Figure 2.

Measurement of the attachment force of a single adhesive seta. (a,b) Experimental set-ups for measuring adhesive and shear forces, respectively. The vertical force was measured using a microbalance, whereas horizontal shear resistance was measured using a force sensor. (c) Force was recorded throughout the attachment and detachment cycle of a seta sample. The preload includes stages i and ii, and the pull-off includes stages iii and iv. The adhesive force generated by a seta can be quantified as the maximum pull-off force. (d) Shearing directions for the test sample. The circular seta (left) is tested in two perpendicular directions; the spatula seta (right) is tested in distal, proximal and lateral directions with respect to the seta contact. (Online version in colour.)