The researchers created a polymer film containing caffeic acid, an organic acid found in plants, as their adhesive. Once exposed to a specific wavelength of UV light, the adhesive becomes inert. "This film shows no adhesion when stored at room temperature," the researchers explain, "but can be repeatedly bonded and unbonded when heated." The principle is similar to old-school lick-and-stick stamps, except these stamps can be un-licked and cleanly detached.
"Furthermore, when the film is exposed to 254 nm UV light at the end of its service life, the cross-linked portions break and return to the same state as before application, allowing both the adhesive and the substrate to be recovered and reused."
In other words: Your smartphone that's irreversibly glued together, and thus difficult to recycle? It could be heated up (we assume the required temperature is well above normal conditions) and separated into parts. Any adhesive residue could be cleared off with UV light, making the parts easier to recycle.
"With increasing awareness of the need to balance environmental concerns with economic growth, there is a demand for technologies that enable the separation and recovery of multi-component molded products."
"In future research, the team will investigate the effectiveness of this adhesive in repairing various technologies, including electronic devices, transport equipment, medical equipment and physical infrastructure with the aim of contributing to a circular economy."
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