Cavitation rheology of the eye lens

Abstract

The anisotropic mechanical properties of bovine eye lenses were measured using cavitation rheology over a range of length scales. The technique involves inducing a cavity at the tip of a syringe needle in different regions of the lens. Effective Young's moduli of the nucleus and cortex of the lens were determined, as approximately 11.8 and 0.8 kPa, respectively, on macroscopic length scales. We also measured the mechanical properties of the lens on the length scale of a single cell, suggesting that the stiffness significantly decreased from that in the bulk measurements for both the nucleus and cortex. In addition, during the growth of the cavity anisotropic propagation in the cortex was observed, while in the nucleus, the propagation was isotropic. We further explored the elasticity of the cavity deformation, showing both elastic and inelastic deformation occurred in the nucleus with equal contributions while deformation in the cortex was elastic and reversible.

Cavity growth in a triblock copolymer polymer gel

“…To measure the deformation rate during a cavitation experiment, we have used a high speed camera (Photron) to image the growth of the bubble in a PMMA 9 To understand why the gel becomes liquid at large deformation rates, we consider the fact that glassy PMMA domains can be disintegrated at high stress. Seitz et al 18 consider that when the pressure is higher than 2 Â 10 6 Pa, the micelles of the gel can be destroyed.…”

“…The selected triblock copolymer is poly-(methyl methacrylate)-poly(n-butyl acrylate)-poly(methyl methacrylate) (PMMA-PnBA-PMMA). Two different triblock copolymer architectures were kindly provided by Kuraray Co. Ltd. One copolymer, referred to as PMMA 9 , has PMMA endblocks with a molecular weight of 9 000 g mol…”

“…13 Here, we primarily study two concentrations. For PMMA 9 , the polymer volume fraction is equal to 7%. For PMMA 25 , the polymer volume fraction is equal to 5%.…”

“…1d and previously. 9,10 Most importantly, this Fig. 1 a) Schematic of a cavitation rheology experiment.…”

“…9,11 In this paper, we wish to determine whether or not a finite air volume influences the results in such a way that limits the validity of this technique.…”