The future intelligent era that will be brought about by 5G technology can be well predicted.For example,the connection between humans and smart wearable devices will become increasingly more intimate.Flexible wearabl...The future intelligent era that will be brought about by 5G technology can be well predicted.For example,the connection between humans and smart wearable devices will become increasingly more intimate.Flexible wearable pressure sensors have received much attention as a part of this process.Nevertheless,there is a lack of complete and detailed discussion on the recent research status of capacitive pressure sensors composed of polymer composites.Therefore,this article will mainly discuss the key concepts,preparation methods and main performance of flexible wearable capacitive sensors.The concept of a processing“toolbox”is used to review the developmental status of the dielectric layer as revealed in highly cited literature from the past five years.The preparation methods are categorized into types of processing:primary and secondary.Using these categories,the preparation methods and structure of the dielectric layer are discussed.Their influence on the final capacitive sensing behavior is also addressed.Recent developments in the electrode layer are also systematically reviewed.Finally,the results of the above discussion are summarized and future development trends are discussed.展开更多
In this research paper,we have presented variable area type capacitive sensor signal conditioning system for angular displacement measurement and for this purpose we have used timer LM555 based astable multivibrator a...In this research paper,we have presented variable area type capacitive sensor signal conditioning system for angular displacement measurement and for this purpose we have used timer LM555 based astable multivibrator and universal frequency to digital converter (UFDC). Due to variation in angular displacement in the variable area type capacitor which is connected in the timer based astable circuit,capacitance changes which in turn changes the time period of the timer circuit output. The time period of the timer output waveform is linear with the capacitance and hence linear with angular displacement. The timer output is further processed with UFDC for the measurement. The experimental results show that the time period is linear with the angular displacement in the range of 0- 180° and the uncertainty we should associate it with this average time period value is the standard deviation of the mean,often called the standard error (SE),which is ± 0.023 μs. Because of the simplicity,this measurement system can be used in both electronic and industrial instrumentation.展开更多
A uniplanar capacitive sensor with 5-electrodes on one plane substrate and a large reflector electrode,was designed to get the corresponding capacitance information for weathering damage detection of non-metallic mate...A uniplanar capacitive sensor with 5-electrodes on one plane substrate and a large reflector electrode,was designed to get the corresponding capacitance information for weathering damage detection of non-metallic materials exposed to a service environment.A 2-D finite-element method was employed to simulate the electric potential distribution and capacitance measurements for the sensor.2 marble slabs,one was healthy and the other was notched,were experimentally detected.Both the simulation and the preliminary experimental results show that the measured capacitances decrease after weathering damage occurs in nonmetallic material.The reflector can enlarge the sensitive depth.The weathering assessment of nonmetallic materials can be done by processing the measured capacitances.The proposed approach can effectively detect the weathering damage of nonmetallic material and can be practically used for in-situ weathering damage evaluation.展开更多
Reverse-offset printing(ROP)enables microscale patterning on flexible substrates,making it ideal for fabricating interdigital capacitive(IDC)sensors for atopic dermatitis(AD)monitoring.AD,characterized by skin dryness...Reverse-offset printing(ROP)enables microscale patterning on flexible substrates,making it ideal for fabricating interdigital capacitive(IDC)sensors for atopic dermatitis(AD)monitoring.AD,characterized by skin dryness and inflammation,demands precise hydration tracking.Tailoring IDC electrode gaps to 50µm concentrates the electric field within the stratum corneum(SC),enhancing sensitivity beyond the capabilities of traditional screen printing.Finite element modelling and ROP were employed to assess the impact of electrode geometry and encapsulation thickness on sensor performance.Findings indicate that 50µm electrodes with encapsulation layers under 10µm maintain high sensitivity and consistent operation.A clinical case study demonstrated the 50µm sensor’s ability to distinguish lesional from non-lesional skin.These results inform the optimization of encapsulation-performance balance and advance the design of wearable,high-resolution IDC sensors for continuous skin hydration monitoring in personalized dermatological care.展开更多
In recent decades,capacitive pressure sensors(CPSs)with high sensitivity have demonstrated significant potential in applications such as medical monitoring,artificial intelligence,and soft robotics.Efforts to enhance ...In recent decades,capacitive pressure sensors(CPSs)with high sensitivity have demonstrated significant potential in applications such as medical monitoring,artificial intelligence,and soft robotics.Efforts to enhance this sensitivity have predominantly focused on material design and structural optimization,with surface microstructures such as wrinkles,pyramids,and micro-pillars proving effective.Although finite element modeling(FEM)has guided enhancements in CPS sensitivity across various surface designs,a theoretical understanding of sensitivity improvements remains underexplored.This paper employs sinusoidal wavy surfaces as a representative model to analytically elucidate the underlying mechanisms of sensitivity enhancement through contact mechanics.These theoretical insights are corroborated by FEM and experimental validations.Our findings underscore that optimizing material properties,such as Young’s modulus and relative permittivity,alongside adjustments in surface roughness and substrate thickness,can significantly elevate the sensitivity.The optimal performance is achieved when the amplitude-to-wavelength ratio(H/)is about 0.2.These results offer critical insights for designing ultrasensitive CPS devices,paving the way for advancements in sensor technology.展开更多
