Five Ten’s Mi6 sticky rubber may have gotten Tom Cruise up the side of a glass building in Mission Impossible, but now a group of students at Stanford University created something even stickier. Mimicking the natural properties of gecko feet, the new synthetic adhesive enables robots and even humans to climb vertical surfaces with ease.
Developed by Stanford Ph.D. student Elliot Hawkes, the synthetic adhesive consists of arrays of microscopic wedges made from silicone rubber, similar to what you’d find in a cooking spatula. When unloaded, the material is non-sticky as only the sharp tips of the wedges make contact with the surface. However, if you gently touch it to a surface and then apply a tangential load, the microscopic wedges bend over and form a continuous contact area that is large enough for van der Waals forces (the same forces a gecko uses to scale walls) to produce significant adhesion.
Unlike other adhesives, the gecko-inspired material delivers the same strength at all sizes. The key to making the adhesive stick under human size loads was to first ensure close contact to a surface at all times, as no surface is perfectly flat. The Stanford team did this by creating paddles divided into 24 different postage stamp-sized tiles, with tendons and softening springs to ensure the load is distributed evenly between them.
As most of the load goes to your feet when climbing, small climbing rungs were attached by rope to the paddles, enabling Hawkes to scale a vertical glass wall. The adhesive is controllable–lifted straight up from the surface the gecko tiles release instantly. But when the sheer force of gravity pulls the tiles sideways when climbing, the wedges bend over and come into contact, creating more adhesion.
Don’t count on climbing vertical rock faces just yet, as the adhesive needs a smooth surface to adhere to–glass, plastic panels, painted or varnished wood panels, and metal. But Hawkes is supposedly already looking into the possibility of making gloves that could aid rock climbers in ascending more difficult faces.
Ready to climb 6.0 anyone?