Development of a Wireless Capacitive Sensor for Ambulatory ECG Monitoring over Clothes

We present a wireless capacitive sensor for ambulatory ECG monitoring. The device is capable of detecting electrocardiographic potential through underwear. It is based on capacitive coupling involving the electrode, the underwear, and the skin. Validation of the system revealed the following: (1) The frequency response of the device with the underwear revealed that the gain of the detected signal was reduced, but distortion of the signal within the pass-band (from 6 to 45 Hz) was minimal even with the underwear. (2) The signal displayed a periodic waveform synchronized with the simultaneously recorded ECG, even when the underwear was inserted between the electrode and the skin. (3) Although the signal was seemed deteriorated slightly while walking, R-waves were recognized easily. Although there is still room for improvement in terms of its practical use, the proposed approach appears promising for application to ambulatory ECG monitoring.