The development of intelligent electronic power systems necessitates advanced flexible pressure sensors.Despite improved compressibility through surface micro-structures or bulk pores,conventional capacitive pressure ...The development of intelligent electronic power systems necessitates advanced flexible pressure sensors.Despite improved compressibility through surface micro-structures or bulk pores,conventional capacitive pressure sensors face limitations due to their low dielectric constant and poor temperature tolerance of most elastomers.Herein,we constructed oriented polyimide-based aerogels with mechanical robustness and notable changes in dielectric constant under compression.The enhancement is attributed to the doping of surface-modified dielectric nanoparticles and graphene oxide sheets,which interact with polymer molecular chains.The resulting aerogels,with their excellent temperature resistance,were used to assemble high-performance capacitive pressure sensors.The sensor exhibits a maximum sensitivity of 1.41 kPa^(−1)over a wide working range of 0-200 kPa.Meanwhile,the sensor can operate in environments up to 150℃during 2000 compression/release cycles.Furthermore,the aerogel-based sensor demonstrates proximity sensing capabilities,showing great potential for applications in non-contact sensing and extreme environment detection.展开更多
Bio-inspired near-sensor computing,which integrates sensing and processing functions,presents a promising strategy to enhance efficiency and reduce latency in such applications.Here,we introduce tactile sensory nerve ...Bio-inspired near-sensor computing,which integrates sensing and processing functions,presents a promising strategy to enhance efficiency and reduce latency in such applications.Here,we introduce tactile sensory nerve systems with biologically realistic energy efficiency,utilizing starfish-inspired capacitive pressure sensors integrated with flexible memristors.These starfish-inspired sensors,with their high aspect ratio(~3)and stress-focusing,hourglass-shaped dielectric microstructures,enable highly sensitive tactile detection across a broad pressure range,effectively mimicking the properties of human skin.Artificial tactile sensory nerves,which integrate the capacitive sensor with a flexible memristor exhibiting synaptic plasticity,function reliably as energy-efficient near-sensor computing systems by bio-realistically transducing mechanical stimuli into transient electrical signals.The developed system operates as both an artificial nociceptor and a tactile near-sensor computing unit,with energy consumption approaching biological levels at approximately 140 pJ and 2.2 fJ,respectively.This neuro-inspired localized computing strategy offers a physical platform for advanced smart user interface applications.展开更多
A planar capacitive sensor(PCS) capable of 2D large-scale measurement is presented in this paper.Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the chang...A planar capacitive sensor(PCS) capable of 2D large-scale measurement is presented in this paper.Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the change in the overlapping area of sensing electrodes on a moving plate and a fixed plate.By accumulating the number of quarters in each direction and the specific position in the final quarter,the large-scale measurement is fulfilled.Displacements in Xand Y-direction can be measured independently and simultaneously.Simulation shows that a shorter gap distance and a longer electrode guarantee better sensitivity.Experiments based on a PCS test bench demonstrate that the PCS has a sensitivity of 0.198 mV/μm and a resolution of 0.308 μm.An electric fringe effect and other possible measurement errors on displacement interpretation accuracy are discussed.The study confirms the high potential of PCSs as innovative 2D long-range displacement sensors.展开更多
Capacitive sensors are efficient tools for biophysical force measurement,which is essential for the exploration of cellular behavior.However,attention has been rarely given on the influences of external mechanical and...Capacitive sensors are efficient tools for biophysical force measurement,which is essential for the exploration of cellular behavior.However,attention has been rarely given on the influences of external mechanical and internal electrical interferences on capacitive sensors.In this work,a bionic swallow structure design norm was developed for mechanical decoupling,and the influences of structural parameters on mechanical behavior were fully analyzed and optimized.A bionic feather comb distribution strategy and a portable readout circuit were proposed for eliminating electrostatic interferences.Electrostatic instability was evaluated,and electrostatic decoupling performance was verified on the basis of a novel measurement method utilizing four complementary comb arrays and applicationspecific integrated circuit readouts.An electrostatic pulling experiment showed that the bionic swallow structure hardly moved by 0.770 nm,and the measurement error was less than 0.009% for the area-variant sensor and 1.118% for the gap-variant sensor,which can be easily compensated in readouts.The proposed sensor also exhibited high resistance against electrostatic rotation,and the resulting measurement error dropped below 0.751%.The rotation interferences were less than 0.330 nm and(1.829×10^(-7))°,which were 35 times smaller than those of the traditional differential one.Based on the proposed bionic decoupling method,the fabricated sensor exhibited overwhelming capacitive sensitivity values of 7.078 and 1.473 pF/μm for gap-variant and area-variant devices,respectively,which were the highest among the current devices.High immunity to mechanical disturbances was maintained simultaneously,i.e.,less than 0.369% and 0.058% of the sensor outputs for the gap-variant and area-variant devices,respectively,indicating its great performance improvements over existing devices and feasibility in ultralow biomedical force measurement.展开更多
