Make a Microbial Fuel Cell (MFC) - Part 1

Step 3 Making the salt bridge

Now that we've prepared the agar/salt electrolyte solution we're going to fill the salt bridge with it. Here's what I recommend.

Get a short glass large enough to hold the bridge PVC upright. Cut a piece of cardboard large enough to span the glass and at least double the size of the bridge pipe. Cut a circular hole in the center that matches the outer diameter of the bridge.

Place a PVC nipple on one end of the pipe. Insert the pipe though the hole in the cardboard and place in the glass so that it is standing on the flat end of the nipple. This should hold the bridge upright while the agar cools and solidifies.

Now carefully take the melted agar/saline solution and using the funnel fill the salt bridge to the top. I found that wrapping a wash cloth around the base of the pipe where it exits the cardboard made overflow much easier to deal with when filling the bridge. Carefully place a second PVC cap on the end to prevent accidental spillage and allow to cool.

Once the agar has cooled and solidified remove it from the assembly. It may be stored in the refrigerator.

Now using a drill or drill press with a large diameter bit drill out the end of two PVC slip caps leaving a short collar around the end. When the slip is placed over the end of the salt bridge it should hold a circular piece of non-conductive/non-reactive mesh such as plastic silk screen material firmly in place.