Figure 1.
Wet and dry Tokay gecko (Gekko gecko) toe pads.
(A) Dry foot in contact with a glass substrate where the setal mats appear white in color and (B) a wet foot in contact with a glass substrate where the setal mats appear grey in color. When wet the toe pads are no longer superhydrophobic and water droplets fall into the setal mat, completely wetting it.
Figure 2.
Time to maximum shear adhesion and total number of steps taken by Tokay geckos (Gekko gecko) with wet toe pads.
Time to maximum shear adhesion (min) and total number of steps until maximum shear adhesion was reached for each treatment group (GNS = Glass non-stepping, GS = Glass stepping, PNS = PMMA non-stepping and PS = PMMA stepping). Bars with the same letter are statistically indistinguishable. Error is reported as mean ±1 s.e.m. The “*” represents the approximated time to maximum shear adhesion (min) in the GNS treatment group.
Table 1.
Repeated measures MANOVA shows a significant difference in time to regain maximum shear adhesion based on substrate (glass or PMMA), treatment (stepping or no stepping) and their interaction.
Figure 3.
Schematic of the work of adhesion model geometry.
Schematic depicts a patterned gecko surface (pattern of four setae represented as yellow pillars) filled with water (blue) both prior to and during contact with the substrate (either glass or PMMA) in air (white space).
Figure 4.
Tokay gecko (Gekko gecko) active and passive toe pad drying patterns.
Appearance of toe pads at 15-soak in non-stepping (A) and stepping (B) groups. Areas that are grey in color are wet and areas that are white in color are dry. Without stepping toes heterogeneously dry, where some toes are wet and others show an irregular evaporation line (A). Conversely, when allowed to actively step toes dry in a more homogenous fashion, where the outside of the toe dries first, leaving a wet patch (grey in color) in the center of each of the toes (B).
Figure 5.
Schematic of the self-drying model.
Schematic depicts a patterned gecko surface (pattern of four setae represented as yellow pillars) filled with water (blue) nearly contacting a substrate (glass or PMMA). Using the tree frog adhesive system as a model, we describe the inter-setal distance or microchannel width as W and the height of the intervening water layer as h. During a step, where the gecko setae approach the substrate, h→0 and W>h (purple arrow), causing water to move out of the microchannels (small purple arrows). When the gecko removes the foot, using digital hyperextension, h increases and at h>W (red arrow), remaining water is moved back into the microchannels (small red arrows). The movement of water in and out of the microchannels is due to the pressure difference in the microchannels and thin water film.