Piezoelectric Thin Film Sensor Research Articles

Structural design and analysis of a picking robot arm using parallel grippers

The development of a versatile and reliable robotic arm for agricultural picking is essential for modern farming. This study presents the design of a picking robotic arm inspired by bionics principles. The end-effector features a parallel gripper structure to efficiently pick crops of various shapes and sizes, with finite element simulations confirming its structural rationality. The gripping force is measured by an LDTI-028K PVDF piezoelectric thin-film sensor, adjustable within a crop-safe range to prevent damage. Additionally, a new signal conditioning circuit is proposed to improve the signal-to-noise ratio by amplifying the sensor’s output signal and minimizing noise, addressing the relatively low surface charge produced by the PVDF film under external pressure. Adams simulation analyses show that the end-effector is highly adaptable. Furthermore, picking experiments demonstrate that the robotic arm can reduce costs and lower the attrition rate by approximately 23.2 ± 5% compared to manual picking, while also exhibiting high reliability and stability.

A Closed-Loop Nanosystem Based on Piezoelectric Sensor and Pd-Nanoshell Photothermal Ablation for Renal Denervation to Treat Hypertension.

Renal sympathetic nerves play a crucial role in the pathogenesis of hypertension, and renal denervation (RDN) is a new solution for patients with refractory hypertension. However, current RDN techniques show inconsistent results in clinical application probably owing to incomplete endovascular ablation of the sympathetic nerves and a lack of measures to localize and assess efficacy. In this study, a closed-loop RDN system consisting of a sensing unit with a piezoelectric thin-film sensor (PTFS) and a treatment unit with a hollow Pd nanoparticle shell (PdNPS) with a diameter of 202.0nm for photothermal neural ablation is constructed. The PTFS can monitor and collect arterial pulsation and blood pressure (BP) and direct PdNPS to maximize RDN. PdNPS maintains a local temperature of 58-62°C under near-infrared-II irradiation (1,064nm) to achieve effective RDN within a range of 90-120s treatment window. Photothermal ablation significantly inhibits the activities of renal sympathetic nerves post-procedure and after one month and reduces the elevation of BP by > 50%. The novel closed-loop system enables safe and efficient targeting, dynamic monitoring, and ablation of the renal sympathetic nerves. This closed-loop system provides a new strategy for RDN technology and even for treating sympathetic nerve-related chronic diseases.

Fabrication and characterization of smart titanium alloy bolt based on high-frequency piezoelectric thin-film.

We reported here on the fabrication and characterization of a smart titanium alloy bolt based on a high-frequency piezoelectric thin-film sensor. The thin-film sensor was directly deposited on a titanium alloy bolt head with radio frequency magnetron sputtering and characterized by a scanning electron microscope and an atomic force microscope. The ultrasonic characteristics of the smart bolt, which include a pure and broad frequency spectrum peaked at 14.81MHz, high measurement accuracy below 3%, and high repeatability free from some interference from bolt detection position change, were fully characterized. No obvious frequency shift was observed with the increase in axial preload. Based on the mono-wave method [TOF (time of flight) of longitudinal mode wave], TOF change increased linearly with preload force in the range of 0-20kN. With the increase in temperature from 22 to 150°C, the TOF linearly increases while the longitudinal wave velocity linearly decreases. The results indicate the prepared smart titanium alloy bolt is suitable as a smart aviation and automotive fastener.

High Signal to Noise Ratio Piezoelectric Thin Film Sensor Based on Elastomer Amplification for Ambulatory Blood Pressure Monitoring.

Continuous pulse wave detection can be used for monitoring and diagnosing cardiovascular diseases, and research on pulse sensing based on piezoelectric thin films is one of the hot spots. Usually, piezoelectric thin films do not come into direct contact with the skin and need to be connected through a layer of an elastic medium. Most views think that the main function of this layer of elastic medium is to increase the adhesion between the sensor component and the skin, but there is little discussion about the impact of the elastic medium on pulse vibration transmission. Here, we conducted a detailed study on the effects of Young's modulus and the thickness of elastic media on pulse sensing signals. The results show that the waveform amplitude of the piezoelectric sensing signal decreases with the increase of Young's modulus and thickness of the elastic medium. Then, we constructed a theoretical model of the influence of elastic media on pulse wave propagation. The amplitude of the pulse wave signal detected by the optimized sensor was increased to 480%. Our research shows that by regulating Young's modulus and thickness of elastic media, pulse wave signals can undergo a similar amplification effect, which has an important theoretical reference value for achieving ambulatory blood pressure monitoring based on high-quality pulse waves.

