Infectious biohazards seem to be unstoppable – horror stories of stubborn drug resistant infections picked up during a hospital visit are becoming more frequent. The trouble is that it’s currently very hard to tell whether or not a surface has been cleaned thoroughly of all such nasties. But a new idea in development could provide a versatile and simple tool – a biodegradable napkin, impregnated with antibodies to major bacteria and viruses that are designed to change colour in the presence of their enemies. One swift wipe of a surface could indicate the presence of pathogens without the need for extensive training. Ideal for the third world, or even battlefield surgeries, for example.