that this effect can dramatically delay the bending due to reduction of the effective light intensity, which is further validated experimentally. This work demonstrates programmable and predictable spatiotemporal morphing of SMPs, and provides design guidelines for SMP morphing structures and robots.
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This content will become publicly available on April 1, 2027
Programmable Multimodal Shape Evolution of Shape Memory Polymers Through Non‐Equilibrium Processes
Abstract Stimuli‐responsive soft materials (SRSMs) can change shape in response to external stimuli, such as heat or light, through non‐equilibrium kinetic processes like diffusion and viscoelastic relaxation. Steering the non‐equilibrium kinetic processes is crucial to enable programmable spatiotemporal shape morphing of SRSMs. However, achieving such behavior through simple control and facile fabrication remains a challenge. Herein, by regulating the non‐equilibrium kinetic processes in photothermally responsive shape memory polymer (SMP) strips, their programmable spatiotemporal shape‐morphing is demonstrated with a simple material system and constant external stimuli. Specifically, it is shown that how varying the angles of light incidence, light intensity, and material properties encode the programmable spatiotemporal behaviors. These experiments manifest that an SMP strip displays convexity inversion, flip‐forward motion, and rolling behavior in response to constant light illumination. Furthermore, it is shown that a twisted SMP strip exhibits different untwisted directions under different concentrated illumination areas. Finally, materials are patterned with different kinetic properties in an SMP strip, demonstrating the capability of SMPs to undergo more complex spatiotemporal shape‐morphing behaviors, such as twisted bending. This work achieves programmable spatiotemporal shape‐morphing behaviors of SMP by utilizing material intelligence, and provides essential design guidelines for morphing structures and soft robots.
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- Award ID(s):
- 2048219
- PAR ID:
- 10707860
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 36
- Issue:
- 30
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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