1. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 Background 20  m 1 cm 75  m 1  m Geckos are known for their remarkable wall-climbing ability. Microscopic structures on toe pads are responsible for adhesion.

2. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 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. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 Experimental Goals 1.Is van der Waals attraction the dominating adhesion mechanism? Comparing magnitudes of experimental data with calculated van der Waals attraction. 2.Kinematics of adhesion: Identifying important parameters for good adhesion.

4. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 Measurement Methods 1.  25  m Al wires 2.A micromachined 2-axis piezoresistive force sensor.

5. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 Typical Force Curves 0246810 -100 -50 0 50 100 150 200 Time (sec) Sensor Output (  N) 0246 -50 0 50 Time (sec) Sensor Output (  N) D A B C Vertical Lateral To facilitate adhesion: preload & lateral pull

6. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 Adhesion vs. Preload Measured frictional coefficient  0.25. Detachment force increases with increasing preload.

7. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 Detachment Angle Detachment at   30    >30º

8. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 Work in Progress 1.Further adhesion measurements using new device. 2.Effect of adsorbed water layer. 3.Comparison of Setae from other lizards and insects: anoles, skinks, and kissing bugs.

9. MURI Low-Level Control Biomimetic Robots - ONR Site Visit - August 9, 2000 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.