Intro: Making Squishy Circuits From COTS Playdough
Part of the work Eureka Factory does involves providing staff development training for area librarians interested in implementing makerspaces and creative programming in their libraries. One of the tools we use for that training is Squishy Circuits, which libraries can put to fun use for youth and adults. The training workshops have been fun and successful, giving librarians a familiar medium - clay - to use in a new way - introductory electronics.
Like just about everyone else utilizing Squishy Circuits, we turned to the Squishy Circuits Project Page at St. Thomas University for the basics. And like most folks employing this fun project, we cooked up and kneaded batches of both insulating and conducting dough for the training sessions.
It's not hard to do, but it does take time and, here in Florida, we discovered the homemade dough doesn't keep very long, turning from an electronics project into microbiology projects as hairy growths of mold take over the dough - even when it hasn't been handled beyond preparation.
We wondered if plain old over-the-counter Play Doh would work.
It does - beautifully, better and with respect to providing an easy roll out resource for libraries and schools, OTC Play Doh is clearly the way to go. While much of the time, DIY solutions are preferred. Sometimes the DIY solution that works best is sitting right on a store shelf - for about $3.
Step 1: The Scratch Method
The scratch method involves lots of flour, oil and water to create two different kinds of dough - an insulating dough, with sugar in it, and a conductive dough, with salt. To make the amount of dough we needed for a training session for 30 to 40 librarians it took some time, and the results were inconsistent - like making dough often is - and the clay varied from batch to batch, despite our best efforts.
Step 2: Storing the Scratch Dough
Storing the scratch dough involved buying little plastic containers, filling them with the dough and labeling appropriately.
Step 3: Success and Limitations
The training sessions were fun, and librarians totally got it and were inspired to providing similar programming in their libraries. And while the results were satisfying, the clay was limited to the colors we produced in our batches, and the librarians had to take the recipes with them where they probably still sit on their desks because they don't have time to cook up batches of dough.
Step 4: Bring in the Play Doh!
But guess what? They already make this great timeless playdough in bright colors and conveniently stored, for about $3 per set of four. For about $60, we save several hours of cooking, kneading and storing, and can provide 40 librarians working in teams of two, a four color choice of playdough. Even better, they know they can just pick this stuff up at the local store - or probably already have it in stock! - and be ready to roll!
Now this isn't a new idea, but it seems to be a rarely employed one. We checked Instructables and browsed online, and while we found some resources suggesting adding salt to commercial Play Do would make it more conductive (which you don't actually even need to do), we found only one site - Science Buddies - that featured the very straightforward instructions for using Play Doh to make Squishy Circuits. (Way to go, Science Buddies!)
Step 5: Playdoh Conductivity Tests
While the make-it-yourself variety can be more electrically conductive, the COTS (Commercial Off-the-Shelf) solution can provide equally satisfactory results for a typical squishy circuit.
To test this, we first wanted to get a baseline on the electrical resistance of Play Doh by measuring the value across a 1 inch diameter ball. We read between 76 and 88 ohms. And plugging in a couple of LEDs, they lit up just fine. Then 3, 4, and 5, still no problems.
Step 6: Stretching the Limits
Next, to see how that resistance varied through a longer stretch, we rolled the same ball out to a 4 inch rope. The resistance went up to about 93 ohms. Fairly negligible when we’re talking about lighting up LED squishies.
But how was the voltage behaving? To check for voltage drop, we rolled up two 6 inch Play Doh ropes, energized them with a 9V battery, and checked the voltage within ½ inch of where the battery voltage enters the clay vs. 6 inches away. Again, the difference was really insignificant for typical squishy projects. At the ½” mark we measured 9.43V (typical for a 9V battery) and 6” away it was only 9.37V.
Step 7: The Power of Play Do
We rolled the Play Doh out to 8”, plugged in 7 LEDs, and all behaved wonderfully, lighting as brightly at the battery end as at the far end.
Step 8: Ditch the Insulating Dough
We had already ditched the insulating dough with the scratch batch, after our first session (and had also suggested to the librarians in our first training session that any insulating material between the conductive dough would work). The insulating dough isn't really needed and eventually gets mixed up with the conductive stuff anyway. We've been using rolled up wax paper for other projects, but cardboard works as well and so do other items.
Step 9: Get Creative!
The joy of COTS Play Doh is its tried and true malleability (and its awesome aroma!) and its familiarity to everyone, from children to adults. It works much better than the scratch dough for sculpting and broadens the range of creative soft circuitry projects you can do. In this case, I molded it around a small plastic bottle to make a funky little critter.
Hopefully this proof of concept opens up Squishy Circuits play and learning to more folks, and provides new avenues of creativity in the process.