Textile-based capacitive sensor for a wireless wearable breath monitoring system

A capacitive sensor is demonstrated as the key component of a wearable breath monitoring system. Its capacitance varies proportional to the pressure acting on it with high linearity and wide working range. All of the components of the sensor, including conductors, insulator, and conductive wires, are textile materials and are thus as soft as ordinary clothes; therefore, the sensor is also washable and durable. By installing one sensor on the chest and another on the lower abdomen, thoracic and abdominal breathing can be detected independently with little crosstalk. Driven by a low-power NE556 oscillator, the capacitances of both sensors can be detected digitally and then transmitted by a Bluetooth low-energy wireless communication module to a smartphone. Thus, a wearable breath monitoring system is implemented to provide continuous and real time breath signal monitoring without mobility constraints.