Research On Flexible And Wearable Blood Pressure Sensor In Complex Environment

Hypertension,as one of the most common diseases in the world,is also known as the "silent killer".About 1/3 people suffer from high blood pressure,and as many as 7.5 million people die from high blood pressure every year.Therefore,people need low-cost,comfortably wearable,continuous health monitoring devices that can detect their vital signs,such as heart rate and blood pressure,and further provide feedback to help maintain a healthy state.Flexible and wearable sensors have attracted the attention of researchers because of their comfortable wear,thinness,and stretchability.This thesis designs a flexible and wearable heart rate and blood pressure sensing systemThe main research contents of this thesis include:First,using flexible PCB processing technology(photolithography,laser cutting,etc.),a double-layer serpentine circuit is produced.After comparing the properties of various flexible substrates,PDMS with good biocompatibility and stretchability was selected as the flexible substrate.A stretchable circuit was achieved using reflow soldering of optoelectronic devices.Based on the flexible photoplethysmography,the heart rate and blood pressure monitoring sensors are designed.Based on the Labview graphical programming environment,synchronized data acquisition of sensors,the visual page,analog-to-digital conversion,control signal input range,and signal sampling frequency setting are realized.And add a low-pass filter to complete the preliminary filtering of the signal.Finally,the synchronous acquisition and storage of data is completed.Secondly,the differences in wearing comfort and signal quality between rigid and flexible PPG sensors are assessed.It is found that the flexible PPG sensor is lighter and more comfortable to wear,and the collected signal quality is better.The influences of ambient light,airflow impact,and high temperature shielded wires on the performance of flexible PPG sensor were investigated.The experimental results show that spin-coating insulating glue on the back of the sensor can eliminate ambient light interference,adding silica nano-insulation aerogel protective felt to the flexible sensor can effectively reduce the impact of airflow shock and temperature,and using a 3 m long hightemperature shielding wire to transmit signals can prevent the signal attenuation.In addition,preprocessing and feature extraction are performed based on the collected raw physiological signals.Finally,based on self-designed heart rate and blood pressure sensors,data from multiple volunteers have been obtained and three blood pressure calculation models are adopted.The blood pressure error of the univariate linear regression equation model is SBP(systolic blood pressure): 3.68 ± 2.37 mm Hg,DBP(diastolic blood pressure): 4.9 ± 3.78 mm Hg.The blood pressure error of the binary linear regression equation model is SBP: 3.61±2.62 mm Hg,DBP:4.72±3.46 mm Hg.The error of the Kalman filter blood pressure calculation model based on the optimization of model 2 is SBP: 2.94±2.35 mm Hg,DBP: 3.41±2.94 mm Hg.The results show that the introduction of Kalman filter algorithm to calculate blood pressure can not only reduce the number of calibrations,but also improve the accuracy of blood pressure detection.The error rate of heart rate calculation reaches 2.0%.