Design and Control Simulation Analysis of Tender Tea Bud Picking Manipulator

Aiming at the current complex problem of the mechanized high-quality picking of tender tea buds, this paper designs a tender tea bud-picking manipulator. In the picking process, the quality of the petiole and leaf blade of the tender tea bud is crucial, as the traditional cutting picking method destroys the cell structure of the tender tea buds, resulting in rapid oxidation of the cuts, thus losing the bright green appearance and pure taste. For this reason, this paper draws on the quality requirements of tender tea buds and traditional manual picking technology, simulating the process of the manual picking action, putting forward a ‘rotary pull-up’ clamping and ripping picking method, and designing the corresponding actuating structure. Using PVDF material piezoelectric thin-film sensors to detect the clamping force of the tender tea bud picking, the corresponding sensor hardware circuit is designed. In addition, the finite element analysis method is also used to carry out stress analysis on the mechanical fingers to verify the rationality of the automatic mechanism to ensure the high-quality picking of tender tea buds. In terms of the control of the manipulator, an SMC-PID control method is designed by using MATLAB/Simulink 2021 and Adam 2020 software for joint simulation. The way to control the closed-loop system angle and angular velocity error feedback is by adjusting the PID parameters, which quickly converts the sliding mode control to the sliding mode surface. The simulation results show that the SMC-PID control method proposed in this paper can meet the demand in tender tea bud picking and simultaneously has high control accuracy, response speed, and stability.

Thin-film sensors for data-driven concentricity prediction in cup backward extrusion

The manufacture of precise metal components by cold forging poses serious challenges to the process reliability under unstable process conditions. The detection of geometrical imperfections, such as concentricity deviations, is necessary for the operator to adjust the forging tool rack properly. In this paper, a novel piezoelectric thin-film sensor disc is introduced to detect such concentricity deviations based on the measurement of eccentric load, that is arising from elastic punch deformation. Experimental results showed, that the concentricity deviation of the produced parts efficiently can be predicted by processing measured force data using a support vector regression algorithm.

A novel ultra-thin and high toughness piezoelectric thin film sensor based on MEMS technology

A novel ultra-thin and high toughness piezoelectric thin film sensor based on MEMS technology

A novel ultra-thin and high toughness piezoelectric thin film sensor based on MEMS technology

A novel ultra-thin and high toughness piezoelectric thin film sensor based on MEMS technology

Ultrasonic Measurement of Axial Preload in High-Frequency Nickel-Based Superalloy Smart Bolt

A high-frequency, piezoelectric thin-film sensor was successfully deposited on a nickel-based superalloy bolt by radio frequency magnetron sputtering to develop a smart, nickel-based superalloy bolt. Ultrasonic response characterization, high accuracy, and repeatability of ultrasonic measurement of axial preload in nickel-based superalloy smart bolts are reported here and were fully demonstrated. The axial preload in the nickel-based superalloy smart bolt was directly measured by the bi-wave method (TOF ratio between transverse and longitudinal-mode waves) without using the traditional integration of a longitudinal and shear transducer. A model concerning the bolt before and after tensioning was established to demonstrate the propagation and displacement distribution of the ultrasonic waves inside a nickel-based superalloy smart bolt. The measured A-scan signal presented significantly favorable features including a mixture of transverse and longitudinal mode waves, a pure and broad frequency spectrum which peaked at 17.14 MHz, and high measurement accuracy below 3% for tension of 4 kN-20 kN. For the temporal ultrasonic signal, the measurement envelopes were narrower than for the counterpart of the simulation, justifying the 'filtration' advantage of the high-frequency sensor. Both the TOF change of the single longitudinal-mode wave and the TOF ratio between transverse- and longitudinal-mode waves increased linearly with preload force in the range of 0 kN to 20 kN. Compared with the commercial piezoelectric probe, the proposed probe, based on the combination of a high-frequency, piezoelectric thin-film sensor and a magnetically mounted transducer connector, exhibited high tolerance to temperatures as high as 320 °C and high repeatability free from some interference factors such as bolt detection position change and couplant layer thickness. The results indicate that this system is a promising axial preload measurement system for high-temperature fasteners and connectors, and the proposed sensor is a practical, high-frequency ultrasonic sensor for non-destructive testing.

