Deflection Of Microcantilever Research Articles

Modeling the mechanical response of microelectromechanical system (MEMS)-based sensors to volatile alcohol vapors: A finite element analysis

The development of microelectromechanical system-based sensors, such as microcantilever sensors, has garnered considerable interest across various fields. Notably, there is a significant focus on the detection of volatile alcohol vapors, which holds promise in mitigating breath-related illnesses. This study employed finite element analysis to simulate the deflection of a silica-based microcantilever coated with polymethyl methacrylate in response to different volatile alcohol vapors (VAVs), such as methanol, ethanol, and isopropanol. A Multiphysics framework was used to analyze the time-dependent response of a microcantilever to different concentrations of VAVs incorporating fluid–structure interaction. This complex model integrated the aspects of laminar flow, solid mechanics, and transport of dilute species. Significant agreement has been achieved between finite element analysis-simulated results and the experimental findings that we had previously documented. This alignment revealed consistent trends, with methanol exhibiting higher levels than ethanol, followed by isopropanol, further validating the robustness and reliability of the sensor system in VAV detection.

Label free detection of vitamin D by microcantilever-based aptasensor

Vitamin D deficiency or insufficiency is a growing public health problem. In this work, a novel and sample approach based on microcantilever for measuring the level of 25-hydroxyvitamin D (25(OH)D) was proposed. The Bruno aptamer was utilized to functionalize the microcantilevers, serving as a sensing layer for detecting 25(OH)D. The working principle of the sensor is based on the changes of the microcantilever deflection and frequency as a result of the aptamer removal from the surface of the microcantilever resulting from its interaction with vitamin D. The results showed a linear dependence between vitamin D concentration and the microcantilever deflection and frequency shift in a range of concentrations from 1 to 300 nM. For this biosensor, the limit of detection (LOD) was calculated to be ∼ 0.3 nM. The biosensor selectivity was tested against vitamin C and the sensor showed high selectivity towards vitamin D.

Magneto‐Nanomechanical Array Biosensor for Ultrasensitive Detection of Oncogenic Exosomes for Early Diagnosis of Cancers (Small 9/2023)

Early Diagnosis of Cancers In article 2205445, Shangquan Wu, Qingchuan Zhang, and co-workers develop an ultra-sensitive nanomechanical sensor, which uses a magnetic-driven microcantilever array to selectively detect oncogenic exosomes. The magnetic force produces a far greater deflection of microcantilever than that produced by the intermolecular interaction force, even in the presence of very low concentrations of target substances. This method reduced the detection limit to less than 10 exosomes mL−1.

Magneto-Nanomechanical Array Biosensor for Ultrasensitive Detection of Oncogenic Exosomes for Early Diagnosis of Cancers.

Exosomes are a class of nanoscale vesicles secreted by cells, which contain abundant information closely related to parental cells. The ultrasensitive detection of cancer-derived exosomes is highly significant for early non-invasive diagnosis of cancer. Here, an ultrasensitive nanomechanical sensor is reported, which uses a magnetic-driven microcantilever array to selectively detect oncogenic exosomes. A magnetic force, which can produce a far greater deflection of microcantilever than that produced by the intermolecular interaction force even with very low concentrations of target substances, is introduced. This method reduced the detection limit to less than 10 exosomes mL-1 . Direct detection of exosomes in the serum of patients with breast cancer and in healthy people showed a significant difference. This work improved the sensitivity by five orders of magnitude as compared to that of traditional nanomechanical sensing based on surface stress mode. This method can be applied parallelly for highly sensitive detection of other microorganisms (such as bacteria and viruses) by using different probe molecules, which can provide a supersensitive detection approach for cancer diagnosis, food safety, and SARS-CoV-2 infection.

MEMS Technology for Early Stage Diesis Detection Using Micro-Cantilever Structure in Support of Biomedical Applications

This research work is addressing the goal of achieving good health and well-being of human being by attempting the detection of a target analyte (HIV or other bimolecular analyte) using microcantilever. It is helpful to detect the bio-analytes because of its high sensitivity, selectivity, and structural simplicity. Depending on deflection of microcantilever by achieving maximum displacement, the device can be made extremely sensitive. The reason of making the device more sensitive is to detect even a single molecule also. Design has been done in three different stages. In the first stage it was estimated of the more suitable and sensitive sensing material. A second stage investigation has been done for the suitable construction of different shapes by introducing different holes in structure. At third stage research has been done about the multilayer to make the device more sensitive. Finally, concentration is to produce a high sensitive structure to detect the analyte quickly.

