Smart T-Shirt Based on Wireless Communication Spiral Fiber Sensor Array for Real-Time Breath Monitoring: Validation of the Technology

In this paper, we present the design and the validation of a new smart textile developed for real time monitoring of human breath. The smart textile is a wearable stretching T-shirt featuring an array of six contactless and non-invasive sensors placed on human's thoraco-abdominal walls. The wireless sensors communicate quasi-simultaneously the data to a detection base station through Bluetooth protocol. The sensor is composed of a spiral shaped multi-material fiber antenna with a central frequency at 2.4 GHz connected to a compact Bluetooth transmitter. The sensors are integrated on the stretchable T-shirt without compromising the user's comfort. The sensing mechanism of the system is based on the shift of the central frequency of the spiral fiber antenna induced by the deformation of the thorax and the abdomen during the breath. As a consequence, the breathing pattern is obtained through the received signal strength indicator recorded by a portable detection base station. With the sensor array integrated into a T-shirt, we demonstrate the feasibility assessment for monitoring breathing of seven volunteers in seating and standing positions. Using an array of sensors strategically placed on the T-shirt provides a more reliable approach to detect interpretable breathing patterns by sensing the movement of the abdomen and the thorax at the same time. Using a commercial spirometer as a standard reference, we assessed the validity of breathing parameters (ie; expiration and inspiration times, breathing period, and breathing rate) measured with the T-shirt. Based on Bland-Altman statistical analysis, a good agreement between textile-based sensors and the standard reference was obtained. We were able to show that the smart T-shirt could detect breathing patterns and pauses in breathing, which could be very useful to monitor sleep apnea and clinical monitoring of patients.