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
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
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
We propose a twin-array capacitance (TAC) sensor for the measurement of concentration, velocity, and flowrate of gas-solid two-phase flow. Using the sensitivity non-uniformity of a neighboring electrode, the regiona...We propose a twin-array capacitance (TAC) sensor for the measurement of concentration, velocity, and flowrate of gas-solid two-phase flow. Using the sensitivity non-uniformity of a neighboring electrode, the regional concentration of the cross-section was reconstructed directly. Additionally, the finite element method was used to analyze the capacitance of the sensors composed of a different number of electrodes. TAC sensors with 4, 6, and 8 electrodes were found to be the best for regional concentration measurements. Based on this, the 8-electrode twin-plane electrical capacitance tomography (ECT) sensor, the 4-electrode TAC sensor, and the 6-electrode TAC sensor were used to measure the concentration, velocity, and fiowrate of granules in granular flow. The flowrates measured by ECT and TAC were compared with the flowrate obtained by a gravity sensor to verify the measurement accuracy. Experiments on vertical and inclined pipelines with granular flow were carried out. We found that the flowrate accuracy of the 4-electrode TAC is distinctly better than that of the 6-electrode TAC in the vertical pipeline while the flowrate accuracy of the 4-electrode TAC and the 6-electrode TAC were similar for the inclined pipeline.展开更多
Generally,soil moisture and salinity in reclaimed land are monitored using soil dielectric sensors such as time domain reflectometry,frequency domain reflectometry,and capacitance.The soil dielectric sensor measures a...Generally,soil moisture and salinity in reclaimed land are monitored using soil dielectric sensors such as time domain reflectometry,frequency domain reflectometry,and capacitance.The soil dielectric sensor measures apparent dielectric permittivity.However,apparent dielectric permittivity is affected by soil moisture,salinity,and texture.In this study,performance evaluation and calibration of a dielectric sensor(5TE;METER Group,Inc.,Pullman,WA,USA)for monitoring soil salinity were performed.Laboratory calibration tests were completed,incorporating various levels of dry density,water content,and salinity.The soil salinity was determined by the electrical conductivity(EC)1:5 method.The volumetric water content as measured by the sensor was affected by dry density and water content.Generally,it linearly increased as dry density and water content increased.However,when dry density or water content was high,the measured value of the sensor increased nonlinearly.The bulk EC measured by sensor had no specific correlation with EC 1:5.The EC 1:5 measurement had a linear relationship with the gradient ofθandθs.Therefore,it can be estimated with a simple linear equation usingθfrom the soil test andθs from the capacitance sensor.The R 2 value of the EC 1:5 estimation equation was 0.98.The proposed equation requiresθfrom the gravimetric sample andθs from the sensor.Therefore,in the case of monitoring salinity using a sensor,it is recommended to measure the water content with a tensiometer.展开更多
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
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
The unpredictable rupture of saccular aneurysms especially of the intracerebral aneurysm is a knotty problem that always results in high mortality. Traditional diagnosis of medical images, which gives the aneurysm siz...The unpredictable rupture of saccular aneurysms especially of the intracerebral aneurysm is a knotty problem that always results in high mortality. Traditional diagnosis of medical images, which gives the aneurysm size and compares with a speculated critical size from clinical statistics, was demonstrated inadequate to forecasting rupture. Here, we propose a new detecting strategy that uses a dielectric elastomer (DE) capacitance sensor to monitor the growth of saccular aneurysms and deliver both the wall stress and geometric parameters, Based on the elastic growth theory together with the finite deformation analyses, the correlation between the real-time output capacitance of the DE sensor and the wall stress and/or geometry of an aneurysm is derived. Compared to clinic statistics and biomechanics simulations, the wall stress and geometric size may be used as combined indicators to assess the rupture risk of a saccular aneurysm, Numerical results show that an output relative capacitance of 30 indicates a high risk of rupture, Finally, the sensitivity and resolution of the DE sensor are proved adequately high for monitoring the growth state and evaluating the rupture risk of a saccular aneurysm.展开更多
Continuous,real-time monitoring and identification of bacteria through detection of microbially emitted volatile molecules are highly sought albeit elusive goals.We introduce an artificial nose for sensing and disting...Continuous,real-time monitoring and identification of bacteria through detection of microbially emitted volatile molecules are highly sought albeit elusive goals.We introduce an artificial nose for sensing and distinguishing vapor molecules,based upon recording the capacitance of interdigitated electrodes(IDEs)coated with carbon dots(C-dots)exhibiting different polarities.Exposure of the C-dot-IDEs to volatile molecules induced rapid capacitance changes that were intimately dependent upon the polarities of both gas molecules and the electrode-deposited C-dots.We deciphered the mechanism of capacitance transformations,specifically substitution of electrode-adsorbed water by gas molecules,with concomitant changes in capacitance related to both the polarity and dielectric constants of the vapor molecules tested.The C-dot-IDE gas sensor exhibited excellent selectivity,aided by application of machine learning algorithms.The capacitive C-dot-IDE sensor was employed to continuously monitor microbial proliferation,discriminating among bacteria through detection of distinctive“volatile compound fingerprint”for each bacterial species.The C-dot-IDE platform is robust,reusable,readily assembled from inexpensive building blocks and constitutes a versatile and powerful vehicle for gas sensing in general,bacterial monitoring in particular.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
Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate capacitors.In the present investigation biopolyo...Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate capacitors.In the present investigation biopolyol was synthesized from Latvia-grown rapeseeds’oil by the transesterification method with triethanolamine,in an environmentally friendly process,without emission of harmful substances,at temperatures 175℃±5℃.Rigid,closed-cell rapeseed oil polyol polyurethane biofoams and petrochemical foams were made ensuring content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.Dielectric permittivity of the polyurethane foams and the underlying monolithic petrochemical-origin polyurethane and biopolyurethane was measured with a non-destructive dielectric spectrometer equipped with a capacitive sensor of one-side access type at 16 discrete frequencies distributed geometrically over the band 10 Hz,…,330 kHz.Permittivity value of the gaseous phase in the closed-cells was estimated to beεg≈1.001 that corresponds to the values,characteristic for the most of gases.Dielectric permittivity of petrochemical polyurethane foams and the mentioned biofoams was compared with permittivity of polyurethane foams from industrial producers Sika JSC and General Plastics Manufacturing Co.Polyurethane foams of the developed formulation exhibit competitive,low dielectric permittivity,not exceeding that of the foams from industrial producers:petrochemical foams up to 550 kg/m^(3) and the mentioned biofoams,comprising the renewable rapeseed oil polyol,up to densities 230–250 kg/m^(3).Considering petrochemical-origin polyurethane foams as a heterogeneous media“Polymer—gaseous phase”,the applicability of the rule of mixture and Maxwell–Garnett equation to model mathematically the dependence of effective dielectric permittivity on the volume fraction of phases was showed.展开更多
Flexible pressure monitoring device can help correct the sitting posture and prevent health problems(e.g.,deformity of spinal column and musculoskeletal disease).Currently,most measurement systems hinder their wide ap...Flexible pressure monitoring device can help correct the sitting posture and prevent health problems(e.g.,deformity of spinal column and musculoskeletal disease).Currently,most measurement systems hinder their wide applications owing to the high cost or low accuracy.In this study,a flexible sitting pressure measurement system was proposed based on a textile-based capacitive pressure sensor array in order to measure sitting pressure distribution simply and conveniently.The capacitive pressure sensor array is sandwich structure composed of a high-density sponge layer and two electrode array fabrics,which possesses high resolution(2.26 sensors/cm2),high sensitivity(0.701 kPa-1)and fast response(≤35 ms).It is worth noting that the raw materials of the sensing fabric include commercialized copper sheets and polyester yarns.The as-prepared pressure measurement system can accurately measure the pressure distribution nephogram for sitting posture analysis.The sitting pressure of 10 volunteers was measured and six types of posture were distinguished clearly.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
