Post-it Frogs, Doesn't Lose Grip

The toe pads of tree frogs and crickets have inspired a new supersticky—yet reusable—adhesive, scientists report.

The material is the latest example of a boom in adhesives that take their cues from nature's greatest clingers: frogs, lizards, and insects.

For example, several science teams have fabricated adhesives that directly mimic the microscopic, spatula-tipped hairs on gecko feet.

Another breakthrough is "geckel," an adhesive combination of gecko hairs and mussel proteins.

The new adhesive, however, does not exactly imitate the natural structures of frog and cricket toe pads, said Anand Jagota, an adhesion scientist at Pennsylvania's Lehigh University who was not involved in the study.

"[It] captures the physics rather than ... the actual structure," he said.

Lead study author Abhijit Majumder and colleagues at the Indian Institute of Technology in Kanpur describe the new adhesive in tomorrow's issue of the journal Science.

Preventing Cracks

Conventional tape cracks when it is pulled off a surface. The cracks enable removal, but usually also render the tape useless for reapplication, the authors said.

The toe pads of tree frogs and crickets, on the other hand, contain microscopic channel patterns that prevent cracking.

The researchers embedded the same type of microchannels in the new adhesive, which thwarted cracks, said study co-author Animangsu Ghatak.

In addition, the researchers found they could increase the adhesive strength by partially filling the microchannels with fluid. The surface tension of the liquid creates a capillary effect—the ability of one substance to draw another toward it like a sponge soaking up water.