Researchers have created a highly sensitive and effective sensor out of an unusual combination of materials - graphene sheets and a commercial polymer known as Silly Putty. The combination yielded a sensor sufficiently responsive to detect heart rates through human skin, and even a spider's tiny footsteps scuttling across the material. In recent years, graphene has gained much interest in the scientific community because of its exceptional physical characteristics; it is often added to other materials to enhance their electrical, mechanical, or barrier properties. Yet the addition of graphene to materials that are both viscous (tending to resist flow) and elastic (capable of returning to their original shape) has remained largely unexplored. Here, Conor Boland and colleagues added sheets of graphene to lightly cross-linked silicone polymers - the same stretchy material that children play with, in the form of Silly Putty. They dubbed the new combined material "G-putty." A closer look at G-putty under the microscope revealed that the nanosheets of graphene become arranged in a dense and uniformly oriented network. In testing the conductivity of G-putty, the researchers found that resistance within the material increases sharply as pressure is applied, but that this response changed with time as the graphene sheets could move within the soft putty material. These qualities suggest that it would make an excellent sensor. Indeed, G-putty's sensitivity values surpass those of most strain sensors, the authors report. They tested the unique substance in various experiments, finding that it can sense joint motion, breathing, and heartbeat. Lastly, they report that G-putty can detect the individual footsteps of a spider. The researchers' new material - a breakthrough in the field of composites - has an array of possible technological applications.