Maskless fabrication of nano-fluidic channels by two-photon absorption (TPA) polymerization of SU-8 on glass substrate

We present a simple, fast, and repeatable method for fabricating nano-fluidic channels based on two-photon absorption (TPA) polymerization.  Since our method does not require any mask, it is relatively cheaper and faster than other conventional lithography techniques.  We illustrate that SU-8 has pronounced photoinitiation threshold behavior, which linearly decreases as the repetition rate increases.  If the pulse energy and the repetition rate are controlled, channel width can be easily controlled.  We report fluidic channels up to 110 nm in width, between polymerized parallel ribs, utilizing TPA and the photoinitiation threshold properties of SU-8.  Finally, we also show that high repetition rate laser presents greater controllability in size of the polymerized region by varying fluence.