Current-voltage characteristics and self-sustained oscillations in dioleyl phosphate-millipore membranes

For an artificial membrane prepared by infiltrating dioleyl phosphate (DOPH) into pores of a Millipore filter, we propose a theoretical model for explaining observed data on electric behavior, such as d.c. current-voltage characteristics and self-sustained oscillations of the electric potential. The model consists of a simple electric circuit composed of electric resistances and capacitances as given functions of internal variables which represent conformational states of DOPH molecules and salt concentration inside the pore concerned. The kinetic equations for these variables are the same as those presented previously for describing a phase transition of DOPH. except for a slight modification taking account of effects of salt accumulation inside the pore. The present theory can describe well the I-V hysteresis and various features of spike-like oscillations with long periods of up to a few hours in the absence of external force and also short-period oscillations with periods of the order of 1 s under pressure difference.