Teaching Aid Wish List: February 2019



  • @ajcox @trkelley I have looked into bio-balls for aquariums and into rate of degredation of PLA plastic in water, and concluded that this is something that is very do-able! My initial idea is to create a rectangular layer of fused spheres to mimic a structure like a sponge except with more open paths through it. Imagine a box filled with tiny ball bearings. If the ball bearings were fused and the box taken away, that is the plan. Let me know if this is what you had in mind. It would be interesting to run a before-after-treatment-control experiment with these. I could include plans for such a classroom experiment in the lesson plan idea sheet, and thus hit some scientific practices.



  • I would love to be able to have models of the 4 biomolecules that could somehow show how the individual monomers connect together to show the polymer. Or something that shows what these biomolecules look like.



  • Welcome @kfaust ! I have an idea of how to make this work.
    Okay, we now have two models in the running for the February model-of-the-month! I actually tried coding up a 3D ray-tracing render of a DNA molecule and posted a bit about that adventure over on BugsMapsandMath.com a while back. Maybe I should revisit that code.



  • By my count, the vote stands at:
    Biomolecules — 2 votes
    Bio-beads — 3 votes

    Recruit some more voters!



  • February is shaping up (ba-dum) to be an exciting month! We now have two models running neck-and-neck with three votes each. We will soon have an intuitive graphic method of voting, but for now in case you are wondering where I am getting my numbers, in the above thread it looks like the votes are:

    Aquarium bio-beads (3): trkelley, zrmckeever, ajcox
    Bio-macromolecultes(3): kfaust, JShukle, cgarber

    Eight hours remaining to recruit more votes to your teaching aid model. Go get some votes!



  • February 2019 Results!
    Okay, we have a tie! I propose that because I love this community, I will do both models. @kfaust: to pick your most needed bio-macromolecule from the 4 types, and I will do that one to start. The other types will follow in the future as time allows. Is this a good compromise in the case of a tied vote? Let me know your thoughts---this is your community.
    Cheers all. On to the March model!



  • Designing the Bio-beads. Shapes have more surface area the further they are from spheres. Spheres have a low surface area:volume ratio. As shapes increase the number of sides, they get closer to a sphere and the surface area:volume ratio increases. Think of a 20-sided polyhedron. Therefore, if you want to have maximum surface area for bacteria in a given volume, you need shapes with few sides but that will still stave each other off.
    I initially considered a four-sided pyramid shape with the sides concave. This would create a good amount of surface area. I discarded this idea as I pictured dropped beads becoming foot-puncturing caltrops in the classroom.
    Cubes could work, but may be prone to packing tightly together. I therefore am going to test an eight-sided polyhedron with concave sides. This should avoid tight packing and be safe if dropped or misplaced as the pointy parts will not face upwards. If I make them really concave, I picture these packing together into something like a network like a looser sponge.
    Prototype images coming soon! Let me know what you think!



  • What if you settle on a single shape for the beads that packs well (lenticular is always a good shape for maximum packing) and then simply increase the porosity of the shapes to vary surface area. This would get you orders of magnitude higher surface area than simply increasing the side count of plane solids.

    This is how high surface area minerals/solids work in nature too, an example would be activated carbon, so it might help the students get a more intuitive grasp of natural surface area variation.



  • @JShukle Yes, a good plan. I was going to something like this if the concavity of the sides is not too extreme. I do need to be careful to not design anything too close to existing products.
    My plan is not to simply increase the number of sides on a polyhedron, but to also increase the concavity until they are little more than spines from the centers out to the surface nodes, allowing them to pack together quite a bit.



  • @JeffHolland Hmmm, I can understand staying away from existing product designs ...

    Since this is intended to be for a teaching tool, what about designing a simple system for students to modify the bioballs for their own experiments. Maybe your bioballs can hinge open easily to allow students to fill them with different materials, to explore filtering techniques, or even distinct chemical substrates.

    Alternatively, you could design yours around more advanced filament materials, some of the new wood filaments on the market could be interesting.



  • @JeffHolland That's awesome! Thanks for the tie! I will ask my fellow Bio teachers what would be most useful to us and I will let you know!



  • @JeffHolland I think we've decided that we'd like a DNA model. We teach about those the most so we can start there.
    The big misunderstanding and struggle most students have is the idea of how a monomer fits within a polymer. So we'd love to be able to have something that shows how an individual nucleotide fit within a DNA molecule. Or if that's not possible, how nucleotides fit together to form the overall shape. There are a lot of simplistic DNA models out there, so it would be helpful to have something that showed the structure a little better that students could manipulate and see how it all fits!



  • @kfaust Okay, I will use those ideas as the design criteria and get to work! I do have 3-D coordinates of each individual atom, so I should be able to work up from there to build some realistic monomers. I will post a draft render here before I finalize the design so that you and everyone else can offer design tweaks. This is going to be a fun challenge.



  • I am printing out a first draft of the aquaculture bio-medium right now. I think you are going to be surprised and happy with it. I took inspiration from two sources for two different scales: at the micro-scale, the lining of a mammalian intestine for surface area, and at the macro-scale, the business end of a crinoid. Photos of the finished draft print coming soon. For up-to-the-moment updates of printing progress, as always, follow our Instagram, ShapeOfScience, which will have a new photo in 20, 19, 18 ...



  • A first photographic look at the concept for the new aquaculture biomedium. I call it the Crinoid. The idea is to pack a lot of surface area per volume, but keep it "granular" so that it can be packed into different tubes or tubs unlike a fixed dimension cartridge. I should have the four other "arms" printed out tonight and will post a complete photo later. Let me know what you think!
    Crinoid_draft1.jpg



  • Almost there. A bacterial sinus infection and the resulting feverish conditions is slowing progress so that I did not finish last night. I know that I don't need to tell THIS group about the prevalence of germs brought home by school children. I am back at it though and will have the finished draft up soon.



  • First draft print of the Crinoid is ready! Let me know what you think, especially those that voted for this model in February: @ajcox @zrmckeever @trkelley .
    Crinoid_draft2.jpg



  • @JeffHolland Love this idea! Very clever 😊



  • The Crinoid will be up on our sales page in about a week, after the one-page lesson plan ideas document is complete.
    The DNA molecule model is being looked at now.



  • The Crinoid, a bio-medium for aquaculture, is now available! Thanks for all those that voted for this model.


 

© 2019 The Shape of Science