An academic research team with members from Duke Kunshan has completed a study of gecko-inspired adhesives with a wide range of applications from medical tape to safety devices for mountain climbers.
Published by the American Chemical Society science journal Langmuir, the research provides an insight into the design and fabrication of adhesives with anisotropic adhesion behavior – strong grip and easy release – which would simplify the fabrication process and lower manufacturing costs.
“Researchers have previously mimicked the adhesive qualities of a gecko’s grip using conventional and complex fabrication methods,” said Weiwei Shi, assistant professor of material science at DKU, who worked on the project.
“We have been able to replicate the anisotropic adhesive qualities – the ability to change grip in different directions, which allows a gecko to grab and release – involving the 3D printing process and soft lithography,” she added.
Shi worked with Ke Cheng, a professor at North Carolina State University and UNC Chapel Hill, using micro-precision 3D printing, to create a patterned surface material with asymmetrical tilting micro-pillars, to mimic the hairs on a gecko’s feet. Like a gecko, the material showed anisotropic adhesion behavior, meaning it could be easily attached or detached depending on direction of pull, while still demonstrating a strong grip.
They measured the material’s adhesive forces using a universal materials tester, recording their results automatically to a connected computer. The material’s ability to release its grip was tested on a customized set-up in the team’s laboratory, using a jack and hanging weight, connected through a pulley via a high-strength thread.
“Our structured adhesives outperformed plain surfaces in terms of grip by four times under certain loads,” said Shi.
“They also exhibited anisotropic adhesion behaviors with two-fold stronger adhesion along the grip direction than the release direction due to the asymmetric stress distributions at the edges of the contact interface, as well as the stresses caused by the moment created when the top is sheared,” she added.
The research could help to bring down the complexity and therefore cost of manufacturing adhesives where a strong grip and easy release are helpful, such as medical sutures and soccer goalkeeping gloves, said Shi.
The team is now looking at the possibility of conducting further research focusing on the practical applications of structured adhesives with a view to learning more about their properties, such as durability and degradation.
Author: John Butcher
