Research group of Professor Lin Liwei of Tsinghua Berkeley Shenzhen University and University of California Berkeley: Wearable piezoelectric electret sensor system for pulse diagnosis and health monitoring

The rapid development of portable and wearable electronic devices greatly promotes the application of mobile health technology in people's daily life Existing sensors can monitor physiological signals including heart rate, blood pressure and body temperature The pulse wave signal of human radial artery contains more abundant information, which has been used for thousands of years as a diagnostic method (pulse diagnosis) by traditional Chinese medicine How to use flexible wearable sensors to accurately collect pulse waves, and combine with big data analysis, to achieve real-time monitoring of personal health, has been widely concerned and studied by scholars Recently, the research team of Professor Lin Liwei of Tsinghua Berkeley Shenzhen University and University of California Berkeley proposed an active flexible pulse wave sensor based on piezoelectric electret, which can accurately collect the pulse waves of human radial artery under different pressures (floating, middle, sinking) and at different positions (inch, close, ruler), and be used for health monitoring and disease diagnosis (DOI: 10.1002/adfm.201803413 ）。
Brief introduction of Professor Lin Liwei's research group/ The research of nano electromechanical system, microfluidic system and micro nano materials in sensor, actuator and energy fields mainly includes the research of piezoelectric ultrasonic micro transducer, graphene gas sensor, flexible wearable equipment, micro actuator and new two-dimensional materials in sensor, super capacitor and energy collection Prof Lin Liwei, Prof James Marshall wells, Department of mechanical engineering, University of California, Berkeley, CO vice president of Tsinghua Berkeley Shenzhen University, CO director of Berkeley sensor and actuator Research Center, winner of the national "Thousand Talents Program" and Chair Professor of Changjiang University Professor Lin is mainly engaged in the research of micro / nano electromechanical systems and micro / nano materials in the fields of sensors, actuators and energy Cutting edge research results: Recently, Professor Lin Liwei's research group of Tsinghua Berkeley Shenzhen University published a paper entitled "human pulse diagnosis for medical assessments using a wearable piezoelectret sensing system" on the international top-level journal advanced functional materials High sensitivity pulse wave sensor provides hardware foundation for wearable medical health Inspired by pulse diagnosis of traditional Chinese medicine, pulse wave signals under different pressures (floating, middle, sinking) and at different positions of radial artery (inch, close, ruler) contain rich physiological information reflecting human health At present, the pulse sensor based on optical method is widely used in the extraction of heart rate signal, but its sensitivity is poor and its drift is large, so it can not achieve high-precision extraction of pulse wave under different pressures A flexible piezoelectric electret sensing system with sandwich structure is proposed The sandwich structure is composed of FEP / ecoflex / FEP The piezoelectric electret structure is composed of two layers of FEP electret film and two layers of FEP electret film After that, the air in the cavity is ionized by corona discharge, so that the FEP film inside the cavity can sense the same amount of heterogeneous charge When there is pressure, the space between cavities will change, and current will be generated in the external circuit Compared with other sensors which use friction to generate charge transfer, the sandwich structure can keep the charge polarized by corona discharge in the inner side of the cavity without direct contact with the human body, which can keep longer and have higher stability This work compares the pulse waveforms collected by piezoelectric electret pulse wave sensor and commercial optical sensor under different pressures, shows the pulse signals at three positions of inch, off and foot of volunteers, and realizes the classification and recognition of volunteers by using the pulse wave details Figure 1: piezoelectric electret sensing system for pulse wave monitoring a) The concept map of pulse wave monitoring in the radial artery b) Pulse wave sensor structure diagram In the upper left corner is the SEM image of the cross section of FEP / ecoflex / FEP sandwich structure c) Equivalent piezoelectric coefficient D 33 d) Schematic diagram of working principle of pulse wave sensor e) Peak short circuit current versus applied pressure (0.125 to 22.5 kPa) (source: adv funct Mater.) Fig 2: pulse wave acquisition results and performance analysis of optical sensor and piezoelectric electret pulse wave sensor under different static pressure a) Apply static pressure at the wrist from 120 mmHg to 20 mmHg through the inflatable wrist strap b) A 28 year old male volunteer's pulse signal, red is the signal collected by the pulse wave sensor, and blue is the signal obtained by the commercial optical sensor c) The relationship between pulse wave amplitude and static pressure Single period pulse wave signal (gray), average waveform and spectrum analysis results (D, f) 30 mmHg and (E, g) 120 mmHg collected under different static pressures by using piezoelectric electret pulse wave sensor (red) and commercial optical sensor (blue) (source: adv funct Mater.) Figure 3: schematic diagram of imitating the three vessels of Chinese medicine: Cun, Guan and chi a) Use the sensor to collect the schematic diagram of pulse wave of "inch", "close" and "ruler" b) The signals collected by the three-channel pulse wave sensor first pass through the current amplifier, and then pass through the data acquisition card for sampling and transmission to the notebook computer for visualization and analysis c) A 26-year-old female volunteer and a 28-year-old male volunteer's pulse wave at the foot of cunguan (source: adv funct Mater.) Summary: Professor Lin Liwei's research group proposed a sandwich structure piezoelectric electret sensor system, which has high sensitivity and stability, and can accurately collect pulse waves of human radial artery at different pressures and positions Combined with the experience and concept of traditional Chinese medicine pulse diagnosis, and the tools of big data analysis, piezoelectric electret pulse wave sensor will have a wide range of application prospects and practical application value in wearable mobile health and disease diagnosis This research group will also further study the objectification of traditional Chinese medicine pulse diagnosis The first author of the research results is Chu Yao, Ph.D student of Tsinghua Berkeley Shenzhen University, and the instructor is Professor Dong Ying, Professor Wang Xiaohao and Professor Lin Liwei of Tsinghua University The related research work has been supported by the national high tech research and development plan and Shenzhen Science and technology research and development fund project Nowadays, people and scientific research have been paid more and more attention in the economic life China has ushered in the "node of science and technology explosion" Behind the progress of science and technology is the work of countless scientists In the field of chemistry, in the context of the pursuit of innovation driven, international cooperation has been strengthened, the influence of Returned Scholars in the field of R & D has become increasingly prominent, and many excellent research groups have emerged in China For this reason, CBG information adopts the 1 + X reporting mechanism CBG information, chembeangoapp, chembeango official microblog, CBG wechat subscription number and other platforms jointly launch the column of "people and scientific research", approach the domestic representative research group, pay attention to their research, listen to their stories, record their demeanor, and explore their scientific research spirit.