Microfluidics meets analytical chemistry. Paul Bohn talks to Jenna Wilson about molecular transport in small channels.
|Paul Bohn is the Schmitt professor of chemical and biomolecular engineering at the University of Notre Dame, US, and associate editor of The Analyst. His research focuses on understanding and controlling molecular transport on the nanometre length scale.|
How did you become interested in microfluidics?
It has been a bit of a random walk. However, I have always been fascinated with the notion of molecular transport and the movement of molecules on the supramolecular level but on relatively short timescales. I am interested in how to control the placement of molecules in space and time and potential applications of this.
What projects are you working on at the moment?
We work on integrated microfluidics - three dimensional structures capable of performing successively linked chemical analysis tasks. It is a way of performing complicated processing to obtain valuable information. We concentrate on three dimensions ways to do this, using electrochemical activated fluid transfer in different microfluidic layers so we can achieve multidimensional chemical analysis directly on the chip.
We are also interested in optoelectronic materials and devices for chemical sensing, especially the Group 13 nitrides. These materials are extremely robust so can be used in harsh chemical environments, as well as, as the name implies, having useful optical and electronic properties. In particular, the aluminium nitride and gallium nitride end of the family are solar blind so they are useful for applications where other semiconductors are not.
The final area we work in is chemical mapping, which is a way of mapping chemical reactions onto surfaces of arbitrary geometry. This is done by using electrochemical potentials that are anisotropic in the plane, allowing us to create materials that are directly or spatially anisotropic.
What do you hope will be your next breakthough?
We are on the cusp of demonstrating the first powerful two-dimensional separation in a three-dimensional intergrated microfluidic circuit - this based on electrophoresis separation followed by chiral separation. The idea is to take a complex mixture of biological molecules, separate them by chemical identity, and then take the racemic mixture that is represented by the particular component we are interested in and separate the enantiomers in a chiral column. Ultimately, we want to be able to pick out a particular component from a mixture and move it into a different region of the channel, and then operate on that. If we can achieve that once, then the opportunity to do it in parallel presents itself and it could become a powerful technique.
You could imagine replacing 2D gels that people run and cut out for mass spectrometry for proteomic experiments, with an intergrated microfluidic format that would be simpler and able to handle smaller volumes, and hopefully lower the copy number in those kinds of assays.
What do you think is the biggest challenge faced by people working in your area?
The Holy Grail is to take a complex mixture and provide a chemical catalogue of its components, and to do this in a way which preserves both spatial and temporal information. I have just described probably the next 500 years of analytical chemistry, but perhaps a smaller goal for the immediate future in chemical sensing is to provide a complete inventory of a complex chemical mixture, and to do that with single molecule sensitivity.
What achievement are you most proud of so far in your career?
I would have to say my 25 PhD students that I have graduated. I am most proud of the fact that they have gone on to do so many different things, from academia to government to industrial laboratories. They have all continued to grow but some of them have grown dramatically in their new positions. Keeping up with them and watching them grow and develop has been very satisfying for me.
What message do you have for young scientists?
Chemistry continues to be an endlessly fascinating piece of the contemporary science scene because so much of what happens in science is tied up in the way in which molecules organise themselves and interact with each other. You only have to look below the surface a little bit to see that chemistry has been an enduring and very broad spread substructure to advances in science as a whole. If I have any advice, I would encourage people to look for the problems at the interface between traditional subject areas, where a good chemical knowledge can have an impact.
If you went back into the lab, what experiment would you do?
Our most exciting current project involves incorporating optoelectronic materials into traditional microfluidic formats. I would like to do experiments that use these exciting advances in electrokinetic transport in order to further develop microfluidics. Unfortunately, I have given that project to a student so he would be mad if I showed up and did the experiments myself!
What do you hope to achieve in your new role as associate editor for The Analyst?
It is important to have a number of top international analytical chemistry journals which provide different outlets for people to publish in. I would like to provide a venue for analytical science that has good visibility on both sides of the Atlantic. Analytical chemistry constantly comes into contact with various aspects of more broadly focused sciences like, for example, nanoscience. Certainly not all areas of nanoscience are orientated towards analytical science, but there are many people who are exploiting various exciting properties of nanomaterials to do chemical analysis. I would like to think that we can capture some part of that in The Analyst.
Finally, if you weren't a chemist, what would you be?
That's easy... I would be a professional golfer. The only thing that gets in my way is lack of talent!