| Title: |
Ultrahydrophobicity indicates a non-adhesive default state in gecko setae |
|
| Type: |
Journal Article |
|
| Secondary Title: |
J Comp Physiol A |
|
| Authors: |
Autumn, K.; Hansen, W. |
|
| Pages: |
1205-1212 |
|
| Volume: |
192 |
|
| Publication Year: |
2006 |
|
| Keywords: |
Adhesion, Contact mechanics, Locomotion, Reptilia, Nanotechnology |
|
| Abstract Excerpt: |
Geckos may represent the world’s most demanding adhesives application. The adhesive setae on the toes of climbing geckos must adhere strongly yet avoid fouling or attachment at inappropriate times. We tested the hypothesis that gecko setae are non-adhesive in their unloaded default state by comparing the water droplet contact angle (Ø) of isolated setal arrays to the smooth surface of eye spectacle scales of tokay geckos (Gekko gecko). At equilibrium, Ø was 98.3 ± 3.4 in spectacle scales of live geckos and 93.3 ± 3.5 in isolated spectacles. Isolated setal arrays were ultrahydrophobic, with Ø of 160.6 ± 1.3 (means ± SD). The difference in Ø of setal arrays and smooth spectacles indicates a very low contact fraction. Using Cassie’s law of surface wettability, we infer that less than 6.6% of the surface of unloaded setae is solid and at least 93.4% is air space. We calculated that the contact fraction must increase from 6.6% in the unloaded state to 46% in the loaded state to account for previously measured values of adhesion. Thus gecko setae may be non-sticky by default because only a very small contact fraction is possible without mechanically deforming the setal array. |
|
Email this referenceMaterial
Give feedback
Download a PDF