Piezoelectric Microcantilever Research Articles

Construction of AuNPs/UiO‐66−NH2 Decorated Microcantilever Immunosensor for Efficient Detection of Procalcitonin

AbstractIn this study, gold nanoparticles (AuNPs) were grown on the surface of a metal‐organic framework (UiO‐66−NH2). The resulting AuNPs/UiO‐66−NH2 composite nanomaterials were further used for antibody immobilization on a microcantilever surface. By harnessing the robust signal processing capabilities of integrated circuits, a highly sensitive piezoelectric microcantilever sensor was constructed. The incorporation of nanomaterials resulted in enhanced antibodies immobilization amount, thereby improving the immunosensor‘s sensitivity. Under optimized experimental conditions, a promising linear correlation (R=0.993) was observed between the voltage output intensity of the microcantilever sensor and the logarithmic PCT concentration within a range of 0.1–50 ng/mL. The constructed microcantilever immunosensor based displayed several advantages such as simplicity, rapidity, high sensitivity, and low cost. Moreover, it potentially provided a novel approach to detect other biomolecules.

Machine Learning-Assisted Multifunctional Environmental Sensing Based on a Piezoelectric Cantilever.

Multifunctional environmental sensing is crucial for various applications in agriculture, pollution monitoring, and disease diagnosis. However, most of these sensing systems consist of multiple sensors, leading to significantly increased dimensions, energy consumption, and structural complexity. They also often suffer from signal interferences among multiple sensing elements. Herein, we report a multifunctional environmental sensor based on one single sensing element. A MoS2 film was deposited on the surface of a piezoelectric microcantilever (300 × 1000 μm2) and used as both a sensing layer and top electrode to make full use of the changes in multiple properties of MoS2 after its exposure to various environments. The proposed sensor has been demonstrated for humidity detection and achieved high resolution (0.3% RH), low hysteresis (5.6%), and fast response (1 s) and recovery (2.8 s). Based on the analysis of the magnitude spectra for transmission using machine learning algorithms, the sensor accurately quantifies temperatures and CO2 concentrations in the interference of humidity with accuracies of 91.9 and 92.1%, respectively. Furthermore, the sensor has been successfully demonstrated for real-time detection of humidity and temperature or CO2 concentrations for various applications, revealing its great potential in human-machine interactions and health monitoring of plants and human beings.

Piezoelectric unimorph microcantilevers for measuring direct and converse piezoelectric coefficients

In this study, we propose a new piezoelectric measurement method using unimorph microcantilevers to evaluate precise values of direct and converse piezoelectric coefficients for piezoelectric microelectromechanical system applications. We fabricated unimorph microcantilevers comprising 3-μm-thick polycrystalline Pb(Zr,Ti)O3 (PZT) thin films on a 20-μm-thick silicon (Si) layer. The converse piezoelectric coefficient was measured as |e31,f| = 3.9–5.8 C/m2, which was in good agreement with the measurement results of PZT thin films without microfabrication. The direct piezoelectric properties of the PZT microcantilevers were measured at the resonance frequency of each microcantilever, and |e31,f| was ∼2 C/m2, which was consistent with previous reports on the piezoelectric properties of a PZT thin film on Si. Since the measurement results included the effects of the stress condition and microfabrication damage, the measurement method of this study can evaluate the actual piezoelectric coefficient of piezoelectric properties in microdevice structures.

Vibration and sensitivity analysis of double-layered non-uniform piezoelectric microcantilever as a self-sensing mass sensor

Piezoelectric microcantilevers are specially popular in microelectromechanical system (MEMS) devices due to their high accuracy, environmental friendliness, low response time, and compatibility with compact designs. Since mass sensors are an important application of piezoelectric microcantilevers (PMCs), it is particularly important to determine PMCs sensitivity to nanoparticle absorption. For this purpose, a dynamic analysis was carried out to derive the equation governing vibrations of a PMC in air and water environments. A sphere chain model was used to model hydrodynamic forces acting on the PMC. In order to utilize the bending of the PMC for determining the output current from the piezoelectric layer, the resulting equation was solved by taking into account how the PMC geometrical discontinuities affected eigenvalues. In addition to the sensitivity of natural frequency and amplitude of these sensors, sensitivity of output electric current from their piezoelectric layer is also important. Therefore, the sensitivity of these parameters to nanoparticle absorption was analyzed and compared so as to select the suitable parameter for achieving satisfactory performance of PMC mass sensors in air and liquid working environments. The importance of selecting proper geometrical dimensions in the design of PMC mass sensors is realized by considering the fact that their sensitivity can be enhanced by properly selecting their dimensions. Accordingly, the effects of geometrical dimensions of the sensor on its sensitivity were determined through Sobol sensitivity analysis. The simulation results indicated that the sensitivity of output current from the piezoelectric layer and that of the vibration amplitude in the first three modes were the suitable parameters determining the performance of the PMC mass sensor in air and fluid environments, respectively.

