Dec 17 2018
It may soon become a lot less painful to rip off a Band-Aid. A new type of adhesive designed by the scientists from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) and Xi’an Jiaotong University in China can strongly adhere wet materials—such as living tissue and hydrogel—and be easily detached using a specific frequency of light.
These two hydrogels, adhered with an aqueous solution of polymer chains, come apart easily In the presence of UV light. (Image credit - courtesy of Zhigang Suo/Harvard SEAS)
The new adhesives could be used to attach and painlessly detach wound dressings, wearable robotics, and transdermal drug delivery devices.
The paper has been published in Advanced Materials.
“Strong adhesion usually requires covalent bonds, physical interactions, or a combination of both,” said Yang Gao, first author of the paper and researcher at Xi’an Jiaotong University. “Adhesion through covalent bonds is hard to remove and adhesion through physical interactions usually requires solvents, which can be time-consuming and environmentally harmful. Our method of using light to trigger detachment is non-invasive and painless.”
The adhesive consists of an aqueous solution of polymer chains spread between two, non-sticky materials—similar to jam between two slices of bread. On their own, the two materials stick poorly together but the polymer chains serve as a molecular suture, stitching the two materials together by creating a network with the two preexisting polymer networks. This process is called topological entanglement.
When ultraviolet light is beamed on the area, the network of stitches dissolves, causing the two materials to separate.
The scientists, led by Zhigang Suo, the Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials at SEAS, experimented with adhesion and detachment on a variety of materials, sticking together hydrogels; hydrogels and elastomers; hydrogels and organic tissue; elastomers; and hydrogels and inorganic solids.
“Our strategy works across a range of materials and may enable broad applications,” said Kangling Wu, co-lead author and researcher at Xi’an Jiaotong University in China.
While the scientists concentrated on using UV light to cause detachment, their work indicates the prospect that the stitching polymer could detach with near-infrared light, a feature which could be applied to a variety of new medical procedures.
In nature, wet materials don’t like to adhere together. We have discovered a general approach to overcome this challenge. Our molecular sutures can strongly adhere wet materials together. Furthermore, the strong adhesion can be made permanent, transient, or detachable on demand, in response to a cue. So, as we see it, nature is full of loopholes, waiting to be stitched.
Zhigang Suo, Allen E. and Marilyn M. Puckett Professor of Mechanics and Materials, SEAS
This research was aided by the National Natural Science Foundation of China and by the NSF MRSEC.