A process for fabricating multi-layer plastic/glass microfluidic systems has been realized. The process allows for integration of electrical conductivity/impedance detectors directly into the system as well as addition of on-column optical detection using resonance light scattering. The process includes provisions for fluidic and electrical interfaces between the microsystem and macro world. The methods can be used to fabricate microfluidic systems with layers of various plastics, glasses and combinations thereof. The methods can be used to fabricate micro analysis systems for a variety of applications.