Abstract
This research introduces an idea of producing both nanoscale and microscale pores in piezoelectric material, and combining the properties of the molecular β-phase dipoles in ferroelectric material and the space charge dipoles in order to increase the sensitivity of the sensor and modulate the response frequency bandwidth of the material. Based on this idea, a bi-nano-micro porous dual ferro-electret hybrid self-powered flexible heart sound detection sensor is proposed. Acid etching and electrospinning were the fabrication processes used to produce a piezoelectric film with nanoscale and microscale pores, and corona poling was used for air ionization to produce an electret effect. In this paper, the manufacturing process of the sensor is introduced, and the effect of the porous structure and corona poling on improving the performance of the sensor is discussed. The proposed flexible sensor has an equivalent piezoelectric coefficient d33 of 3312 pC/N, which is much larger than the piezoelectric coefficient of the common piezoelectric materials. Experiments were carried out to verify the function of the flexible sensor together with the SS17L heart sound sensor (BIOPAC, Goleta, CA, USA) as a reference. The test results demonstrated its practical application for wearable heart sound detection and the potential for heart disease detection. The proposed flexible sensor in this paper could realize batch production, and has the advantages of flexibility, low production cost and a short processing time compared with the existing heart sound detection sensors.
Highlights
A variety of flexible sensors have been developed to detect physiological signals of the human body in a wearable way
Before the sensor was applied to a specific scenario, its inherent performance was tested
With the microscale and nanoscale pore structures and the corona polarization treatment as variables, four different sample sensors were prepared for contrast experiments to test the effects of multiscale pores and corona poling on sensor performance through comparing the piezoelectric coefficients
Summary
A variety of flexible sensors have been developed to detect physiological signals of the human body in a wearable way. Flexible sensors based on resistance and capacity need an external power supply, and triboelectric sensors are greatly affected by external humidity, but sensors with a piezoelectric effect avoid an external power supply and have a quick response with a fast charge transfer speed They are more suitable for measuring highfrequency dynamic signals such as heart sounds [5,6,7,8]. Combining the microstructure of fibers and pores together, this paper proposes a flexible sensor for heart sound detection. The sensor adopts a sensitive threelayer structure composed of two non-polar material PDMS films as the electret layers, and a porous polar material polyvinylidene fluoride trifluoroethylene (P(VDF-TrFE)) film as the sandwiched piezoelectric induction layer
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