STEM Fun: How to Make Bristle Bots

Ready to make some robots?! This week at our Homeschool Science Day, my kids had a blast learning how to make Bristle Bots — tiny robots using the heads off toothbrushes as the body/legs. We taught them how to build an electric circuit connecting a vibrating motor to the battery with wires. The resulting tiny robots were really quite adorable, and this project is a perfect fun STEM activity. As the motor vibrated, the Bristle Bots zipped around — they worked so much better than I expected!

I shared a quick photo on my Instagram feed, and many of you wanted to know how to make robots of your own. So here we go!

If you want to make Bristle Bots with your kiddos, it’s super easy and fun, but first a word of CAUTION… this project includes tiny parts that could be choking hazards, but also the button batteries can be extremely dangerous if swallowed. Be alert and keep track of those batteries!

Supplies to Make Bristle Bots

To make Bristle Bots you’ll need some basic supplies, and I’d recommend picking up most of them from the dollar store. It actually seemed like the cheaper toothbrushes worked better for this project since they tend to have simpler, flat bristles. The most unique item is the pager motor — you can buy a pack of these on Amazon. Your total supply cost to make Bristle Bots will vary depending on how many you want to make. The price for many of the supplies went down per unit when you were buying more bulk. We made about 40 Bristle Bots at our homeschool science activity, and it worked out to about $2 per robot for supplies.

REQUIRED SUPPLIES:
:: Toothbrush
:: Wire Cutters (to remove the toothbrush head from the handle)
:: Double-sided Foam Tape
:: 1-1/2 inch Finish Nails
:: Pager Motor
:: 1.5-volt Button Battery
:: Clear Scotch Tape

OPTIONAL DECORATIONS:
:: Pom Poms
:: Googly Eyes
:: Pipe Cleaners
:: Plastic Jewels
:: Yarn
:: Stickers

These micro pager motors are compatible with both the smaller 1.5-volt and larger 3-volt button batteries. The motors spin faster using a 3-volt battery, but they almost have too much steam, causing the lightweight toothbrush heads to tip over. Though if you want to use something larger for the legs, or if your design ends up being on the heavy side, use the larger batteries.

How to Make Bristle Bots

On to assembling our robots! To make the Bristle Bots you’ll first need to cut your toothbrush head off it’s handle using wire cutters or some other kind of snipper. If the cut edge is sharp, you could use a nail file or sandpaper to smooth.

Cut two similar pieces of foam tape, just wide enough to fit on your toothbrush. Take the paper backing off one side of the tape, and stick the pointy part of three finish nails onto the tape in a Y formation. Take the backing off one side of the other piece of foam tape, and place it over the nails to create a nail-tape sandwich. Peel the backing off the other side of your first piece of tape. With the two nails facing the front (they will look like antennas), adhere the tape-nail sandwich onto the plastic part of your toothbrush, and the bristles will set on the ground like legs. Many of the bristle bots I’ve seen just spin around fast in circles. These nails provide weight to stabilize the robot so it can move further.

Now for the Circuit: inspect your tiny pager motor, and you should see a tiny metal shaft that spins. Remove the last piece of backing from the top side of your nail-tape sandwich, and press on your motor with the shaft hanging off a bit, ensuring it can spin unobstructed.

Our motors came with two wires attached, and the blue wire needs to touch the negative side of the battery, and the red touches positive. Once both wires are connected, the circuit is complete, and the motor will vibrate. This is where you can to teach your kids how electric circuits work.

Button batteries can be extremely dangerous if swallowed. Be alert and keep track of those batteries!

Press the blue wire down into the foam tape, but use your nail to pop the bare wire at the end upward a bit so it will touch the battery. Press your button battery over the top of the exposed blue wire, with the negative side down (so it contacts the blue wire). Bring the red wire over the top and secure with a piece of clear tape. This tape will kind of act as your switch, as you pull it on or off to activate your robot.

Here comes the fun part where you make your Bristle Bot into a creature with googly eyes, pom poms, yarn and pipe cleaners. Let the kids use their imaginations! As you decorate, keep in mind that the tape “switch” will need to stay exposed.

I can’t help but feel like it could be fun to try to make these fuzzy DIY Spiders into robots — maybe we’ll try that next!

If you’re serious about making Bristle Bots, I suggest you watch this video. There are actually quite a few YouTube videos on how to make Bristle Bots, but I love that this one showed how to remove the vibrating motors from an old cell phone. Buying the motors in a pack on Amazon is just so easy, but still it was fascinating to watch. Of course if you don’t want to wait for them to be shipped chances are you probably have an old cell phone lying around somewhere.

I also found useful this tutorial from PBS Kids. I really liked the background info found in the “Did You Know” section, which can help you explain to your kids why the Bristle Bots move the way they do. The PBS tutorial uses rubberbands instead of foam tape, which I haven’t tried. They also use the larger 3-volt battery, which has a lot of juice and seemed to make Bristle Bots fall on their side.

Troubleshooting

If your robot suddenly stops working, the problem is usually that one of the wires is no longer connected to the battery, breaking the circuit. Since this provides a great learning experience for the kiddos, perhaps let them try to figure out the problem.

So you can provide a few hints… the problem is usually one of two issues: (1) the blue wire has sunk down into the foam tape too much so it’s no longer making contact with the battery. Remove the battery and sort of dig the wire tip out so it can make contact again. (2) It could be that your clear tape is no longer holding the red wire in place in which case you simple need to get a fresh piece of tape.

Want more robots? Check out this fun Scribbling Robot!

Your little scientist might also like making slime with this easiest slime recipe:

This Mad Laboratory Game is also lots of fun: