Image: Universal Studios
Scientists Invent Self-Healing Hydrogel Strong Enough to Replace Plastics
Hydrogels are not new. Contact lenses and replacement skin are just two examples of uses of these high-water content gels. But hydrogels currently suffer from problems like being too brittle or quite soft. This week in Nature, scientists announce the invention of a new type of hydrogel, one that could replace plastics.
The humble scientists reporting on their wonder material have only gone so far as to say that it could reduce our dependence on fossil fuels, solve environmental problems with plastics and... it is self-healing. Imaginative souls will immediately speculate on the amazing applications materials engineers might dream up. Visionaries have gone so far as to compare this new hydrogel to the liquid robot from Terminator 2. What is the trick? The University of Tokyo team led by Takuzo Aida abandoned the usual route of trapping water into the covalent bonds of a polymer matrix. Instead, they mixed water with a tiny amount of clay, a dendritic organic binding agent ("glue") and a polyacrylate salt. The polyacrylate causes the clay to disperse into thin Clay NanoSheets (CNSs) which then provide structural strength as they are bound up by non-covalent forces acting between the ingredients in the resulting gel. The addition of more clay can achieve a stronger material, but dimishes the transparency.
How does it work?
A covalent bond is like a nut and bolt: atoms are attached firmly together by a specific bond and if that bond is broken, it takes energy to put it all back together again. On a macro scale, it means once your plastic toy or tool is busted, it's busted.
You can think of a non-covalent bond as similar to the attraction of two magnets. If you bump one of the two connected magnets, and displace it a little bit, the magnet will be pulled back into its original position as soon as the object that bumped it gets out of the way. Also, this hydrogel retains catalytic properties of the organic "glue" to help out. The molecules will re-attach to each other, and the hydrogel is healed!
The "dendritic" part is pretty important too. The word dendrite means fingers; the organic glue and the surfactant used to shape the Clay NanoSheets used in this hydrogel both have fingers that reach out and grab the nearby elements, holding it all together. Like two children holding hands while skipping to school, reclasping across a separation is just a grasp away.
Image: Takuzo Aida and Nature
What Can a Self-healing Hydrogel do?
Well, the new hydrogel has been compared to the liquid robot from Terminator 2. It can be punched into mush but will slowy recover its solid form. It can be stressed to the point of failure, but will recover as soon as you turn your back.
The hydrogel takes only about three minutes to form, so it is attractive from an industrial processing perspective. The version written up in this report is strong enough to hold its own weight when suspended (image), but that is not so impressive next to the technical specs of your average polymer plastics. Nonetheless, scientists will be jumping to modify this recipe to come up with new materials with a whole range of great capabilities. Maybe early uses will include a dent-proof laptop case, or a stabilizer in industrial processes. But the imagination is the limit when it comes to materials engineering. Perhaps there are products we don't even know of yet that can be invented with this fantastic new material. Practically petroleum free.
And if it comes to a Terminator Robot....well, Amir Ahmed of the University of Toronto says it best: "Needless to say, an environmentally friendly alternative to traditional plastics in industry and in commerce would be a definite step up to lengthening the life of our civilization or, if they're used to make terminator robots, will at least make our final moments really, really cool."
Thanks to tipster Anne Schram.
More on Advances in Plastics:
Sun-Powered Self-Healing Plastic - The End of Scratched Gadgets?
Bioplastics Recycling Consortium Wants to Reuse Every Last Bit of Plastic
Earthshell Opens First Bioplastic Factory in Missouri
NEC Releases Phone Made With Bioplastic and Kenaf
Targets Introduces "Mirel" Bioplastic Gift Cards
Bioplastic Made from...Cow Poo?