Making microbe-powered tea lights in 7 steps: An adventure in hacking

Anne A. Madden, Ph.D.
Oct 1 · 7 min read

You know how excited people get when they share photos of their newly adopted dog, or their child dressed up as a tall latte for the holidays? I get this excited when I get to show photos of microbes on petri plates.

What can I say? With the natural ability to make most of our commercial antibiotics, cholesterol-lowering medication, laundry detergents that help us fight climate change, and most of my favorite foods, I am forever fascinated at how humans can harness their powers to make life better… or at least more interesting.

Me, posing with a petri plate covering half my face
Me, posing with a petri plate covering half my face
Me, posing with some microbes on a petri plate for a “cell-fie”

And so when I learned that some microbes create electricity, i knew what I would do for my next project.** I wanted to replace the battery-powered tea lights I use in my life with tea lights powered by microbes. Extra benefit: unlike the tea lights that produce an actual flame, my kitten would be less likely to use a microbe-powered tea light to burn down the apartment.

** Project: Definition. Noun. A science engagement adventure to do when one should be writing a talk, a company pitch, or a manuscript for peer-review. See also “Productive procrastination.”

GOAL: Create a microbe-powered tea light using non-GMO bacteria and supplies that can be purchased at standard electronic supply companies.

Step 1: Strategize a microbial power source

The Mudwatt microbial battery kit
The Mudwatt microbial battery kit
The Mudwatt microbial battery kit

The great news is that most of this work is already done for me. The fantastic people at Magical Microbes have already created an easy way of harnessing the power of microbial electricity: The Mudwatt.

I purchased the simple kit online. My eventual goal is to make this look candle-like, so I purchased the kit without the vessel.

I unpacked the kit and was immediately impressed by the work done on the descriptions of microbiology, as well as the basics of electronics and circuits. I have spent a career trying to hack together things in the rain forest and lab in a MacGyver-like fashion, but rarely has that included anything electronic. I appreciate that this information provided a helpful intro into a field I wish i knew more about.

In terms of the microbiology, I think it’s best summed up by the Muddwatt info packet:

Among the diverse communities of microbes are particular species with unique metabolic abilities that enable them to expel electrons onto oxidized metal compounds, such as rust. In a sense, these so-called “electrogenic” microbes are able to “breathe” metal compounds much like humans and other organisms breathe oxygen.”

The kit I purchased contains an anode, a cathode, wires, a circuit board, a capacitor, a little red LED bulb and gloves.

Step 2: Find the microbes

An image of soil in a small glass vase with wires and a blinker LED board coming out of it.
An image of soil in a small glass vase with wires and a blinker LED board coming out of it.
My Mudwatt, soil, and vase set-up.

I set out to wrangle microbes, which means I set out to find mud. I live in an urban jungle on the outskirts of Boston. Good news, really cool microbes live here in between the concrete side walk and the detritus left over from the perennial construction efforts. I went on a hunt for soil in medians that smelled rich in geosmin — the often microbial-made molecule that smells like fresh turned earth. I won’t give the specifics of where I found this dirt, but let’s just say the public property is likely not going to miss the few handfuls I took.

Step 3: Making the microbes grow

Next was making a mud mush in my kitchen and threading wires through the different components of the Mudwatt circuit board. The glass jar I used formerly housed a candle. We’ll see if it’s large enough. Now it’s time to let the microbes grow.

My cat trying to eat the wires on the Mudwatt
My cat trying to eat the wires on the Mudwatt
World’s worst assistant, Puffin the adventure cat.

Step 4: POWER!

A few days later it worked! The microbes are making electricity and it is being captured by the circuit. The little red light is flashing (albeit, infrequently). I’ve never been so excited by a blinking light. I feel like yelling “IT’s ALIVE” in a nod to Mary Shelley’s work. I need to highlight how cool this is. THE MICROBES ARE MAKING POWER! No battery. No need for genetic manipulation. No need for hard-to-recycle materials. No need for additional fertilizer. Invisible life forms are making my desk glow! Now I’d like to replace the red blinking light that reminds me of a smoke detector with a bulb that is reminiscent of a candle.

Step 5: Replacing the LED bulb

My next step again relied on other groups who have done beautiful things in the education space. I purchased an LED Flickery Flame Soldering Kit from Evil Mad Scientist at my local Microcenter. Someday I’ll use this kit to learn to solder, but right now I will be borrowing one of the warm yellow LEDs in the kit.

