In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve th...In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve the energy utilization efficiency,but this technique is not compatible with state-of-the-art devices such as cantilever-based PMUTs.A closed back cavity provides an alternative method for effectively utilizing the backside acoustic energy.This paper investigates the effects of a closed back cavity on PMUT performance through theoretical analysis,simulations,and experimental verification.Increasing the cavity depth produces a periodic modulation of several key PMUT metrics,such as the relative frequency deviation and quality factor.The optimal cavity depth for PMUTs that ensures a robust resonant frequency and high quality factor is defined as a function of the acoustic wavelength.A closed back cavity also provides an effective method for continuously tuning the quality factor,and thus the bandwidth,of PMUTs.This work paves the way for air-coupled PMUTs with adjustable performance for various applications.展开更多
The World Health Organization has declared COVID-19 a pandemic.The demand for devices or systems to diagnose and track COVID-19 infections noninvasively not only in hospitals but also in home settings has led to incre...The World Health Organization has declared COVID-19 a pandemic.The demand for devices or systems to diagnose and track COVID-19 infections noninvasively not only in hospitals but also in home settings has led to increased interest in consumer-grade wearables.A common symptom of COVID-19 is dyspnea,which may manifest as an increase in respiratory and heart rates.In this paper,a novel piezoelectric strain sensor is presented for real-time monitoring of respiratory and heartbeat signals.A highly sensitive and stretchable piezoelectric strain sensor is fabricated using a piezoelectric film with a serpentine layout.The thickness of the patterned PVDF flexible piezoelectric strain sensor is only 168μm,and the voltage sensitivity reaches 0.97 mV/με.The effective modulus is 13.5 MPa,which allows the device to fit to the skin and detect the small strain exhibited by the human body.Chest vibrations are captured by the piezoelectric sensor,which produces an electrical output voltage signal conformally mapped with respiratory–cardiac activities.The separate heart activity and respiratory signals are extracted from the mixed respiratory–cardiac signal by an empirical mode decomposition data processing algorithm.By detecting vital signals such as respiratory and heart rates,the proposed device can aid early diagnosis and monitoring of respiratory diseases such as COVID-19.展开更多
In this work,a monolithic oscillator chip is heterogeneously integrated by a film bulk acoustic resonator(FBAR)and a complementary metal-oxide-semiconductor(CMOS)chip using FlexMEMS technology.In the 3 D-stacked integ...In this work,a monolithic oscillator chip is heterogeneously integrated by a film bulk acoustic resonator(FBAR)and a complementary metal-oxide-semiconductor(CMOS)chip using FlexMEMS technology.In the 3 D-stacked integrated chip,the thin-film FBAR sits directly over the CMOS chip,between which a 4μm-thick SU-8 layer provides a robust adhesion and acoustic reflection cavity.The proposed system-on-chip(SoC)integration features a simple fabrication process,small size,and excellent performance.The oscillator outputs 2.024 GHz oscillations of-13.79 dB m and exhibits phase noises of-63,-120,and-136 dB c/Hz at 1 kHz,100 kHz,and far-from-carrier offset,respectively.FlexMEMS technology guarantees compact and accurate assembly,process compatibility,and high performance,thereby demonstrating its great potential in SoC hetero-integration applications.展开更多
This paper investigates the issues on acoustic energy reflection of flexible film bulk acoustic resonators(FBARs). The flexible FBAR was fabricated with an air cavity in the polymer substrate, which endowed the resona...This paper investigates the issues on acoustic energy reflection of flexible film bulk acoustic resonators(FBARs). The flexible FBAR was fabricated with an air cavity in the polymer substrate, which endowed the resonator with efficient acoustic reflection and high electrical performance. The acoustic wave propagation and reflection in FBAR were first analyzed by Mason model, and then flexible FBARs of 2.66 GHz series resonance in different configurations were fabricated. To validate efficient acoustic reflection of flexible resonators, FBARs were transferred onto different polymer substrates without air cavities. Experimental results indicate that efficient acoustic reflection can be efficiently predicted by Mason model. Flexible FBARs with air cavities exhibit a higher figure of merit(FOM). Our demonstration provides a feasible solution to flexible MEMS devices with highly efficient acoustic reflection(i.e. energy preserving) and free-moving cavities, achieving both high flexibility and high electrical performance.展开更多
