Design and fabrication of nanofluidic devices by surface micromachining

Abstract

Using surface micromachining technology, we fabricated nanofluidic devices with channelsdown to 10 nm deep, 200 nm wide and up to 8 cm long. We demonstrated that differentmaterials, such as silicon nitride, polysilicon and silicon dioxide, combined with variationsof the fabrication procedure, could be used to make channels both on silicon and glasssubstrates. Critical channel design parameters were also examined. With the channels asthe basis, we integrated equivalent elements which are found on micro total analysis(μTAS) chips for electrokinetic separations. On-chip platinum electrodes enabled electrokineticliquid actuation. Micro-moulded polydimethylsiloxane (PDMS) structures bonded to thedevices served as liquid reservoirs for buffers and sample. Ionic conductance measurementsshowed Ohmic behaviour at ion concentrations above 10 mM, and surface charge governedion transport below 5 mM. Low device to device conductance variation (1%) indicatedexcellent channel uniformity on the wafer level. As proof of concept, we demonstratedelectrokinetic injections using an injection cross with volume below 50 attolitres(10−18 l).