Dynamic antifouling structures and actuators using EAP composites

By utilizing strain gage technology it is possible to directly and continuously measure the electrochemically induced strain response of EAP actuators. Strain sensitive actuators were constructed by directly vapor depositing gold (EvAu) on polyimide strain gages which are capable of measuring strain with an accuracy of +/- 1 muepsilon. Strain sensitive actuators were used to evaluate the strain response of polypyrrole (PPy), poly(3,4-ethylenedioxypyrrole) (PEDOP) and poly(3,6-bis(2-(3,4-ethylenedioxy)thienyl)-N-carbazole) (PBEDOT-Cz). PPy was shown to produce significantly higher strain when compared to PEDOP and PBEDOT-Cz. The resulting overall strain for the materials was 236, 33, and 35 muepsilon respectively. From the initial investigation, adhesion of the EAP to the EvAu layer was identified as a major factor in the resulting lifetime and strain response of these actuators. Therefore an electrochemically deposited Au layer (EcAu) was deposited on top of the EvAu layer to improve the adhesion of the EAP to the working electrode. By changing the surface roughness from r = 3.43 (EvAu) to r = 8.26 and 18.00 (EcAu) the normalized strain response after 2000 cycles increases from 45% to 60% and 68% respectively. Also by changing the surface roughness from r = 5 to r = 23, the resulting strain response increases from ∼100 muepsilon to 600--800 muepsilon for PPy.; By incorporating conducting polymers such as polypyrrole into elastomeric base materials such as PDMSe and Santopene TPEs a tough durable dynamic non-toxic antifouling surface coating was formed. These coatings utilize the dynamic changes in polymer charge, modulus, and swelling that naturally occur during the redox cycling of conducting polymers to dynamically change the surface properties of the resulting films. Dynamic changes in contact angle (surface energy) of 11° and 21° have been measured for PPy/TPE (+/-0.5V driving potential) and PPy/PDMSe (+/-1.0V driving potential) IPN systems.; Using a Hysitron TriboindenterRTM equipped with a electrochemical fluid cell setup; dynamic fluid cell nano-DMA mapping measurements were conducted on PPy/TPE systems. Dynamic surface modulus changes of ∼20--40% were measured for the PPy/TPE composite systems when switched between their reduced to oxidized states. All samples showed a decrease in the sample modulus when switched from the reduced to the oxidized state. This is mainly associated with the influx of water and counter ions into the conducting polymer phase during the oxidation process. This in turn increases the free volume of the conducting polymer phase and also acts to plasticize the phase. Changes in the surface topography associated with the redox cycling of the composite structure were also observed during these experiments. This in turn results in a dynamic surface coating that is capable of changing its surface energy, modulus, and topography by changing applied electrical potential.