Engineers at the Ulsan National Institute of Science and Technology (UNIST) were recently inspired by another amazing octopus attribute: their tentacles.
The researchers have been working towards developing an adhesive with the following properties:
- Reversibility
- Repeated usage
- Stronger bonds and faster bonding time
- No toxicity
- Effectiveness in wet conditions and other various extremes
After studying the suction capabilities of octopus tentacles, a tentacle-inspired bio-adhesive could meet all these criteria.
According to the team, “Flexible pressure sensors might give future prosthetics and robots a better sense of touch; building them requires a lot of laborious transferring of nano- and microribbons of inorganic semiconductor materials onto polymer sheets.”
To facilitate transfer printing, the team, led by Hyunhyub Ko at UNIST’s School of Energy and Chemical Engineering, further studied tentacles to develop an adhesive that could match their suction properties.
Octopus Tentacle Suction Cups
Octopus movement is governed by suction cups under each tentacle—each suction cup contains a cavity, the pressure of which is controlled by surrounding muscles. By changing the air pressure inside the cup, the octopus can make its cavities thinner or thicker in order to provide the necessary release or suction.
By imitating how octopus’ muscles work for contraction and release, Ko and his team engineered smart adhesive pads.
Schematic representation of microcavity arrays within the octopus-inspired smart adhesive pad. (Image courtesy of UNIST.)
They used a silicon-based organic polymer, polydimethylsiloxane (PDMS), to create microscale suckers. PDMS is also nontoxic and nonflammable. By adding the component of pores coated with thermally responsive polymers, adhesives function similar to how muscles contract and release.
Tests showed that the walls of the pads contract when the material heats to 32ºC, creating suction. At room temperature, each wall pit remains in an ‘open’ state. Application of high temperature increases adhesive strength from 0.32 to 94 kilopascals.
Applications for Smart Adhesive Pads
The team also reported that they made some indium gallium arsenide transistors that sat on a flexible substrate and used it to move nanomaterials to a different type of flexible material. This means that the smart adhesive pads can act as a substrate for wearable health sensors. Other applications include Band-Aids or sensors that stick to skin at normal body temperatures and fall off when rinsed under cold water.
For another example of biomimicry in engineering, check out this article on developing smarter concrete.