ELECTROCHEMICAL MUSCLES - BENDING STRIPS BUILT FROM CONJUGATED POLYMERS

Conjugated polymers usually show gel properties with volume changes of 1-100% in response to various external stimuli. We find that the bending beam method provides an effective and sensitive way to detect and make use of these volume changes. Bipolymer strips made up of a polypyrrole (PPy) layer and a polyethylene layer bound together were prepared. These strips bend, corresponding to volume changes in the PPy layer, during electrochemical doping and undoping of PPy in aqueous solutions. The bending degree and speed depend on the thickness of the two polymer layers, and on dopants in the PPy layer and electrolytes in the solutions. We are able to obtain reversible significant bending back and forth in seconds. In addition, the bending beam method also provides a novel way to measure in-situ volume changes in conjugated polymers during doping-undoping.