Week Six: Designing Life on Different Scales II
Fall 2015 | Ji Won Woo | First Year MFA
This week we continued to explore biological design at different scales with our ‘MudWatt’ Microbial Fuel Cells (MFC) and a Winogradsky Column. We learned that electron-releasing bacteria exist in all types of soils and sediments, therefore anyone can build a Microbial fuel cells (MFC) to generate electricity by directing electrons given off by certain, electrogenic, bacteria through a circuit. By opportunity of a Skype call conference with Professor Derek Lovley, we were able to further understand about MFCs and its possible future implications. A Winogradsky Column were also built with soil collected from UPenn's Kaskey Garden to observe the growth of microbes in a column of mud.
In class, we began with revisiting the diagram of Microbial Fuel Cells (MudWatt we built last Wednesday) and further studied steps of using electrons as a battery with full circuit diagram.
-An MFC works because anaerobic electrogenic bacteria create a thin biofilm on an anode buried in soils (carbon or graphite fiber). The anaerobic bacteria obtain electrons by metabolizing organic material in the mud and the bacteria conduct the electrons through appendages on their cell membrane surface to the conductive surface on the anode. The electrons travel from the conductive surface through a wire attached to the anode to the Hacker Board. Afterwards, electrons travel back down through the Cathode wire to aerobic bacteria growing as a biofilm on the cathode that sits on top of the soil. The flow of electrons (anode to cathode) completes a circuit and generates an electrical current.
- MFC is a electron source (like a well), in order to transform it into a battery,
- Resistor pulls electron
- Capacitor loads and stores electrons
- Boost converter amplifies voltage or batteries can be built in series or parallel to increase voltage
- Microcontroller can be used to light up LED, to make sounds, and more.
- Our MFC creates 0.8V (which is 1/2 of AA battery), but voltages need to be boosted to 3V or 5V (universal standards) in order to use for most of electronic devices.
Then we spent rest of the class time discussing our project ideas with inspirational pieces from Anthony Dunne & Fiona Raby.
- How to think of Energy differently (what kinds of extreme situations can you think of, what are the sacrifices from energy uses, what kinds of wastes or savings follow energy use, what is energy excess and what is good about it, think about wasting time in relation to energy...)
- Problem VS Proposition
- Thinking in Scenario (where does your design live, who is your audience, what does it do, what medium or object is used, is it fictional or provocative...)
- Thinking in Culture/ Ethics/ Morality along with the idea
Our MudWatts have been growing for one week and electricity was generated by the microbes! We connected the anode and cathode wires to the Hacker Board, and connected a capacitor and LED light to it as well. All of our MudWatts collected electricity from microbes however only James and Morgan's MudWatt collected enough electricity at this point to be able to blink LED. Later we found out that some of our MudWatts formed short circuits (meaning the anode and cathode wires are touching each other). Adding vinegar (as Professor Lovley suggested) showed great boosts in Voltages.
Kaskey Park, Turtles, and Professor Lovley
We went outside to UPenn's Kaskey Garden briefly (behind the Goddard Building) to gather mud from the bottom of the pond for our Winogradsky Columns. The weather was very nice and the turtles were tanning :-) After we came back to the lab Professor Lovley called for a Skype conference and answered the questions that we prepared about MFCs. Below is a brief summary of some of the ideas we discussed with Dr. Lovley:
- By playing range of conductivity (wires with different materials have capability of transistor or capacitor), ability of switch is possible
- Instead of transferring electrons to electrodes, Geobacter also can transfer electrons to other species of microbes (so feeding into different environment is possible)
- Definite life of biofilm is unclear, but the oldest that Professor Lovley has is over 12 years old
- Efficiency of one giant MFC over small ones in parallel is also unclear (as some sediments are conductive, multiple small MFCs sometimes talk to each other and influence power output or work backwards)
- Transforming Geobacter to do the work encoded in biological circuits is being researched (e.g. designing plasmids to plug them into Geobacters, using different promoters)
In today's lab, we also constructed a Winogradsky Column to observe the growth of microbes in a cylinder with mud we collected from pond, shredded newspaper, hard boiled eggs, and water. This Column will be a self-contained recycling system powered by sunlight. The concentration of oxygen, nutrients, and light will affect the types amount of microbes that grow at each location within the column.
- Cylinder: A transparent container that light can get through allows photosynthetic microbes to grow
- Mud: Billions of microbes!
- Shredded newspaper: A source of cellulose (provides energy to the cellulose-degrading microbes so they can grow)
- Hardboiled Egg: A source of sulfur (also provides energy to the microbes)
- Pond Water: Also source of microbes
We end up making our Winogradsky Column a MFC as well. One was covered in foil to compare with the other one that will sit near the sunlight.