Halloween Brush Bots: STEM it Up Like a Mad Scientist

Electric spiders! Flapping bats! Jittering ghosts! What happens when you mix Halloween spooks and a young mad scientist? Why, Monster Brush Bots, of course! Brush Bots are a super simple way to introduce kids to robotics. The hardest part is finding the tiny little motor to drive them, but I’ve got a few ideas to help you out there…more on that later!

This project is part of #CampSCI and my pals at Monsanto sent us the parts to make our first Brush Bots. We did a little modifying of our own…but that’s what good engineers do, right? At the end of this post is a video from a Monsanto scientist to show you how to make a Brush Bot and more on what you can do with them.

What’s a Brush Bot Anyway?

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A brush bot is a very simple “robot” that moves by vibration! They are often made of tooth brushes, but any brush will work if the motor is big enough! The bristles act as the legs of the bot and the motor vibrates the whole bot. They have no directional control, but that’s half the fun! 

You might be familiar with Hexbugs, which are a commercially made brush bot.

Stuff you need to make a Brush Bot

• Small motor with two wires 
• Button cell battery
• Toothbrush
• Pliers/wire cutter
• Double stick foam tape
• Tiny rubberbands (like for tiny braids)
• Wire cutter, wire stripper (if needed)

The motor is the most interesting–and critical–part of the brush bot. These are usually pager motors, which you can find online at places like Evil Mad Scientist or on eBay. You can also buy a whole Brush Bot Kit from MakerShed, a great resource for your kid’s STEM projects. If you’re handy enough, you can also salvage the motors from any (no longer used) device that vibrates!

I wonder if Doofenshmirtz shops at Evil Mad Scientist?

Make a Brush Bot!

First, cut MOST of the handle off the tooth brush. A pair of wire snips works well for this. You might want to do this bit yourself, unless you’re working with an older kid.

If the wires of your motor are covered, you’ll need to strip the ends so about half an inch of the metal wire shows. Test the motor and battery by touching one wire to each side of the battery–you won’t get shocked. The motor should spin quickly!

Use the double stick tape to attach one wire to the battery, then use the other side of the foam tape to stick to the top of the brush. Use a tiny rubber band (or more tape) to stick the motor to the brush handle. (not shown) The weight on the motor’s shaft should be able to spin freely.

Use a second piece of foam tape to stick the OTHER wire to the top of the battery. 

Unfortunately, there’s no on/off switch with a home made brush bot. To turn it off, you’ll have to pry the tape off too. But now is a good time to test your bot. Does it streak across the table? Spin in circles? Fall over? 

If it falls over, you can make the bot more stable by smashing the bristles into the table–this will push the bristles out and give it a wider stance. If you want to make the bot travel in one direction, try smashing the brush in a heavy book for 5-10 minutes. My favorite smash-stuff-flat book is my 1996 Unabridged Webster’s Dictionary!

At this point you have a functional brush bot. But it’s kinda boring looking, don’t you think? Now you need to decorate it!

Spook up your Brush Bot for Halloween

Mitch and I decorated our brush bots with spiders, bats and one eyed monsters! You’ll need black construction paper, googly eyes, glue and pom poms to make monsters like these! We also made one weird little monster bot by gluing eyes and antenna right to the brush. 

 

You can also make a fun Ghost Bot by placing your bot inside a small white cup decorated with ghostly features. Use a permanent marker to draw the face! I found these plastic bathroom cups (like Dixie Cups) at Walmart in the paper aisle.

Monster Bots Habitat

Make your monster bots feel at home by creating a habitat just for them! We let our spiders wander around this spider web we drew on piece of black paper with a white pencil. It’s placed in a cheap-o frame without glass.

Here’s more science stuff about Brush Bots from my science pals at Monsanto. Watch to see how to make a brush bot and a little science lesson on batteries! 

BrushBots from Monsanto STEM Education Outreach on Vimeo.