Squishy Circuits

We were introduced to Squishy Circuits at last year's Maker Faire. I thought they were very interesting, but J was a little too young as a new 3 yr old. Almost a year later, I've decided that J's old enough to try playing with circuits.

What is a circuit? 

It's a connection of electrical items through wires/conductive material. Metal, water, human skin are all examples of conductive materials. Metal is intuitive when it comes to conducting electricity. You can feel electricity conduct through your skin if you rub your feet on the carpet and then touch someone else or something metal (static electricity is shocking). You also don't want to be in the water during a lightning storm since water conducts electricity.

How do circuits work?

Each circuit needs a power source (ie. a battery pack) and at least one component (ie an LED, motor, buzzer, etc). Basically, the items in a circuit all need to "hold hands" in some way, without the battery pack being connected to the same side of a component or itself, without a component. If a connection is missing/broken, the circuit won't work. Electricity is also lazy. It likes to take the easiest path around the circuit. If there are two wires, one has a component and one does not, the electricity will go through the wire without the component since it's less work (be careful since this can also "short" your circuit - read below).

Making the Squishy Dough

The "conductive dough" is basically the standard homemade play dough recipe we've been using for J. The salt + tap water makes it conductive.

The "insulating dough" is basically pie crust. It uses distilled water which doesn't conduct electricity. There is also no salt in the insulating dough.

Prepping the components

Per the suggestion of Squishy Circuits, we crimped terminals onto our wires to increase the contact area for better conduction. For consistency, we made all of our positive (+) wires red and negative (-) wires black. The LEDs did not get crimped terminals.

Constructing circuits

Please closely supervise your kids to prevent short circuits. The circuit gets grumpy if you try to plug both ends of the battery into the same wire/piece of dough or the electricity goes around a path without a component. This causes a short circuit. The battery can get very hot or explode when shorted.

The best way we found to start with the circuits was to make a "hot dog". We rolled out two "worms" of conductive dough (ours was colored purple) and one "worm" of insulating dough (ours wasn't colored, kind of whitish in color). We made the insulating dough longer than the conductive dough, so the conductive dough didn't accidentally touch. Touching conductive dough pieces together is bad and could cause a short circuit.

With the + (red) side of the battery plugged into on side of the hot dog bun and the - (black) side of the battery plugged into the other side of the hot dog bun, we placed an LED straddling the insulating dough, with a leg in each of the buns. Note that LEDs are directional and only work in the proper orientation. The longer side of the LED is +. If the LED does not work, flip it around. If it still doesn't work, check your connections and make sure everything is properly attached (or "holding hands").

You can add rows of LEDs down the hot dog. We made ours look like a stoplight with red, yellow, and green lights. These lights are in parallel. If I remove a light, all of the other lights remain lit at the same level as they were before I removed the light.

Now if we were to make a "Big Mac" with 3 buns, we can connect the lights in series. If you remove a light, the other light is affected.

You can also add motors, buzzers, and vibrators to your circuits too to see what they do and how they react.

J and his friends' favorite thing was trying to make a face with a light-up nose. We connected a side of the battery to each eye and then connected the LED for the light-up nose. We used extra dough for eyebrows and smiley faces.

So what does this cost?

The dough cost is pretty minimal. We had everything except distilled water in our cupboards.

LEDs run under $1/light. I found 60 larger ones for $20 at a local store.

Motors, buzzers, and vibrators are ~$2-4/piece. Some of these components came with wires already attached.

The battery pack was $1.30. We had leftover wires from our homemade shake table.

The dough is supposed to keep in a zipped baggie for a few weeks. J has already requested to play circuits 4 times since yesterday. Remember, this is a closely supervised activity for the kids. Short circuits are easy to come by and can be quite dangerous. Please do not let your kid do this activity alone.

We'll be doing Squishy Circuits at the next Science Saturday (tentatively April 20th, morning). If you'd like specific details of when and where, please email me using the address on the sidebar << . I give details the week of the event since we depend on the weather.

Update December 2018:

Remember to clean off your component leads before you store for any length of time. Salt of the dough corrodes the metal. Use rubbing alcohol to clean any parts that touch the conducting dough. The little boy above is now a cub scout doing the science elective for Webelos!