Special types of plastic gels that can be induced chemically to undergo self-oscillating changes in shape and color have been known for many years. Van Vliet and Balazs have now found that the oscillations of these self-beating gels can be controlled by their shape and size, as well as by externally applied forces. With change in chemistry, the gels can oscillate on their own from red to blue or green to yellow, for many hours. When these gels are made small enough (
Figures: Images of plastic gels undergoing color changing self-oscillations that can be controlled by shape and size of the gel. These new experiments (top of image below) validate computational simulations (bottom of image below) of the oscillations, to enable design of new materials and devices.