Today,the vast majority of microelectromechanical system(MEMS)sensors are mechanically rigid and therefore suffer from disadvantages when used in intimately wearable or bio-integrated applications.By applying new engi...Today,the vast majority of microelectromechanical system(MEMS)sensors are mechanically rigid and therefore suffer from disadvantages when used in intimately wearable or bio-integrated applications.By applying new engineering strategies,mechanically bendable and stretchable MEMS devices have been successfully demonstrated.This article reviews recent progress in this area,focusing on high-performance flexible devices based on inorganic thin films.We start with the common design and fabrication strategies for flexibility and stretchability,summarize the recent application-oriented flexible devices,and conclude with criteria and opportunities for the future development of flexible MEMS sensors.展开更多
This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in t...This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in the in-plane flexural mode is investigated based on a set of resonators with different electrode lengths,widths,and ratios.Experimental and simulation results show that the electrode design impacts greatly the multimode effect induced from torsional modes but has little influence on other loss mechanisms.Optimizing the electrode design suppresses the torsional mode successfully,thereby increasing the ratio of impedance at parallel and series resonant frequencies(R_(p)/R_(s))by more than 80%and achieving a quality factor(Q)of 7753,an effective electromechanical coupling coefficient(kt_(eff)^(2))of 0.066%,and an impedance at series resonant frequency(R_(m))of 23.6 kΩ.The proposed approach shows great potential for high-performance piezoelectric resonators,which are likely to be fundamental building blocks for sensors with high sensitivity and low noise and power consumption.展开更多
This paper proposes an air-coupled piezoelectric micromachined ultrasonic transducer(PMUT)for detection and imaging of surface stains.A 508 kHz PMUT array is designed,fabricated,and characterized in terms of its elect...This paper proposes an air-coupled piezoelectric micromachined ultrasonic transducer(PMUT)for detection and imaging of surface stains.A 508 kHz PMUT array is designed,fabricated,and characterized in terms of its electrical and acoustic properties,and it is used in a pulse echo validation test.Imaging of stains on metal blocks is successfully demonstrated.Compared with existing optical methods for stain detection,the proposed approach can work in a dark environment without color requirements.This work provides a new and promising route for the development of miniaturized stain detection systems.展开更多
One of the key requirements for MEMS speakers is to increase the sound pressure level(SPL)while keeping the size as small as possible.In this paper we present a MEMS speaker based on piezoelectric bimorph cantilevers ...One of the key requirements for MEMS speakers is to increase the sound pressure level(SPL)while keeping the size as small as possible.In this paper we present a MEMS speaker based on piezoelectric bimorph cantilevers that produces a higher SPL than conventional unimorph cantilever speakers.The active diaphragm size is 1.4×1.4 mm^(2).The bimorph cantilevers are connected in parallel to make full use of the actuation voltage.At 1 kHz,the measured SPL reached 73 dB and the peak SPL reached 102 dB at the resonance frequency of 10 kHz in a 711 ear simulator under a driving voltage of 10 V_(rms).The total harmonic distortion of the MEMS speaker was less than 3%in the range from 100 Hz to 20 kHz.Although the absolute SPL was not the highest,this work provides a better SPL for all piezoelectric MEMS speakers.展开更多
Heavy metal pollution in water environments poses a great threat to public health and to the ecological environment due to its high toxicity and non-degradability.However,many existing detection methods require labora...Heavy metal pollution in water environments poses a great threat to public health and to the ecological environment due to its high toxicity and non-degradability.However,many existing detection methods require laboratory-based bulky instruments and time-consuming manual operations.Although some on-site systems exist,they are difficult to deploy on a large scale owing to their large size and high cost.Here,we report a sensing node featuring low power consumption and low cost,achieved by integrating microsensor,microfluidic,and electronic modules into a compact size for automatic and scalable heavy metal pollution monitoring.Digital microfluidic and electrochemical sensing modules are integrated on a chip,thereby combining the procedures of sample pretreatment,electrochemical sensing,and waste removal for automatic and continuous monitoring.The feasibility of the platform is demonstrated by Pb2+detection in tap water.With a 3500 mAh battery,the compact sensing node could work for several years in principle.There is scope for further improvements to the system in terms of wider functionality and reductions in size,power consumption,and cost.The sensing node presented here is a strong candidate for distributed monitoring of water quality as an Internet-of-Things application.展开更多
