Driven by the trend of device miniaturization and high-density integration,the interaction between adjacent electrodes has become a critical factor affecting the interfacial reliability of thermoelectric(TE)structures...Driven by the trend of device miniaturization and high-density integration,the interaction between adjacent electrodes has become a critical factor affecting the interfacial reliability of thermoelectric(TE)structures.This study investigates the influence of adjoining electrode interactions on the interfacial response of a multi-electrode/TE substrate structure,including interfacial stresses and stress intensity factors at the electrode ends.To solve the corresponding boundary-value problem,the Fourier transforms are adopted to derive a governing integro-differential equation for the interfacial shear stress in multi-electrode systems,incorporating the TE effects as generalized forces on the right-hand side.The results show that both the interfacial tension and transverse stress in the electrodes are significantly affected by the presence of adjacent electrodes.The interaction between neighboring electrodes diminishes as their spacing increases or when an adhesive interlayer is introduced.Furthermore,the softer and thinner electrodes,the softer and thicker adhesive interlayer,and the smaller TE loads are found to be beneficial for improving the interfacial performance.These findings may contribute to the accurate measurement in surface sensors and layout design of multi-point health monitoring systems for TE structures.展开更多
The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic...The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS（poly-dimethylsiloxane） hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP（n DEP） forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.展开更多
Air-coupled ultrasonic transducers(ACUTs)have been applied in industrial non-destructive testing,structural health monitoring,and medical ultrasound.However,conventional passive focusing methods often result in undesi...Air-coupled ultrasonic transducers(ACUTs)have been applied in industrial non-destructive testing,structural health monitoring,and medical ultrasound.However,conventional passive focusing methods often result in undesired effects on sensitivity due to variations in acoustic impedance matching conditions,which are critical in ACUT design,where sensitivity is the top priority.Accordingly,a novel active focusing method for ACUTs is proposed in this study.The key idea is to create multiple concentric ring electrode patterns on a bulk planar piezoelectric plate so that a quarter-wavelength acoustic impedance matching layer of uniform thickness can be attached onto the plate.The initial structural parameters of the electrode patterns are determined based on the design methodology of a Fresnel zone plate(FZP).Those parameters are optimized through finite element simulation,with the transducer’s sensitivity as the objective function,while ensuring only slight variations to the focal length and lateral resolution.Single-sided multiple concentric ring electrode patterns are then fabricated on 1-3 piezoelectric fiber/epoxy resin composite plate by screen printing and combined with a high-performance acoustic impedance matching layer made from epoxy resin composite filled with hollow glass microspheres.The planar active focusing ACUT is developed,while two types of conventional passive focusing ACUTs using FZP and concave lens are fabricated with the same piezoelectric and acoustic matching materials.Comparative experimental testing is carried out.The developed planar active-focusing ACUT achieves significant sensitivity improvements of 7.1 and 17.4dB,respectively,while maintaining comparable radial and axial full-width at half maximum.The results of this study offer a novel approach for the design of high-performance ACUTs.展开更多
基金Project supported by the National Natural Science Foundation of China(Nos.12502117,12272269,11972257)the Natural Science Foundation of Ningxia of China(No.2024AAC03018)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Shanghai Gaofeng Project for University Academic Program Development。
文摘Driven by the trend of device miniaturization and high-density integration,the interaction between adjacent electrodes has become a critical factor affecting the interfacial reliability of thermoelectric(TE)structures.This study investigates the influence of adjoining electrode interactions on the interfacial response of a multi-electrode/TE substrate structure,including interfacial stresses and stress intensity factors at the electrode ends.To solve the corresponding boundary-value problem,the Fourier transforms are adopted to derive a governing integro-differential equation for the interfacial shear stress in multi-electrode systems,incorporating the TE effects as generalized forces on the right-hand side.The results show that both the interfacial tension and transverse stress in the electrodes are significantly affected by the presence of adjacent electrodes.The interaction between neighboring electrodes diminishes as their spacing increases or when an adhesive interlayer is introduced.Furthermore,the softer and thinner electrodes,the softer and thicker adhesive interlayer,and the smaller TE loads are found to be beneficial for improving the interfacial performance.These findings may contribute to the accurate measurement in surface sensors and layout design of multi-point health monitoring systems for TE structures.
基金Supported by National Natural Science Foundation of China(Grant No.51305106)Fundamental Research Funds for the Central Universities,China(Grant Nos.HIT.NSRIF.2014058,HIT.IBRSEM.201319)Open Foundation of State Key Laboratory of Fluid Power Transmission and Control,China(GZKF-201402)
文摘The need to continuously separate multiple microparticles is required for the recent development of lab-on-chip technology. Dielectrophoresis（DEP）-based separation device is extensively used in kinds of microfluidic applications. However, such conventional DEP-based device is relatively complicated and difficult for fabrication. A concise microfluidic device is presented for effective continuous separation of multiple size particle mixtures. A pair of acupuncture needle electrodes are creatively employed and embedded in a PDMS（poly-dimethylsiloxane） hurdle for generating non-uniform electric field thereby achieving a continuous DEP separation. The separation mechanism is that the incoming particle samples with different sizes experience different negative DEP（n DEP） forces and then they can be transported into different downstream outlets. The DEP characterizations of particles are calculated, and their trajectories are numerically predicted by considering the combined action of the incoming laminar flow and the n DEP force field for guiding the separation experiments. The device performance is verified by successfully separating a three-sized particle mixture, including polystyrene microspheres with diameters of 3 μm, 10 μm and 25 μm. The separation purity is below 70% when the flow rate ratio is less than 3.5 or more than 5.1, while the separation purity can be up to more than 90% when the flow rate ratio is between 3.5 and 5.1 and meanwhile ensure the voltage output falls in between 120 V and 150 V. Such simple DEP-based separation device has extensive applications in future microfluidic systems.
基金supported by the National Natural Science Foundation of China(Grant No.52205564)the Foundation of Natural Science Foundation of Hubei Province,China(Grant No.2022CFB898).
文摘Air-coupled ultrasonic transducers(ACUTs)have been applied in industrial non-destructive testing,structural health monitoring,and medical ultrasound.However,conventional passive focusing methods often result in undesired effects on sensitivity due to variations in acoustic impedance matching conditions,which are critical in ACUT design,where sensitivity is the top priority.Accordingly,a novel active focusing method for ACUTs is proposed in this study.The key idea is to create multiple concentric ring electrode patterns on a bulk planar piezoelectric plate so that a quarter-wavelength acoustic impedance matching layer of uniform thickness can be attached onto the plate.The initial structural parameters of the electrode patterns are determined based on the design methodology of a Fresnel zone plate(FZP).Those parameters are optimized through finite element simulation,with the transducer’s sensitivity as the objective function,while ensuring only slight variations to the focal length and lateral resolution.Single-sided multiple concentric ring electrode patterns are then fabricated on 1-3 piezoelectric fiber/epoxy resin composite plate by screen printing and combined with a high-performance acoustic impedance matching layer made from epoxy resin composite filled with hollow glass microspheres.The planar active focusing ACUT is developed,while two types of conventional passive focusing ACUTs using FZP and concave lens are fabricated with the same piezoelectric and acoustic matching materials.Comparative experimental testing is carried out.The developed planar active-focusing ACUT achieves significant sensitivity improvements of 7.1 and 17.4dB,respectively,while maintaining comparable radial and axial full-width at half maximum.The results of this study offer a novel approach for the design of high-performance ACUTs.