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
The design of a maskless exposure system for fabricating the microstructured surface based on the grainy light illumination generated by laser speckle is reported. Upon combining with soft lithography, we obtained mic...The design of a maskless exposure system for fabricating the microstructured surface based on the grainy light illumination generated by laser speckle is reported. Upon combining with soft lithography, we obtained microstructured polydimethylsiloxane electrodes with microstructure sizes of 20 μm and 40 μm and microstructure fill factors ranging from 10% to 90%. The feasibility of using this method in fabricating high-sensitivity capacitive pressure sensors was demonstrated. The sensor shows the highest sensitivity of 2.14 k Pa-1under 0–100 Pa pressures, the low detection limit of 4.9 Pa, and the excellent stability and durability of 10000 cycles. The method of employing laser speckle in fabricating microstructures with different morphologies is simple and robust, which is superior to other methods such as traditional photolithography.展开更多
A capacitive tactile sensor(CTS)has been developed by assembling a double-sided patterned dielectric layer and novel electrodes.The patterned aluminium foil-supported electrode comprises zinc-aluminium layered double ...A capacitive tactile sensor(CTS)has been developed by assembling a double-sided patterned dielectric layer and novel electrodes.The patterned aluminium foil-supported electrode comprises zinc-aluminium layered double hydroxides(Zn AlLDH),MXene,and Ag NWs via electrostatic interaction.This flexible device enables greater structural deformation,thereby enhancing sensitivity to a wide range of pressure.The sensitivity of the CTS can be customized to meet specific requirements by matching the microstructured electrodes with the patterned dielectric layer.An optimized sensor exhibits a sensitivity of 2.752 kPa^(–1)within 30 kPa,a response time of approximately 100 ms,and a wide detection range of 0–300 kPa.The strong physical interaction among the electrode materials ensures a reliable conductive network,ensuring the long-term stability of the sensor,even after 7500 loading and unloading cycles.Furthermore,the fabricated CTS device presents a promising prospect for the integration into wearable electronics,with the ability to effectively respond to both human activities and external physical stimuli.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
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
The wind pressure measurement,especially on curved surfaces is imperative in revealing flow characteristics.The flexible sensor with high linear sensitivity over large pressure range is still a significant challenge,e...The wind pressure measurement,especially on curved surfaces is imperative in revealing flow characteristics.The flexible sensor with high linear sensitivity over large pressure range is still a significant challenge,especially for commutatively positive and negative pressure measurement.Here,we propose a conformable,range-programmable capacitive sensor that can extremely extend the measuring range but with high linear sensitivity.The key point is to precisely control the reference pressure of the flexible capacitive sensor array through microchannel network.The proposed sensor with reference pressure 0 kPa keeps stable at a highly-linear sensitivity of 0.28 kPa-1 in an initial measurement regime from 0 to 3 kPa,beyond which the linearity changes significantly.Via the tunable reference pressure,the linear ranges can be customized arbitrarily according to different flight conditions and measured positions,but without any deterioration of sensitivity.The theoretical model is built for the flexible capacitive sensor with tunable reference pressure,agreeing well with the experimental and finite element method results.Additionally,the bending effect is discovered when the flexible sensor is conformed on curved surfaces.This surface-mounted sensor skin is tested on a plate and is integrated with acquisition circuits on a standard airfoil NACA0012 in a wind tunnel and compares with the standard destructive method of pressure taps.It shows great potential applications in measuring wind pressure on curved surfaces,such as for"Fly-by-Feel"of unmanned aerial vehicles and wind tunnel test.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
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 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.
