Before leaving Chicago State University in 2017, I took a sabbatical to explore a very different avenue of research from which I was originally trained.  I became interested in learning how digital fabrication tools, such as 3D printing, can be used to create inexpensive or customized scientific instrumentation that could be used for education or specialized research applications.  Now at The College at Brockport, I’ve finally put together my first 3D printed scientific instrument, which was recently published in the journal HardwareX.  The article, OMIS: The Open Millifluidic Inquiry System for small scale chemical synthesis and analysis, is open access, which means that anyone can read and download the article by heading here.

I’d like to think that when people do something important (like publish an article) they get interviewed.  Unfortunately, it’s that time of the semester where students are so stressed out, the last thing they want to do is talk to professors about anything other than “what’s on the test.”  So, if I were to give an interview, here’s the questions I’d answer (and ask) about the paper.

So, what is OMIS, really?

I’m glad you asked that, BoB.  OMIS, as mentioned earlier, stands for Open Millifluidic Inquiry System.  It’s a scientific instrument that you can build using a 3D printer, some electronics and a few parts from the local hardware store.  It consists of a syringe pump and a container for performing reactions.  It looks like this.

OK, but what is it good for?

The primary use is to perform small-volume reactions under continuous-flow conditions.  The syringe pump can dispense fluid at rates of about 100 µL/min.  the user can then direct different streams of fluids into the same vessel so they can react in a controlled fashion.

What do you mean by “controlled fashion”?

Let’s first describe what I would mean by “uncontrolled fashion”.  Picture your morning cup of coffee.  When you add milk to the cup, you will typically stir the mixture until all the milk is distributed evenly throughout the coffee. This mixing process is chaotic and very difficult to control. For example, it would be hard to predict the shortest time needed to stir the coffee until it is completely mixed.

On the other hand, when two liquids are slowly directed into a small channel, they do not mix immediately. Instead, they form two individual streams in the channel. At the interface, the two liquids do mix through a process called diffusion. Diffusion is a form of mass transfer that is well understood and can be modeled and controlled precisely.  The video below demonstrates this process.  On the left hand side, the two streams of food coloring are moving very slowly, and they have time to mix. On the right hand side, they are moving through the channel quickly, and do not mix completely even though they traveled through the same channel.

So, back to the earlier question of “what’s it good for”. Being able to control the mixing of two liquids makes it possible to precisely control how long a reaction is allowed to happen. Because we are using small volumes, it will also be possible to control other parameters such as temperature, although we haven’t done that yet.

Why did you build it?

Commercial syringe pump systems run in the hundreds to thousands of dollars. They do a lot of neat things with plenty of cool features. Sometimes, all of that functionality is not needed and a user doesn’t want to spend all that money for features that won’t be used. I wanted to build a syringe pump that was inexpensive and easy to fabricate. The syringe pump materials cost about $50.

Additionally, I wanted to have a simple platform for teaching students about small scale synthesis and some chemical engineering processes. What I described earlier about liquids going through the channel is called Laminar flow, and this is not a topic that comes up in the chemistry curriculum. OMIS provides a simple entry into this important topic.

Who is the intended audience?

I’ve provided detailed build instructions in the paper and have had several undergraduate students build and use the device. They’ve even broken it (several times) and proposed modifications to improve the robustness of the device. Because I teach at a primarily undergraduate institution, I envision its use in teaching and research laboratories. If you have access to a 3D printer or fab lab and have an interest in building a scientific instrument, I think OMIS is a great place to start.

What’s next?

Now I’m interested in exploring some chemistry. There is some neat coordination chemistry that produces differently colored complexes when different ratios of reagents are mixed together. The experiment will be easy to do with OMIS, once we complete development of compatible sensors. We’re also looking at using OMIS as an automatic titrator, which opens up possibilities in quantitative analysis of liquids.

But most importantly, what’s next depends largely on what others do with OMIS. The whole point of publishing the article and detailed build instructions was to promote the use of digital fabrication in the development of scientific instrumentation. I hope that there are scientists (and science enthusiasts) out there who are intrigued by OMIS, build it, and let me know what they do with it.

Where can I find more about OMIS?

Right here!  I’ve got a special section of my website for OMIS information.  I’ll update that section with news as it becomes available.  (For example, I’m working on a user interface for OMIS that relies on Mathematica running on a Raspberry Pi.  People who visit this website shouldn’t be surprised at that mix.)