Pulse-length dependence of the electrical breakdown in lipid bilayer membranes

Charge-pulse experiments were performed on artificial lipid bilayer membranes with charging times in the range between 10 ns and 10 mus. If the membranes are charged to voltages in the order of 100 mV, the membrane voltage at the end of the charge pulse is a linear function of the injected charge. However, if the membranes are charged to voltages in the range of 1V, this relationship no longer holds and a reversible high conductance state occurs. This state is defined as an electrical breakdown and it does not allow the membranes to charge to higher voltages than the breakdown voltage, Vc. Between charging times of 300 ns and 5 mus at 25 degrees C and between 100 ns and 2 mus at 40 degrees C, Vc showed a strong dependence on the charging time of the membrane and decreased from 1.2 to 0.5 V (25 degrees C) and from 1 to 0.4 V (40 degrees C). For other charging times below and above these ranges, the breakdown voltage seemed to be constant. The results indicate that the breakdown phenomenon occurs in less than 10 ns. The pulse-length dependence of the breakdown voltage is consistent with the interpretation of the electrical breakdown mechanism in terms of the electromechanical model. However, it seems possible that below a charging time of the membrane of 300 ns (25 degrees C) and 100 ns (40 degrees C) other processes (such as the Born energy) become possible.