Microfluidics is a fascinating field that has a wide range of scientific applications. It’s the science of manipulating and controlling fluids at a very small scale, usually through channels that are narrower than a human hair. At that scale, fluids act in very interesting ways as forces like surface tension and capillary action become more pronounced. But, because of the extremely small scale, it’s very difficult to fabricate your own microfluidic flow cells at home. Luckily, YouTuber The Thought Emporium has a great video explaining how you can do that with inexpensive materials.
A typical microfluidic system is made up of one or more channels, usually less than 100 microns in diameter, that follow a specific pattern or intersect to accomplish some task. The inputs and outputs of those channels are connected to some kind of syringe or pump in order to force fluid through the system. That can be used to mix two fluids, for example. Or to draw large cells out of a blood sample for cancer testing. In all cases, the channels need to be as precise as possible in order to achieve the predicted effect. In the mixing example, one input’s channel being larger than the other’s would result in an uneven mixture.
To achieve that, The Though Emporium used a CNC mill and Shrinky Dinks film. Shrinky Dinks is a brand name for a polystyrene film that shrinks under heat, and is marketed as a toy for kids. As it shrinks in the X and Y dimensions, it thickens in the Z dimension. This technique relies on that fact to create very small, yet still precise, channels. First, the channel designs are very lightly milled into a sheet of Shrinky Dinks film. That’s then placed in an oven, where it will shrink to a fraction of the original size. Another piece of the film is placed on top to seal the channels. As The Thought Emporium demonstrates, this fabrication method works very well, and you can use it to start experimenting with microfluidics at home.