High Energy Density Nastic Materials: Parameters for Tailoring Active Response

The engineered active material considered mimics bulk deformation similar to nastic movements in the plant kingdom. Controlled transport of charge and fluid across a selectively permeable membrane employing biological processes is employed to achieve bulk deformation. The membrane may contain biological ion pumps, ion channels, and ion exchangers surrounding a spherical inclusion in a polymer matrix; in this study only ion pumps and exchangers are considered. This work examines parameters of significance to designs employing active materials, including free strain, blocked stress, impedance matched work, and rate of response. The effects of varying material design parameters, such as system geometry and membrane permeability are considered to aid in the custom design of an active material appropriate to a given application. Predictions suggest that the rate of initial response may be on the order of msec with impedance matched work in excess of 200 kJ/m(3).