What is a feather?

Yes, I enjoy birdwatching but no, this is not some ornitho-existential question on the existence of birds. I just returned from the National ACS conference in San Diego, where I spoke about my feather-chem project. As this was the first time I’ve talked extensively about the project to someone who wasn’t a student or my wife, I realized there are still a number of concepts that I take for granted. One of those is related to the feather microcontroller development board created by Adafruit. Here is their 3-minute video introducing the product line:

I decided to use a feather microcontroller for my instrumental methods project because of the advanced microcontrollers used, the diversity of featherwings (and you know what those are because you watched the video, right?), and the small form factor which makes prototyping and creating custom featherwings pretty cheap. Plus, “feather” can be spelled with chemical symbols from the periodic table, which is something I like to do. That’s why you’ll see my project called FeAtHEr-Cm.

Now that you know what a feather is, head on over to the documentation for my project and learn a bit more about how I’m using feathers.

Proof that professor has a heart

I tried a different approach to my Instrumental Methods course this semester, which culminated in students building their own heart beat monitor using the Adafruit Feather M4 Express microcontroller. The project is an adaptation of this one from Analog Devices. The main part of the project was for students to add a voltage divider (which they have seen and used in previous projects during the semester), build the circuit on a breadboard and adjust a few of the components in light of the different voltage (3.3 V vs 5 V). Each student was successful in developing a device, and one was able to confirm that the pulse rate was consistent with the fit bit he was wearing.

Students collecting data on their own potentiostats

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.

OK, so my class only has 2 students, but each student is working on their own potentiostat (which they 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%).

Jarrod is collecting data on ferrocyanide using a 2 mm platinum disk electrode.

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 using a 25 micrometer diameter platinum electrode with the FeAtHEr-Cm. The image is hard to see, but yes, that is a steady state voltammogram with a steady state current of 15 nA!

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.

FeAtHEr-Cm spectrometer

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.

The btm100-alpha version

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.

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