Balanced asymmetric electronic pulse patterns for operating electrode-based pumps

An apparatus for pumping liquid with an electrode-based pump having a liquid flow pathway, the apparatus comprising:

• a channel of capillary dimensions forming at least part of the flow pathway;
• a pump comprising at least two electrodes inserted into the flow pathway;
• a controller for controlling the voltages applied to the electrodes such that the pumps operate under a sequentially repeated pattern of polarity cycles, and such that over the period of the repeated pattern either (a) a first ratio of a voltage-integrated area A.sub.1 associated with a first polarity to a voltage-integrated area A.sub.2 associated with the other polarity or (b) a second ratio of a charge q.sub.1 carried by the current associated with a first polarity to a charge q.sub.1 carried by the current associated with the other polarity is less than 1:1/2 and more than about 1/2:1.

A method of operating a capillary electrophoresis apparatus having at least one electrode at each end of an electrophoresis pathway and operating with an electrophoresis liquid, the method comprising

• periodically reversing the voltage polarity applied to the electrodes while maintaining a net electrophoretic migration of one or more solutes in a desired direction;
• wherein the periodic reversal of the voltage polarity comprises a pattern of polarity reversals and an associated voltage amplitude profile selected to reduce or eliminate the nucleation of gas at the electrodes, wherein the frequency of the polarity cycle is at least 100 Hz.

A method of operating an electrophoresis apparatus having at least one electrode at each end of an electrophoresis pathway and operating with an electrophoresis liquid, wherein the electrodes are enclosed within a microfluidic device such that nucleations of gas at the electrodes interfere with current flow between the two electrodes, the method comprising

• periodically reversing the voltage polarity applied to the electrodes while maintaining a net electrophoretic migration of one or more solutes in a desired direction, wherein a pattern of polarity reversals and an associated voltage amplitude profile are selected to reduce or eliminate the nucleation of gas at the electrodes, and wherein the voltage polarity reversals are applied by repeating a defined pattern with a frequency of at least 100 Hz.

A method of operating an electrode-based pump to pump a liquid, the method comprising

• periodically reversing the voltage polarity applied to the electrodes of the pump while maintaining a net flow of liquid in a desired direction;
• wherein over an operating period of time encompassing at least one polarity cycle either (a) a first ratio of a voltage-integrated area A1 associated with a first polarity to a voltage-integrated area associated with the other polarity or (b) a second ratio of a charge q1 carried by the current associated with a first polarity to a charge q2 carried by the current associated with the other polarity is less than 1:1/2 and more than about 1/2:1.

A method of operating a liquid distribution system comprising, in a substrate, channels of capillary dimensions for conveying liquids and, for moving the liquids, one or more electrode-based pumps each such pump comprising electrodes in electrical contact with one of said channels, the method comprising periodically reversing the voltage polarity applied to the electrodes of a given said pump while maintaining a net flow of liquid in a desired direction in the corresponding channel, wherein the voltage polarity cycles are applied by repeating a defined pattern with a defined frequency of at 10 Hz.