muri low-level control biomimetic robots - onr site visit - august 9, 2000 background 20 m 1 cm 75 ...
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MURI
Low-LevelControl
Biomimetic Robots - ONR Site Visit - August 9, 2000
Background
20 m1 cm 75 m 1 m
• Geckos are known for their remarkable wall-climbing ability.
• Microscopic structures on toe pads are responsible for adhesion.
MURI
Low-LevelControl
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.
MURI
Low-LevelControl
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.
MURI
Low-LevelControl
Biomimetic Robots - ONR Site Visit - August 9, 2000
Measurement Methods
1. 25m Al wires
2. A micromachined 2-axis piezoresistive force sensor.
MURI
Low-LevelControl
Biomimetic Robots - ONR Site Visit - August 9, 2000
Typical Force Curves
0 2 4 6 8 10-100
-50
0
50
100
150
200
Time (sec)
Sensor Output (N)
0 2 4 6-50
0
50
Time (sec)
Sensor Output (N)
D
A
BC
VerticalLateral
• To facilitate adhesion: preload & lateral pull
MURI
Low-LevelControl
Biomimetic Robots - ONR Site Visit - August 9, 2000
Adhesion vs. Preload
• Measured frictional coefficient 0.25.
• Detachment force increases with increasing preload.
Line fit :y = 2.9x + 9.0R2 = 0.77
0
10
20
30
40
50
60
70
0 5 10 15Preload (uN)
Det
achm
ent F
orce
(uN
)
Frictional force
MURI
Low-LevelControl
Biomimetic Robots - ONR Site Visit - August 9, 2000
Detachment Angle
Detachment at 30
>30º
MURI
Low-LevelControl
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.
MURI
Low-LevelControl
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.