MURI Background LowLevel Control 1 cm Geckos are
MURI Background Low-Level Control 1 cm • Geckos are known for their remarkable wall-climbing ability. • Microscopic structures on toe pads are responsible for adhesion. 75 m 20 m 1 m Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Low-Level Control • 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. Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Experimental Goals Low-Level Control • 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. Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Low-Level Control Measurement Methods 1. 25 m Al wires 2. A micromachined 2 -axis piezoresistive force sensor. Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Typical Force Curves Sensor Output ( N) 50 B C 0 D A -50 0 200 Vertical Lateral Sensor Output ( N) Low-Level Control 150 100 50 0 -50 2 Time (sec) 4 6 -100 0 2 4 6 Time (sec) 8 10 • To facilitate adhesion: preload & lateral pull Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Low-Level Control Adhesion vs. Preload • Measured frictional coefficient 0. 25. • Detachment force increases with increasing preload. Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Low-Level Control Detachment Angle >30º Detachment at 30 Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Low-Level Control 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. Biomimetic Robots - ONR Site Visit - August 9, 2000
MURI Low-Level Control Spinoff Application : Artificial Adhesive Structures • Many applications for a manufactured adhesive material. • We are investigating microfabrication methods to constructures similar to gecko setae. • Commercial interest: a patent being filed (Berkeley, Lewis & Clark, and Stanford) is already the subject of a license negotiation with 3 M. Biomimetic Robots - ONR Site Visit - August 9, 2000
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