Human Pulse Diagnosis for Medical Assessments Using a Wearable Piezoelectret Sensing System

Real‐time and continuous monitoring of physiological signals is essential for mobile health, which is becoming a popular tool for efficient and convenient medical services. Here, an active pulse sensing system that can detect the weak vibration patterns of the human radial artery is constructed with a sandwich‐structure piezoelectret that has high equivalent piezoelectricity. The high precision and stability of the system result in possible medical assessment applications, including the capability to identify common heart problems (such as arrhythmia); the feasibility to conduct pulse palpation measurements similar to well‐trained doctors in Traditional Chinese Medicine; and the possibility to measure and read blood pressure.     

聚丙烯压电驻极体薄膜声电传感器的性能

压电驻极体（也称为铁电驻极体）是以空间电荷驻极体为基体的一类新型压电功能材料,这种材料不仅具有与压电陶瓷相近的压电活性,同时拥有柔韧、低介电常数和低声阻抗等特点。本研究制备了基于聚丙烯（PP）压电驻极体薄膜的声电传感器,并采用电压放大电路和电荷放大电路对其在声频下的灵敏度进行了测量。结果表明,PP压电驻极体声电传感器在1 kHz下的电压灵敏度约为0.8 mV/Pa,并在300 Hz~10 kHz的声频范围内有良好的线性输出特性。     

压电驻极体材料与电声器件

含封闭孔洞结构的聚合物薄膜经过适当的电极化处理后表现出突出的压电活性。由于它同时具有压电材料和驻极体的特点．被命名为压电驻极体。说明了压电驻极体薄膜的制各方法,以及在传声器上的应用,并给出了制备样品的电声参数：采用的压电驻极体薄膜的准静态压电系数d33为200pC／N,其制成的传声器灵敏度为-61,74dB．与理论计算结果相符。新型的压电传声器的优点在于其设计简单,体积小,可靠性高和成本低,同时外观和尺寸有较大可变空间范围。     

Theoretical Study of Cellular Piezoelectret Generators

The cellular piezoelectret generator (CPG) has drawn considerable attention as an emerging flexible energy harvester because of its advantages of a simple structure, easy assembly, a low cost, and eco‐friendliness. To facilitate practical applications, an initial theoretical study of CPGs is presented in this work, in which the output characteristics of CPGs can be optimized through an appropriate choice of parameters, including the electret dielectric permittivity, device structure, polarization process, and external load. A good agreement with experimental results is achieved, verifying the validity of the theoretical study. The reported theory offers a complete interpretation of the dynamic working mechanism of CPGs and provides significant guidance for the design of a CPG with enhanced yield.     

Cellular Polypropylene Piezoelectret for Human Body Energy Harvesting and Health Monitoring

Self‐powered and wearable electronics, which are away from the problems of batteries, can provide the sustainable and comfortable interactive service for people. In this work, cellular polypropylene piezoelectret, which is with excellent physical and electrical properties, is utilized to build the human body energy harvesting and self‐powered human health monitoring systems. The cellular polypropylene piezoelectret flexible generator can reach a maximum peak power density of ≈52.8 mW m^?2. Simultaneously, self‐powered human body biological signals detecting sensors are demonstrated to detect the human physiological signals, such as coughing action and arterial pulses. This study strongly indicates the great compatibility and potential applications in human healthy monitoring may pave a new developing way for portable and wearable electronics systems.     

压电传声器的设计与改进

用多孔压电驻极体薄膜替代传统驻极体电容式传声器(ECM)的声电转换单元,制作出压电传声器。利用压电驻极体超薄的优势和对结构进行改进,将压电传声器的厚度从3mm降低到了1mm。为了解决压电传声器灵敏度低的问题,在后端电路采用了30dB增益的管芯。同时,为了减小寄生电容对灵敏度的影响,采用了单面布铜的印刷线路板(PCB),但将该传声器接入手机使用时会有电磁干扰(EMI)。改进PCB的设计,采用双面布铜的PCB,加强了电磁屏蔽,成功解决了压电传声器的EMI问题。最后,利用压电驻极体薄膜的防水性,并对压电传声器的电路进行了防水保护,使得压电传声器达到了IPX7防水标准。     

新型压电驻极体脉搏分析仪

利用多孔压电驻极体薄膜制备压电传感器,贴在手腕上采集脉搏振动的信号,并配上相应的后端电路和显示装置,制造出一种新型的压电驻极体脉搏分析仪。由于采用压电驻极体薄膜作为脉搏传感器的换能器,脉搏分析仪的灵敏度高,失真度低,重复性好。在脉搏分析仪中,采用塑化膜的形式封装压电电极,易引入干扰。采用压电麦克风的封装形式的传感器抗干扰能力强,且场效应晶体管(FET)易集成,成本低,实测的波形图近似于典型心电图波形,具有很大的医疗参考价值。     

压电膜叠层对微型压电传声器性能的影响

对比分析了在微型传声器中采用4种不同的叠层方法来提高压电传声器灵敏度的效果。证实了在微型传声器中,采用直接压合或用导电胶粘接多张压电膜串联的叠层方式无效果。采用导电环连接的方式进行微型压电传声器中的叠层,叠层后压电传声器的灵敏度提高约6dB。实验表明,采用薄导电环连接的叠层压电传声器性能比采用厚导电环连接的叠层压电传声器性能更稳定,频响曲线更平整。