Each sheet contains millions of microcapsules, about as wide as a human hair, filled with negatively-charged white pigments and positively-charged black pigments.
But they're really just positively-charged cations — like calcium, sodium, and potassium — and negatively-charged anions, like phosphate, sulfate, and bicarbonate.
Bacterial cell walls are often negatively charged, which means that they repel any potential harmful molecules that also happen to be negatively charged.
When energized wires strip negatively charged electrons from the air ionizing the molecules that move toward negatively charged electrodes at the planes tale.