Table 2.

Ratios of wet to dry adhesion on all four surfaces used in whole-animal experiments and modeling

The ratio in the smooth and patterned surface models is calculated as the work of normal adhesion of two surfaces coming into contact in water and the work of normal adhesion of two surfaces coming into contact in air . Models were calculated using a chemically similar gecko hair-like surface (n-hexadecane), represented as the yellow surface, and each of the four surfaces used for whole-animal experiments (glass, PMMA, OTS-SAM–coated glass, and PTFE), represented as the gray surface. Ratios for normal adhesion of a patterned surface may be separated into four cases of precontact (separated) and in-contact (shown by the arrow) with the gecko hair-like surface and the four experimental surfaces. When submerged in water (blue), the space between the patterned unit cell pillars is filled with either air or water. These are shown schematically, where case 1 shows a consistently dry interpillar region and case 4 shows one that is consistently wet. Case 2 represents the scenario in which the interpillar region first is wet and then becomes dry on contact, and case 3 represents the opposite, in which the interpillar region first is dry and then becomes wet after contact. The wet-to-dry ratios for whole-animal shear adhesion on each of the four surfaces are shown in the last column.