Figure 2.

(A) Calibration curve of the paper-based H₂O₂ sensors with different hydrogen peroxide concentrations: 5–320 μM H₂O₂ in 1 M KCl solution. Herein, the frontside of the chip was insulated with an adhesive tape since the sensor is placed into the filter with the backside toward the patient, and thus, the frontside of the electrodes has no direct contact with the exhaled breath. Error bars represent ±standard deviation (SD) of n = 7 replicates. (B) Scheme of measurement setup for simulation of respiration, including a lung simulator, a humidifier, a H₂O₂ evaporator, and a filter housing with an integrated H₂O₂ sensor. (C) Cyclic voltammograms of a dry chip with a PB-coated working electrode, pretreated with 1 M KCl, in vapor after 9 (gray), 24 (red), 70 (blue), 185 (green), 195 (orange), and 198 (black, dashed) breaths at a scan rate of 100 mV s^–1.