Theoretical study on the sensitivity of dynamic acoustic force measurement through monomodal and bimodal excitations of rectangular micro-cantilever

We present a detailed analysis on measurement sensitivity of dynamic acoustic forces via numerical simulation of the micro-cantilever responses. The rectangular micro-cantilever is regarded as a point mass in the dynamic model of forced and damped harmonic oscillator. We use single- and bimodal-frequency excitation schemes for actuation of the micro-cantilever in the presence of dynamic acoustic forces. In bimodal-frequency excitation scheme, the micro-cantilever is excited at its first two eigenmode frequencies simultaneously as opposed to single-frequency excitation. First, we numerically obtain micro-cantilever deflections by solving the equations of Motions (EOMs) constructed for the first two eigenmodes. Then, we determine oscillation amplitude and phase shift as a function of acoustic force strength within different frequency regions. Moreover, we relate amplitude and phase shift to virial and energy dissipation in order to explore the interaction between flexural modes in multifrequency excitation. The simulation results point out that bimodal-frequency excitation improves the measurement sensitivity of dynamic acoustic forces at particular frequencies. Herein, simultaneous application of driving forces enables higher sensitivities of observables and energy quantities as acoustic force frequencies become around the eigenmode frequencies. For our case, we obtain the highest phase shift (∼178°) for the acoustic force strength of 100 pN at the frequency of around 307.2 kHz. Therefore, this method can be easily adapted to improve measurement sensitivity of dynamic acoustic forces in a wider frequency window.

High temperature fracture toughness of single-layer CrAlN and CrAlSiN hard coatings

Hardness and toughness are among of the most important physical properties of hard coatings and it is important to analyze them at temperatures present during coating applications. CrAlN and CrAlSiN are hard coating materials frequently used in high temperature applications. While both possess high oxidation resistance and thermal stability, they differ in their microstructure. In this work, the fracture toughness of magnetron-sputtered single-layer CrAlN and CrAlSiN hard coatings was determined up to 700 °C by in-situ scanning electron microscopy micro-cantilever deflection tests. The results show a decreasing trend of the fracture toughness with increasing temperature. While both coatings' fracture toughness trends are similar up to 400 °C, they diverge at higher temperatures. In general, the evolution of the fracture toughness with increasing temperature shows similarities to the observed changes in hardness in the same temperature range.

Active atomic force microscope cantilevers with integrated device layer piezoresistive sensors

Active atomic force microscope cantilevers with on-chip actuation and sensing provide several advantages over passive cantilevers which rely on piezoacoustic base-excitation and optical beam deflection measurement. Active microcantilevers exhibit a clean frequency response, provide a path-way to miniturization and parallelization and avoid the need for optical alignment. However, active microcantilevers are presently limited by the feedthrough between actuators and sensors, and by the cost associated with custom microfabrication. In this work, we propose a hybrid cantilever design with integrated piezoelectric actuators and a piezoresistive sensor fabricated from the silicon device layer without requiring an additional doping step. As a result, the design can be fabricated using a commercial five-mask microelectromechanical systems fabrication process. The theoretical piezoresistor sensitivity is compared with finite element simulations and experimental results obtained from a prototype device. The proposed approach is demonstrated to be a promising alternative to conventional microcantilever actuation and deflection sensing.

A Numerical Model of a Perforated Microcantilever Covered with Cardiomyocytes to Improve the Performance of the Microcantilever Sensor.