Piezoelectric MEMS speakers,an emerging technology with great promise,face significant challenges in performance evaluation and rational design.Their broadband nature means that responses at every frequency point acro...Piezoelectric MEMS speakers,an emerging technology with great promise,face significant challenges in performance evaluation and rational design.Their broadband nature means that responses at every frequency point across the whole operating bandwidth contribute to performance,yet there is no widely recognized weighting approach for fair evaluation.This absence of quantitative criteria makes objective comparisons of different designs difficult,slowing the adoption of new design concepts;and it leads to ambiguous design goals without response balance across frequency bands.Additionally,the current design methods rely on labor-intensive simulations,further prolonging the development process.To address these challenges,two figures of merit(FOMs)obtained via theoretical deduction are proposed in this study.These FOMs facilitate the evaluation of key metrics,such as sound pressure level and energy efficiency over a wide frequency range,enabling quantitative comparisons among various speaker designs.On the basis of FOMs,the design process can be simplified into a single-objective optimization problem,significantly streamlining the speaker design.Using this method,piezoelectric MEMS speakers with ultra-high FOMs and superior performance are demonstrated.The normalized SPLs at 1 and 10 kHz reach an impressive 76.6 and 86.6 dB/mm^(2)/V_(rms),respectively,with normalized sensitivities of 91.2 and 91.5 dB/mm2/mW.This achievement validates our FOM theory,representing a notable advancement in the field.展开更多
Eye blinking is closely related to human physiology and psychology.It is an effective method of communication among people and can be used in human-machine interactions.Existing blink monitoring methods include videoo...Eye blinking is closely related to human physiology and psychology.It is an effective method of communication among people and can be used in human-machine interactions.Existing blink monitoring methods include videooculography,electro-oculograms and infrared oculography.However,these methods suffer from uncomfortable use,safety risks,limited reliability in strong light or dark environments,and infringed informational security.In this paper,we propose an ultrasound-based portable approach for eye-blinking activity monitoring.Low-power pulse-echo ultrasound featuring biosafety is transmitted and received by microelectromechanical system(MEMS)ultrasonic transducers seamlessly integrated on glasses.The size,weight and power consumption of the transducers are 2.5 mm by 2.5 mm,23.3 mg and 71μW,respectively,which provides better portability than conventional methods using wearable devices.Eye-blinking activities were characterized by open and closed eye states and validated by experiments on dfferent volunteers.Finally,real-time eye-blinking monitoring was successfully demonstrated with a response time less than 1 ms.The proposed solution paves the way for ultrasound-based wearable eye-blinking monitoring and offers miniaturization,light weight,low power consumption,high informational security and biosafety.展开更多
Continuous and quantitative monitoring of knee joint function has clinical value in rehabilitation assessment and the timing of return to play for anterior cruciate ligament injury patients.However,the existing approa...Continuous and quantitative monitoring of knee joint function has clinical value in rehabilitation assessment and the timing of return to play for anterior cruciate ligament injury patients.However,the existing approaches,including clinical examination,arthrometry and inertial solutions,can only be used for qualitative,off-line and low-quality evaluations,respectively.Burgeoning Kirigami stretchable sensors could be a disruptive candidate solution,but they usually suffer from structural buckling issues when used for large strain applications,such as knee joint motion capture where the buckling degrades sensor reliability and repeatability.Here,we propose a buckling-resistant stretchable and wearable sensor for knee joint motion capture.It enables continuous and precise motion signal capture of the knee joint and provides high wearing comfort and reliability.Clinical tests were conducted on 30 patients in the field,tracking data provided by the sensor from their initial hospitalization to later surgery.And the full rehabilitation of one subject was recorded and analyzed.The test results show that our sensor can dynamically assess knee function in real time and recommend the best timing for return to play,which paves the way for personalized and telerehabilitation.展开更多
基金supported in part by the National Natural Science Foundation of China(NSFC)(Grant No.62001322)in part by the National Key Research and Development Program(Grant No.2020YFB2008800).
