South Korean scientists have found a way to build flexible pressure sensors more easily by mimicking the suction cups on an octopus’ tentacles—a development that could help facilitate the manufacture of bio-adhesives that combine reversibility, repeated usage, stronger bonds and faster bonding time.

An octopus uses its tentacles to propel itself from one location to the next, employing suction cups underneath each tentacle for gripping. Each suction cup contains a cavity whose pressure is controlled by the surrounding muscles. These can be made thinner or thicker on demand, increasing or decreasing air pressure inside the cup and allowing for sucking and releasing as desired.

A photograph of an octopus tentacle with suckers (left) and a magnified SEM image of an octopus sucker. Image credit: UNIST.Hyunhyub Ko, professor in the School of Energy and Chemical Engineering at Ulsan National Institute of Science and Technology, and his colleagues have now engineered "smart" adhesive pads by successfully mimicking the muscle actuation of the octopus' suction cups to control cavity-pressure-induced adhesion. The team utilized the rubbery material polydimethylsiloxane to create an array of microscale suckers that incorporate pores coated with a thermally responsive polymer to create sucker-like walls.

The researchers discovered that the best way to replicate the organic nature of muscle contractions was through applied heat. At room temperature, the microcavity arrays within the octopus-inspired smart adhesive pad sit in an "open" state, but when the pad is heated to 32 degrees Celsius, the walls contract, creating suction and thereby allowing the entire pad to adhere to a material (mimicking the suction function of an octopus). The adhesive strength also spiked from .32 kilopascals to 94 kilopascals at high temperature.

Ko and his team expect that their smart adhesive pads can be used as the substrate for wearable health sensors, such as in bandages that stick to the skin at normal body temperatures but fall off when rinsed under cold water.