An Opto-Electric Micropump for Saline Fluids

A novel method to pump fluid in lab on chip devices with velocities up to tens of micrometer per second is introduced. A focused laser beam locally heats up an electrolyte. A net charge tends to accumulate in the heat-absorbing area, due to unequal tendencies of positive and negative ions to move in the presence of the temperature gradient. An external electric field then exerts a net force on the accumulated charge and consequently on water. This causes flow of water, with velocities up to tens of micrometer per second, for a simple NaCl+water solution. The method lets us change direction and amount of fluid pumping, simply by replacing the focal area.