Welcome Physics World  November 2020

The materials at hand

A handy liquid-metal lattice. (Courtesy: Pu Zhang)

“Materials science explores the kinds of things you can find in an average 10-year-old’s pocket.” That, at least, is the view of Lin Hobbs, a materials scientist whose lifelong interest in everyday substances is the subject of a charming profile in Physics World (“It’s a material world” by Robert P Crease, September 2020). Hobbs’ own career at the Massachusetts Institute of Technology offers an excellent case in point: much of his research there focused on “salt, sand, string, rust and bone”, while his post-retirement interest in green silicate glass bottles (as well as the wine inside them) suggests a depth of interest stretching well beyond the day job.

Yet even as I read about Hobbs’ work, I had a nagging feeling that his view of materials science represents only one side of the story. The other side is nicely encapsulated by Deji Akinwande, an applied physicist and electrical engineer whose group recently developed flexible electronic switches made from 2D materials. None of these materials existed 20 years ago, and their numbers are staggering. “It’s not one or two or five or a dozen materials,” Akinwande observes. “We’re talking about a thousand materials, and there’s a lot in this landscape that is undiscovered from a basic physics and science point of view.”

It would be very unusual indeed for 10-year-olds to keep these new 2D materials in their pockets. The same is true for many other substances that appear in this Physics World Materials Briefing. The ferroelectric nematic liquid crystal shown on the cover is the first of its kind. So, too, is the futuristic hand pictured above, which is made from a liquid-metal lattice that returns to its original shape when crushed. Then there’s the hydrogel that cools solar photovoltaic panels, the photocatalyst that converts carbon dioxide and water into formic acid, the ultra-porous metal-organic framework that can store 66% of its own weight in methane, and so on.

None of these examples, however, is intended to downplay the importance of the everyday. The fact that common materials like silk and tooth enamel still harbour so many mysteries, despite being known to humans since antiquity, is surely one of the reasons why materials research is such a vibrant discipline. So whether you’re fascinated by the familiar or excited by the exotic, I hope you find something in this Briefing that’s intriguing enough to remind you why you entered the field in the first place.