Fig. 5.

Locust friction mechanisms. (A) The locust’s foot with spines and adhesive pads (3D surface profilometer micrograph). The passive two-axis joint allows for nearly 180° in the sagittal plane and a difference of −10° in the frontal plane. (Magnification: 100$\times$.) (B) Spine-asperity interaction plot which determines the potential increases in the effective loading angle ${\theta }_{SL}^{*}$ as a function of the spine tip radius, $r_s$, asperity radius, $r_a$, and asperity height, $h_a$. The average asperity radius ratios, $r_a/r_s$, of the tested materials are listed above the plot. (C) Adhesive pad interaction plot, which determines the passive loading coefficient, $C_{NF}$.