Electronic skin(e-skin) and flexible wearable devices are currently being developed with broad application prospects. Transforming electronic skin(e-skin) into true ¨skin¨is the ultimate goal. Tactile sensin...Electronic skin(e-skin) and flexible wearable devices are currently being developed with broad application prospects. Transforming electronic skin(e-skin) into true ¨skin¨is the ultimate goal. Tactile sensing is a fundamental function of skin and the development of high-performance flexible pressure sensors is necessary to realize thus. Many reports on flexible pressure sensors have been published in recent years,including numerous studies on improving sensor performance, and in particular, sensitivity. In addition,a number of studies have investigated self-healing materials, multifunctional sensing, and so on. Here,we review recent developments in flexible pressure sensors. First, working principles of flexible pressure sensors, including piezoresistivity, capacitance, and piezoelectricity, are introduced, as well as working mechanisms such as triboelectricity. Then studies on improving the performance of piezoresistive and capacitive flexible pressure sensors are discussed, in addition to other important aspects of this intriguing research field. Finally, we summarize future challenges in developing novel flexible pressure sensors.展开更多
In this paper, first a circular diaphragm is modeled using the classical plate theory. An analytical solution based on differential transformation method （DTM） and Runge-Kutta method is employed for solving the gove...In this paper, first a circular diaphragm is modeled using the classical plate theory. An analytical solution based on differential transformation method （DTM） and Runge-Kutta method is employed for solving the governing differential equation for the first time. Then the influences of various parameters on central deflection of the diaphragm, stress distribution and capacitance of pressure sensor with a time-dependent pressure are examined. Several case studies are compared with simulations to confirm the proposed method. The analytical results compared with ABAQUS simulation show excellent agreement with the simulation results. This method is very promising for time saving in calculating micro-device characteristics.展开更多
Calcium copper titanate(CCTO)/polystyrenepolyethylene-polybutylene-poly styrene(SEBS)dielectric elastomers were prepared via blending method.A capacitive strain sensor using CCTO/SEBS as dielectric layer and polyanili...Calcium copper titanate(CCTO)/polystyrenepolyethylene-polybutylene-poly styrene(SEBS)dielectric elastomers were prepared via blending method.A capacitive strain sensor using CCTO/SEBS as dielectric layer and polyaniline-dodecylbenzensulfonic acid(PANI-DB S A)/SEBS as electrodes was designed and manufactured by thermoforming process.X-ray diffractometer(XRD),scanning electron microscopy(SEM)and Raman spectra analyses were carried out;no impurities were found in the composite and CCTO particles were well dispersed.The dielectric tests showed that the samples filled with 20 wt%CCTO have their permittivity improved by 70%.The capacitive strain sensors have a stabilized capacitance variety range at different strain ranges or stretch speeds,and could remain synchronized after 500-time-stretching,showing high reproducibility.展开更多
Soil properties and water content vary from place to place. The calibration method based on capacitive soil moisture and humidity sensor is carried out. The sensor readings are compared with the mass water content mea...Soil properties and water content vary from place to place. The calibration method based on capacitive soil moisture and humidity sensor is carried out. The sensor readings are compared with the mass water content measured by the oven dried method,and the calibration formula of sensor reading and mass moisture content is established.Results show that the sensor reading has a good linear relationship with the mass water content measured by the oven dried method,and has high precision. It can calibrate the mass moisture content of the data obtained from the moisture migration test in the soil column.展开更多
Flexible pressure sensors have many potential applications in the monitoring of physiological signals because of their good biocompatibil-ity and wearability.However,their relatively low sensitivity,linearity,and stab...Flexible pressure sensors have many potential applications in the monitoring of physiological signals because of their good biocompatibil-ity and wearability.However,their relatively low sensitivity,linearity,and stability have hindered their large-scale commercial application.Herein,aflexible capacitive pressure sensor based on an interdigital electrode structure with two porous microneedle arrays(MNAs)is pro-posed.The porous substrate that constitutes the MNA is a mixed product of polydimethylsiloxane and NaHCO3.Due to its porous and interdigital structure,the maximum sensitivity(0.07 kPa-1)of a porous MNA-based pressure sensor was found to be seven times higher than that of an imporous MNA pressure sensor,and it was much greater than that of aflat pressure sensor without a porous MNA structure.Finite-element analysis showed that the interdigital MNA structure can greatly increase the strain and improve the sensitivity of the sen-sor.In addition,the porous MNA-based pressure sensor was found to have good stability over 1500 loading cycles as a result of its bilayer parylene-enhanced conductive electrode structure.Most importantly,it was found that the sensor could accurately monitor the motion of afinger,wrist joint,arm,face,abdomen,eye,and Adam’s apple.Furthermore,preliminary semantic recognition was achieved by monitoring the movement of the Adam’s apple.Finally,multiple pressure sensors were integrated into a 33 array to detect a spatial pressure distribu-×tion.Compared to the sensors reported in previous works,the interdigital electrode structure presented in this work improves sensitivity and stability by modifying the electrode layer rather than the dielectric layer.展开更多
