Almost all microfluidic channel and microreaction chamber systems has been produced by soft-lithography.
The main fabrication steps are as follows. A silicon wafer with multi-plane patterned photoresist combination of SU 8-25 and SU 8-2100 (Microlithography Chemical Corp., Newton, MA) serves as a mould master. For polymer moulding a degassed 10:1 solution mixture of PDMS prepolymer (Sylgard 184, Dow Corning) and the curing agent is then cast against the master. Curing the polymer for 24 h at room temperature and releasing it from the master yielded a replica containing one up to three levels of different heights of required microchannels and -chambers.
The clear-transparent microfluidic channel structures resulted from the soft-lithography process have been sealed by a silicon cover (optionally with the electronic layer of the developed ChµP-chip containing a combinatorial array of microelectrodes).