Researchers from Illinois have introduced a new, state-of-the-art reusable adhesive that activates in seconds, runs under water, and is strong enough to do a 11-pound ground survey: polymers with shape memory (SMPs).
The team – Associate Professor in Science and Mechanical Engineering Seok Kim, student Jun Kyu Park and former graduate student Jeffrey D. Eisenhaure (PhD ME & # 39; now with Northrop Grumman) – proved that SMPs can retain adhesion properties while submerged. His study, "Reversible Underwater Dry Adhesion of a Polymer with Shape Memory," was recently published in the scientific journal Advanced Materials Interfaces (Wiley-VCH).
Classified as a smart material, SMPs have the ability to manually transition between the original state and a deformed state. By manipulating the state of their SMPs, Kim and her team achieved successful adhesion to water-submerged surfaces as well as to other liquid media such as oil.
"Dry adhesives, such as those inspired by gecko feet, are believed to be unsuitable for high adhesion to a wet or submerged surface," Kim said. "However, this belief was nullified because of our SMP reversible dry adhesives."
By applying pressure to the submerged SMP in its original rubber state, the liquid can be squeezed from the contact interface. Under sufficient pressure, the SMP then transits into a vitreous state, essentially creating an airtight contact condition which maintains a highly strong dry adhesion. However, this state is not permanent; the shape retrieval properties of the SMP allow the adhesion reversal. In addition, because the SMP can make the transition smooth between the two states, its membership is reusable.
The researchers found that the maximum adhesion strength of SMP, while submerged in a freshwater condition, was 18 atm, which is at least 18 times greater than that of vacuum suction cups. Similar results were obtained for submersion in salt water and oil. They performed several experiments to explore the applications of their SMPs – for example, they used the adhesive to attach a hook to a damp wall. Once the SMP joined, they managed to hang a backpack loaded on the hook without feeling any weakness in adhesion.
Seok Kim "These findings will result in reusable high strength adhesive fasteners for mounting on wet or submerged walls," said Kim, who plans to market its results through a start-up.
"The next step for this technology will be to further explore SMP adhesive systems to enable reversible adhesive claws."
This article has been republished from materials provided by the Faculty of Engineering of the University of Illinois. Note: Material may have been edited for length and content. For more information, please contact the cited source.
Reversible underwater dry adhesion of a shape memory polymer. Jun Kyu Park Jeffrey D. Eisenhaure Seok Kim. Advanced materials interfaces, https://doi.org/10.1002/admi.201801542.