The battery connects to positive and negative electrodes in the patch.
Iron wire would do similar things, merely having a different set of corrosion reactions and colors at the positive electrode.
At the positive electrode, the cathodic reaction is shown as:
The positive electrode doubles as the nozzle head where the flame is produced.
The negative electrons in the N-type material are attracted to the positive electrode.
Trays of agarose were slipped into the unit, which had positive and negative electrodes at either end.
DNA has a negative charge and so will move to the positive electrode in an electric field.
The field flows from a positive electrode to the negative electrode.
Then, when radiation makes free electrons, they "fall" hard towards the positive electrode.
Bit by bit, the cosmic dust particles began to build up around the positive electrode.