Dew-Based Wireless Mini Module for Respiratory Rate Monitoring

Miniaturized humidity sensors combined with ZigBee transceiver and efficient data processing offer a powerful system for the monitoring of human breath. Every 10 ms, the expiration/inspiration phase is transmitted, allowing a medical diagnosis as efficient as required by the application. For the sensing system, a micro interdigitated capacitor, covered with a dense hydrophilic alumina layer, is connected to a capacitance-to-frequency circuit interface. A customized nasal canula-prototype embeds the microsystem underneath the patient´s nostrils while offering cabling until the belt-fixed radio transceiver. The fast data processing, executed in a mini notebook process unit, gives to the medical staff a live broadcast of the patient´s respiratory rate. In order to improve the size and the functionality of our sensing module, novel techniques for processing complementary metal oxide semiconductor (CMOS) in Silicon-on-Insulator (SOI) technology now allow for the construction of microsensors and CMOS circuits together on the same chip. These sensors consume extremely low power, of the order of 0.1 μW, present high sensitivity, occupy small chip area (1.25 mm²) and offer the prerequisite platform for a large variety of new sensors.