Fig. 2.

Effect of chirality on non-linear elastic modulus and yield stress. (a) Fluorescence images of 50/50 (racemic) and 75/25 r-DPPC/s-DPPC and 100% r-DPPC. As the ratio of r-DPPC to s-DPPC increases, the counterclockwise rotation of the domains increases. (b) The chiral nonlinear elasticity ratio G’_c/G’_cc increases linearly from 1 to 1.5 for (X_r-DPPC – X_s-DPPC) from 0.0 (racemic mixture) to 1.0 (pure r-DPPC) (c) Fluorescence images showing the area of r-DPPC monolayers yielded by microbuttons rotating at 6 Hz in the counter-clockwise (CC) and clockwise (C) directions. The yield radius R_y (arrow) is larger for monolayers with lower surface yield stresses. (d) Yield radius increases with rotation rate according to Eqn. 1, revealing the surface yield stress for C-sheared monolayers, $Y_S^C~4.9\pm 0.4\mu N/m$, to be ~ 1.8 times higher than for CC-sheared $Y_S^{\mathit{\text{CC}}}~2.8\pm 0.5\mu N/m$, reminiscent of the nonlinear elasticity ratio.