Flexible Piezoresistive Sensor Patch Enabling Ultralow Power Cuffless Blood Pressure Measurement

Noninvasive and real‐time cuffless blood pressure (BP) measurement realizes the idea of unobtrusive and continuous BP monitoring which is essential for diagnosis and prevention of cardiovascular diseases associated with hypertension. In this paper, a wearable sensor patch system that integrates flexible piezoresistive sensor (FPS) and epidermal electrocardiogram (ECG) sensors for cuffless BP measurement is presented. By developing parametric models on the FPS sensing mechanism and optimizing operational conditions, a highly stable epidermal pulse monitoring method is established and beat‐to‐beat BP measurement from the ECG and epidermal pulse signals is demonstrated. In particular, this study highlights the compromise between sensor sensitivity and signal stability. As compared with the current optical‐based cuffless BP measurement devices, the sensing patch requires much lower power consumption (3 nW) and is capable of detecting subtle physiological signal variations, e.g., pre and postexercises, thus providing a promising solution for low‐power, real‐time, and home‐based BP monitoring.     

Enabling the Unconstrained Epidermal Pulse Wave Monitoring via Finger-Touching

Unconstrained measurement of physiological signals including electrocardiograph, respiration, and temperature by sensors through incorporation into commonly used objects has sparked a notable revolution in healthcare monitoring. However, unconstrained precision epidermal pulse wave monitoring is rarely reported. Although the current flexible skin-mounted sensors can capture pulse waves, they lack the capability to perceive tiny pulse pressure in an unconstrained manner. Herein, utilizing thin-film materials and multilevel microstructure design, an ultrathin and flexible sensor (UFS) with the features of high flexibility, shape-adaptability, and ultra-broad-range high pressure sensitivity is proposed for unconstrained precision pulse wave sensing. Given these compelling features, the UFS is mounted to the surfaces of commonly used objects and successfully detects the fingertip pulse wave even under an ultra-broad-range finger-touching force. Key cardiovascular parameters are also extracted from the acquired fingertip pulse wave accurately. Furthermore, a proof-of-concept healthcare system, by combining the UFS and flexible devices (for example, flexible phones or E-newspapers) is demonstrated, offering a great advancement in developing an all-in-one system for IoT-based bio-health monitoring at all times and places.     

Large‐Scale and Washable Smart Textiles Based on Triboelectric Nanogenerator Arrays for Self‐Powered Sleeping Monitoring

Sleeping disorder is a major health threatening in high‐pace modern society. Characterizing sleep behavior with pressure‐sensitive, simple fabrication, and decent washability still remains a challenge and highly desired. Here, a pressure‐sensitive, large‐scale, and washable smart textile is reported based on triboelectric nanogenerator (TENG) array as bedsheet for real‐time and self‐powered sleep behavior monitoring. Fabricated by conductive fibers and elastomeric materials with a wave structure, the TENG units exhibit desirable features including high sensitivity, fast response time, durability, and water resistance, and are interconnected together, forming a pressure sensor array. Furthermore, highly integrated data acquisition, processing, and wireless transmission system is established and equipped with the sensor array to realize real‐time sleep behavior monitoring and sleep quality evaluation. Moreover, the smart textile can further serve as a self‐powered warning system in the case of an aged nonhospitalized patients falling down from the bed, which will immediately inform the medical staff. This work not only paves a new way for real‐time noninvasive sleep monitoring, but also presents a new perspective for the practical applications of remote clinical medical service.     

MXene Functionalized,Highly Breathable and Sensitive Pressure Sensors with Multi-Layered Porous Structure

Breathable, flexible, and highly sensitive pressure sensors have drawn increasing attention due to their potential in wearable electronics for body-motion monitoring, human-machine interfaces, etc. However, current pressure sensors are usually assembled with polymer substrates or encapsulation layers, thus causing discomfort during wearing (i.e., low air/vapor permeability, mechanical mismatch) and restricting their applications. A breathable and flexible pressure sensor is reported with nonwoven fabrics as both the electrode (printed with MXene interdigitated electrode) and sensing (coated with MXene/silver nanowires) layers via a scalable screen-printing approach. Benefiting from the multi-layered porous structure, the sensor demonstrates good air permeability with high sensitivity (770.86–1434.89 kPa⁻¹), a wide sensing range (0–100 kPa), fast response/recovery time (70/81 ms), and low detection limit (≈1 Pa). Particularly, this sensor can detect full-scale human motion (i.e., small-scale pulse beating and large-scale walking/running) with high sensitivity, excellent cycling stability, and puncture resistance. Additionally, the sensing layer of the pressure sensor also displays superior sensitivity to humidity changes, which is verified by successfully monitoring human breathing and spoken words while wearing a sensor-embedded mask. Given the outstanding features, this breathable sensor shows promise in the wearable electronic field for body health monitoring, sports activity detection, and disease diagnosis.     