The repeated usage of frying oil has been proven hazardous due to the degradation process by chemical reactions that lead to changes in the quality of the oil.Currently,the degree of frying oil degradation is indicate...The repeated usage of frying oil has been proven hazardous due to the degradation process by chemical reactions that lead to changes in the quality of the oil.Currently,the degree of frying oil degradation is indicated by the percentage of its total polar compounds(TPC).In this study,a capacitive sensor was designed to assess frying oil degradation at several heating time intervals by measuring changes on its electrical capacitance.The sensor was designed using interdigitated electrode structure.A total of 30 samples of 130 ml palm oil were heated at 180℃ up to 30 h.For each one hour interval,one sample was moved out from the laboratory oven.The electrical capacitance,total polar compound(TPC)and viscosity of the samples were measured for analysis.Preliminary results demonstrated significant correlation between oil electrical capacitance with TPC and viscosity with R^2 ranged from 0.83 to 0.90.The designed sensor has good potential for simple and inexpensive way of determining frying oil quality.展开更多
In this paper, a micro capacitive sensor with nanometer resolution is presented for ultra-precision measurement of micro components, which is fabricated by the MEMS （micro electromechanical systems） non-silicon tech...In this paper, a micro capacitive sensor with nanometer resolution is presented for ultra-precision measurement of micro components, which is fabricated by the MEMS （micro electromechanical systems） non-silicon technique. Based on the sensor, a micro capacitive tactile probe is constructed by stylus assembly and packaging design for dimension metrology on micro/nano scale, in which a data acquiring system is developed with AD7747. Some measurements of the micro capacitive tactile probe are performed on a nano positioning and measuring machine （NMM）. The measurement results show good linearity and hysteresis with a range of 11.6 μm and resolution of better than 5 nm. Hence, the micro capacitive tactile probe can be integrated on NMM to realize measurement of micro structures with nanometer accuracy.展开更多
Sensing structure of grid strip capacitors can be used in the design of capacitive micro-electromechanical system （MEMS） resonators, accelerometers etc. A grid strip structure consists of nonentirely overlap plates ...Sensing structure of grid strip capacitors can be used in the design of capacitive micro-electromechanical system （MEMS） resonators, accelerometers etc. A grid strip structure consists of nonentirely overlap plates so that the capacitor fringe effect cannot be neglected in the design. Electricmagnetic Finite Element Method （FEM） software ANSOFF-Maxwell is employed to analyze the fringe effect of a grid strip capacitor. The analysis includes capacitance changes with change of overlap length, overlap width, plate thickness, grid strip density etc. The results show that fringe effect leads to non-linear change of grid strip capacitance with the change of overlap length and width, that the capacitance increases with the increase of grid strip width and plate thickness, and that sensitivity can be improved through the increase of grid strip density in the condition of identical total overlap area, but linearity is reduced.展开更多
This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity...This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.展开更多
For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar c...For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar capacitance sensor. A boundary element method （BEM） was used to compute the relationship between capacitance and the dielectric constant. A functional relationship between MC and the dielectric constant was identified by LSFM. The agreement of this final computation result with the experimental data indicates that this method can be used to estimate the WMC quickly and effectively with engineering analysis. Compared with popular statistical methods, a large number of experiments are avoided, some costs of testing are reduced and the efficiency of testing is enhanced.展开更多
Recently,electronic skins and fl exible wearable devices have been developed for widespread applications in medical monitoring,artifi cial intelligence,human–machine interaction,and artifi cial prosthetics.Flexible p...Recently,electronic skins and fl exible wearable devices have been developed for widespread applications in medical monitoring,artifi cial intelligence,human–machine interaction,and artifi cial prosthetics.Flexible proximity sensors can accurately perceive external objects without contact,introducing a new way to achieve an ultrasensitive perception of objects.This article reviews the progress of fl exible capacitive proximity sensors,fl exible triboelectric proximity sensors,and fl exible gate-enhanced proximity sensors,focusing on their applications in the electronic skin fi eld.Herein,their working mechanism,materials,preparation methods,and research progress are discussed in detail.Finally,we summarize the future challenges in developing fl exible proximity sensors.展开更多
基金The authors gratefully acknowledge the financial support of this work by National Natural Science Foundation of China(51773139,51922071).
文摘The future intelligent era that will be brought about by 5G technology can be well predicted.For example,the connection between humans and smart wearable devices will become increasingly more intimate.Flexible wearable pressure sensors have received much attention as a part of this process.Nevertheless,there is a lack of complete and detailed discussion on the recent research status of capacitive pressure sensors composed of polymer composites.Therefore,this article will mainly discuss the key concepts,preparation methods and main performance of flexible wearable capacitive sensors.The concept of a processing“toolbox”is used to review the developmental status of the dielectric layer as revealed in highly cited literature from the past five years.The preparation methods are categorized into types of processing:primary and secondary.Using these categories,the preparation methods and structure of the dielectric layer are discussed.Their influence on the final capacitive sensing behavior is also addressed.Recent developments in the electrode layer are also systematically reviewed.Finally,the results of the above discussion are summarized and future development trends are discussed.