文摘In conventional piezoelectric micromachined ultrasonic transducers(PMUTs),the backside acoustic energy is often used inefficiently,resulting in up to half of the energy being wasted.Vacuum encapsulation can improve the energy utilization efficiency,but this technique is not compatible with state-of-the-art devices such as cantilever-based PMUTs.A closed back cavity provides an alternative method for effectively utilizing the backside acoustic energy.This paper investigates the effects of a closed back cavity on PMUT performance through theoretical analysis,simulations,and experimental verification.Increasing the cavity depth produces a periodic modulation of several key PMUT metrics,such as the relative frequency deviation and quality factor.The optimal cavity depth for PMUTs that ensures a robust resonant frequency and high quality factor is defined as a function of the acoustic wavelength.A closed back cavity also provides an effective method for continuously tuning the quality factor,and thus the bandwidth,of PMUTs.This work paves the way for air-coupled PMUTs with adjustable performance for various applications.
基金We are grateful for funding from the Natural Science Foundation of China(NSFC Grant No.62001322)the Tianjin Municipal Science and Technology Project(No.20JCQNJC011200)+1 种基金the National Key Research and Development Program(No.2020YFB2008801)the Nanchang Institute for Microtechnology of Tianjin University.
文摘The World Health Organization has declared COVID-19 a pandemic.The demand for devices or systems to diagnose and track COVID-19 infections noninvasively not only in hospitals but also in home settings has led to increased interest in consumer-grade wearables.A common symptom of COVID-19 is dyspnea,which may manifest as an increase in respiratory and heart rates.In this paper,a novel piezoelectric strain sensor is presented for real-time monitoring of respiratory and heartbeat signals.A highly sensitive and stretchable piezoelectric strain sensor is fabricated using a piezoelectric film with a serpentine layout.The thickness of the patterned PVDF flexible piezoelectric strain sensor is only 168μm,and the voltage sensitivity reaches 0.97 mV/με.The effective modulus is 13.5 MPa,which allows the device to fit to the skin and detect the small strain exhibited by the human body.Chest vibrations are captured by the piezoelectric sensor,which produces an electrical output voltage signal conformally mapped with respiratory–cardiac activities.The separate heart activity and respiratory signals are extracted from the mixed respiratory–cardiac signal by an empirical mode decomposition data processing algorithm.By detecting vital signals such as respiratory and heart rates,the proposed device can aid early diagnosis and monitoring of respiratory diseases such as COVID-19.
基金supported by National High Technology Research and Development Program of China(863 Program)under Grant No.2015AA042603the 111 Project under Grant No.B07014Nanchang Institute for Microtechnology of Tianjin University
文摘In this work,a monolithic oscillator chip is heterogeneously integrated by a film bulk acoustic resonator(FBAR)and a complementary metal-oxide-semiconductor(CMOS)chip using FlexMEMS technology.In the 3 D-stacked integrated chip,the thin-film FBAR sits directly over the CMOS chip,between which a 4μm-thick SU-8 layer provides a robust adhesion and acoustic reflection cavity.The proposed system-on-chip(SoC)integration features a simple fabrication process,small size,and excellent performance.The oscillator outputs 2.024 GHz oscillations of-13.79 dB m and exhibits phase noises of-63,-120,and-136 dB c/Hz at 1 kHz,100 kHz,and far-from-carrier offset,respectively.FlexMEMS technology guarantees compact and accurate assembly,process compatibility,and high performance,thereby demonstrating its great potential in SoC hetero-integration applications.
基金supported by National Natural Science Foundation of China(Grant No.51375341)the National High Technology Research and Development Program of China(“863”Program,Grant No.2015AA042603)the 111 Project(Grant No.B07014)
文摘This paper investigates the issues on acoustic energy reflection of flexible film bulk acoustic resonators(FBARs). The flexible FBAR was fabricated with an air cavity in the polymer substrate, which endowed the resonator with efficient acoustic reflection and high electrical performance. The acoustic wave propagation and reflection in FBAR were first analyzed by Mason model, and then flexible FBARs of 2.66 GHz series resonance in different configurations were fabricated. To validate efficient acoustic reflection of flexible resonators, FBARs were transferred onto different polymer substrates without air cavities. Experimental results indicate that efficient acoustic reflection can be efficiently predicted by Mason model. Flexible FBARs with air cavities exhibit a higher figure of merit(FOM). Our demonstration provides a feasible solution to flexible MEMS devices with highly efficient acoustic reflection(i.e. energy preserving) and free-moving cavities, achieving both high flexibility and high electrical performance.
