Miniature electrocardiography sensor using a flexible printed circuit and MEMS technology

This paper presents the development of flexible electrocardiography (ECG) sensors using both a flexible printed circuit (FPCB) and microelectromechanical systems (MEMS) technology. By using FPCB technology, polymer-based ECG sensors of a bipolar Laplacian-type electrode were fabricated and their ECG measurement capability was examined by both implanting the proposed sensors into subcutaneous fat and attaching the sensor to the skin of a dog. The bipolar ECG sensors, at three different sensing electrode diameters (4, 2 and 1 mm), were then miniaturized using MEMS technology. The MEMS ECG sensors had a hook-shaped sensing electrode and a reference electrode. One MEMS ECG sensor was attached to human skin. The ECG of a human was measured at one point using both a commercial patch-type ECG electrode and the proposed MEMS ECG sensor. Performance of the measured ECG by the MEMS ECG sensor was then compared with ECG measured by the commercially available ECG electrode. The correlation factor, which indicates the similarity in magnitude and wave patterns of the two measured ECGs, was 0.977, 0.86, 0.85 for 4, 2, and 1 mm respectively. Although the correlation factor decreases with decreasing sensing electrode diameter, we have demonstrated that ECG could be measured using a quasi-single-electrode sensor at just one point.