I shall call him SQUISHY and he shall be mine and he shall be my SQUISHY – Dory, Finding Nemo
This is a wonderful idea for teaching electrical circuits and more (thanks to Linda Sandvik for tweeting about something that led me to read another blog post of hers, which led me to Squishy Circuit heaven).
It was developed by some very cool people at St Thomas’s University in Minnesota. Now, we know that regular toy shop PlayDoh conducts enough electricity to trigger a MakeyMakey, and indeed I’ve taught circuits by getting my whole class to join hands to trigger a MakeyMakey hooked up to a GarageBand synthesizer. MakeyMakeys are great and cool, but at about £40 a pop, a little expensive for us impoverished educators.
“What’s for dinner dad?” “Conductive PlayDoh!”
The great thing about this is it’s cheap – to make the conductive PlayDoh you just need some flour, salt (I used dishwasher salt rather than my usual Maldon Sea Salt), lemon juice and a tiny bit of oil – the food colouring is optional. Linda Sandvik posted a recipe with European measurements here, or if you’re in the US you might want to go to the original source. The components aren’t expensive either – just a few LEDs, a motor perhaps or a buzzer.
It’s pretty safe too – though you need to be careful not to connect an LED straight to the batteries; this special PlayDoh isn’t a perfect conductor (shocking, I know), and these projects make use of its natural resistance to remove the need for connecting a resistor in your circuit. There’s very useful information, in as much or as little detail as you need, on the St Thomas’s University Squishy Circuits video page. The video on Ohm’s law (‘LED calculations’) is very useful for a tinkerer like me who’s forgotten some of his O-Level physics, and might otherwise blow a few LEDs up.
Please note: battery compartments made of squishy circuits are probably not viable for long-term engineering solutions – the PlayDoh is full of salt and lemon juice and hence liable to be corrosive!
And finally, here’s Ann Marie Thomas’s inspirational TED talk on what Squishy Circuits can do: