|
| |
|
|
|
|
||||
| Home Help Feedback Subscriptions Archive Search Table of Contents | ||||
|
Fig. 3. Shear and normal forces in isolated gecko setal arrays on a glass surface.
Motion in normal and shear axes was controlled at 50 µm s-1. (A)
Setal array during load (1), drag (2) and pull (3) (LDP) against the curvature
of the setal shafts exhibits Coulomb friction. Negative
F|| represents the reaction forces during a drag to the
left. However, no difference between static and kinetic friction was evident.
Compression force F 
was approx. 3.2 times shear
force F||. (B) Setal array during LDP with the
curvature of the setal shafts compressed initially, and then was pulled into
tension as the setal tips adhered. Positive F||
represents the reaction forces during a drag to the right. Adhesion was
sustained during the 100 µm drag step (2). (C) Normal vs shear
force during LDP against curvature of the setal shafts. F and F|| followed a path along the Coulomb
friction cone (red broken line of slope 1/µ). (D) Normal vs shear
force during LDP with curvature of the setal shafts. F and F|| followed a path that began
initially along the Coulomb friction cone (red broken line of slope 1/µ).
As adhesion developed, the forces converged on F=-F||tan
*, where
*
30° (blue broken line).
|
