Overview Water-free cleaning project

By Yagho Franco Grossi Mota

Fall 2023

The resin 3d printer was readjusted and enhanced a little bit. Also, an ‘infallible’ setup was found by setting heatbed at 60C, extruder at 240C and the removal of the left nostril when dealing with more detailed builds.

These were the results from my predecessor. My idea was to use the inverse of the principle of reducing volume / surface area. Circles and cylinders have the minimum surface area for a given volume, thus being the opposite of the aim. My predecessor did circles, I would do triangles. As many as I could.

I used Fusion for the entirety of this project. I did not know anything about it, but it was extremely useful and fun to learn it!

The latex solution is utterly useless for the goal of the project. Not even accounting for the intolerably strong smell of ammonia, it does not deal well with details, which were my goal for the project. I promptly abandoned it as soon as I could and suggest to any future researcher of this project to do the same.

The ecoflex solution worked wonderfuly!!!!! It worked perfectly fine, gave off a lot of detail (and did not smell of urine!). With such, I was able to give life to more daring ideas regarding my envisioned triangles, including my final design.

The picture shows the dirt absorbance of a beta-prototype still using rectangles before the final design.

This is my current design, to be improved using more detail of the resin printer whenever it is setup. Until so, I cannot think of other ways of improving nor it nor the mould.

More specs on this design follow:

The triangles easily allowed the prototype to increase in size by a factor of 3x without visible strain.

A close-up of the triangular design. One can see that the triangles are not fully developed. That is because of both not enough precision of the printer and because of limitations of the ecoflex. IOW, it they are kind of stuck in the vertices of the triangle.

Just a picture of the workspace and how I arranged it. The mixing station for the ecoflex dual-solution, the standby post for the curing moulds and a historic of failed prototypes while trying to make the printer work accordingly. As well as a lot of wipes since these solutions tend to make a mess.

Analysis of water retention and self-cleaning factor

For this analysis, two procedures were made.

For measuring the water retention, it was measured the mass of water in a plate before and after the prototype was dip into it. The difference of such values was then divided by the area of the prototype so as to give water retention per square inch.

For measuring the self-cleaning factor, a heterogeneous solution of water and mostly hydrophobic dirt was made. Each prototype would, then, be dipped into a plate containing such solution and it would be measured the collective mass of prototype, solution and plate before and after it was stretched and slightly shaken. The difference between such values, divided by the area of each prototype would amount to the self-cleaning factor, which is the self-cleansed solution per square inch.

The 6 prototypes analyzed

From left to right: the first three ones are prototypes of the previous researcher, the first (T1) being a small with cylindrical cuttings, followed by one (T2) with big bulky rectangular blocks and then one (T3) of big cylindrical walls. The fourth (T4) is my final prototype made of many tall triangles, followed by a pair (T5 and T6) of same design rectangles but made out of different materials. The clear one is made of the non-ammonia based solution and the yellow one is made out of the ammoniac resin.

Water-retention:

Self-cleaning factor:

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Reflection

• These informations point out that the best film design is, as I predicted, increase the surface area in a way that allows maximum stretching.

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• The comparison between t3 and t4, which had the same area (and same height) but different shape design (the former being cylinders and the latter being triangles) shows that triangles are, indeed, superior given their bigger area/volume ratio. Also, the fact that t4 is way more compressible allowed it to have way more series of triangular cavities in the same space where t3 would only have 2 cylindrical cavities.

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• The comparison between t1 and t3, which had the same design but different cavity-height shows that deeper cavities are good. This is due to the increase in surface area that such bigger height amounts to.

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• The comparison between t5 and t6, however, which were different only by the chemical composition of each resin shows that the chemical composition matters a lot, as it was seen by the different performance of t6 regarding water retention (which was bigger than t5’s) and self-cleaning factor (which was smaller than t5’s), accounting for a difference of more than 50%.

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Conclusion and future prospects:

• This term’s tests show that the triangular shape is the way to go. That each triangle should be as high as possible and that the design should be as compressible as possible. This increase in height will require both a more refined printer (such as the resin 3d printer) and maybe a more refined moulding resin.

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• One possible idea for increasing the water absorbance factor is to try something that would increase the irregularities on the surface of the mould, so as to increase the surface area and even the friction between mould and water even more. Smooth surface is a detrimental factor that should be addressed.

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During winter term, thus, the main goal will be to make the resin printer work and, meanwhile, get inspiration for some more daring designs that will work better for the polydimethylsiloxane. Also, to test out with actual PDMS is on my plans, so as to know its viscosity, which is a crucial way when deciding the pouring method to be used.

If it is to viscous, it may not spread evenly throughout the mould and form clogs with bad resolution far away from the ideal.

End of presentation.