Zone plate focused soft X-ray lithography for fabrication of nanofluidic devices

Sealed nanofluidic channels with cross sections of sub-100 nm * 100 nm were created in a polymer bilayer using the focused soft X-rays of a scanning transmission X-ray microscope and the direct write method. The width of the nanochannels can be controlled by the area patterned in X and Y, while the height can be controlled by tuning the layer thicknesses. Formation of the desired structures has been confirmed by near edge X-ray absorption fine structure spectromicroscopy and scanning electron microscopy. The maximum length of the nanochannels fabricated by this method was found to be limited by the efficiency of excavation of patterned material out of the channel, as well as the stability of the polymer over-layer which seals it. Schemes toward interfacing these nanochannels with conventional microfluidics are discussed.