To diagnose conditions such as sleep apnea, doctors monitor patients’ respiration rates with devices that can be cumbersome and expensive. George M. Whitesides and coworkers at Harvard University have now developed an inexpensive, lightweight paper-based alternative (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201511805).
To make the device, the researchers print graphite electrodes on paper, which they incorporate into a cloth surgical mask. When the paper absorbs water, the conductivity of the electrodes changes. Because exhaled breath contains more water than inhaled breath, the sensor can measure respiration rate from transient changes in moisture content. The team connects the sensor to a battery-powered reader that digitizes the electrical signal and wirelessly transmits the signal to a tablet running a data analysis app.
They used the device to measure respiration rates in individuals at rest as well as during light exercise such as walking and more vigorous exercise such as climbing several flights of stairs.
The current design can run for about nine hours on a single battery charge, which should be long enough to monitor a full night’s sleep. The paper sensor and mask should be cheap enough for single-use applications. The researchers suggest that the best use for the sensor in the near term will be for characterizing sleep apnea.