Harvey Mudd College has a clinic team with AMYBO! This is where we will be posting our summarized meeting minutes so the larger AMYBO community can see the progress of our project.
Please feel free to reply with comments/suggestions!
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1/24/2025
Subteams: anode, and pinch valve.
This semester, we will be continuing to test different anode materials to find the best balance between safety, effectiveness, and reproducibility. In our research, we found that the most effective anodes are made of various alloys, which we will be testing in the upcoming month. We are considering a nickel alloy, though there are safety concerns associated with ingesting the material. Additionally, as the platinum used in previous experiments has been determined not to be real (or at least pure) platinum. We will work to source some pure platinum so we can plate and test a 3D printed structure as our anode. The solenoid pinch valve team determined last semester that a 5V solenoid cannot produce the force required to pinch the tubing shut, and will be switching to a 12V design. We will be looking into finding an off-the-shelf component that meets our requirements, and, if one cannot be found, will design our own based on our CAD model from last semester. In addition, once the pinch valve deliverable has been met, we intend to transition to our stretch goal of converting the Pioreactor into a flow through cell. This will likely be done in parallel with materials research for the anode, given the breadth of that task.**
On anodes - will you still be investigating graphite? And have you subscribed to this thread on anode material?
On the pinch valve - am I correct in understanding that it is an off the shelf 12V solenoid that you aim to procure to combine with your pinch valve design from last semester?
We are planning on finding an off the shelf valve and modifying it to work better for the application necessary for the pioreactor. If we cannot find one that meets our constraints, we will modify our current design to fit a 12V solenoid. We will not be modifying an off the shelf valve to work with last semester’s design. I hope this clears up any confusion!
1/28/2025
The valve team will begin designing an open-source solenoid pinch valve. The anode team has obtained nickel to test and will also begin testing the graphite for fouling using the HOB acquired last semester (they will likely need to attempt to grow the bacteria using a known anode first, to make sure the sample has HOB). If there is no HOB in the sample, we will source some either from NCYC, or another freshwater source near campus.
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Ah, sorry. Did I mention NCYC - that’s a UK based culture collection. There is bound to be one much nearer to you that would have model HOB. It’s possible that Harvey Mudd already have someone with Cupriavidus necator or a suitable Xanthobacter, etc.
2/4/2025
Valve team: Solenoids have arrived, and we are in the prototyping phase: each subteam member will come to the next meeting with 1 design to present. From there, we will test each design and, at the following meeting, present our results.
Anode team: Tested a nickel anode with a stainless steel cathode. The resulting current density was higher than previous metal tests, but dropped off rapidly. There was also residue in the water (possibly rust) as seen in the attached picture. We are also researching 3D print electroplating to meet our ease of manufacturing constraint (otherwise metal rods would likely have to be machined). We are also looking into titanium electroplating. We will be getting deionized water for future tests and confirmation that the residue in the water is a result of unwanted chemical reactions with water pollutants. Niobium based alloys are also a potential solution. We would need to consider oxidation.
HOB Purchasing: Will source Xanthobacter Flavus from USDA ARS Culture Collection. If this is not possible, we will reach out to professors using the strain and ask for a sample.
Thanks for the update! Can you share where you sourced your nickel anode and stainless steel cathode or their specs?
What were your voltage and current settings during electrolysis?
Hi Gerrit!
We purchased the nickel anode off of amazon rated to be 99.6% nickel and was highly reviewed. Here is the link to that: Amazon.com: SHONAN Nickel Anode- 7.87"x0.3"(Diameter) Nickle Anode, Pure Nickel Bar, Nickel Rod for Nickel Electroplating Solution, 3.4oz 99.6% : Industrial & Scientific
The stainless steel cathodes are just stainless steel bolts we got from our in house stockroom at Mudd. The specifications I could find are as follows: stainless 67? I was under the impression that any stainless steel bolt would work fine but if you have more specifications we should follow, we’d be happy to purchase something else.
The voltage setting is on 5.00V applied voltage and then it is on a current readout setting so rather than setting that, we are reading the values which were 13mA, 6mA, and 4mA through a 24 hour test period while testing the nickel anode.
Thanks for the link, it may help others who would like to replicate the setup!
@Martin has been looking into different types of stainless steel - our preferred option is 316, which is corrosion-resistant. There’s also a low-carbon version called 316L.
I’ve been using 304 grade without any issues, but I can’t say I’ve heard of stainless steel 67 before. That is quite a large amount of sediment in the picture - is it possible the positive and negative were swapped and the stainless steel electrode was oxidizing? How long did you run it for?
Have you tried connecting the electrodes to the Pioreactor and running it at 10% intensity?
Yes, I would say that 316L is the preferred grade (see this post), but I found it difficult to source suitable 316L bolts in the UK as they tend to be sold as ‘A4’ which is defined by Westfield Fasteners as:
“A4 Stainless Steel - Also known as grade 316 or 18/8/3. A higher corrosion resistant, marine grade of stainless steel.”
I believe A4 may be 316 or 316L (low carbon). My plan, if A4 was insufficient, was to move to Duplex which is most likely overkill, but it is at least a grade that bolts are sold in. Given that Gerrit has been using 304 (aka A2) without issues, the assumption is that A4 should be more than sufficient.
Thanks for all the info!
We are currently running a test with deionized water + sodium bicarb to ensure the issue isn’t the water on campus. Then if we are still having issue we will look into getting the stainless steel you recommend and switching the anode and cathode. We aren’t seeing much rust on the electrodes themselves which is what has us suspicious that it may be the water. We will update with more soon.
Thanks!