基金the National Natural Science Foundation of China(No.62001322)the Tianjin Municipal Science and Technology Project(No.20JCQNJC011200)+1 种基金the National Key Research and Development Program of China(No.2020YFB2008801)the Nanchang Institute for Microtechnology of Tianjin University.
文摘Today,the vast majority of microelectromechanical system(MEMS)sensors are mechanically rigid and therefore suffer from disadvantages when used in intimately wearable or bio-integrated applications.By applying new engineering strategies,mechanically bendable and stretchable MEMS devices have been successfully demonstrated.This article reviews recent progress in this area,focusing on high-performance flexible devices based on inorganic thin films.We start with the common design and fabrication strategies for flexibility and stretchability,summarize the recent application-oriented flexible devices,and conclude with criteria and opportunities for the future development of flexible MEMS sensors.
基金supported in part by the National Key Research and Development Program of China (Grant No.2020YFB2008800)the Nanchang Institute for Microtechnology of Tianjin University。
文摘This paper is focused on electrode design for piezoelectric tuning fork resonators.The relationship between the performance and electrode pattern of aluminum nitride piezoelectric tuning fork resonators vibrating in the in-plane flexural mode is investigated based on a set of resonators with different electrode lengths,widths,and ratios.Experimental and simulation results show that the electrode design impacts greatly the multimode effect induced from torsional modes but has little influence on other loss mechanisms.Optimizing the electrode design suppresses the torsional mode successfully,thereby increasing the ratio of impedance at parallel and series resonant frequencies(R_(p)/R_(s))by more than 80%and achieving a quality factor(Q)of 7753,an effective electromechanical coupling coefficient(kt_(eff)^(2))of 0.066%,and an impedance at series resonant frequency(R_(m))of 23.6 kΩ.The proposed approach shows great potential for high-performance piezoelectric resonators,which are likely to be fundamental building blocks for sensors with high sensitivity and low noise and power consumption.
基金This work is supported by funding from the Natural Science Foundation of China(NSFC Grant No.62001322)the Tianjin Municipal Science and Technology Project(No.20JCQNJC011200)+1 种基金the National Key Research and Development Program(No.2020YFB2008801)the Nanchang Institute for Microtechnology of Tianjin University。
文摘This paper proposes an air-coupled piezoelectric micromachined ultrasonic transducer(PMUT)for detection and imaging of surface stains.A 508 kHz PMUT array is designed,fabricated,and characterized in terms of its electrical and acoustic properties,and it is used in a pulse echo validation test.Imaging of stains on metal blocks is successfully demonstrated.Compared with existing optical methods for stain detection,the proposed approach can work in a dark environment without color requirements.This work provides a new and promising route for the development of miniaturized stain detection systems.
基金This work was supported by the funding from Natural Science Foundation of China(Grant No.62001322)the National Key Research and Development Program(Grant No.2020YFB2008800)the Nanchang Institute for Microtechnology of Tianjin University.
文摘One of the key requirements for MEMS speakers is to increase the sound pressure level(SPL)while keeping the size as small as possible.In this paper we present a MEMS speaker based on piezoelectric bimorph cantilevers that produces a higher SPL than conventional unimorph cantilever speakers.The active diaphragm size is 1.4×1.4 mm^(2).The bimorph cantilevers are connected in parallel to make full use of the actuation voltage.At 1 kHz,the measured SPL reached 73 dB and the peak SPL reached 102 dB at the resonance frequency of 10 kHz in a 711 ear simulator under a driving voltage of 10 V_(rms).The total harmonic distortion of the MEMS speaker was less than 3%in the range from 100 Hz to 20 kHz.Although the absolute SPL was not the highest,this work provides a better SPL for all piezoelectric MEMS speakers.
基金supported by the National Natural Science Foundation of China(Nos.51375341,61901295,and 62001322)the Nanchang Institute for Microtechnology of Tianjin University.