A few simple polymeric microsystems, such as microcantilever sensors, have recently been developed for the preliminary screening of cardiac toxicity. The microcantilever deflection produced by a change in the cardiomyocyte (CM) contraction force is important for understanding the mechanism of heart failure. In this study, a new numerical model is proposed to analyze the contractile behavior of CMs cultured on a perforated microcantilever surface for improving the performance of the microcantilever sensor. First, the surface traction model is used to investigate the bending displacement of the plain microcantilever. In order to improve the bending effect, a new numerical model is developed to analyze the bending behavior of the perforated microcantilever covered with CMs. Compared with the designed molds, the latter yields better results. Finally, a simulation analysis is proposed based on a finite element method to verify the presence of a preformed mold. Moreover, the effects of various factors on the bending displacement, including microcantilever size, Young’s modulus, and porosity factor, are investigated. Both the simulation and numerical results have good consistency, and the maximum error between the numerical and simulation results is not more than 3.4%, even though the porosity factor reaches 0.147. The results show that the developed mold opens new avenues for CM microcantilever sensors to detect cardiac toxicity.

Post-buckling involving large deflection of micro-cantilever using the consistent couple stress theory

The paper investigates the post-buckling behavior of micro-cantilevers within the framework of consistent couple stress theory. The theoretical foundation for carrying out the analysis is formulated in terms of moment and curvature which is apt for solving thin beam problems. A differential equation governing the deflection of micro-cantilever subjected to different boundary conditions is obtained from the developed moment-curvature relationship. Axially loaded micro-cantilevers are solved by using an efficient semi-analytical method which involves removal of singularity. On the other hand solutions to eccentrically loaded micro-cantilevers are determined with the help of purely numerical approach based on iterative shooting method. Profiles of post-buckled micro-cantilevers subjected to different loading conditions are furnished. The obtained results for the micro-cantilever display strong size-dependency due to presence of the material length scale parameter in the developed model. Also the non-classical theory results tend to those from classical theory when the length scale parameter is negligible as compared to the characteristic length of the structure.

Fabrication of Freestanding Metallic Ni-Mo-W Microcantilever Beams With High Dimensional Stability

Recent studies have elucidated a promising balance of physical and mechanical properties of sputter deposited nickel-molybdenum-tungsten (Ni-Mo-W) films that have a unique nanotwinned microstructure and promising potential for use in high temperature microelectromechanical systems (MEMS). The current study was undertaken to establish the feasibility of making nanotwinned Ni-Mo-W microcantilevers with standard microfabrication processing, to assess their dimensional stability, and to demonstrate the possibility of using nanotwinned Ni-Mo-W in metal MEMS devices. Deposition of Ni-Mo-W films in commercial sputtering chambers revealed a wide processing window for the formation of the requisite nanotwinned microstructure. Conventional photolithography and etchants were employed to shape blanket Ni-Mo-W films into freestanding microcantilever beams. Monitoring microcantilever deflections via interferometry provided a direct measure of residual stresses and overall dimensional stability. Heat treatments of 200°C and 400°C were used to mimic wafer bonding temperatures. At 400°C, microcantilevers exhibited modest stress relaxation, yielding beam deflection profiles on the nanometer scale and portending dimensional stability and control for future metal MEMS devices.

Multiscale Simulation of Adsorption Based Microcantilever Biosensors for Radiation Exposure Effects.

Background: This article is focused on biological measurements based on molecular interactions. The specific biomarker implemented for radiation biosensor is FLT3, which bears changes in the body regarding radiation exposure. Experimental results of sensing vancomycin verify the overall results of two steps of numerical methods for different scales.Objectives: The aim is to provide adequate modeling procedures to predict sensory data. Multiscale modeling is implemented to simulate molecular interaction and its consequent micro mechanical effects. The method is implemented to calculate surface traction of microcantilever biosensor.Materials and Methods: The method consists of molecular dynamics simulation of adsorption process by implementing classical mechanics theory to calculate the final response of the sensor as tip deflection. The sequential information transaction is assumed between the physical parameters of two governing scales. The numerical method consists of the location of particles providing for a nano-metric periodic boundary conditioned functionalized surface implemented, and the numerical thermodynamic formula is, in turn, use energy parameters to acquire macro-mechanical deflection of a specific microcantilever. Also, novel sensitivity analysis of the results as the adsorption process moves toward more saturated substrate provided.Results: Verification of the simulation method for Vancomycin sensing results enjoys less than 20 percent of deviation regarding the experimental data. The standard deviation of 0.054 in the final expected response of the sensor is calculated as the accuracy of the radiation biosensor based on FLT3.Conclusions: The method is still to reach a correlation between the concentration of target molecules in solution and the number of adsorbed molecules per area of the sensor. A scaled correlation between sensor’s response and the amount of biomarker is found using tip deflection of a sample designed microcantilever. Around one micrometer deflection that can be read out using various conventional methods was observed at saturation of adsorption surface. The analyses provide adequate data to design a sensor capable of measuring the effect of cosmic radiation to the human body.