文摘In this research paper,we have presented variable area type capacitive sensor signal conditioning system for angular displacement measurement and for this purpose we have used timer LM555 based astable multivibrator and universal frequency to digital converter (UFDC). Due to variation in angular displacement in the variable area type capacitor which is connected in the timer based astable circuit,capacitance changes which in turn changes the time period of the timer circuit output. The time period of the timer output waveform is linear with the capacitance and hence linear with angular displacement. The timer output is further processed with UFDC for the measurement. The experimental results show that the time period is linear with the angular displacement in the range of 0- 180° and the uncertainty we should associate it with this average time period value is the standard deviation of the mean,often called the standard error (SE),which is ± 0.023 μs. Because of the simplicity,this measurement system can be used in both electronic and industrial instrumentation.
基金supported by the National Natural Science Foundation of China(60575015)
文摘A uniplanar capacitive sensor with 5-electrodes on one plane substrate and a large reflector electrode,was designed to get the corresponding capacitance information for weathering damage detection of non-metallic materials exposed to a service environment.A 2-D finite-element method was employed to simulate the electric potential distribution and capacitance measurements for the sensor.2 marble slabs,one was healthy and the other was notched,were experimentally detected.Both the simulation and the preliminary experimental results show that the measured capacitances decrease after weathering damage occurs in nonmetallic material.The reflector can enlarge the sensitive depth.The weathering assessment of nonmetallic materials can be done by processing the measured capacitances.The proposed approach can effectively detect the weathering damage of nonmetallic material and can be practically used for in-situ weathering damage evaluation.
文摘Reverse-offset printing(ROP)enables microscale patterning on flexible substrates,making it ideal for fabricating interdigital capacitive(IDC)sensors for atopic dermatitis(AD)monitoring.AD,characterized by skin dryness and inflammation,demands precise hydration tracking.Tailoring IDC electrode gaps to 50µm concentrates the electric field within the stratum corneum(SC),enhancing sensitivity beyond the capabilities of traditional screen printing.Finite element modelling and ROP were employed to assess the impact of electrode geometry and encapsulation thickness on sensor performance.Findings indicate that 50µm electrodes with encapsulation layers under 10µm maintain high sensitivity and consistent operation.A clinical case study demonstrated the 50µm sensor’s ability to distinguish lesional from non-lesional skin.These results inform the optimization of encapsulation-performance balance and advance the design of wearable,high-resolution IDC sensors for continuous skin hydration monitoring in personalized dermatological care.
基金supported by the National Natural Science Foundation of China(Grant No.12272369)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB0620101).
文摘In recent decades,capacitive pressure sensors(CPSs)with high sensitivity have demonstrated significant potential in applications such as medical monitoring,artificial intelligence,and soft robotics.Efforts to enhance this sensitivity have predominantly focused on material design and structural optimization,with surface microstructures such as wrinkles,pyramids,and micro-pillars proving effective.Although finite element modeling(FEM)has guided enhancements in CPS sensitivity across various surface designs,a theoretical understanding of sensitivity improvements remains underexplored.This paper employs sinusoidal wavy surfaces as a representative model to analytically elucidate the underlying mechanisms of sensitivity enhancement through contact mechanics.These theoretical insights are corroborated by FEM and experimental validations.Our findings underscore that optimizing material properties,such as Young’s modulus and relative permittivity,alongside adjustments in surface roughness and substrate thickness,can significantly elevate the sensitivity.The optimal performance is achieved when the amplitude-to-wavelength ratio(H/)is about 0.2.These results offer critical insights for designing ultrasensitive CPS devices,paving the way for advancements in sensor technology.
基金financially supported by the National Key Research&Development Program of China(No.2022YFA1205200).
文摘The development of intelligent electronic power systems necessitates advanced flexible pressure sensors.Despite improved compressibility through surface micro-structures or bulk pores,conventional capacitive pressure sensors face limitations due to their low dielectric constant and poor temperature tolerance of most elastomers.Herein,we constructed oriented polyimide-based aerogels with mechanical robustness and notable changes in dielectric constant under compression.The enhancement is attributed to the doping of surface-modified dielectric nanoparticles and graphene oxide sheets,which interact with polymer molecular chains.The resulting aerogels,with their excellent temperature resistance,were used to assemble high-performance capacitive pressure sensors.The sensor exhibits a maximum sensitivity of 1.41 kPa^(−1)over a wide working range of 0-200 kPa.Meanwhile,the sensor can operate in environments up to 150℃during 2000 compression/release cycles.Furthermore,the aerogel-based sensor demonstrates proximity sensing capabilities,showing great potential for applications in non-contact sensing and extreme environment detection.
