A dash of graphene can transform the stretchy material known as Silly Putty into a pressure sensor that can monitor a human pulse and even the steps of a small spider.
Jonathan Coleman at Trinity College Dublin and his colleagues mixed graphene flakes — consisting of roughly 20 layers of carbon atoms, and measuring up to 800 nanometres in length — with homemade Silly Putty, a cross-linked silicone polymer. This produced a material, dubbed G-putty, that conducted electricity. Its resistance changed markedly when the authors applied the slightest pressure, making it more than ten times more sensitive than typical pressure sensors.
The team used G-putty to take accurate blood-pressure measurements and record the steps of a 20-milligram spider.