文摘Heavy metal pollution in water environments poses a great threat to public health and to the ecological environment due to its high toxicity and non-degradability.However,many existing detection methods require laboratory-based bulky instruments and time-consuming manual operations.Although some on-site systems exist,they are difficult to deploy on a large scale owing to their large size and high cost.Here,we report a sensing node featuring low power consumption and low cost,achieved by integrating microsensor,microfluidic,and electronic modules into a compact size for automatic and scalable heavy metal pollution monitoring.Digital microfluidic and electrochemical sensing modules are integrated on a chip,thereby combining the procedures of sample pretreatment,electrochemical sensing,and waste removal for automatic and continuous monitoring.The feasibility of the platform is demonstrated by Pb2+detection in tap water.With a 3500 mAh battery,the compact sensing node could work for several years in principle.There is scope for further improvements to the system in terms of wider functionality and reductions in size,power consumption,and cost.The sensing node presented here is a strong candidate for distributed monitoring of water quality as an Internet-of-Things application.
基金the funding from National Key Research and Development Program(No.2020YFB2008800)。
文摘Piezoelectric MEMS speakers,an emerging technology with great promise,face significant challenges in performance evaluation and rational design.Their broadband nature means that responses at every frequency point across the whole operating bandwidth contribute to performance,yet there is no widely recognized weighting approach for fair evaluation.This absence of quantitative criteria makes objective comparisons of different designs difficult,slowing the adoption of new design concepts;and it leads to ambiguous design goals without response balance across frequency bands.Additionally,the current design methods rely on labor-intensive simulations,further prolonging the development process.To address these challenges,two figures of merit(FOMs)obtained via theoretical deduction are proposed in this study.These FOMs facilitate the evaluation of key metrics,such as sound pressure level and energy efficiency over a wide frequency range,enabling quantitative comparisons among various speaker designs.On the basis of FOMs,the design process can be simplified into a single-objective optimization problem,significantly streamlining the speaker design.Using this method,piezoelectric MEMS speakers with ultra-high FOMs and superior performance are demonstrated.The normalized SPLs at 1 and 10 kHz reach an impressive 76.6 and 86.6 dB/mm^(2)/V_(rms),respectively,with normalized sensitivities of 91.2 and 91.5 dB/mm2/mW.This achievement validates our FOM theory,representing a notable advancement in the field.
基金the Natural Science Foundation of China(NSFC Grant No.62001322)the Tianjin Municipal Science and Technology Project(No.20JCQNJCo11200)+1 种基金the National Key Research and Development Program(No.2020YFB2008800)the Nanchang Institute for Microtechnology of Tianjin University for funding.
文摘Eye blinking is closely related to human physiology and psychology.It is an effective method of communication among people and can be used in human-machine interactions.Existing blink monitoring methods include videooculography,electro-oculograms and infrared oculography.However,these methods suffer from uncomfortable use,safety risks,limited reliability in strong light or dark environments,and infringed informational security.In this paper,we propose an ultrasound-based portable approach for eye-blinking activity monitoring.Low-power pulse-echo ultrasound featuring biosafety is transmitted and received by microelectromechanical system(MEMS)ultrasonic transducers seamlessly integrated on glasses.The size,weight and power consumption of the transducers are 2.5 mm by 2.5 mm,23.3 mg and 71μW,respectively,which provides better portability than conventional methods using wearable devices.Eye-blinking activities were characterized by open and closed eye states and validated by experiments on dfferent volunteers.Finally,real-time eye-blinking monitoring was successfully demonstrated with a response time less than 1 ms.The proposed solution paves the way for ultrasound-based wearable eye-blinking monitoring and offers miniaturization,light weight,low power consumption,high informational security and biosafety.
基金National Natural Science Foundation of China,Grant/Award Number:62001322。
文摘Continuous and quantitative monitoring of knee joint function has clinical value in rehabilitation assessment and the timing of return to play for anterior cruciate ligament injury patients.However,the existing approaches,including clinical examination,arthrometry and inertial solutions,can only be used for qualitative,off-line and low-quality evaluations,respectively.Burgeoning Kirigami stretchable sensors could be a disruptive candidate solution,but they usually suffer from structural buckling issues when used for large strain applications,such as knee joint motion capture where the buckling degrades sensor reliability and repeatability.Here,we propose a buckling-resistant stretchable and wearable sensor for knee joint motion capture.It enables continuous and precise motion signal capture of the knee joint and provides high wearing comfort and reliability.Clinical tests were conducted on 30 patients in the field,tracking data provided by the sensor from their initial hospitalization to later surgery.And the full rehabilitation of one subject was recorded and analyzed.The test results show that our sensor can dynamically assess knee function in real time and recommend the best timing for return to play,which paves the way for personalized and telerehabilitation.