Geometrical investigations of piezoelectric microcantilever coupled with square/circular shaped micromembrane designs for an energy harvesting application

The Finite element analysis (FEA) plays a vital role for the design and development of microdevices, which provides the solutions to understand the behaviour virtually for the optimization of specific device. In the present work, we designed two different energy harvesting (EH) models with variable dimensions and analyzed the EH performance for wide range of pressure. The proposed models consist of four piezoelectric microcantilevers coupled with square (Design-I) and circular (Design-II) shaped micro-membranes. The piezoelectric material PZT-5H was used as transduction material and the gold electrodes were used as charge collector. The EH designs (I & II) were modelled with variable membrane thickness viz., 1 µm and 0.5 µm and their output performances like total displacement, von Mises stress, volumetric strain and electric potential were studied for the pressure range of 200–2000 Pa. The EH design-I generated the maximum output potential of 167 µV (1 µm) and 186 µV (0.5 µm) for the applied pressure of 2000 Pa. Similarly, EH design-II generated the maximum output potential of 138 µV (1 µm) and 174 µV (0.5 µm) for the applied pressure of 2000 Pa. Relatively, the EH designs I & II with 0.5 µm thickness exhibited best output performance for the maximum applied pressure of 2000 Pa, which generated maximum output potential of 186 µV and 174 µV, respectively. In comparison with the other designs, the piezoelectric microcantilever coupled with square shaped micro-membrane (Design-I) of 0.5 µm thickness exhibited better EH performance than the circular shaped micro-membrane (Design-II).

Design of an effective piezoelectric microcantilever biosensor for rapid detection of COVID-19

Acute respiratory syndrome coronavirus 2 (SARS-CoV-2), also called COVID-19, is one of the most contagious viruses resulting in a progressive pandemic. Since specific antiviral treatments have not been developed yet and its fatal rate is almost high, early and fast detection is critical for controlling the outbreak. In this study, a piezoelectric microcantilever biosensor has been designed for detecting COVID-19 samples directly without requiring preparation steps. The biosensor acts as a transducer and is coated with the related antibody. When the SARS-CoV-2 antigens adsorbed on the microcantilever top surface through their spike proteins, a surface stress due to the mass change would be prompted leading to the measurable tip deflection and floating voltage. To obtain a biosensor with optimum parameters, different shapes and piezoelectric materials have been assessed and it was concluded that a Poly (vinylidene fluoride) (PVDF) biosensor in a shape of a holed punched form triangle, represented the best result. Therefore, the highly sensitive microcantilever biosensor can detect COVID-19 in clinical samples with various viral loads, rapidly. Also, it is selective enough to differentiate SARS-CoV-2 from other viruses with similar symptoms.

High Resolution and Fast Response of Humidity Sensor Based on AlN Cantilever With Two Groups of Segmented Electrodes

Resonant cantilever based on piezoelectric materials is one of the most promising platforms for real-time humidity sensing. In this letter, we propose a humidity sensor based on an AlN piezoelectric microcantilever with a high-order resonant mode and a sensing layer of MoS <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . The top electrode of cantilever is designed into two groups of segmented electrodes in order to achieve a high intensity of the resonance peak of the cantilever resonator operated at a high-order mode. Compared with the humidity sensor based on a standard cantilever with the same dimension, the sensitivity of the newly proposed humidity sensor is increased from 5.99 to 778 Hz/%RH when the humidity is about 80%RH. The resolution is increased from 0.21%RH to 0.025%RH because of the improvement of the ratio of sensitivity to noise, which cannot be achieved simply by increasing the frequency. The sensor shows a low hysteresis (5.8%) in a wide humidity sensing range from 10%RH to 90%RH. Moreover, the proposed humidity sensor has good short-term repeatability, fast response (0.6 s) and recovery (8 s) to humidity changes, indicating its great potential for fast-response detection.