基金supported by the National R&D Program through the National Research Foundation of Korea(NRF),funded by the Ministry of Science and ICT(No.RS-2023-00277635)supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.RS-2024-00411764)+1 种基金supported by a grant of the Basic Research Program funded by the Korea Institute of Machinery and Materials(grant number:NK254H)the Technology Innovation Program(RS-2024-00443121)funded By the Ministry of Trade Industry&Energy(MOTIE,Korea).
文摘Bio-inspired near-sensor computing,which integrates sensing and processing functions,presents a promising strategy to enhance efficiency and reduce latency in such applications.Here,we introduce tactile sensory nerve systems with biologically realistic energy efficiency,utilizing starfish-inspired capacitive pressure sensors integrated with flexible memristors.These starfish-inspired sensors,with their high aspect ratio(~3)and stress-focusing,hourglass-shaped dielectric microstructures,enable highly sensitive tactile detection across a broad pressure range,effectively mimicking the properties of human skin.Artificial tactile sensory nerves,which integrate the capacitive sensor with a flexible memristor exhibiting synaptic plasticity,function reliably as energy-efficient near-sensor computing systems by bio-realistically transducing mechanical stimuli into transient electrical signals.The developed system operates as both an artificial nociceptor and a tactile near-sensor computing unit,with energy consumption approaching biological levels at approximately 140 pJ and 2.2 fJ,respectively.This neuro-inspired localized computing strategy offers a physical platform for advanced smart user interface applications.
基金Project supported by the National Natural Science Foundation of China (No. 51275465)the National Basic Research Program (973) of China (No. 2011CB013300)the Scientific Research Foundation for the Returned Overseas Chinese Scholars,Ministry of Education,China (No. [2011]1568)
文摘A planar capacitive sensor(PCS) capable of 2D large-scale measurement is presented in this paper.Displacement interpretation depends on independently measuring the periodic variation in capacitance caused by the change in the overlapping area of sensing electrodes on a moving plate and a fixed plate.By accumulating the number of quarters in each direction and the specific position in the final quarter,the large-scale measurement is fulfilled.Displacements in Xand Y-direction can be measured independently and simultaneously.Simulation shows that a shorter gap distance and a longer electrode guarantee better sensitivity.Experiments based on a PCS test bench demonstrate that the PCS has a sensitivity of 0.198 mV/μm and a resolution of 0.308 μm.An electric fringe effect and other possible measurement errors on displacement interpretation accuracy are discussed.The study confirms the high potential of PCSs as innovative 2D long-range displacement sensors.
基金supported in part by the National Natural Science Foundation of China(Grant Nos.52105589 and U1909221)in part by the China Postdoctoral Science Foundation(Grant No.2021M692590)+2 种基金in part by the Fundamental Research Funds for the Central Universities,China(Grant No.xzy012021009)in part by the State Key Laboratory of Robotics and Systems(HIT),China(Grant No.SKLRS2021KF17)in part by the Beijing Advanced Innovation Center for Intelligent Robots and Systems,China(Grant No.2019IRS08).
文摘Capacitive sensors are efficient tools for biophysical force measurement,which is essential for the exploration of cellular behavior.However,attention has been rarely given on the influences of external mechanical and internal electrical interferences on capacitive sensors.In this work,a bionic swallow structure design norm was developed for mechanical decoupling,and the influences of structural parameters on mechanical behavior were fully analyzed and optimized.A bionic feather comb distribution strategy and a portable readout circuit were proposed for eliminating electrostatic interferences.Electrostatic instability was evaluated,and electrostatic decoupling performance was verified on the basis of a novel measurement method utilizing four complementary comb arrays and applicationspecific integrated circuit readouts.An electrostatic pulling experiment showed that the bionic swallow structure hardly moved by 0.770 nm,and the measurement error was less than 0.009% for the area-variant sensor and 1.118% for the gap-variant sensor,which can be easily compensated in readouts.The proposed sensor also exhibited high resistance against electrostatic rotation,and the resulting measurement error dropped below 0.751%.The rotation interferences were less than 0.330 nm and(1.829×10^(-7))°,which were 35 times smaller than those of the traditional differential one.Based on the proposed bionic decoupling method,the fabricated sensor exhibited overwhelming capacitive sensitivity values of 7.078 and 1.473 pF/μm for gap-variant and area-variant devices,respectively,which were the highest among the current devices.High immunity to mechanical disturbances was maintained simultaneously,i.e.,less than 0.369% and 0.058% of the sensor outputs for the gap-variant and area-variant devices,respectively,indicating its great performance improvements over existing devices and feasibility in ultralow biomedical force measurement.
