Researchers at the University of Pennsylvania have developed a gecko-inspired gripper. Like the gecko, the device has the ability to grip and release smooth surfaces like glass. The effective stickiness can also be tuned from strong to week.

Unlike other similar technologies, the Penn team’s gripper features a simpler, two-material structure that is easier to mass produce.

At their current millimeter-scale size, the grippers can be used for moving smooth, fragile components, like silicon wafers or glass sheets. Scaled down, they could be employed in arrays to grip to a range of rough and smooth surfaces, making them useful for climbing robots and other larger-scale applications.

The pads of a gecko's feet are sticky because of a phenomenon known as van der Waals adhesion, which is present any time two surfaces are in close contact; the closer the contact, the stronger the attraction. By changing the angle of its feet, a gecko may "tune” its adhesion.

The university team's approach to tunability relies on a gripper with a fundamentally different structure. Rather than being angled or flared, the structure is a set of simple cylindrical posts. A hard plastic core is surrounded by a softer silicone rubber shell. The soft rubber conforms to the roughness of the surface.

To detach the posts, the researchers apply a lateral force, which shifts the stress back to the edge and allows the crack to easily begin from the outside position.