Build a Microbial Fuel Cell: Cathodes and Electrodes Build a Microbial Fuel Cell: Cathodes and Electrodes

What You'll Need
Half-inch compression fittings with endcaps and tubes
Large storage containers or small fish tanks
Aquarium pump tubing
Drill with bits
Glue such as acrylic cement
Paper towels
Carbon cloth
Wire strippers
Copper wire
Metal epoxy resin
Electrical tape
PVC pipe
Aluminum foil
Glass stirring rod
Pond bacteria (benthic mud)

If you are considering green living, then one energy saving device may be a microbial fuel cell. These little devices powers electricity by harnessing bacterial relationships found in the natural world. The bacteria used in a microbial fuel cell are often cultured for the enzymes which work with electricity. In order to create a microbial fuel cell, you will need to create 2 units, an anode and a cathode, which are divided by a membrane. You will also need to build two small units which will constitute your anode and cathode parts.

Step 1 - Create the Anode and Cathode

Open up your compression fittings, and remove the rubber insides. With your sandpaper, rub the edges of the endcaps in your compression fittings until they are rough. Do the same with the insides of your storage containers, until you have a small rough patch on each container. mark the edge of one roughed space, and use a measuring tape or ruler to mark the same area on the other plastic container. These should be exactly opposite each other. Drill small holes on the top of each of your storage containers. On one lid, drill a hole large enough to accommodate your aquarium pump tubing. Drill holes in the marks on each of your containers. Place your acrylic cement around your compression endcaps. Place one of these over one of the holes. Repeat for the other side, and then join the endcaps with the compression fitting tube. Cover with more acrylic cement.

Step 2 - Making the Electrode

Ensure that both of your plastic containers are flat on the table before they are completely dry, and then tighten your caps until the tube is sealed. Once this is done, take your carbon cloth, and cut out a square around 2 1/2 inches. Take some of the copper wire, and remove 6 inches or so of insulation on one end. Remove 1/2 inch from the other end. Cover the 6 inch end with nickel epoxy, and stick it to the edges of the square. Allow the epoxy to harden, and then test the connection with the multimeter.

Step 3 - Make the Membrane

Use some kitchen wrap around the lower half of the petri dish, and then take your compression fitting tubes, and cover one opening with foil. Take 1/4 pint of water, and then measure out 1 ounce of agar, dissolve this in the water, stirring with the glass rod. Add 2 or 3 pinches of salt, and then add this to the tubes. Place them on the petri dish and place in the refrigerator.

Step 4 - Uniting the Microbial Fuel Cell

Take your plastic containers, and connect the chilled tubes to the end caps. Take the mud sample, and add salt. Fill the containers with the mud. Bury one of your electrodes in the mud. Fill the container with 2 holes in the top with water, and float another electrode in this. Add the Aquarium pump tubing.

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