Electrokinetic trapping using titania nanoporous membranes fabricated using sol–gel chemistry on microfluidic devices

We have developed a new method for analyte preconcentration on a microfluidic device using a porous membrane fabricated via sol–gel chemistry. These porous membranes were fabricated within the channels of glass microfluidic devices exploiting laminar flow to bring an alcoholic sol–gel precursor (titanium isopropoxide in 2‐propanol) into contact with an alcohol–water solution at a channel cross intersection. These two streams reacted at the fluidic interface to form a porous titania membrane. The thickness of the membrane could be altered by changing the [H2O]. Analyte concentration was accomplished by applying a voltage across the titania membrane. The level of analyte enrichment was monitored, and enrichment factors of above 4000 in 400 s were obtained for 2,7‐dichlorofluorescein.