基金supported by the National Natural Science Foundation of China(51106070)
文摘We propose a twin-array capacitance (TAC) sensor for the measurement of concentration, velocity, and flowrate of gas-solid two-phase flow. Using the sensitivity non-uniformity of a neighboring electrode, the regional concentration of the cross-section was reconstructed directly. Additionally, the finite element method was used to analyze the capacitance of the sensors composed of a different number of electrodes. TAC sensors with 4, 6, and 8 electrodes were found to be the best for regional concentration measurements. Based on this, the 8-electrode twin-plane electrical capacitance tomography (ECT) sensor, the 4-electrode TAC sensor, and the 6-electrode TAC sensor were used to measure the concentration, velocity, and fiowrate of granules in granular flow. The flowrates measured by ECT and TAC were compared with the flowrate obtained by a gravity sensor to verify the measurement accuracy. Experiments on vertical and inclined pipelines with granular flow were carried out. We found that the flowrate accuracy of the 4-electrode TAC is distinctly better than that of the 6-electrode TAC in the vertical pipeline while the flowrate accuracy of the 4-electrode TAC and the 6-electrode TAC were similar for the inclined pipeline.
基金This research was supported by the Basic Science Research Program through the National Research Foundation of Korea(NRF)funded by the Ministry of Science,ICT&Future Planning(NRF-2014R1A2A1A11051680)the Korea Institute of Planning and Evaluation for Technology in Food,Agriculture,Forestry&Fisheriesand the Ministry of Agriculture,Food and Rural Affairs(114147-3).
文摘Generally,soil moisture and salinity in reclaimed land are monitored using soil dielectric sensors such as time domain reflectometry,frequency domain reflectometry,and capacitance.The soil dielectric sensor measures apparent dielectric permittivity.However,apparent dielectric permittivity is affected by soil moisture,salinity,and texture.In this study,performance evaluation and calibration of a dielectric sensor(5TE;METER Group,Inc.,Pullman,WA,USA)for monitoring soil salinity were performed.Laboratory calibration tests were completed,incorporating various levels of dry density,water content,and salinity.The soil salinity was determined by the electrical conductivity(EC)1:5 method.The volumetric water content as measured by the sensor was affected by dry density and water content.Generally,it linearly increased as dry density and water content increased.However,when dry density or water content was high,the measured value of the sensor increased nonlinearly.The bulk EC measured by sensor had no specific correlation with EC 1:5.The EC 1:5 measurement had a linear relationship with the gradient ofθandθs.Therefore,it can be estimated with a simple linear equation usingθfrom the soil test andθs from the capacitance sensor.The R 2 value of the EC 1:5 estimation equation was 0.98.The proposed equation requiresθfrom the gravimetric sample andθs from the sensor.Therefore,in the case of monitoring salinity using a sensor,it is recommended to measure the water content with a tensiometer.
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.
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.
基金supported by the National Natural Science Foundation of China(11322216,11621062,and 11321202)the Zhejiang Provincial Natural Science Foundation(LR13A020001)
文摘The unpredictable rupture of saccular aneurysms especially of the intracerebral aneurysm is a knotty problem that always results in high mortality. Traditional diagnosis of medical images, which gives the aneurysm size and compares with a speculated critical size from clinical statistics, was demonstrated inadequate to forecasting rupture. Here, we propose a new detecting strategy that uses a dielectric elastomer (DE) capacitance sensor to monitor the growth of saccular aneurysms and deliver both the wall stress and geometric parameters, Based on the elastic growth theory together with the finite deformation analyses, the correlation between the real-time output capacitance of the DE sensor and the wall stress and/or geometry of an aneurysm is derived. Compared to clinic statistics and biomechanics simulations, the wall stress and geometric size may be used as combined indicators to assess the rupture risk of a saccular aneurysm, Numerical results show that an output relative capacitance of 30 indicates a high risk of rupture, Finally, the sensitivity and resolution of the DE sensor are proved adequately high for monitoring the growth state and evaluating the rupture risk of a saccular aneurysm.
基金We are grateful to Dr.Natalya Froumin(XPS),Dr.Yanna Milionshi(TGA),Dr.Jurgen Jopp(AFM),Dr.Igor Mokmanov for assistance with GC-MS experiments and Mrs.Galia Strinkovski for mentoring.
