The rapid advancements in flexible electronic technology have revolutionized various industries, giving rise to innovative devices such as foldable displays, wearables, e-skin, and medical devices. However, these breakthroughs have also created a growing demand for flexible adhesives that can effectively connect different components in these devices while maintaining their shape and adhesive strength. Conventional pressure-sensitive adhesives (PSAs) have struggled to strike a balance between recovery capabilities and adhesive strength, presenting a critical challenge in the field.
In an extraordinary study conducted at UNIST (Ulsan National Institute of Science and Technology), a team of researchers led by Professor Dong Woog Lee from the School of Energy and Chemical Engineering have successfully synthesized new types of urethane-based crosslinkers that tackle this challenge head-on. By developing novel crosslinkers utilizing m-xylylene diisocyanate (XDI) or 1,3-bis(isocyanatomethyl)cyclohexane (H6XDI) as hard segments and poly(ethylene glycol) (PEG) groups as soft segments, they have achieved significant improvements in recoverability compared to traditional methods.
The team incorporated these newly synthesized materials into pressure-sensitive adhesives, resulting in a remarkable breakthrough. The PSA formulated with H6XDI-PEG diacrylate (HPD) demonstrated exceptional recovery properties while maintaining high adhesion strength, measuring approximately 25.5 N 25 mm−1. Through extensive folding tests totaling 100k folds and multi-directional stretching tests spanning 10k cycles, the PSA crosslinked with HPD exhibited remarkable stability under repeated deformation. This showcases its potential for applications that require both flexibility and recoverability.
Even when subjected to strains up to 20%, the adhesive displayed high optical transmittance of over 90%. This makes it ideal for fields such as foldable displays that demand not only flexibility but also exceptional optical clarity. The adhesive formulated with HPD retains its transparency even under significant strain, paving the way for the development of advanced electronic products.
Professor Lee comments on the significance of this breakthrough in adhesive technology, stating, “This breakthrough in adhesive technology offers promising possibilities for electronic products that require both high flexibility and rapid recovery characteristics.” The research conducted at UNIST addresses the long-standing challenge of balancing adhesion strength and resilience, opening up new avenues for the development of flexible electronic devices.
Hyunok Park, a researcher involved in the study, emphasizes the significance of this research by stating, “The introduction of this new crosslinking structure has led to an adhesive with exceptional adhesion and recovery properties.” The novel urethane-based crosslinkers developed by the research team offer a game-changing solution to the challenges faced by conventional pressure-sensitive adhesives.
The groundbreaking research conducted at UNIST has unlocked new possibilities for the future of flexible electronic devices. By successfully synthesizing urethane-based crosslinkers, the team has addressed the critical challenge of achieving a balance between recovery capabilities and adhesive strength. This breakthrough offers a promising path for the development of advanced electronic products that demand both flexibility and rapid recovery characteristics, revolutionizing industries such as display technology, wearables, and medical devices.