Design, modeling, characterization and analysis of a low frequency micro-fabricated piezoelectric cantilever for vibration sensing and energy harvesting applications

The technological advances in electronics have enabled the development of low-power devices with miniaturized sensors that can be used in a wide range of monitoring applications. Research into alternative solutions for powering these devices has led to the study of vibration energy harvesters, of which, the piezoelectric micro-cantilevers are of interest. This paper provides a comprehensive study of a MEMS based micro-cantilever, containing a thin film of Aluminum Nitride used as a piezoelectric material to harvest and sense vibrational energy. The proposed device was designed with a very low resonance frequency of 163 Hz to adequately match the high energy harmonics found in common sources of ambient vibrations. An overview, design and simulation of an integrated MOSFET based rectifier, optimized to enable the energy harvesting and vibration sensing application is presented. A preliminary simulation of the micro-cantilever device is conducted to estimate its power output, and a low budget experimental setup is developed to characterize the device. A power output of 0.491 μW was measured at the resonance frequency of 163 Hz for a vibration intensity of 10 m s−2, and a new semi-empirical model was proposed, which showed only a 1% deviation from that measured peak value. Using an appropriate metric, the performance of the device was compared with similar state-of-art devices reported by other authors. Lastly, a brief applicability discussion is provided, analyzing the potential of the studied device to be used as an energy harvester for low-power electronics and as a vibration sensor.

Multilayered non‐uniform atomic force microscope piezoelectric microcantilever control and vibration analysis considering different excitation based on the modified couple stress theory

Atomic force microscope (AFM) is one of the most powerful tools for surface scanning, force measurement, and nano-manipulation. To improve its performance, vibration and control of AFM micro-cantilever (MC) should be studied. Hysteresis, as an undesired phenomenon affecting vibration amplitude and phase, is also another important issue to be examined. In this paper, vibration analysis and control of a ZnO non-uniform multi-layered piezoelectric MC has been investigated in non-contact mode. A modified couple stress theory has been used to obtain the strain energy for modeling the MC. In order to control the amplitude, a sliding mode controller (SMC) has been utilized on AFM, due to its application in uncertain and nonlinear systems. For applying the control signal, two methods of piezo and base actuation are studied. The results are compared with proportional integral derivative (PID) control method and it is demonstrated that SMC method reduces the control input close to the surface and increases the accuracy near the surface. In addition to MC control, hysteresis amplitude and phase differences are investigated by applying the Prandtl-Ishlinskii model. Also, surface topography is studied with hysteresis. The simulations show backward phase difference and an increase in amplitude, accordingly.

Epitaxial Nanostructured α-Quartz Films on Silicon: From the Material to New Devices.

In this work, we show a detailed engineering route of the first piezoelectric nanostructured epitaxial quartz-based microcantilever. We will explain all the steps in the process starting from the material to the device fabrication. The epitaxial growth of α-quartz film on SOI (100) substrate starts with the preparation of a strontium doped silica sol-gel and continues with the deposition of this gel into the SOI substrate in a thin film form using the dip-coating technique under atmospheric conditions at room temperature. Before crystallization of the gel film, nanostructuration is performed onto the film surface by nanoimprint lithography (NIL). Epitaxial film growth is reached at 1000 °C, inducing a perfect crystallization of the patterned gel film. Fabrication of quartz crystal cantilever devices is a four-step process based on microfabrication techniques. The process starts with shaping the quartz surface, and then metal deposition for electrodes follows it. After removing the silicone, the cantilever is released from SOI substrate eliminating SiO2 between silicon and quartz. The device performance is analyzed by non-contact laser vibrometer (LDV) and atomic force microscopy (AFM). Among the different cantilever's dimensions included in the fabricated chip, the nanostructured cantilever analyzed in this work exhibited a dimension of 40 µm large and 100 µm long and was fabricated with a 600 nm thick patterned quartz layer (nanopillar diameter and separation distance of 400 nm and 1 µm, respectively) epitaxially grown on a 2 µm thick Si device layer. Themeasuredresonance frequency was267 kHz and the estimated quality factor, Q, of the whole mechanical structure was Q ~ 398 under low vacuum conditions. We observed the voltage-dependent linear displacement of cantilever with both techniques (i.e., AFM contact measurement and LDV). Therefore, proving that these devices can be activated through the indirect piezoelectric effect.