文摘Continuous,real-time monitoring and identification of bacteria through detection of microbially emitted volatile molecules are highly sought albeit elusive goals.We introduce an artificial nose for sensing and distinguishing vapor molecules,based upon recording the capacitance of interdigitated electrodes(IDEs)coated with carbon dots(C-dots)exhibiting different polarities.Exposure of the C-dot-IDEs to volatile molecules induced rapid capacitance changes that were intimately dependent upon the polarities of both gas molecules and the electrode-deposited C-dots.We deciphered the mechanism of capacitance transformations,specifically substitution of electrode-adsorbed water by gas molecules,with concomitant changes in capacitance related to both the polarity and dielectric constants of the vapor molecules tested.The C-dot-IDE gas sensor exhibited excellent selectivity,aided by application of machine learning algorithms.The capacitive C-dot-IDE sensor was employed to continuously monitor microbial proliferation,discriminating among bacteria through detection of distinctive“volatile compound fingerprint”for each bacterial species.The C-dot-IDE platform is robust,reusable,readily assembled from inexpensive building blocks and constitutes a versatile and powerful vehicle for gas sensing in general,bacterial monitoring in particular.
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.
文摘Early investigations of dielectric permittivity of rigid polyurethane foams at low frequencies were made on petrochemical-origin foams,mainly by means of parallel plate capacitors.In the present investigation biopolyol was synthesized from Latvia-grown rapeseeds’oil by the transesterification method with triethanolamine,in an environmentally friendly process,without emission of harmful substances,at temperatures 175℃±5℃.Rigid,closed-cell rapeseed oil polyol polyurethane biofoams and petrochemical foams were made ensuring content of the renewable rapeseed oil polyol in ready foams 27 wt.%–29 wt.%.Dielectric permittivity of the polyurethane foams and the underlying monolithic petrochemical-origin polyurethane and biopolyurethane was measured with a non-destructive dielectric spectrometer equipped with a capacitive sensor of one-side access type at 16 discrete frequencies distributed geometrically over the band 10 Hz,…,330 kHz.Permittivity value of the gaseous phase in the closed-cells was estimated to beεg≈1.001 that corresponds to the values,characteristic for the most of gases.Dielectric permittivity of petrochemical polyurethane foams and the mentioned biofoams was compared with permittivity of polyurethane foams from industrial producers Sika JSC and General Plastics Manufacturing Co.Polyurethane foams of the developed formulation exhibit competitive,low dielectric permittivity,not exceeding that of the foams from industrial producers:petrochemical foams up to 550 kg/m^(3) and the mentioned biofoams,comprising the renewable rapeseed oil polyol,up to densities 230–250 kg/m^(3).Considering petrochemical-origin polyurethane foams as a heterogeneous media“Polymer—gaseous phase”,the applicability of the rule of mixture and Maxwell–Garnett equation to model mathematically the dependence of effective dielectric permittivity on the volume fraction of phases was showed.
基金Fundamental Research Fund for the Central Universities,China(Nos.2232020G-01 and 19D110106)Young Elite Scientists Sponsorship Program by China Association for Science and Technology,China(No.2017QNRC001)Graduate Student Innovation Fund of Donghua University,China(No.20D310111)。
文摘Flexible pressure monitoring device can help correct the sitting posture and prevent health problems(e.g.,deformity of spinal column and musculoskeletal disease).Currently,most measurement systems hinder their wide applications owing to the high cost or low accuracy.In this study,a flexible sitting pressure measurement system was proposed based on a textile-based capacitive pressure sensor array in order to measure sitting pressure distribution simply and conveniently.The capacitive pressure sensor array is sandwich structure composed of a high-density sponge layer and two electrode array fabrics,which possesses high resolution(2.26 sensors/cm2),high sensitivity(0.701 kPa-1)and fast response(≤35 ms).It is worth noting that the raw materials of the sensing fabric include commercialized copper sheets and polyester yarns.The as-prepared pressure measurement system can accurately measure the pressure distribution nephogram for sitting posture analysis.The sitting pressure of 10 volunteers was measured and six types of posture were distinguished clearly.
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.
