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Research and sourcing

A project log for Electrospinning functional fibers

eSpinning process and build development

ivorivettaivorivetta 07/11/2016 at 08:570 Comments

Background research -

I first started hopping around Google Scholar to see what people were up to, and for how long. The earliest invention is in 1887, with interesting devices and applications published on a monthly if not weekly basis in present day. On the web, www.electrospintech.com became a heavily used resource. It was humbling for what I thought was a novel and clever invention of mine to already have an article written up, great email newsletter too. With these two resources, I was able to pull most of the operating parameters I needed to inform the rest of these builds.

Sourcing -

From previous experience, I knew that the syringe pump and power supply were going to be the two big budget items. Buying solvents for home delivery is a pain sometimes too. Let’s get into it:

Fluidics

Syringe Pumps can easily get to $200+ for lab applications. Open source community and 3D printing to the rescue! Using this design as my base, I shed any components for retracting the syringe pump to keep things simple since I only need to push during processing/fabrication. Running multiple trials gets tedious quickly so easily resetting the pump between spins was a priority, and I thought manually doing this was fine. Having less clamps helped with that too.

I had spare linear rails, threaded rods, and stepper motors, along with a smoothieboard for the brains. It came together nicely after some tweaking in OpenSCAD to fit my syringes and some reaming to account for my 3D printer tolerances. Some blunt needle tips rounded out the fluidic system. I’ll mention calibration in a future post.

Electronics

The High Voltage Power Supply is another item that could easily cost $3k+. Low quality power supply units (PSU) have caused me hours of debugging headaches, if not destroying entire experiments, in the past.

There are enough variables in electrospinning to control already, plus adjustable range and positive/negative voltage options would be awesome capabilities to have considering this is a process development exercise. eBay, you’re amazing:

Bertan winning bid - web.jpg

What a deal! Plus the guy had an extra so I went ahead and got two. The tradeoff? This power supply is salvaged from an old spectrometer and I’m buying as-is. I’m nervous it won’t work. The extra fun bit? This Bertan company was acquired years ago and no documentation exists besides this little clipping of the pinout:

Bertan 2554 Control Pinout - web.jpg

Tl;dr: Slightly sketchy but I got it working. I’ll do a bonus post later to show off the insides and some of the reverse engineering steps I took to validate this pinout.

High voltage wires are also highly specialized. This one had a very specific connector at the HV output. After I found out what spectrometer this power supply came from, I called up all the listed repair and technician vendors I could find on the west coast. No luck. Looking eastwards, a shop in Texas had some on stock and I bought up the three they had on hand. Cost more than one of the power supplies but equally as essential.

Aluminum foil was the collector of choice to spin on with alligator clips connecting most of the components. Grounding cables for earth ground and the chicken stick are from repurposed extension cords. I polished all the connection points and used conductive grease to keep any capacitive charges from building up in my system as a preventative measure. A DB15 to wire terminal adapter made it easy to interface with the power supply.

Wetware and Enclosure

Hadn’t set-up a wet lab at my home shop before but I knew some sacrifices would have to be made compared to labs I’ve worked at in the past. Was able to find centrifuge tubes for mixing and a scale for measuring easily enough on Amazon. Graduated cylinders, gloves, stir rods too. Already had protective eyewear at home.

Ventilation is absolutely paramount as the solvents that are evaporating are very strong! Nothing extremely carcinogenic but didn’t want to push my luck. My initial hacked together fume-hood used computer fans to push the air through activated carbon. Filtered the air well enough but was too much inconvenience to put into practice. In the end, I bit the bullet and did these experiments outside in a covered patio. I monitored humidity and pressure and in the end, it all worked out fine, I guess if you consider your “system” and “environment” appropriately/sufficiently.

The enclosure was just the biggest plastic storage container I could fit in my car. Didn’t run into any trouble there and drilled into it freely to run the grounding cables and syringe tip + HV cable.

eSpinTech, again, has a great starter guide. Apparently PVP and PEO are two plastics that spin easily. I instead opted for PolyStyrene as a standard material to learn from. I was able to find some detailed papers that had some great parameter experiments I could replicate. It also meant I could use waste Styrofoam and explore the up-cycling potential of our processes. Future project! I was luckily also able to secure a suitable solvent from Amazon, Dimethylformamide (DMF), that dissolved the plastic like a dream, so instantly and to a large concentration with high solubility.

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