The effect of liquid medium on vibration and control of the AFM piezoelectric microcantilever.

This article investigates the vibration motion and control of the piezoelectric microcantilever (MC) of the atomic force microscope in the amplitude mode in a liquid environment for both free and forced vibrations. The modeled MC includes two electrode layers, a piezoelectric layer, and the geometric discontinuities as a result of these layers and the change in the MC cross section at the probe-MC contact point is modeled. The equations of motion are derived using Hamilton's principle and then discretized with the aid of the finite element method. The system frequency and time response in the free vibration mode when placed in a liquid medium are compared with experimental results. Also, the sample surface topography in the noncontact mode, when passing through the surface roughness, has been modeled as rectangular and wedge-shaped. Furthermore, the control of piezoelectric MC in two cases of near and far from the sample surface is examined. In the case of far from the surface, the system is controlled using the piezoelectric layer installed on the beam, whereas in the case of near the surface, the piezo is turned off due to the existence of nonlinear forces such as Van der Waals and Derjaguin, Muller, and Toporov contact forces and the control is achieved through the base excitation. For system control modeling, the robust fuzzy sliding mode control (FSMC) approach is utilized and the results are compared with those of the simple sliding mode control (SMC) as well as proportional, integral, and derivative control. The presented FSMC approach can remarkably reduce the chattering phenomenon at the SMC input in the liquid medium and accordingly improve the results compared to the other two methods.

High Dynamic Range AFM Cantilever With a Collocated Piezoelectric Actuator-Sensor Pair

We present a novel approach to fundamentally eliminate electrical feedthrough (cross-talk) signal in self-sensing piezoelectric microcantilevers, used in dynamic mode atomic force microscopy (AFM). The probe is an Si microcantilever on which a two-layer piezoelectric stack transducer is microfabricated. The top transducer in the stack functions as an actuator, while the bottom transducer is used as a deflection sensor. This arrangement leads to a collocated actuator-sensor pair that co-exist on the same surface area. We report experimental results that establish the sensor’s ability to capture the full dynamic range of the cantilever with minimal feedthrough from the actuator. [2019-0143]

Development of a sensor device with polymer-coated piezoelectric micro-cantilevers for detection of volatile organic compounds

Exhaled breath contains thousands of volatile organic compounds (VOCs), some of which have been associated with respiratory disease. We describe a sensor device with an array of eight polymer-coated piezoelectric micro-cantilevers (two of each polyacrylic acid, polyethylenimine and polyethylene glycol and two uncoated cantilevers) and an electronic resonant frequency readout, designed for analysis of VOCs. We have measured the system’s response to temperature (24 °C to 40 °C), pressure (200 mmHg to 760 mmHg), and humidity (10% to 50% RH), evaluated the reproducibility of measurements between micro-cantilevers (n = 3), and tested the stability of the system over six months. By measuring the frequency shift of the resonating micro-cantilevers, and using the inflection point of a fitted sigmoid model, we show that acetone, ethanol, octane are distinguishable from one another, with a measurement limited of detection of 1568, 383, and 87 ppmv, respectively. From interpolation of the electronic readout, we found the lowest estimated measurement to be 5 ppmv (acetone on polyacrylic acid). We have also shown that polar mixture (acetone, ethanol, and water) and non-polar mixture (increasing octane concentration and decreasing polar mixture constituents) can be differentiated.

