Swelling-induced wrinkling in layered gel beams

• Published in: Proceedings of the Royal Society. A, Mathematical, physical, and engineering sciences Vol. 473; no. 2207; p. 20170454
• Main Authors: Nardinocchi, P., Puntel, E.
• Format: Journal Article
• Language: English
• Published: England The Royal Society Publishing 01.11.2017
• Edition: Royal Society (Great Britain)
• Subjects: Actuation; Beams (structural); Bending machines; Bilayer Beam; Biomedical materials; Finite Strains; Gels; Mechanical devices; Morphing; Morphing And Sensing; Perturbation methods; Stiffness; Strain; Surface Instability; Surface stability; Swelling; Swelling Gel; Wrinkling; bilayer beam; finite strains; surface instability; swelling gel; wrinkling; morphing and sensing
• ISSN: 1364-5021; 1471-2946
• DOI: 10.1098/rspa.2017.0454

Gels are widely employed in smart mechanical devices and biomedical applications. Swelling-induced bending actuation can be obtained by means of a simple bilayer gel beam. We show that this system can also exhibit wrinkling patterns of potential interest for structural morphing and sensing. We study swelling-induced wrinkling at the extrados of a bilayer gel beam with the softer layer on top. The bent configuration at finite strain is recovered first and, starting from it, a linear perturbation analysis is performed. We delimit the zone corresponding to wrinkling modes in a parameter plane encompassing a mechanical stiffness ratio and a geometric top layer to total height ratio. Interestingly, we observe that surface instability precedes and envelopes wrinkling modes of finite wavelength. Finally, we discuss the effect of changes in stiffness and of the Flory–Huggins parameters χ on the size of the wrinkling domain.