基金supported by the National Natural Science Foundation of China(Nos.61775032,61475134 and 11604042)the Fundamental Research Funds for the Central Universities(N170405007,N180406002,N180408018 and N160404009)the 111 Project(B16009)。
文摘Electronic skin(e-skin) and flexible wearable devices are currently being developed with broad application prospects. Transforming electronic skin(e-skin) into true ¨skin¨is the ultimate goal. Tactile sensing is a fundamental function of skin and the development of high-performance flexible pressure sensors is necessary to realize thus. Many reports on flexible pressure sensors have been published in recent years,including numerous studies on improving sensor performance, and in particular, sensitivity. In addition,a number of studies have investigated self-healing materials, multifunctional sensing, and so on. Here,we review recent developments in flexible pressure sensors. First, working principles of flexible pressure sensors, including piezoresistivity, capacitance, and piezoelectricity, are introduced, as well as working mechanisms such as triboelectricity. Then studies on improving the performance of piezoresistive and capacitive flexible pressure sensors are discussed, in addition to other important aspects of this intriguing research field. Finally, we summarize future challenges in developing novel flexible pressure sensors.
文摘In this paper, first a circular diaphragm is modeled using the classical plate theory. An analytical solution based on differential transformation method （DTM） and Runge-Kutta method is employed for solving the governing differential equation for the first time. Then the influences of various parameters on central deflection of the diaphragm, stress distribution and capacitance of pressure sensor with a time-dependent pressure are examined. Several case studies are compared with simulations to confirm the proposed method. The analytical results compared with ABAQUS simulation show excellent agreement with the simulation results. This method is very promising for time saving in calculating micro-device characteristics.
基金financially supported by the National Natural Science Foundation of China(No.51403181)。
文摘Calcium copper titanate(CCTO)/polystyrenepolyethylene-polybutylene-poly styrene(SEBS)dielectric elastomers were prepared via blending method.A capacitive strain sensor using CCTO/SEBS as dielectric layer and polyaniline-dodecylbenzensulfonic acid(PANI-DB S A)/SEBS as electrodes was designed and manufactured by thermoforming process.X-ray diffractometer(XRD),scanning electron microscopy(SEM)and Raman spectra analyses were carried out;no impurities were found in the composite and CCTO particles were well dispersed.The dielectric tests showed that the samples filled with 20 wt%CCTO have their permittivity improved by 70%.The capacitive strain sensors have a stabilized capacitance variety range at different strain ranges or stretch speeds,and could remain synchronized after 500-time-stretching,showing high reproducibility.
文摘Soil properties and water content vary from place to place. The calibration method based on capacitive soil moisture and humidity sensor is carried out. The sensor readings are compared with the mass water content measured by the oven dried method,and the calibration formula of sensor reading and mass moisture content is established.Results show that the sensor reading has a good linear relationship with the mass water content measured by the oven dried method,and has high precision. It can calibrate the mass moisture content of the data obtained from the moisture migration test in the soil column.
基金supported in part by the National Natural Science Foundation of China(Grant No.62104056)the Zhejiang Provincial Natural Science Foundation of China(Grant No.LQ21F010010)+4 种基金the National Natural Science Foundation of China(Grant Nos.62141409 and 62204204)the National Key R&D Program of China(Grant No.2022ZD0208602)the Zhejiang Provincial Key Research&Development Fund(Grant Nos.2019C04003 and 2021C01041)the Shanghai Sailing Program(Grant No.21YF1451000)the Key Research and Development Program of Shaanxi(Grant No.2022GY-001).
文摘Flexible pressure sensors have many potential applications in the monitoring of physiological signals because of their good biocompatibil-ity and wearability.However,their relatively low sensitivity,linearity,and stability have hindered their large-scale commercial application.Herein,aflexible capacitive pressure sensor based on an interdigital electrode structure with two porous microneedle arrays(MNAs)is pro-posed.The porous substrate that constitutes the MNA is a mixed product of polydimethylsiloxane and NaHCO3.Due to its porous and interdigital structure,the maximum sensitivity(0.07 kPa-1)of a porous MNA-based pressure sensor was found to be seven times higher than that of an imporous MNA pressure sensor,and it was much greater than that of aflat pressure sensor without a porous MNA structure.Finite-element analysis showed that the interdigital MNA structure can greatly increase the strain and improve the sensitivity of the sen-sor.In addition,the porous MNA-based pressure sensor was found to have good stability over 1500 loading cycles as a result of its bilayer parylene-enhanced conductive electrode structure.Most importantly,it was found that the sensor could accurately monitor the motion of afinger,wrist joint,arm,face,abdomen,eye,and Adam’s apple.Furthermore,preliminary semantic recognition was achieved by monitoring the movement of the Adam’s apple.Finally,multiple pressure sensors were integrated into a 33 array to detect a spatial pressure distribu-×tion.Compared to the sensors reported in previous works,the interdigital electrode structure presented in this work improves sensitivity and stability by modifying the electrode layer rather than the dielectric layer.
基金This study is funded by the Prototype Research Grant Scheme,Ministry of Higher Education,project number PGRS/1/12/TK02/UPM/02/2.