Investigation of the axial load effect on the vibration and topography of the AFM oblique four-layered piezoelectric micro-cantilever

In this paper, the vibration behavior of atomic force microscopy (AFM) micro-cantilever (MC) with a piezoelectric layer in the non-contact mode considering the axial load in the air medium was studied. In the dynamic modes of AFM nano-robot, parameters such as amplitude, frequency and motion phase are used as feedback factors in the control system in order to extract sample surface information and the nanoparticle voltage. Consequently, to extract these parameters, the vibration analysis of the MCs of this nano-robot is essential. Additionally, because of the wide-spread applications of oblique MCs, applying the axial and transverse forces into the model is absolutely necessary. In order to simulate the AFM four-layered piezoelectric MC with the axial displacement, Timoshenko beam theory as well as modified couple stress theory has been used. Considering the axial displacement in the modeling not only leads to more degrees of freedom, but also has increased the amount of calculations. To extract the equations of the system, energy method has been used, and then, the FEM was applied to discrete the equations. To verify the accuracy of the results, the frequency and time responses of FEM have been compared with the results of the 3D mode simulation obtained by COMSOL software and experimental results. The comparison of results indicates that modifying the modeling by considering the axial displacement has increased the accuracy of the frequency and time responses. The error percentage of the first frequency response is 0.42% and the error percentage of the time response is 0.0053%. Furthermore, to examine the effect of MC geometry on its vibrational behavior, frequency and time responses of three common geometries of AFM MCs have been extracted. The results illustrate the improvement of modeling in all three geometries. Then, the sample surface topography of MCs at the first and second excitation frequencies in contact with rectangular roughnesses demonstrated the decline of time delay at the second excitation frequency. The results of the topography simulation in the air environment show that the roughness’s trend is better at the second mode than at the first mode. Finally, the effect of MC angle on the topography of the rectangular MC surfaces in contact with the rectangular roughness in 2D and 3D modes was examined in the presence and the absence of axial load. The results show that in the presence of the axial displacement in modeling, by increasing of MC angle, the topography quality increases drastically.

Modeling the Amplitude Mode of Piezoelectric Microcantilever AFM in Contrast to the Surface of the Sample in a Liquid Medium

This paper deals with the modeling and simulation of the vibration behavior of piezoelectric microcantilever based on the Timoshenko theory and using multi-scale method in the liquid environment, considering the interaction forces in the liquid medium. The effect of viscosity and density is investigated on first four bending modes. The results of topographic simulation for rectangular roughness in the liquid medium and the amplitude mode indicate a reduction in the latency of the first mode from 1.54 to 0.48 and in the second mode from 0.49 to 0.18 compared to the air environment. According to the results of simulation in different working environments, with the increase in the radius of the probe tip, the squeeze force of the liquid will also increase; this increase in the force reduces the amplitude of the vibration motion and the natural frequency. According to the results of the simulation, solution based on the theory of string of spheres with 0.1% error has less accuracy than on multi-scale method with 0.031% error. Regarding the multi-scale method, the Rankl model with a percentage error of 13.47 and the string of sphere model with a percentage error of 0.10 have had a higher accuracy than the similar model of FEM with 14.64% error; the accuracy of the Hosaka model with a percentage error of 18.62 is less than the Rankl model; therefore, the Rankl model has the least error for multi-scale method solving in Timoshenko beam theory.

Free and forced vibrations of atomic force microscope piezoelectric cantilevers considering tip-sample nonlinear interactions

Abstract The aim of this article is to investigate the vibrational behavior of rectangular and V-shaped atomic force microscopy (AFM) microcantilevers with an extended piezoelectric layer using the finite element method (FEM). Firstly, the results of 3D FEM simulation are compared to the experimental and analytical ones to assess the accuracy of the method. Then, the free and forced vibrations of rectangular and V-shape piezoelectric microcantilevers in the absence and presence of nonlinear interactions between the microcantilever tip and the surface sample are studied. A nonlinear spring is used in the finite element modeling to simulate the nonlinear attraction-repulsion interactions between the tip and the sample. The amplitude of the AFM microcantilever is considered to be comparably small, hence the geometric nonlinearity of the microcantilever is insignificant. In the free vibration part, the resonance frequencies and mode shapes are obtained. In the forced vibration cases, an AC voltage with the resonance frequencies obtained in the free vibration analysis is applied to the piezoelectric layer to operate the microcantilever. The resonance amplitude of the tip of AFM microcantilever is derived accordingly. All simulations are performed for two cases; the first one is a fixed microcantilever at the end and free to move and rotate, and the second one is a microcantilever whose rotational degree of freedom and lateral displacement is tied up with applying a symmetric constraint. So, an important study parameter in this work is the effect of torsional modes on the vibrational behavior of AFM piezoelectric microcantilevers.