Transcatheter Self‐Powered Ultrasensitive Endocardial Pressure Sensor

Changes in endocardial pressure (EP) have important clinical significance for heart failure patients with impaired cardiac function. As a vital parameter for evaluating cardiac function, EP is commonly monitored by invasive and expensive cardiac catheterization, which is not feasible for long‐term and continuous data collection. In this work, a miniaturized, flexible, and self‐powered endocardial pressure sensor (SEPS) based on triboelectric nanogenerator (TENG), which is integrated with a surgical catheter for minimally invasive implantation, is reported. In a porcine model, SEPS is implanted into the left ventricle and the left atrium. The SEPS has a good response both in low‐ and high‐pressure environments. The SEPS achieves the ultrasensitivity, real‐time monitoring, and mechanical stability in vivo. An excellent linearity (R ² = 0.997) with a sensitivity of 1.195 mV mmHg^?1 is obtained. Furthermore, cardiac arrhythmias such as ventricular fibrillation and ventricular premature contraction can also be detected by SEPS. The device may promote the development of miniature implantable medical sensors for monitoring and diagnosis of cardiovascular diseases.     

Bubble‐Decorated Honeycomb‐Like Graphene Film as Ultrahigh Sensitivity Pressure Sensors

Recently, macroporous graphene monoliths (MGMs), with ultralow density and good electrical conductivity, have been considered as excellent pressure sensors due to their excellent elasticity with a rapid rate of recovery. However, MGMs can only exhibit good sensitivity when the strain is higher than 20%, which is undesirable for touch‐type pressure sensors, such as artificial skin. Here, an innovative method for the fabrication of freestanding flexible graphene film with bubbles decorated on honeycomb‐like network is demonstrated. Due to the switching effect depended on “point‐to‐point” and “point‐to‐face” contact modes, the graphene pressure sensor has an ultrahigh sensitivity of 161.6 kPa^?1 at a strain less than 4%, several hundred times higher than most previously reported pressure sensors. Moreover, the graphene pressure sensor can monitor human motions such as finger bending and pulse with a very low operating voltage of 10 mV, which is sufficiently low to allow for powering by energy‐harvesting devices, such as triboelectric generators. Therefore, the high sensitivity, low operating voltage, long cycling life, and large‐scale fabrication of the pressure sensors make it a promising candidate for manufacturing low‐cost artificial skin.     

Emerging Technologies of Flexible Pressure Sensors: Materials,Modeling, Devices,and Manufacturing

As an important branch of wearable electronics, flexible pressure sensors have attracted extensive research owing to their wide range of applications, such as human–machine interfaces and health monitoring. To fulfill the requirements for different applications, new material design and device fabrication strategies have been developed in order to manipulate the mechanical and electrical properties and enhance device performance. In this paper, the important progresses in flexible pressure sensor development over recent years are selectively reviewed from a material and application perspective. First, an overview of the fundamental working mechanism and the systematic design approach is presented. Particularly, how the theoretical modeling has been used as an auxiliary tool to achieve better sensing performance is discussed. A number of applications, including human–machine interfaces, electronic skin and health monitoring, and certain application‐driven functions, e.g., pressure distribution visualization and direction‐sensitive force detection, are highlighted. Lastly, various advanced manufacturing methods used for realizing large‐scale fabrication are introduced.     

阵列式无线压力传感器系统设计与迟滞补偿研究

为提高传统硅压阻式压力传感器的测量精度,针对性地设计与实现了一种带有迟滞误差校正功能的阵列式无线压力传感器系统。该系统采用了硅压阻式传感器阵列和高精度模数转换器AD7794,以STM32微处理器作为数据采集和信号处理的核心部件,并通过无线蓝牙传输模块将测量数据发送至手机接收端,以手机APP显示测量结果有利于用户对压力实现无线监测。针对硅压阻压力传感器的迟滞非线性,基于最小二乘法与函数校正法对压力传感器阵列的输出信号进行了非线性和迟滞误差补偿,结果表明：迟滞误差从原来的±0.152%降为±0.077%,,有效地提高了系统的测量精度。     

基于脉搏波速法的动态血压测量系统设计

提出一种利用脉搏波传导速度法的血压测量方案。采用新型可穿戴式光电传感器分别采集人体左侧桡动脉和指端的脉搏波,摆脱传统袖带式的测量方式。通过分析脉搏波的波形,计算脉搏波传导速度,建立数学模型方程,对非侵入式的动态血压测量进行研究,并采用听诊法进行校准和误差分析,实现连续血压测量。实验结果表明,该系统测量方便,精度较高,与听诊法具有良好的一致性。     

A Quadruple Hole Resonant Cavity based Optical Pressure Sensor for Blood Pressure Measurement

Wireless Personal Communications - This day and age, blood pressure (BP) is one of the serious cardiovascular diseases. For the continuous monitoring of BP, a small, light weight and cuff less...     

