Building Soap Film Slides

I've been playing around with distance minimization problems using soap films.  It's cool stuff, as you can see in this video.

I'm still figuring out exactly how to use it in my classes.  It has application to all of the courses I teach -- geometry, algebra 2 and calculus.  I made a Desmos activity that gives an idea of one way I used it last year.

My biggest excitement came from figuring out how to make the "Soap Slides" (to coin a phrase.)  Here's what I did.

1.   The slides are actually cases for 15 collectible cards (baseball, Pokemon, etc.) I found them for 25-cents each at a local store.  They can also be purchased online for a little more.

2.  You need some posts.  There are two options.  I was able to 3-D print mine.  I made cylinders with holes in the middle.  I figured this would give the glue more surface area to grab onto.  If you have a 3-D printer my .stl file can be downloaded here.  Important:  It should be rescaled first to your liking -- I used a vertical size (z-axis) of 28mm and x-y axis sizes of 7mm.  Alternately, you can use small wooden dowels that can be found at hardware stores and online.  The ones I found were "fluted" and they tapered toward the ends, both of which made them a little more difficult to use.  There are probably better ones out there.  Still, these did the job.

With the wooden dowels (and bad glue)

My 3-D printed posts

3.   Pull the two halves of the card case apart.  (It can be fun to break things!). Using Desmos, I printed a template of the figure I wanted to make.  In this case, it was a square.  Place one half of the case on the template.  This will tell you where to glue the posts.  IMPORTANT:  The posts should be glued to what was originally the outside of the case.  If the curved edges turn to the inside, the soap film gets stuck to it, which means we don't get the desired result.

                 

3.  I used Gorilla Glue Gel (pictured below).  Earlier, I'd used a type of Gorilla Glue that expands as it dries.  This was not ideal.  Place a dot of the Gorilla Glue in the spot where each post will go.

           

4.  Place a post on each spot.

5.  Place a dot of glue at the top of each post.

6.  Put the second half of the card box on top of the posts.  Remember to have what was the outside of the box facing down (so the edges are curving up.

Let it dry, and you're done.

Last advice:  Find a container for your soap solution that is deep enough for you to dip the entire slide into the solution vertically as well as horizontally.  This will allow you to get different formations (aka local minima) when you play.

I'd love to know if anyone does this.  Let me know!  Meanwhile, I'm going to figure out where it fits in my year.