In this work, a microfluiclic free-flow electrophoresis device, obtained by thermal toner transferring on glass substrate, is presented. A microdevice can be manufactured in only 1 h. The layout of the microdevice was designed in order to improve the fluidic and electrical characteristics. The separation channel is 8 Am deep and presents an internal volume of 1.42 mu L. The deleterious electrolysis effects were overcome by using a system that isolates the electrolysis products from the separation channel. The Joule heating dissipation in the separation channel was found to be very efficient up to a current density of 8.83 mA/mm(2) that corresponds to a power dissipation per unit volume of running electrolyte of 172 mW/mu L. Promising results were obtained in the evaluation of the microdevices for the separation of ionic dyes. The microfluidic device can be used for a continuous sample pretreatment step for micro total analysis system.