Development and Characterization of ZnO Piezoelectric Thin Film Sensors on GH4169 Superalloy Steel Substrate by Magnetron Sputtering.

At present, piezoelectric sensors are primarily applied in health monitoring areas. They may fall off owing to the adhesive’s durability, and even damage the monitored equipment. In this paper, a piezoelectric film sensor (PFS) based on a positive piezoelectric effect (PPE) is presented and a ZnO film is deposited on a GH4169 superalloy steel (GSS) substrate using magnetron sputtering. The microstructure and micrograph of ZnO piezoelectric thin films were analyzed by an X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), scanning electron microscope (SEM), and atomic force microscope (AFM). The results showed that the surface morphology was dense and uniform and had a good c-axis-preferred orientation. According to the test results of five piezoelectric sensors, the average value of the longitudinal piezoelectric coefficient was 1.36 pC/N, and the average value of the static calibration sensitivity was 19.77 mV/N. We selected the sensor whose parameters are closest to the average value for the dynamic test experiment and we drew the output voltage response curve of the piezoelectric film sensor under different loads. The measurement error was 4.03% when repeating the experiment six times. The research achievements reveal the excellent performance of the piezoelectric film sensor directly deposited on a GH4169 superalloy steel substrate. This method can reduce measurement error caused by the adhesive and reduce the risk of falling off caused by the aging of the adhesive, which provides a basis for the research of smart bolts and guarantees a better application in structural health monitoring (SHM).

A new blood pressure prediction method using wrist pulse examination

Wrist pulse examination plays an imperative role in clinical practice including contemporary medicine systems like Ayurveda. Wrist pulse measurement system can also be used for blood pressure (BP) monitoring. This article proposes an extension of wrist pulse analysis system for BP monitoring. Wrist pulse signals are captured using three piezoelectric thin film sensors at the radial artery of the wrist as per Ayurvedic pulse diagnosis method. The wave features such as Spatial Pulse Transit Time (SPTT) and Spatial Pulse Wave Velocity (SPWV) are extracted from the captured wrist pulses. Pearson’s correlation coefficient is computed to find the correlation between SPTT and BP measured using standard measuring instrument (Omron HEM-6131). A moderate correlation is found between SPTT and Systolic Blood Pressure (SBP) with correlation coefficient of 0.72. SPWV values computed from SPTT are used to develop an empirical model for BP in terms of SPWV. Limitations of the empirical model lead to a theoretical model using Poiseuilli law. The Mean Artery Pressure (MAP) using theoretical model is recorded for 41 participants. The deviation of MAP thus computed as compared to the readings taken from clinically validated BP monitoring device is found to be varying in the range of 4.5 ± 2.3 mmHg.

Experimental investigation on the suitability of flexible pressure sensor for wrist pulse measurement

Pulse examination at the radial artery of the wrist is a most apparent diagnosis technique. Wrist pulse carries rich information about the cardiovascular system of human body. An investigation is made here to suggest suitable flexible type of thin film pressure sensor to measure the wrist pulse as per Ayurvedic medicine system. Primary objective of this work is to suggest a sensor which exhibits optimum spatial features and SNR values. Force Sensing Resistor (FSR), piezoresistive and piezoelectric thin film sensors are considered under this study. Piezoelectric sensor shows good performance in the quality of the pulse with 22 dB SNR. Further experimentation is conducted to find out transmissivity, repeatability and susceptibility to motion artifact. Trasnsmissivities of 0.91, 0.68 and 0.64 are obtained for piezoelectric, piezoresistive and FSR sensors respectively. Piezoresistive and FSR show repeatability error of ±8% and ± 7% while measuring pulse amplitude under standard force. Noise due to motion artifact for each type of sensors are recorded and compared with the standard Gaussian distribution function with the help of histogram. Collectively, piezoelectric sensor exhibits good spatial features, high transmissivity and comparatively low susceptibility to motion artifact.

