Film-Type Sensor Materials PVDF and EMFi in Measurement of Cardiorespiratory Signals─A Review

IEEE SENSORS JOURNAL, VOL. 12, NO. 3, MARCH 2012

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Film-Type Sensor Materials PVDF and EMFi in Measurement of Cardiorespiratory Signals—
A Review
Satu Rajala and Jukka Lekkala

Abstract—In this paper, some recent results obtained with filmtype sensor materials polyvinylidenefluoride (PVDF) and electromechanical film (EMFi) are presented. The materials generate a voltage when they are mechanically deformed, however, because of their capacitive nature only the change of an external force can be measured. Hence, the sensors made of these materials are useful especially in the measurements of physiological pulsatile signals (e.g., heart rate and respiration). The entire measurement process with the PVDF and EMFi sensors is considered here; from the design and construction of the sensors and measurement electronics to the analysis of the measured data. The paper also presents some examples of the physiological signals (heart rate, respiration, and heart sounds) measured with the PVDF and EMFi sensors. Flexible and thin sensor materials are useful especially in physiological applications where the sensor is integrated into clothing or into daily life objects (e.g., a chair or a bed). The sensor attachments to human can be minimized and the measurement systems can be designed to be unobtrusive and comfortable for the user.
Index Terms—Electromechanical film (EMFi), heart rate, heart sounds, polyvinylidenefluoride (PVDF), respiration.

I. INTRODUCTION

M

EASUREMENT of physiological signals reveals valuable information on the physiological state of a person.
Common variables to monitor are heart rate and respiration.
Body movements reflecting the physiological activity are sometimes measured, too. Signals arising from these movements are usually massive and they interrupt the recognition of the other signals. Thus the heart rate and respiration are often measured at rest. To obtain more information on the cardiovascular system, heart sounds

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