Snails produce a mucous that functions like super-glue, enabling them to stick to rough surfaces such as rocks.
Motivated by this feature of snail biology, researchers at the University of Pennsylvania, Lehigh University, and the Korea Institute of Science and Technology have developed an “intrinsically reversible,” super-glue-like material. Simply put, it can be separated easily from the surface to which it was adhered.
Adhesives are used ubiquitously in everyday life as well as in industrial applications. It is difficult to achieve strong adhesion and reversibility (or the ability to reverse the adhesion). Anand Jagota, professor and founding chair of Lehigh University’s Department of Bioengineering, stated that this is particularly true in the case of hydrogels, which consist of 90% water.
According to him, adhesives generally come under one of two categories: strong but irreversible, such as super-glues, or reusable and reversible but weak.
The research group was able to overcome these challenges. They have described the study outcomes in a paper titled “Intrinsically reversible superglues via shape adaptation inspired by snail epiphragm” published on June 17th, 2019 in Proceedings of the National Academy of Sciences.
We report a hydrogel-based, reversible, superglue-like adhesive by combining the benefits of both liquid and dry adhesives in a single material.
Anand Jagota, Professor and Founding Chair, Department of Bioengineering, Lehigh University
The scientists explain that upon being hydrated, the softened gel developed by them conformally adapts to the target surface via low-energy deformation, which is subsequently locked when dried in a way comparable to the action of the epiphragm of snails.
An epiphragm is a temporary structure produced by mollusks and snails. It is composed of dried mucus, retains moisture at the time of inactivity, and allows snails to stick to surfaces such as rocks.
The researchers demonstrate that it is possible to achieve reversible super-strong adhesion from a non-structured material upon fulfilling the condition of shape adaption, with very less residual strain energy stored in the system. The scientists report that the new material can be applied to flat as well as rough target surfaces.
We demonstrate that in this system adhesion strength is based on the material’s intrinsic, especially near-surface, properties and not on any near surface structure, providing reversibility and ease of scaling up for practical applications.
Shu Yang, Study Lead Author and Professor of Materials Science and Engineering and Chemical and Biomolecular Engineering, University of Pennsylvania