Vibration and sensitivity analysis of piezoelectric microcantilever as a self-sensing sensor

Piezoelectric microcantilevers (MCs) have extensive applications in microelectromechanical systems. One of the applications of piezoelectric MCs is in self-sensing sensors. These sensors are highly popular due to their high accuracy, quick response, and environmental compatibility. Since the output current of piezoelectric layer is used as the sensing parameter in piezoelectric MCs, sensor optimization requires the maximum output current for each specific vibration. This paper uses dynamic piezoelectric MC analysis in different operating environments (air and liquid) to determine the factors influencing the output current of a piezoelectric layer. To obtain the differential equation of vibration, the hydrodynamic force applied to the piezoelectric MC by using the sphere string model. The equation was obtained via the Euler-Bernoulli beam theory and the Lagrange equation. The differential equation of the movement would yield both the MC deformation and the piezoelectric layer current. Using the Sobol statistical method for sensitivity analysis, the effect of each geometric parameter of the piezoelectric MC on the output current was studied to find the optimal geometry for the maximum output current. Results show that the output power of the piezoelectric layer is reduced in a liquid environment. Moreover, increasing the density of the liquid further exacerbates the drop in the output power. Therefore, in cases where the MC is to be used in a liquid environment (such as in biosensors), it is best to use a low-density liquid. The results also show that the electric current produced in the piezoelectric layer increases by reducing the length of the MC.

Analysis of the atomic force microscopy vibration behavior using the Timoshenko theory by multi-scale method in the air environment.

This article deals with the modeling and simulation of the vibration behavior of piezoelectric micro-cantilever (MC) based on the Timoshenko theory and using multi-scale (MTS) method in the air environment. In this regard, the results are compared with the previous literature, such as the finite element method and the MTS method. The analysis of the piezoelectric MC vibrating behavior is investigated in a dynamical mode including non-contact and tapping modes. The dynamics of this system is affected by interferential forces between probe tip and sample surface, such as van der Waals, capillary, and contact forces. According to the results, the forces applied to the probe tip reduce the amplitude and the resonance frequency. The simulation of surface topography in non-contact mode and tapping for rectangular and wedge-shaped roughness in the air environment are presented. Various experiments have been conducted in Ara research Company using the atomic force microscopy device in the amplitude mode. In the NSC15 Cantilever, the first natural frequency is derived from the results of the MC simulation based on Timoshenko beam theory, the practical results are 295.85 and 296.12 kHz, and the error rate is 0.09; at higher natural frequencies, the error rate has been increased. The γ f coefficient is a measure of the nonlinear effects on the system; the effect of the piezoelectric length and width on γ f coefficient is also investigated.

Eigen Frequencies Analysis of Pre-Charged and Uncharged Piezoelectric Microcantilevers Beams

Eigen Frequencies Analysis of Pre-Charged and Uncharged Piezoelectric Microcantilevers Beams

Vibration Analysis and Control of AFM Microcantilever Based on the MCS Theory Using the FSMC Control in the Air

This study is aimed to find out the relation between the vibration motion and control of an atomic force microscope (AFM) piezoelectric microcantilever for free and forced vibrations in the air environment. In fact, the MC is the most important part of AFM, performing the most vital operations. Hence, the dynamic analysis and control of the MC are mandatory to obtain optimal performance. Enhancing the optimization of this system increases the sampling rate as well as the accuracy and resolution of the obtained images. MCs with a piezoelectric layer possess a higher speed and accuracy compared to conventional MCs which are simpler and less expensive. Also, in the MC vibration modeling, the Timoshenko beam model based on the modified couple stress theory is used. Next, using the Hamilton’s principle, the MC motion equations are derived by considering the geometric discontinuities as a result of the piezoelectric layer and two electrode layers. These equations are solved by using the finite element method. The MC frequency and time responses at different distances from the sample surface are obtained and compared with experimental results. In addition, the sample surface topography in the non-contact mode when the MC passes through different roughnesses in the first and second vibration modes has been investigated. Moreover, the fuzzy-sliding mode control (FSMC), which is a robust control method, is employed due to uncertainties when modeling the system. The results are compared with those of the sliding mode control (SMC) and PID control methods. For the cases of far from the surface and close to it, the MC is actuated by the piezoelectric layer and piezo-stack base, respectively. The proposed FSMC control can properly reduce chattering in the SMC to improve the results.