Self-beating plastic gels can be induced to change size and color on demand
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 (<1 mm), they can change their shape and color at the same time. Additionally, these researchers have shown that a non-beating gel can be made to self-oscillate simply by applying a force to the gel. These amazing effects were first predicted theoretically, and have now been confirmed by experiment. Such self-beating gels provide intriguing analogues for self-oscillating reactions in cells and tissues, and may find application as pressure sensors, pumps and acid sensors.
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.