Molecular Biology is certainly different than a discipline like electrical engineering. One of the more obvious examples are the consumables. In general, things are always being added to little containers, like say a restriction enzyme. After the reaction, the restriction enzyme doesn't go back up on the self, it's consumed. Or let's say, the experiment is to identify a protein using two dimensional electrophoresis. The protein of interest is identified spatially, cut out of the gel, dropped into a tiny vile, and the rest of the gel dumped in the trash.

Suppose instead that the goal is to make a large microfluidic signal processor in which all the operations of mixing fluids, adding various proteins, and performing separation process occur within a machine.

If one wishes to go about building a device in which the build of the operations occur in a very small space, "Lab on a Chip", then it will be necessary to generate artworks that define the physical pathways, electrodes, reservoirs, fluid connections, and components, that make up that device.

As mentioned earlier the substrate for the devices will be constructed on a ceramic. The electrodes will be made of silver. For the fluid pathways, there is really only one choice, polydimethylsiloxane (PDMS). PDMS has a very low surface energy. What that means is that nothing sticks to it. It sticks to itself when it is cast from a liquid, but once it cures it pretty much won't stick to anything, including itself. So if a shape is cast, cured, and another layer cast on top of the first layer, don't expect the two to be one integral body. If it is necessary to join two layers, it is necessary to etch the first with ozone to prepare the surface. Once prepared, the is only a very sort period of time, according to the literature, no more than 20 minutes, before the second layer must be poured.

Because PDMS is an elastomer it does make a great mechanical seal.

So, where exactly does the pattern of fluid pathways come from? Is it a positive photo mask system or a negative one? Are the pathways made by first patterning the desired shape in another material like SU8 or are they made by xurography, Latin for a cutting plotter?

No matter the polarity, may I recommend the open source triumph, Kicad. As one of Kicads attributes is the ability to export SVG files. From there, one may import a SVG graphic into another open source wonder, Inkscape. From Inkscape it is an easy path to generate G-code for a CNC machine, or HPGL for a graphic plotter, And there you have it. Tremendous power at your fingertips.

Be prepared for some serious study, Kicad and Inkscape are seriously proficient programs that require practice.