One of the problems I am trying to solve with the FeAtHEr-Cm platform is to eliminate the instrument bottleneck that we see in analytical chemistry courses. For example, a class of 12 students, even if paired up, will unlikely be able to perform an electrochemistry experiment simultaneously because there are few institutions that would be equipped with a half dozen potentiostats.
That is, unless your institution is equipped with FeAtHEr-Cm potentiostats that your students built.
Each student is using python on their own computer to communicate with the potentiostat they built. In a previous class, we calibrated the feedback resistor in the current-to-voltage converter to ensure that the current reported by the instrument is correct (both students obtained relative errors better than 0.1%).
In this experiment, the students are collecting cyclic voltammograms at scan rates ranging from 1 V/s to 0.01 V/s. This range requires them to change the feedback resistor so that the current range is appropriate for the measurement. They also explore the impact of including a filtering capacitor in the feedback circuit.
Nate is trying a slightly different experiment, using a 10 MOhm feedback resistor, he is determining whether or not the home-built potentiostat can measure nanoamp levels of current. Turns out, we can! Here, the filtering capacitor plays a very important role in the integrity of the voltammogram. The 0.1 uF capacitor used for microamp current ranges is much too large, and when Nate saw that the voltammogram was “too smoothed”, he broke out the Santana lyrics. For everyone’s benefit, we ended class at that point.
If you’ve been following (and I know one or two of you are), then you know that FeAtHEr-Cm is my Adafruit Feather microcontroller-based approach to building scientific instrumentation for the chemistry teaching laboratory. Not only does the platform allow for inexpensive instruments to be distributed throughout a classroom (at under $50/unit, each student in an analytical chemistry lab could have their own potentiostat), but the instruments are designed so that students can understand what makes them tick.
Joining the team is the btm100 which is a spectroscopic instrument designed to perform turbidity and nephelometry experiments. These techniques help scientists explore heterogenous solutions by measuring their cloudiness, and the techniques are used widely in fields such as environmental analysis. As an added bonus, the response from turbidity/nephelometry measurements mimics that of absorption/fluorescence measurements which are commonly covered early in the chemistry curriculum, so we have a fine opportunity to build on fundamental concepts (Beer’s Law) while expanding the suite of tools students are exposed to.
This summer, my student Hannah worked on one of my research projects with the goal of developing a flow-through analysis of total antioxidant capacity. Measuring antioxidant content is difficult because the term “antioxidant” can mean any variety of compounds in a substance, and therefore different approaches to analyzing antioxidant capacity can yield very different results.
Our hope is to design a system that can perform multiple analyses on the same sample. To do so, we need to be able to perform each analysis in a small volume. That’s where Hannah’s project comes in. After learning how to perform one of the assays “the normal way”, she worked on performing the analysis using the OMIS millifluidic system coupled to a spectrometer. Much of her summer was spent dealing with background stability and learning how to program using the Wolfram Language, but she did end up with a system that could measure ascorbic acid in small volumes.
Here’s Hannah, working on her project (and in the cleanest part of my lab, mind you). Brockport students involved in summer research are encouraged to present their work at a fall poster session. You can download Hannah’s poster below (not quite sure what WordPress is doing, but hopefully it works).
I have this little Star Wars lunch box, and just noticed that it is big enough to fit the Adafruit Feather along with my potentiostat featherwing. What does that mean? I have the most awesome Faraday cage!
We are several weeks into the semester, and my Instrumental Approach to Chemical Analysis students are knee deep in learning about instrument design and preparing their own potentiostats. None of my students had soldered before, and Jarrod gave me permission to share his performance with the world (so long as I mentioned that he’s wearing his Department of ENVIRONMENTAL science shirt to show off his true colors).
And here’s his completed bob173-gamma potentiostat.