Thermal-Variation Insensitive Force-Touch Sensing System Using Transparent Piezoelectric Thin-Film

A force-touch (z-axis) sensor for display applications has attracted considerable attention. The z-axis sensing layer can be realized by a transparent piezoelectric thin film due to its superior characteristics, such as thinness, flexibility, and an optical transparency. However, this film responds not only to pressure but also to thermal changes (pyroelectric characteristic), which is a major obstacle to commercialization. This paper presents a thermal-variation insensitive, force-touch sensing system using a transparent piezoelectric thin film. In conjunction with optimizations in analog front-end design for high gain and high speed, the threshold-based digital processing scheme, which effectively rejects pyroelectric signals and noises, is proposed. To validate the proposed design and method, the electronic readout system board composed of analog circuits and an eight-bit microcontroller unit was implemented, and it read out the force-touch signal with a ten-bit resolution in power consumption of 6.5 mW. The implemented readout system was experimentally verified with a 3.9-inch polyvinylidene fluoride-copolymer piezoelectric thin-film sensor, with a thickness of 20 $\mu \text{m}$ . The system achieves a force-to-signal gain of 0.6 V/N in a range of 0.3–2.5 N with high linearity. The capability to reject a pyroelectric signal up to ± $\Delta$ 10 °C/s was also proved through a thermal-shock experiment.

Analysis of skeletal muscle performance using piezoelectric film sensors.

A flexible piezoelectric thin film sensor has been proposed recently in several studies for detection of muscle movements. The objective of this study was to investigate the ability of this sensor to assess skeletal muscle performance and fatigue under isokinetic contractions. Simultaneous noninvasive measurements of muscles activity were done using surface electromyography (EMG) electrodes and two thin film piezoelectric sensors. Measurements were taken from the biceps during slow and fast elbow flexion with and without strong grip, during different weight lifting and from the gastrocnemius during treadmill marching at speeds of 4 and of 10 kph. The results shows correlation between the onset of EMG and the piezoelectric sensors (Piezo) signals during muscle contraction. Increasing contraction intensity increase significantly both EMG and Piezo signals. Higher contractions velocity increased Piezo signal. Opposite linear relation was found between the average maximal EMG envelope amplitudes and the average maximal Piezo peaks with increasing loads. The significant decrease in the maximal Piezo peaks with time of all 3 subjects during elbow flexion while holding weight suggests the ability of piezoelectric thin film sensor to track muscle fatigue during isokinetic contractions.

Impact of Optimized Electrodes on Generation Characteristics of Vacuum-Discharge Plasmas

Electrode structures have an important effect on the electric-field strength at the cathode tip in vacuum. Effectively increasing the electric-field strength at the cathode tip can contribute to increasing the density and energy of vacuum-arc discharge plasmas. In this paper, a tubular electrode is designed and employed as the anode. The electric-field distribution of the electrode was simulated using the software package Maxwell 3-D. Through a series of simulated experiments, the factors that affect the electric-field distribution were explored, including the length of the tubular anode and the relative positions of the electrodes. In addition, the effect of an insulator situated between the cathode and the anode and optimal designs for the electrode structures are discussed. The plasma parameters and thrust were measured using a Langmuir probe and a piezoelectric thin-film sensor, respectively. The experimental and simulated results indicate that optimizing the electrode structure can effectively reduce the weight of the electrodes, increase the field strength at the cathode tip, and generate higher plasma density and greater thrust.

The Process Optimization of Smart Nanostructured AlN Thin Films Sputtered by Pulsed DC

A ‘Smart’ coating design, based on the incorporation of an AlN piezoelectric thin film sensor into a tribological coating system, has been explained in this paper. As part of the overall coating system, piezoelectric AlN thin films with highly preferred (002) orientations have been deposited by a pulsed closed field unbalanced magnetron sputtering system using Cr, Mo and Pt as the seed/adhesion layer. The texture, orientation and piezoelectric properties of AlN films were characterized by means of x-ray diffraction, field emission scanning electron microscopy and laser interferometry. A Michelson laser interferometer was designed and constructed to obtain the converse piezoelectric response of the deposited AlN thin films. It was found that the incorporation of different seed layers at various working pressure in the sandwiched structure, significantly affected the (002) orientation and the piezoelectric response of AlN thin films.