A Honda key fob taken apart to reveal the battery
A Honda key fob taken apart to reveal the battery
Key fob I took apart to check that the LED I had was a flickering LED

In order to see if the LEDs had a built-in flicker mechanism (rather than the flickering component being in the circuit board), I borrowed a battery from my car fob. Success! The LED bulb I had flickered like a candle when attached to a battery. With enough power from the microbes this should look like a real tea light. Now to connect the new bulb to the Mudwatt. I put the new bulb in the pins specified for the clock. I’m hoping this will provide enough power for a flicker.

Step 6: Candle enclosure:

A picture of the paper, paper towel roll and LEDs I used to make a paper tea light enclosure.
A picture of the paper, paper towel roll and LEDs I used to make a paper tea light enclosure.
The paper tea light holder I made from scrap paper and an old paper towel roll.

Right now the mudwatt looks a bit like a small bomb attached to a vase of mud. This is not the aesthetic of a tea light I’m going for. After playing around with things I had in the house, I decided to make a paper tea-candle proxy to plug the bulb into. In this way the Mudwatt vase can sit in a box below the candle the way that any good magic illusion can suggest a person’s head has been cut off. I used scrap paper from a talk and a paper towel roll to make the enclosure. I then pierced the top and thread the LED through it. I then connected the LED back to the mudwatt circuit board.

Step 7: Success! (Sort of)

Good news: after a few days my mudwatt-tea candle produces a warm yellow light that is powered by microbes. Less good news: it’s still flashing, rather than flickering. We’ll see if this changes over the next few days as the number of electricity-producing microbes in my MudWatt increases. No matter what, I consider this a success. Like many projects, it will improve in future iterations (I have BIG plans for these), but right now these microbes are doing something even more remarkable than making power. With every flash they remind that tiny creatures living around me are working hard and doing things I could barely imagine. Rather than getting more familiar with electronics and soil microbiology, this is the lesson I really needed this week.

Check out my twitter and instagram account for videos of this process.

A tea light glowing, powered by microbes
A tea light glowing, powered by microbes
The final glowing microbe-powered tea light!

Key Take-Aways:

  1. In the future, I will chain more Mudwatts together to get more power.
  2. Cats make really bad microbe/electronic hacking assistants. I never thought I would ever say “Don’t drink from the cathode!” in my life.
  3. V2.0 should probably feature connector wires to go directly from the mudwatt into a candle LED. This will save significant construction time and increase the chance of this looking like a a real tea light.
  4. I’m really impressed with the MudWatt kit. I can’t wait to buy more and use them FOR EVERYTHING (get ready Defcon 28!!!)
  5. MICROBES ARE SO AMAZING! I made power with microbes that live in dirt. And this was crappy dirt. Not pristine organic, pampered, virgin dirt. This is crappy city dirt that has shards of broken bottles and plastic in it. Every time the little candle system blinks I’m reminded of the crazy fact that microbes are doing cool things around us ALL THE TIME.

Summary

Total time: A few days for the microbes to ramp up, but construction is <1 hour

Total cost: 1 Mudwatt: <$39.99 (this is with the vessel included):, Evil Science kit: ~$7 (but bulbs can be purchased separately for less), joy of seeing microbes power my new little pet?: Priceless.

Extra supplies on hand: Paper, tape, scissors, paper towel roll, Honda Accord key fob battery, tiny screw driver to get into Honda Accord key fob, a couple youtube videos on LEDs.

Skills gained: Basic understanding of circuit boards and LEDs… plus some patience as I’m learning how to water my mudwatt.

Knowledge acquired: 1.) A better understanding of the microbial ecology and physiology of certain soil microbes I’ve never had the pleasure of conducting research on. 2.) A basic understanding of electricity (I think this is one of the things covered in middle school that I missed out on).

Ethics statement: No animals were hurt in the production of this project, though my cat was frustrated on multiple occasions that she couldn’t eat the Mudwatt wires. I declare I am not sponsored by any of the groups I have mentioned at the time of this posting. I further do not have equity in any of the companies I have mentioned.

Happy microbe wrangling!

© Anne A. Madden 2019

Anne A. Madden, Ph.D.

Written by

Microbiologist, inventor, and TED speaker Anne Madden studies the microscopic creatures that live in, on, and among us. Find out more at www.AnneAMadden.com

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