Observation of Strong Nonlinear Elasticity in a Cellulose-Based Material as Predicted by the Hygroelastic Theory

Moisture-responsive biological materials are abundant, and their unique properties facilitate a wide range of applications. Originally emerged from the studies of hygroscopic spores of bacteria, the hygroelastic theory [1] offers a microscopic theory of elasticity that could potentially be applicable to many forms of moisture-responsive biological matter. An unusual prediction of the hygroelastic theory is the existence of strong nonlinear elasticity in moisture-responsive biological matter. The theory quantitatively predicts the elastic modulus and how the modulus would change with strain (i.e., nonlinear elasticity) from known microscopic interactions (i.e., the hydration force). Based on the assumptions of the hygroelastic theory, these principles may be applicable to other hygroscopic biological matter. In this work, we present atomic force microscopy-based experiments on thin, regenerated cellulose films. The measurements provide evidence for the existence of strong nonlinear elasticity in these materials which align well with the quantitative predictions of the hygroelastic theory. The findings raise the possibility that many forms of hygroscopic biological matter could be hydration solids [1].

Reference:

[1] Harrellson, S.G. et al. Hydration solids. Nature 619, 500–505 (2023).

Funding acknowledgment: This work was supported by National Institute of General Medical Sciences of the National Institutes of Health, award no R35GM145382 and by the Office of Naval Research, award no. N00014-21-1-4004.