文摘The repeated usage of frying oil has been proven hazardous due to the degradation process by chemical reactions that lead to changes in the quality of the oil.Currently,the degree of frying oil degradation is indicated by the percentage of its total polar compounds(TPC).In this study,a capacitive sensor was designed to assess frying oil degradation at several heating time intervals by measuring changes on its electrical capacitance.The sensor was designed using interdigitated electrode structure.A total of 30 samples of 130 ml palm oil were heated at 180℃ up to 30 h.For each one hour interval,one sample was moved out from the laboratory oven.The electrical capacitance,total polar compound(TPC)and viscosity of the samples were measured for analysis.Preliminary results demonstrated significant correlation between oil electrical capacitance with TPC and viscosity with R^2 ranged from 0.83 to 0.90.The designed sensor has good potential for simple and inexpensive way of determining frying oil quality.
基金supported by the Nano Special Projects of Shanghai Science and Technology Commission of China(Grant No.11nm0560800)the Young Scientists Fund of the National Natural Science Foundation of China(Grant No.11104284)
文摘In this paper, a micro capacitive sensor with nanometer resolution is presented for ultra-precision measurement of micro components, which is fabricated by the MEMS （micro electromechanical systems） non-silicon technique. Based on the sensor, a micro capacitive tactile probe is constructed by stylus assembly and packaging design for dimension metrology on micro/nano scale, in which a data acquiring system is developed with AD7747. Some measurements of the micro capacitive tactile probe are performed on a nano positioning and measuring machine （NMM）. The measurement results show good linearity and hysteresis with a range of 11.6 μm and resolution of better than 5 nm. Hence, the micro capacitive tactile probe can be integrated on NMM to realize measurement of micro structures with nanometer accuracy.
基金Supported by the National Natural Science Foundation of China （ No. 60903195 ） and the Key Technological Problems Tackling Project of Wuhan （No. 200750499172）.
文摘Sensing structure of grid strip capacitors can be used in the design of capacitive micro-electromechanical system （MEMS） resonators, accelerometers etc. A grid strip structure consists of nonentirely overlap plates so that the capacitor fringe effect cannot be neglected in the design. Electricmagnetic Finite Element Method （FEM） software ANSOFF-Maxwell is employed to analyze the fringe effect of a grid strip capacitor. The analysis includes capacitance changes with change of overlap length, overlap width, plate thickness, grid strip density etc. The results show that fringe effect leads to non-linear change of grid strip capacitance with the change of overlap length and width, that the capacitance increases with the increase of grid strip width and plate thickness, and that sensitivity can be improved through the increase of grid strip density in the condition of identical total overlap area, but linearity is reduced.
基金Supported by the National Natural Science Foundation of China(50974095,41174109,61104148)the National Science and Technology Major Projects(2011ZX05020-006)
文摘This paper presents the characteristics of a double helix capacitance sensor for measurement of the liquid holdup in horizontal oil–water two-phase flow. The finite element method is used to calculate the sensitivity field of the sensor in a pipe with 20 mm inner diameter and the effect of sensor geometry on the distribution of sensitivity field is presented. Then, a horizontal oil–water two-phase flow experiment is carried out to measure the response of the double helix capacitance sensor, in which a novel method is proposed to calibrate the liquid holdup based on three pairs of parallel-wire capacitance probes. The performance of the sensor is analyzed in terms of the flow structures detected by mini-conductance array probes.
基金supported by the Central University Basic Research Professional Expenses Special Foundation of Harbin Engineering University (Grant No. HEUCFL10101109)
文摘For our research, a new hybrid experimental-computational method is presented. We applied a least squares fitting method （LSFM） to reconstruct the wood moisture content （WMC） from the data measured with a planar capacitance sensor. A boundary element method （BEM） was used to compute the relationship between capacitance and the dielectric constant. A functional relationship between MC and the dielectric constant was identified by LSFM. The agreement of this final computation result with the experimental data indicates that this method can be used to estimate the WMC quickly and effectively with engineering analysis. Compared with popular statistical methods, a large number of experiments are avoided, some costs of testing are reduced and the efficiency of testing is enhanced.
基金supported by the National Key R&D Program of China(Nos.2022 YFF 1202700 and 2022YFB3203500)National Natural Science Foundation of China(Nos.62225403,62375046,51973024,an d U19A2091)+2 种基金“111”Project(No.B13013)Natur al Sci ence Foundation of Jilin Pro vin ce(No.20230101113JC)the Funding from Jilin Pr ovince(No.20220502002GH).
文摘Recently,electronic skins and fl exible wearable devices have been developed for widespread applications in medical monitoring,artifi cial intelligence,human–machine interaction,and artifi cial prosthetics.Flexible proximity sensors can accurately perceive external objects without contact,introducing a new way to achieve an ultrasensitive perception of objects.This article reviews the progress of fl exible capacitive proximity sensors,fl exible triboelectric proximity sensors,and fl exible gate-enhanced proximity sensors,focusing on their applications in the electronic skin fi eld.Herein,their working mechanism,materials,preparation methods,and research progress are discussed in detail.Finally,we summarize the future challenges in developing fl exible proximity sensors.
