A team of researchers led by Scott White at the University of Illinois have designed a revolutionary new prototype for a material that can self-heal after sustaining relatively large injuries.
The polymer developed by this group is host to two embedded “vascular” capillaries, and is designed such that damage sufficient to compromise its structural integrity evokes capillary rupture. This allows the contents of the capillary – polymer building blocks – to spill out and create a monolithic coating at the damage site. This mechanism is reminiscent of the process by which platelets coagulate to form solid scabs that “plug” wounds in the human body.
The team was able to achieve complete healing for the material from radial punctures of up to 9mm in diameter using just two capillaries under half a millimetre in diameter each. Instrumental to this high regenerative capacity is a strategic two-stage healing process – when a hole is punched through the material and the vessels are ruptured, two gelator (gel-forming) species contained separately in the two vessels rapidly cross-link to form a gel matrix that expands and covers the damaged area. HEMA monomers, which polymerize less rapidly, are supported in liquid form by the matrix before finally solidifying and restoring up to 62% of the original solid material’s strength. In the absence of the gelators, these building blocks are not held at the damage site long enough to polymerize and “bleeds out” due to gravity, resulting in a 33% reduction in the maximum puncture diameter that can be fully healed.
This strategy has achieved regeneration orders of magnitude greater than that seen in earlier notable works in this field (such as the “Terminator” polymer and the self-healing battery electrode). White’s team hope that their design could be applied in engineering fields such as aeronautics, where a self-healing material could save hundreds of lives. Closer to home, this development could mean an end to cracked Smartphone screens.