Jell-O microfluidics for teaching physics of fluid flow

As this is the first post to this site, I will begin with a technology I know well, because I helped design it.  Jell-O microfluidics!  My lab was looking for a way to help the Michael Smith Laboratories outreach team showcase some of the cool things going on at UBC in the microfluidics arena.  Specifically, they wanted a way to teach younger students why microfluidics was useful and how such systems work.

Microfluidics is exactly what it sounds like, fluid flow at small length scales.  The typical size of features in a microfluidic device range from 10-100 microns, or from 1/10 the width of a human hair to the width of a human hair.  Microfluidics show up everywhere, but our and others’ work focuses on using this technology for biomedical diagnostics (detecting diseases like cancer or bacterial infection).  Microfluidic systems are useful because:

  1. they use smaller volumes of valuable reagents to do their work
  2. they can be “batch-fabricated” dozens to thousands at a time
  3. due to 1) and 2), they are potentially less expensive than other diagnostics
  4. due to their unique physics, they can do things than larger systems cannot

It’s number (4) that’s really cool.  It turns out that as you shrink the dimensions of fluids down, they begin to behave in very strange and useful ways.  One of these ways is that parallel streams of fluid will not mix except by diffusion.  This is in stark contrast to our everyday experience, in which you mix your coffee and your milk and they, well, mix.  If you were to do this experiment at tiny length scales, you would be able to mix and unmix the coffee and milk with only minor distortion of the original flow.  This minor distortion is the tiny amount of mixing that would happen by diffusion.  Diffusion is a slow process compared to convection, which is how fluids mix in our human-sized lives.  You can get a feel for the unique fun these fluids provide by watching a demo by the inimitable Steve Spangler, in which two fluids are mixed under so-called laminar flow conditions, which is the way that fluids flow in microfluidic systems as well.  As the demo shows, you can get laminar flow even at larger length scales if you change other parts of the fluid flow (like the viscosity).

Steve Spangler:  A twist in time demo

This is where Jell-O comes in.  We were looking for a way to make microfluidic systems even faster and less expensive than what we do in our lab.  Jell-O is a polymer that is very easy to acquire, but that can be used in a molding process exactly analogous to how we make microfluidics in research settings.  Using coffee stirrers and double-sided tape, we make a mold, and then pour concentrated Jell-O over it.  Once the Jell-O is cured, it can be peeled off and put onto a flat plate forming a channel.  If you put fluids like water into this channel, you can achieve neat microfluidics effects like the one I discussed above, where fluid streams flow side-by-side but don’t mix.

Jell-O microfluidic chip

A microfluidic channel made from Jell-O demonstrating laminar flow

We have used these Jell-O “chips” in various teaching workshops at UBC, and they have also been used at high schools and universities around the world (US, Canada, and the Netherlands to date).  Our results and protocol were published in Analytical Chemistry in 2010, and Tony Yang, one of the graduate students on the project, was interviewed by the editor for their monthly podcast.  You can download his interview below.  If you can’t get access to the paper, please contact me and I’ll see that you get a copy.

Jell-O microfluidics paper

Tony Yang Jell-O microfluidics interview

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