基金supported by the National Key Research and Development Program of China (Grant No. 2017YFA0304203)the Key Research and Development Program of Shanxi Province (Grant No. 202102030201002)+3 种基金the Changjiang Scholars and Innovative Research Team in University of Ministry of Education of China (Grant No. IRT_17R70)the State Key Program of National Natural Science of China (Grant No. 11434007)the111 Project (Grant No. D18001)the Fund for Shanxi “1331 Project”。
文摘The design of a maskless exposure system for fabricating the microstructured surface based on the grainy light illumination generated by laser speckle is reported. Upon combining with soft lithography, we obtained microstructured polydimethylsiloxane electrodes with microstructure sizes of 20 μm and 40 μm and microstructure fill factors ranging from 10% to 90%. The feasibility of using this method in fabricating high-sensitivity capacitive pressure sensors was demonstrated. The sensor shows the highest sensitivity of 2.14 k Pa-1under 0–100 Pa pressures, the low detection limit of 4.9 Pa, and the excellent stability and durability of 10000 cycles. The method of employing laser speckle in fabricating microstructures with different morphologies is simple and robust, which is superior to other methods such as traditional photolithography.
基金supported by the Natural Science Foundation of Guangdong Province(Grant No.2021A1515010691)the College Innovation Team Project of Guangdong Province(Grant No.2021KCXTD042)+1 种基金the Major Program of Basic Research and Applied Research of Guangdong Province(Grant No.2019KZDXM051)Wuyi University-Hong Kong-Macao Joint Research and Development Fund(Grant Nos.2019WGALH06 and 2021WGALH15)。
文摘A capacitive tactile sensor(CTS)has been developed by assembling a double-sided patterned dielectric layer and novel electrodes.The patterned aluminium foil-supported electrode comprises zinc-aluminium layered double hydroxides(Zn AlLDH),MXene,and Ag NWs via electrostatic interaction.This flexible device enables greater structural deformation,thereby enhancing sensitivity to a wide range of pressure.The sensitivity of the CTS can be customized to meet specific requirements by matching the microstructured electrodes with the patterned dielectric layer.An optimized sensor exhibits a sensitivity of 2.752 kPa^(–1)within 30 kPa,a response time of approximately 100 ms,and a wide detection range of 0–300 kPa.The strong physical interaction among the electrode materials ensures a reliable conductive network,ensuring the long-term stability of the sensor,even after 7500 loading and unloading cycles.Furthermore,the fabricated CTS device presents a promising prospect for the integration into wearable electronics,with the ability to effectively respond to both human activities and external physical stimuli.
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 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.
基金the National Natural Science Foundation of China(Grant Nos.51635007 and 51925503)the Fundamental Research Funds for the Central Universities(Grant No.2016YXZD068)。
文摘The wind pressure measurement,especially on curved surfaces is imperative in revealing flow characteristics.The flexible sensor with high linear sensitivity over large pressure range is still a significant challenge,especially for commutatively positive and negative pressure measurement.Here,we propose a conformable,range-programmable capacitive sensor that can extremely extend the measuring range but with high linear sensitivity.The key point is to precisely control the reference pressure of the flexible capacitive sensor array through microchannel network.The proposed sensor with reference pressure 0 kPa keeps stable at a highly-linear sensitivity of 0.28 kPa-1 in an initial measurement regime from 0 to 3 kPa,beyond which the linearity changes significantly.Via the tunable reference pressure,the linear ranges can be customized arbitrarily according to different flight conditions and measured positions,but without any deterioration of sensitivity.The theoretical model is built for the flexible capacitive sensor with tunable reference pressure,agreeing well with the experimental and finite element method results.Additionally,the bending effect is discovered when the flexible sensor is conformed on curved surfaces.This surface-mounted sensor skin is tested on a plate and is integrated with acquisition circuits on a standard airfoil NACA0012 in a wind tunnel and compares with the standard destructive method of pressure taps.It shows great potential applications in measuring wind pressure on curved surfaces,such as for"Fly-by-Feel"of unmanned aerial vehicles and wind tunnel test.
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.