基于光电脉搏传感器的踝臂指数测量

利用发光二极管(LED)和硅光电池研制了一种能检测人体表浅动脉及微动脉血管网脉搏波的光电脉搏传感器,设计开发了基于该传感器的踝臂指数(ABI)测量系统,通过血压事件的光电信号判定算法,提高了ABI的测量精度。对30名实验对象进行了与"金标准"听诊法的对比实验,采用Bland-Altman法对实验数据进行了分析,结果表明,使用研制的系统测量ABI与听诊法具有较好的一致性。     

一种基于多参数融合的无袖带式连续血压测量方法的研究

针对现有基于脉搏波传输时间的无创连续性血压测量算法精度不高的问题,该文综合考虑心电信号和血氧容积波与血压变化的相关性,提出一种基于BP神经网络的无创连续性血压测量方法。该文首先利用改进的心电信号算法提取出心电信号的R点,利用差分、阈值的方法提取出血氧容积波的特征参数,再经过特征解析,提取出与血压相关的15维特征向量,构建基于BP神经网络的血压计算模型,计算出逐拍的血压值。该方法在天坛医院等单位进行了医学临床比对测试,并通过因子分析法分析了15个特征参数的权重比。实验证明：在预测血压上,脉搏波传输时间的权重,大于相邻特征点之间的时间信息权重,大于脉搏波面积信息权重,大于脉搏波幅值信息权重;该方法精度优于其它相近方法,单次测量的舒张压和收缩压误差的平均值标准差分别是-1.576.12 mmHg和-0.624.82 mmHg,重复测量误差的平均值标准差分别是-2.125.10 mmHg和-2.524.41 mmHg。收缩压和舒张压的测量精度均达到了BHS血压标准的Grade A类和AAMI标准。     

Bioresorbable Wireless Sensors as Temporary Implants for In Vivo Measurements of Pressure

Pressures at targeted locations inside the human body serve as critically important diagnostic parameters for monitoring various types of serious or even potentially fatal medical conditions including intracranial, intra‐abdominal, and pulmonary hypertension, as well as compartment syndromes. Implantable commercial sensors provide satisfactory accuracy and stability in measurements of pressure, yet surgical removal is required after recovery of the patient to avoid infections and other risks associated with long‐term implantation. Sensors that dissolve in biofluids (or, equivalently, bioabsorb or bioresorb) avoid the need for such surgeries, yet current designs involve either hard‐wired connections and/or fail to provide quantitative measurements over clinically relevant lifetimes. Here, a bioresorbable, wireless pressure sensor based on passive inductor‐capacitor resonance circuits in layouts and with sets of materials that overcome these drawbacks is reported. Specifically, optimized designs offer sensitivity as high as ≈200 kHz mmHg^?1 and resolution as low as 1 mmHg. Encapsulation approaches that use membranes of Si₃N₄ and edge seals of natural wax support stable operation in vivo for up to 4 days. The bioresorbable pressure sensing technology reported here may serve as an important solution to temporary, real‐time monitoring of internal pressure for various medical conditions.     

基于BP神经网络的脉搏触压觉与血压关系分析

本研究旨在探究脉搏触压觉与血压之间的关系,自制的脉搏图像采集系统获得触压觉参数的同时,通过袖带法得到动脉血压值,并进行二者关系预测。首先在不同切脉压力下,采集探头的薄膜搏动视频图像,并从中提取脉搏信号的脉幅最大值、重心频率、功率谱密度最大值等时频域特征。然后采用反向传播神经网络对动脉血压的舒张压和收缩压进行分析。实验结果表明通过以上特征参数可以较准确地预测出血压值。     

Microchannel‐Confined MXene Based Flexible Piezoresistive Multifunctional Micro‐Force Sensor

Multifunctional micro‐force sensing in one device is an urgent need for the higher integration of the smaller flexible electronic device toward wearable health‐monitoring equipment, intelligent robotics, and efficient human–machine interface. Herein, a novel microchannel‐confined MXene‐based flexible piezoresistive sensor is demonstrated to simultaneously achieve multi‐types micro‐force sensing of pressure, sound, and acceleration. Benefiting from the synergistically confined effect of the fingerprint‐microstructured channel and the accordion‐microstructured MXene materials, the as‐designed sensor remarkably endows a low detection limit of 9 Pa, a high sensitivity of 99.5 kPa^?1, and a fast response time of 4 ms, as well as non‐attenuating durability over 10 000 cycles. Moreover, the fabricated sensor is multifunctionally capable of sensing sounds, micromotion, and acceleration in one device. Evidently, such a multifunctional sensing characteristic can highlight the bright prospect of the microchannel‐confined MXene‐based micro‐force sensor for the higher integration of flexible electronics.     

