Fig. 5

Different microbial electrode jacket-dish (MEJ-dish) used during this study a 3D, b 3D design, c Rubber, d K3 MEJ-dish, and e–g junction between the electrode and MEJ-dish: partly opened (closed), open, and locked (closed). Locked (closed) indicates no space between the electrode and MEJ-dish, partly open shows the upper part is open, but the lower part is partially open or closed, and open means the connection part is exposed for microbial attachment