Flexible Piezoelectric Strain Sensor Based Wearable Device And Its Application

The World Health Organization has announced that COVID-19 can be characterized as a global pandemic.One of its common symptoms is dyspnea,which is mainly manifested as an increase in respiratory rate and heartbeat.Therefore,wearable devices that can continuously monitor breathing and heartbeat have attracted attention.The large size of traditional detection equipment limits its development and application in vital signs measurement systems.Flexible wearable sensors have emerged as the times require.The main applications include the measurement of human body pressure and strain.However,wearable sensors are limited by sensitivity and reliability,which have weak response to many human pressure or strain signals,and the acquired signals are interfered by different types of noise.In this paper,a set of high signal-to-noise ratio wearable strain sensing device based on flexible piezoelectric film is developed to measure the breathing and heartbeat signals of the chest cavity.By improving the existing serpentine patterns,an innovative arc structure design with different included angles is proposed,which can make the organic piezoelectric film have high stretchability.The thickness of the patterned PVDF flexible piezoelectric strain sensor is only 168μm and the voltage sensitivity reaches 0.97mV/μe.The effective modulus is 13.5MPa,which can fit the skin to detect the small strain of the human body.The device is composed of a highsensitivity stretchable piezoelectric strain sensor with a serpentine layout,a signal module,and a data acquisition and analysis module.The sensor is fixed on the appropriate part of the chest cavity.The surface vibration is captured by the piezoelectric sensor,and the output voltage signal that is conformally mapped with the heartbeat and breathing activity is generated.The signal processing module is used to achieve amplification and filtering to improve the signal quality.The collected data is passed through the empirical mode The decomposition algorithm extracts the corresponding heartbeat signal and breathing signal.Detecting important physiological signals such as breathing and heartbeat through wearable devices can help early diagnosis and control of respiratory diseases such as COVID-19.