You will need:
* A 600 dpi laser printer.
* A toaster oven.
* Some shrinky-dinks (a children's toy; sheets of plastic that you can draw on, then shrink by warming them up, causing the ink on them to become denser and somewhat textured/raised).
* Some Polydimethylsiloxane plastic. (PDMS is a variety of silicone, and a key ingredient in Silly Putty; it's capable flowing and being shaped, but under pressure is highly elastic -- if you left an uncured ball sitting around for a few days, it would flow to become a puddle, but if you then rolled it into a ball again and threw it at the same surface, it would bounce.)
* A sheet of glass and a bonding agent.
Print a pattern on a shrinky-dink. Shrink it, causing the inked patterns to rise, forming a mold. Pour some PDMS over your mold. Cure, peel away. Bond to glass.
You are now the proud owner of a microfluidic device. If you design it well enough, you might be able to do things like separate and recombine liquids in precise proportions; generate electricity in a fuel cell; or create DNA microarrays.