Self ‐Powered Insole Plantar Pressure Mapping System

Sensitive monitoring and real‐time foot pressure mapping have important applications for medical treatment/diagnostics, sports training, and even security. In this work, a facile plantar pressure mapping system with a large pressure detection range using piezoelectric nanogenerators serving as the sensor array to acquire pressure signals, and a self‐designed data acquisition (DAQ) circuit board to process and wirelessly send the signals to a mobile terminal, such as a smart phone, are developed. Working with an application program developed in Android, the whole system can accurately monitor and visually display the real‐time pressure distribution during walking. More importantly, by combining a hybridized triboelectric–electromagnetic nanogenerator, a self‐powered, continuous, and real‐time pressure distribution monitoring system is developed, which provides a feasible solution for sport/exercise biomechanics information acquisition, injury prevention, and ulceration prediction in the feet.     

Flexible Polymer Transducers for Dynamic Recognizing Physiological Signals

Ferroelectric polymers are of interest as most promising electroactive materials. Flexible transducers from ferroelectric polymer thin film with underneath semiconducting polymer active layer for high sensitive and versatile detection of physiological signals are described. When attached directly on the wrist, the flexible transducers can distinguish the transient pulse waves non‐invasively and in situ, due to their fast response (milliseconds) and high sensitivity (down to several Pascal) to instantaneous change of blood pressure. High‐resolution picture of one pulse wave is available to provide two most common parameters for arterial stiffness diagnosis. The transducers are also suitable for dynamic recognizing physiological signals under both physical exercise and medicine treatment, demonstrating their enormous potential for warning the risk of cardiovascular disease, and evaluating the efficacy of heart medicines. The transducers are easy to carry around with an operating voltage of 1 V and the power consumption less than 1 μW. Thus, they are valuable for applications like electronic skin and mobile health monitoring.     

Flexible pressure sensor with high sensitivity and fast response for electronic skin using near-field electrohydrodynamic direct writing

Electronic skin imitates the function of human skin. The flexible pressure sensor is an important sensor of electronic skin. Although the flexible pressure sensor has made some progress, electronic skin is still a challenging subject with good pressure resolution, high sensitivity, and fast response ability in biomedical, human motion detection, personal health monitoring, and other fields. The PEDOT:PSS/GR/SWCNTs multicomponent solution was directly written on the flexible PDMS substrate by the near-field electrohydrodynamic direct-writing method, a serpentine shaped pressure sensitive unit was prepared, which was encapsulated with the PDMS thin film, and the flexible pressure sensor was fabricated. The sensitivity of the flexible pressure sensor is about 0.39 kPa⁻¹ at 0–0.5 kPa and 1.04 kPa⁻¹ at 0.5–2.4 kPa, and the response/recovery speed is 75 ms/150 ms, respectively. The fabricated flexible pressure sensor can detect a small pressure of about 6.4 Pa. The experimental results show that the fabricated flexible pressure sensor has high sensitivity, fast response capability, and low detection limit. The flexible pressure sensor for electronic skin demonstrates good performance in the application of finger joint movement and word pronunciation recognition, which indicates that it has great potential application in human motion detection and personal health monitoring.     

Textile‐Based Flexible Tactile Force Sensor Sheet

The next generation of electronics will include human‐interactive flexible sensor sheets to monitor health. One approach is to realize practical macroscale low‐cost sensor arrays to monitor pressure distribution and health conditions without directly attaching a device onto the body. However, practical requirements such as reliability, scalability, and washability are not often discussed as most studies focus on the sensing sensitivity and validations. This study demonstrates an all textile‐based tactile force sensor sheet that covers the above requirements. By considering the device design and materials, high reliability/repeatability (≈250 000 cycles at ≈5 kPa) and washability are realized. These are important factors for practical applications for human‐interactive macroscale sensor sheets. In addition to the fundamental characteristics, pressure distribution mapping and respiration rate monitoring are confirmed by placing the sensor sheets on a bed, chair, and floor.     

基于压电传感器的木材轴压损伤监测

木结构在受压荷载作用下,会造成木材承载力不足及内部损伤,但对木结构进行无损监测的方法较少。该文基于压电传感器对木材在轴压和局压作用下进行了损伤监测可行性研究,在木材表面贴装压电传感器,利用应力波的主动传感方法,以一个压电传感器作为信号发射器,另一个压电传感器作为信号接收器,在木材结构产生损伤时,监测到的应力波相应减小。基于应力波的衰减,可以采用小波包能量法将其转换为损伤指标,以此来监测结构损伤。结果表明,压电信号幅值与木材的损伤程度相关性较强,该木材无损监测方法具有良好可行性。