The greatest material on Earth?
So what would you vote as the greatest material on Earth? The question recently arose in discussion with an IOM3 colleague, and with the current media vogue for lists, leagues and assorted rankings, it would make for an interesting members’ vote.
There are probably as many opinions as there are readers of this column, but a common theme in the history of material science has been how natural products are being replaced by man-made alternatives. Nowhere is this more true than in the field of polymers, as was demonstrated admirably on BBC4’s recent How it Works programme entitled Plastics and presented by Mark Miodownik, Professor of Materials and Society at University College, London. Miodownik took a fascinating journey through nineteenth and twentieth Century developments of rubber and plastics, beginning with Charles Goodyear who, in 1839, first vulcanised natural rubber with the addition of sulphur, and moving on to John Wesley Hyatt who, in 1870, mixed cellulose nitrate (guncotton) with alcohol and camphor to create celluloid, widely recognised as the first moulded plastic. Rubber and celluloid were both adapted from natural products and it was not until 1909 that the first truly synthetic polymer was discovered by Leo Baekeland, who treated carbolic acid with formaldehyde to create the product that bears his name, Bakelite. Since then, nylon, polystyrene, polyester and PVC have all replaced natural products such as silk, cork, cotton, wool and wood to shape the world as we see it today.
In an interesting illustration of history going full circle, material scientists are now turning back to nature for inspiration. A good example of this was explained by Stanislav Gorb of the Zoological Institute at the University of Kiel in Germany. Researchers there have developed a silicone tape that not only boasts impressive bonding strength, but can also be attached and detached thousands of times without losing its adhesive properties. According to Gorb, this was inspired by the physiology of gravity-defying ceiling walkers, such as the dog beetle. The secret to this wall climbing ability lies in the thousands of tiny hairs that cover the beetle’s feet and legs, coupled with flattened tips that splay out to maximise contact. These make it sufficient for the Van der Waals forces, which operate at a molecular level and are relatively weak compared to normal chemical bonds, to provide the requisite adhesive strength that allows the beetle to scurry along walls and ceilings.
But there is one totally natural material that has traditionally evaded our ability to copy artificially, not least because the Statement of Requirements is so exacting. It is self-generating and self-repairing, while remaining completely waterproof, yet porous. It moulds itself into complex shapes and adapts to different uses. It is also completely organic and biodegradable: human skin. Traditionally, skin replacement has only been possible by painful and disfiguring skin grafts. But for a number of years, Avita Medical in Cambridge has been successfully harvesting patients’ skin cells to put in suspension. Those cells are then sprayed back on to the wound, where they multiply and create new skin tissue. The spray-on skin has been used in thousands of treatments with incredible results. Would this make it into the Materials World League – does it even count as a material in the strict sense? I’m not so sure, but it would be stimulating to have the debate.
What do you think?
If you had to vote for the greatest material on Earth, what would you pick? Vote for your choice or suggest your own in our Greatest material on Earth poll