Squishy Circuits

A few weeks ago, I was asked to sub for Homeschool Art and Science – a program run at the library where I intern designed for homeschool children ranging from age 4-14. It’s a drop in program, so there’s a range of ages and attendance that have to be accounted for. I’d never worked on Thursdays, so I’d never seen it in action. I planned to stop in the week before to see how it went. Then I was asked to sub that week too. It was going to be a trial by fire, apparently.

Having survived the first week (Jackson Pollock – the mothers were very forgiving of the amount of paint being flung around), I went into the second week with a better idea of what I was facing. And I was (hopefully) ready.

I’ve been reading up on makerspaces, which are a bit of a buzzword in libraries and museums (even colleges and corporations, sometimes). Wikipedia defines a makerspace as “a community-operated workspace where people with common interests, often in computers, technology, science, digital art or electronic art, can meet, socialize and/or collaborate.” The general idea in a public library makerspace, however, is to provide opportunities and resources for design thinking and skill learning.  I’d recently read a really top-notch book called Design, Make, Play that included articles from makerspace innovators across the country. Some were big – the Exploratorium in San Francisco or NYSCI in New York, where other ideas were more adaptable to my purposes – like squishy circuits.

Squishy circuits were developed at the University of St. Thomas by an engineering professor, Annmarie Thompson, and a few of her students. The challenge was to make something that little hands could play with to explore circuitry. Existing products were frustrating for many children, and were rarely intuitive. Playdough, they figured, was as intuitive as it got. Physics professors had been using its conductive properties for years to demonstrate in classrooms, and Thompson and her team figured they could make something better. Something that could be made at home. Something that could be shaped and molded by little hands. Something that could form not only circuits, but circuit SCULPTURES. And they were going to make it using only things available in the grocery store.

Here’s what they came up with:

Conductive dough recipe

  • 1/2 cup tap water
  • 1/2 cup flour
  • 2 tablespoons salt
  • 1 ½ tablespoons Cream of tartar (or 4 ½ tablespoons lemon juice to substitute)
  • ½ teaspoons of vegetable oil
  • food coloring (optional)

I made this is MUCH bigger quantities, since I was prepping for a dozen kids, but it still only took me about 15 minutes to make. I strongly suggest a non-stick pot, however. I didn’t have one handy, and there was a lot of scrubbing between batches.

Put all of that in a pot and mix it up a little. Put the pot on medium heat and keep stirring. It will start to clump up as you go. This will likely feel counter-intuitive if you’re used to baking, where you want most things nice and smooth – deep breaths, you’re doing it right. Eventually, it will get to a consistency where you can form a lump in the middle of the pot. Put the lump of dough on a floured surface (a floured sheet cake pan is great if you want kids to be involved in the next part). You might want to squish it down a bit (I used the bottom of the pot) and let it cool before you knead it. Once it’s cool enough to really get hands on with, knead it to incorporate about another 1/4 cup flour. You’ll feel when it’s at a playdough-y consistency. Don’t add too much flour or it will be crumbly – I made that mistake with my second batch. It worked, but it made things a lot messier.

Insulating dough recipe

  • 1/2 cup flour
  • 1/4 cup sugar
  • 1 1/2 tablespoons vegetable oil
  • Distilled water (tap water is ok if you don’t have this, but resistance will be lower in the dough)
  • food coloring (optional)

This one is more kid-friendly to make. Put the flour, sugar, and oil in a bowl and mix it up. Then add the water 1 Tbsp at a time, making sure to mix it all in before adding more. Eventually, it will get clumpy and doughy. Put it on a floured surface and knead to incorporate flour until it feels right. This is where you can make up ground if you added a wee bit too much water, too.

The doughs are ready to experiment with right away, and can be stored in plastic bags in the fridge to max out shelf life (about 2-3 weeks). If you do store them in the fridge, take them out a little bit before playing with them, as they need to warm up a bit to be pliable.

Once the doughs are made, basic experiments can be done with things bought at Radio Shack (some may be cheaper online – I wasn’t willing to risk delivery problems).

Squishy circuit dough in lots of colors

 

the doughs

 

 

 

 

 

LED diode

 

 

LEDs (10mm diodes are better for small fingers)

 

 

 

Closed battery casing with switch

 

 

and a battery pack with terminals

 

 

There are lots of experiment packets online, and I’ll include a few of my favorites at the bottom. Mostly, the kids played around and came up with their own problems and solutions. They started with basic circuits, then moved up to serial vs. parallel circuits, short circuiting, circuit load, and lots more great discoveries – all in less than an hour.

Helpful tips

I made the conductive dough green to help show the kids that it was a like a green light for electricity – power could move through it easily. The insulating dough was red, to show that it was a stop light for electrons. It seemed to help them understand what was happening. It also helped me see when the dough was too “contaminated” to be effective. At the end, we had a lump of brown playdough, rather than red and green, because it had been so mixed up.

We also broke a few of the LEDs legs from bending them a lot. It’s going to happen, so don’t stress too much over it.

The kids also came up with the idea of testing what other materials in their houses were conductive or resistant by using the battery pack and LED rather that a multimeter. This is great, just make sure to take a gander at the safety tips before letting them run free.

Don’t connect the battery pack directly to the LED, it may burn the LED out (or even make it explode).

LEDs only work in one direction, unlike normal lights, due to polarity. To make them work, make sure the long leg of the LED is attached to the same piece of dough as the red (positive) wire from the battery pack. 

Sometimes, thin strands of insulating dough will still conduct some electricity, and the LED will become dimly lit.  If this happens, use it as an opportunity to discuss resistance! This will happen more often if you use tap water for the insulating dough, rather than distilled water. It will also happen more often with certain types of LEDs that require less power. This can also be tied back to the idea that smaller pieces of dough are more conductive (it will make the LEDs glow brighter). This applies to both types of dough.

Crossing the wires on the battery pack is the most dangerous potential – it can short out, heat up, and explode of left too long. Be careful of this if kids are experimenting with putting the leads in the same piece of dough.

Resources

 

Squishy Circuits – Sylvia’s Mini Maker Show – a great intro video. It’s about 7 minutes long and covers how to make the dough, along with basic concepts of electricity and circuits, all presented by a 9-year-old girl. This was my go-to.

Squishy Circuits Project Page  – this is where it started. This provides recipes for bigger batches of the dough, and has some project ideas and a toolbox that shows possible additions to your squishy circuit explorations (including a squishy battery!).

Squishy Circuits Lesson Plan from UCLA – a PDF that contains a lot of background info to help you brush up on circuits, plus a guided exploration that asks kids to test different configurations and see what happens.

Liza Stark’s Squishy Circuits – a PDF that goes over key terms, troubleshooting your circuits, and has great pictures of different configurations.

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