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. Author manuscript; available in PMC: 2016 Dec 26.
Published in final edited form as: ACS Appl Mater Interfaces. 2016 Sep 8;8(37):24306–24309. doi: 10.1021/acsami.6b07440

Figure 1.

Figure 1

Schematic illustration of the possible selective antibacterial mechanism of polarized KNN. After polarization, the electric domains of the piezoelectric KNN become aligned, which results in the distribution of positive charges on one surface and the distribution of negative charges on the opposite surface. Consequently, an electric field is generated around the KNN substrates that promotes the formation of ROS (e.g., H2O2, HO2− and •OH) at the cathode surface through the reactions listed in the figure. Due to the presence of the electric double layer, the positive surface of KNN is the cathode of the micro electric field. Consequently, when bacteria are cultured on the positive surfaces (termed positively polarized surfaces) of the KNN substrates, they are killed by ROS. Conversely, when bacteria are cultured on the negative surfaces (termed negatively polarized surfaces) of the KNN substrates, they are not killed because of the low levels of ROS.