Despite several decades of development, microfluidics lacks a sealing
material that can be readily fabricated, leak-tight under high liquid water
pressure, stable over a long time, and vacuum compatible. In this paper, we
report the performances of a micro-scale processable sealing material for
nanofluidic/microfluidics chip fabrication, which enables us to achieve all
these requirements. We observed that micrometric walls made of SU-8
photoresist, whose thickness can be as low as 35 μm, exhibit water pressure
leak-tightness from 1.5 bar up to 5.5 bar, no water porosity even after 2
months of aging, and are able to sustain under 10−5 mbar vacuum. This
sealing material is therefore reliable and versatile for building microchips,
part of which must be isolated from liquid water under pressure or vacuum.
Moreover, the fabrication process we propose does not require the use of
aggressive chemicals or high-temperature or high-energy plasma treatment. It
thus opens a new perspective to seal microchips where delicate surfaces such as
nanomaterials are present