Disposable Sensor Array Embedded in Facemasks for the Identification of Chronic Kidney Disease

The increasing global burden of chronic kidney disease (CKD) necessitates the development of simple and inexpensive diagnostic tools. Capitalizing on the relationship between breath composition and CKD, we introduce a disposable array of four resistive gas sensors printed on a low-cost, disposable substrate and embedded in the internal layers of FFP2 facemasks. Sensors are based on blends of porphyrins─a molecular family often used in breath analysis─and the PEDOT/PSS conducting polymer. The individual sensors demonstrate remarkable sensitivity to ammonia and other CKD-related volatile compounds, while the combinatorial selectivity of the sensor array enables the identification of volatile compounds regardless of their concentration. The diagnostic capabilities of the device were tested on a cohort of CKD patients and a control group. To address the absence of a reference gas inside the facemask, we developed a measurement protocol based on breathing cycles at different rates. The application of a continuous wavelet transform to the sensor signals produces stable and reproducible features. Linear Discriminant Analysis of sensor features achieved the identification of CKD patients with 93.3% true positives and 86.7% true negatives. Additional evidence suggests that the sensor array can stratify CKD patients according to the severity of renal dysfunction, indicating its potential use in monitoring disease progression.