Material sample with a healed break [Image: Dr. Keivan Davami]
A team of researchers from Lamar University in Texas, led by assistant professor Dr. Keivan Davami, recently developed a self-healing material using advanced SLA 3D printing technology, which has all kinds of applications, from fixing shoe soles and cell phone screens to cartilage. By exposing the material to UV light, it is capable of “autonomic self-repair,” and the researchers believe that it could help reduce how much waste is generated when a material is damaged – if it can heal itself, the damage can be repaired without any waste.
Dr. Davami, who is also the director of the university’s Nano-Micro-Macro manufacturing group, and his group published a paper on their work, titled “Additively Manufactured Self-Healing Structures with Embedded Healing Agent Reservoirs,” in Scientific Reports; co-authors are Mehrdad Mohsenizadeh, Morgan Mitcham, Praveen Damasus, Quintin Williams, and Michael Munther.
The team’s material was inspired by nature – the seal-healing resin is trapped inside the material through a series of reservoirs, and it’s only released when a fracture occurs. Does this sound familiar? It’s comparable to the microvascular blood networks in our skin that, when injured, help restore our tissue. Only in this case, rather than blood coming up to an injury’s surface, capillary action allows the UV-sensitive resin to escape, so that only the necessary amount is used in order to fix isolated damage.
“Self-healing materials with the ability to partially or completely restore their mechanical properties by healing the damage inflicted on them have great potential for applications where there is no or only limited access available to conduct a repair,” the researchers wrote. “Here, we demonstrate a bio-inspired new design for self-healing materials, where unit cells embedded in the structure are filled with a UV-curable resin and act as reservoirs for the self-healing agent. This design makes the repeated healing of mechanical damage possible. When a crack propagates and reaches one of these embedded reservoirs, the healing agent is released into the crack plane through the capillary action, and after polymerization through UV light exposure, bonds the crack faces. The structures here were fabricated using a stereolithography technique by a layer-by-layer deposition of the material. “Resin trapping” as a unique integration technique is developed for the first time to expand the capability of additive manufacturing technique for creating components with broader functionalities. The self-healing materials were manufactured in one step without any needs for any sequential stages, i.e. filling the reservoir with the healing agent, in contrast with the previously reported self-healing materials. Multiscale mechanical tests such as nanoindentation and three-point bending confirm the efficiency of our method.”
As a story in New Atlas explained it, “As long as those objects remain undamaged, the liquid stays contained. If the polymerized resin gets cracked, however, capillary action draws some of the liquid resin out. Once quickly exposed to an artificial UV light source, that liquid resin then polymerizes, sealing up the crack.”
[Image: Dr Keivan Davami]
According to the university, hardly any intervention other than short exposure to UV light will be necessary to repair any damage the material sustains, due to the “autonomic functionality of the self-healing mechanism.” The UV light exposure can be done remotely, which will be especially helpful when it comes to device components that are difficult to reach.The potential benefits of this self-healing 3D printable material are far-reaching – it would be far quicker to use the material to fix everyday items that are easily damaged, like device components, eyeglasses, and tools. In addition, if more items are made with this kind of self-repairing mechanism, the amount of waste delivered to landfills due to broken products would be drastically reduced.
For their paper, Dr. Davami’s research group fabricated test specimens of their material, which were designed in SOLIDWORKS, on the Formlabs Form 2 SLA 3D printer. They are now working to further develop the technology, with the goal of reducing how much light energy is required to cause the self-healing. This would mean that human intervention would not be necessary, and self-repair could occur with only ambient UV sources, like sunlight.
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