Background

1
Background

• Geckos are known for their remarkable
  wall-climbing ability.
• Microscopic structures on toe pads are
  responsible for adhesion.

2
Adhesion Mechanisms

• Many mechanisms have been suggested and
  experimentally rejected
• suction, friction, electrostatics, capillary wet
  adhesion, micro-interlocking.
• Only Remaining Theory
• Adhesion by van der Waals attraction.

3
Experimental Goals

• Is van der Waals attraction the dominating
  adhesion mechanism?
• Comparing magnitudes of experimental data with
  calculated van der Waals attraction.
• Kinematics of adhesion
• Identifying important parameters for good
  adhesion.

4
Measurement Methods

• ?25?m Al wires
• A micromachined 2-axis piezoresistive force
  sensor.

5
Typical Force Curves

• To facilitate adhesion preload lateral pull

6
Adhesion vs. Preload

• Measured frictional coefficient ? 0.25.
• Detachment force increases with increasing
  preload.

7
Detachment Angle
Detachment at ? ? 30?
8
Work in Progress

• Further adhesion measurements using new device.
• Effect of adsorbed water layer.
• Comparison of Setae from other lizards and
  insects anoles, skinks, and kissing bugs.

9
Spinoff Application Artificial Adhesive
Structures

• Many applications for a manufactured adhesive
  material.
• We are investigating microfabrication methods to
  construct structures similar to gecko setae.
• Commercial interest a patent being filed
  (Berkeley, Lewis Clark, and Stanford) is
  already the subject of a license negotiation with
  3M.