Polymeric trapezoidal microelectrospray emitter integrated with a microfluidic chip

Abstract

We have demonstrated an electrospray of fluid from a tip made from a shaped thin polymer tip bonded to a microfluidic channel. A trapezoidal electrospray emitter was fabricated using lithography and plasma etching. This was integrated with a channel and used for electrospray ionization of small molecules. A lithographically produced silicon master was used to emboss a microfluidic channel in a cyclo olefin substrate. The electrospray emitter was sandwiched between the two plastic pieces at the exit of the microfluidic channel and thermally bonded. The microfluidic channel dimensions were 40 /spl mu/m wide, 20 /spl mu/m deep and 2.5 cm long. One end of channel was directly connected to the electrospray emitter and another end of channel was connected to the silica capillary tubing which was connected to an external syringe pump. 70/30 methanol/DI water with 1% acetic acid was used for testing the spraying characteristics. A grounded aluminum plate was placed 0.6 cm from the electrospray emitter and 2500 volts applied at the reservoir. A Taylor cone was formed on the trapezoid electrospray emitter film. A stable liquid flow of 300 nl/minute was created by the syringe pump for supplying liquid to the electrospray emitter and to maintain a constant spray. 40 nA of total ion current was measured by a picoammeter for 40 minutes.