PVDF压电薄膜传感器在便携式宫缩监测仪器中的应用

针对于传统压力传感器在宫缩监测中普遍存在的测量精度低、舒适度差等问题，在分析PVDF薄膜压电效应基础上，探讨了用于便携式宫缩压力监测仪器的PVDF压电薄膜传感器制作工艺，设计了宫缩压力信号放大和滤波预处理电路。在医院临床对PVDF压电薄膜传感器进行性能测试，结果表明：此传感器能够精准地感测到孕妇的子宫收缩变化，降低对孕妇正常活动造成的影响，符合当前医疗设备向便携化、移动化、可穿戴发展的趋势。 For the low accuracy and poor comfort of traditional pressure sensors in uterine contraction pressure monitoring, a PVDF piezoelectric thin film sensor was fabricated. In this paper, PVDF film piezoelectric effect, fabrication process of sensors and design of signal preprocess were discussed. The performance testing in hospital for this sensor was made and the experimental results showed that this sensor can detect uterine contraction pressure accurately and reduce the impact on the normal activities of pregnant women, complying with the trend that current medical instrumenta-tion is becoming portable, mobile and wearable.

Study on the Discharge Characteristics of a Coaxial Pulsed Plasma Thruster

A new coaxial pulsed plasma thruster (PPT) laboratory model is designed and employed in this study. A Teflon sleeve is connected with the anode, which is shaped as a nozzle, and a cathode is mounted in the cavity of the Teflon sleeve and kept in close contact with it. A thread is then designed in the internal surface of the Teflon sleeve, and because of the strong field strength of the cathode triple junction (CTJ), vacuum flashover occurs and a plasma jet is acquired behind the anode. The electric field distribution of the designed coaxial PPT laboratory model is simulated by MAXWELL 3D simulation software, and the plasma density and thrust are measured by a Langmuir probe and a piezoelectric thin-film sensor, respectively. Through a series of comparative experiments, we discuss the impact of optimal designs, such as the thread and the nozzle-shaped anode, on the discharge characteristics of the coaxial PPT. The experimental and simulation results indicate that the designed coaxial PPT laboratory model presents better discharge characteristics in view of its higher plasma density and greater thrust.

Performance analysis of an integrated piezoelectric ZnO sensor for detection of head–disk contact

Integrated capability for detection of head–disk contact is desired for magnetic sliders with near-contact flying height. At the same time, fabrication of added features should be compatible with the existing slider micromachining process which is highly specialized and cost sensitive. Aimed at meeting the two requirements, a novel sensor configuration is explored in the present study. The new sensor configuration consists of a piezoelectric zinc oxide (ZnO) thin-film sensor sandwiched in the magnetic slider on its trailing side. Coupled structural and piezoelectric finite-element analysis for a sensor–slider–suspension assembly was performed to investigate the dynamic sensing performance. Output voltages on the millivolt level were obtained under typical head–disk interactions. The second in-plane bending mode of the slider was found to be the major contributor to the output voltage. Parametric study further showed that a thicker ZnO layer generally generated a larger output, while the thickness of the slider overcoat had only minimal effect. Simulation results from harmonic and transient analyses demonstrated that the piezoelectric thin-film ZnO sensor was sufficiently sensitive for detection of head–disk contact.

Low-Temperature Solution Processable Electrodes for Piezoelectric Sensors Applications

Piezoelectric thin-film sensors are suitable for a wide range of applications from physiological measurements to industrial monitoring systems. The use of flexible materials in combination with high-throughput printing technologies enables cost-effective manufacturing of custom-designed, highly integratable piezoelectric sensors. This type of sensor can, for instance, improve industrial process control or enable the embedding of ubiquitous sensors in our living environment to improve quality of life. Here, we discuss the benefits, challenges and potential applications of piezoelectric thin-film sensors. The piezoelectric sensor elements are fabricated by printing electrodes on both sides of unmetallized poly(vinylidene fluoride) film. We show that materials which are solution processable in low temperatures, biocompatible and environmental friendly are suitable for use as electrode materials in piezoelectric sensors.