The Future is Here: Self-Healing Metal

self-healing_metalYou’ve heard of self-healing concrete, you’ve heard of self-healing polymers. And now, it seems that researchers at MIT have found a way to make metals heal themselves after tiny cracks form. As the latest in a series of materials that is capable of maintaining itself, this discovery could very well help pioneer the revolution in manufacturing everyone has been waiting for.

Led by graduate student Guoqiang Xu and professor Michael Demkowicz, the process of getting metals to heal themselves was made almost entirely by accident. The discovery first came when they were modelling a sheet of nickle and tiny microscopic cracks were applied. Once tension was applied, the cracks became smaller and then disappeared as the edges fused together.

crystallineApparently, the key has to do with the fact that most metals are composed of microscopic crystalline grains, the size and orientation of which affect the overall strength and characteristics of the material. Nickel has always been of interest because of its use in so many superalloys, many of which are used in harsh environments – jet turbines, deep sea oil rigs, heavy industry joints.

It turns out that the grains making these materials so strong are not as static as scientists thought. As the metal is pulled outward, the edge of the crystalline grains begins to migrate and can eventually fill in the crack completely. The migration of this crystalline boundary is what heals the gaps in the material. And while it is not exactly polymorphic alloy (see pic below), its certainly big news.

metal_fatigueAnd while researchers have only been able to reproduce this healing behavior with cracks at the microstructural level (known as disclination), these micro-defects are the source of much larger and sometimes catastrophic cracks and metal fatigue. The geometry of disclinations can actually reverse an applied force locally, which is how the tension leads to the metal pulling itself back together.

The team believes this newfound knowledge can be used to prevent superalloys from accumulating structural cracks that could lead to real damage with time. Materials could also be designed to direct damage into disclination-type structures, areas that could absorb damage and then heal themselves. Given time, it could even lead to metals that don’t weaken with age.

t1000Still, you shouldn’t be expecting something like this guy anytime soon! And be sure to enjoy this brief but poignant video of the self-healing effect in action:


The Future is Here: Self-Healing Polymer

t1000I’ve heard of biomimetics – machinery and synthetics that can imitate organic materials – but this really takes the cake! In an effort to pioneer components and devices that would posses the regenerative powers of skin, a Spanish researcher Ibon Odriozola – who works for the CIDETEC Centre for Electrochemical Technologies in Spain – has created a polymer that could lead to a future where repairing machinery is as easy as suturing an open wound.

Comprised of a poly (urea-urethane) elastomeric matrix, the material is basically a network of complex molecular interactions that will spontaneously cross-link to “heal” most any break. In this context, the word “spontaneous” means that the material needs no outside intervention to begin its healing process, no catalyst or extra reactant.

healing-polymer-headerTo experiment with the material, Odriozola cut a sample in half with a razor blade at room temperature. And in just two hours, the cut healed itself with 97% efficiency. The reaction, called a metathesis reaction, has led Odriozola to dub the material his “Terminator” polymer, in reference to you-know-who (pictured above). Though the transition process takes a little longer, and involves polymers instead of metal, the basic principle is the same.

Unlike other self-healing materials, this one requires no catalyst and no layering. In addition to being very impressive to behold, this technology can extend the life spans of plastics that are under regular stress.  The group’s main goal now is to make a harder version, perhaps one that could be formed into such parts itself. As it exists today, the polymer is squishy and somewhat soft.

???????????In addition, a good self-healing material like this is a boon for ongoing efforts to find a viable material for artificial skin. Self-healing technology could also open the door to growth materials, as new units of the matrix could be incorporated as the material stretches and tears on the microscopic level. This would be especially useful when it comes to artificial skin, since it could grow over time and remove the need for replacement.

And if the healing mechanism proves strong enough, it could even be used as an adhesive or a sealant in other materials and even electronics. Just think of it! Everything from windows, to personal devices, to joints that are in need of padding. A simple injection of this type of material, and the breaks and aches go away. And given the progress being made with androids and life-like robots, its use as a source for artificial skin could go a long way to making them anthropomorphic.

And as usual, there’s a cool demonstration video. Enjoy!