There is a project happening by the Prakash Lab called Project 1000 x 1000. The idea is distributed manufacturing of N95 mask filter material. It’s called this name because using this approach of medium scale manufacturing (enough fibre for 10,000 masks per day), then if 1000 Fab Labs / makers / small biz replicate this, it could be enough material for 1-10 million masks per day. Hence, 1000 x 1000. By the way, current manufacturing can’t scale beyond 1 or 2 million masks / day per factory. This is an alternate method.
I first heard about this project through the Fab Lab update video. It blew my mind – making fibres by spinning? Except for cotton candy, didn’t even realise this was possible! There’s more info about electro-spinning here. Seeing the Project 1000 x 1000 “Anyone can join, help or replicate these efforts elsewhere.”, I want to try it out too. The first step is reading this document. Here are some highlights:
As hospitals run out of N95 masks (critical protective gear necessary to capture 95% of particles at 0.3um or greater) and the supply chain isn’t yet able to keep up with the escalating demand, we have been looking for alternative means to produce similarly-performing filter materials. The fabrication of micro- and nanofibers to produce N95-equivalent filters is currently done via a melt-blow based extrusion process which requires extensive tooling of the head (too complex to be scaled up in a short period of time). At a smaller scale though, other methods such as electro-spinning, and rotary jet spinning can be used to make nanofibers. Our own calculations and literature review, we find that rotary jet spinning (RJS) has the capacity to meet the demand of medium-scale production of N95 grade nano-fiber material and seems to be the one that would be most applicable in this scenario. RJS can produce nanofibers about 50x faster than electrospinning and does not involve the danger of high voltage  and is very simple to set up.
We propose to use waste styrofoam – commonly available everywhere – as a raw material to convert it into N95 grade nano-fiber material which provides the key ingredient needed for making high grade PPE masks necessary for health care workers.Source: Project 1000 x 1000 by Prakash Lab COVID-19 Response Group
They posted 3D print files for the cup that spins on the dremel. However, these designs rely on a 24 gauge needle. My hunch as to why this is is perhaps they were using the metal for electro spinning, rather than just rotary jet spinning (without the high voltage). It can also be tricky to get that amount of precision on a print.
We don’t have the needle heads on hand, but a quick search online shows its diameter is 0.55mm. Later learned that the inner diameter is smaller, at 0.311mm.
There were a few different methods I thought about. Could use the precision mill on some single sided copper clad to make the exit hole and attach that to the print. Might be prone to leakage though. Or, by orienting the print properly and cutting it in half, make it that way at 0.1mm layer height. Here’s the test:
The process for this is, cut the model in half and 3D print the halves. Sand the top layer down to be flat. There are channels outside of the ‘nozzle’ area, these are for hot glue. Apply the hot glue in the channels for one of the halves. Attach both halves together, apply more glue to the outer perimeter.
A quick water test showed no leakage when the exit hole was blocked. Water flowed fine when the exit hole was uncovered.
After seeing the test worked, now it’s time to move on to the cup. There will be 6 ‘nozzles’. Here’s what the design looks like:
The pieces are 3D printing now. The next steps are:
- Once the prints finish, post processing, then checking tolerances and little modifications if necessary
- Figuring out a mount for the dremel
- Testing the dispensing with water + food colouring, covered by a translucent box
Questions and thoughts on my mind:
- What if the fluid ‘adheres’ to the plastic via surface tension, and what if the centrifugal force isn’t enough to fling it away from the piece? Is that one of the reasons why needle heads were used? If this happens, what can be ways of fixing it?
- How does the distance of the exit holes from the axel of the dremel impact the formation of the fibres?
- This might work with drone motors (BLDC) too. Will it work? This could be an interesting way to scale it with drones having 4 (or more!) motors.
- What is the ratio between styrofoam and acetone needed?
- Is my dremel fast enough?
- How will I set up an area to test in my room?
- What else can we make by recycling materials in this way? What else will these fibres be good for (besides pillows etc)?
- Remember to stay healthy and not project overwhelm