Silicon Microcantilever Sensors to Detect the Reversible Conformational Change of a Molecular Switch, Spiropyan.

The high sensitivity of silicon microcantilever sensors has expanded their use in areas ranging from gas sensing to bio-medical applications. Photochromic molecules also represent promising candidates for a large variety of sensing applications. In this work, the operating principles of these two sensing methods are combined in order to detect the reversible conformational change of a molecular switch, spiropyran. Thus, arrays of silicon microcantilever sensors were functionalized with spiropyran on the gold covered side and used as test microcantilevers. The microcantilever deflection response was observed, in five sequential cycles, as the transition from the spiropyran (SP) (CLOSED) to the merocyanine (MC) (OPEN) state and vice-versa when induced by UV and white light LED sources, respectively, proving the reversibility capabilities of this type of sensor. The microcantilever deflection direction was observed to be in one direction when changing to the MC state and in the opposite direction when changing back to the SP state. A tensile stress was induced in the microcantilever when the SP to MC transition took place, while a compressive stress was observed for the reverse transition. These different type of stresses are believed to be related to the spatial conformational changes induced in the photochromic molecule upon photo-isomerisation.

Nano-scale residual stress depth profiling in Cu/W nano-multilayers as a function of magnetron sputtering pressure

Residual stresses in thin films and multi-layered coatings fabricated by physical vapour deposition largely affect their mechanical and thermal reliability during operation in numerous fields of applications. By changing the argon working pressure in between each multilayer planar DC magnetron sputter deposition step, it is possible to control the residual stress distribution within coatings. A combination of FIB-DIC ring-core strain analysis, synchrotron XRD analysis based on the sin2(Ψ) method and micro-cantilever deflection analysis is used to reconstruct the in-plane stress state of multilayer coatings at different deposition pressures, with a residual stress depth profile resolution of 50 nm. A clear transition from compressive to tensile residual stresses is observed with an increase of working pressure, with pronounced stress peaks near the substrate-coating interface. These peak stresses resolved by FIB-DIC ring-core analysis exceed the average XRD stress measurements significantly, thus providing a reasonable explanation for multilayer failure. Experimental results are presented and comprehensively discussed in the context of deposition conditions for different thin film applications.

Microcantilever aptasensor for detecting epithelial tumor marker Mucin 1 and diagnosing human breast carcinoma MCF-7 cells

In this paper, a simple and novel method based on microcantilever for detecting tumor biomarker MUC1 and diagnosing human breast carcinoma MCF-7 cells was proposed. With thiolated aptamers of MUC1 self-assembled on the sensing microcantilever, the targets interact with aptamers resulting in the change of surface stress on the microcantilever. As a result, MUC1 and MCF-7 cells were successfully detected. Among them, the differential deflection of the microcantilever is linear with the logarithm of the MUC1 concentration in the range of 5–500 nM with low detection limit of 0.9 nM. However, for MCF-7 cells, the linear relationship between cantilever deflection and cell concentration ranges from 2.0*103 to 5.4*104 cells/mL with low detection limits of 213 cells/mL. In the meantime, according to the characteristics of real-time recording the change of microcantilever deflection over time, we have speculated the dynamic process of the binding of MUC1 to the aptamers. This work has confirmed that the aforementioned microcantilever aptasensor could sensitively detect other biomarkers and provide dynamic information of binding, and also could be used to identify tumor cells.

Large-area high-speed scanning probe microscopy using legacy scanners.

In scanning probe microscopy, the scanner dynamically positions the sample relative to the probe, and the upper limit of the imaging speed is governed primarily by the first eigenfrequency of the scanner. The mechanical oscillations of the scanner-even when it operates far from resonance-give rise to image artifacts and negatively affect the image resolution. This paper analytically and experimentally investigates the scanner's dynamics at high scan rates upon scanning over a large area. At slow scan speeds, the frequency spectra of the microcantilever's deflection signal exhibit only the excitation frequency and its harmonics; in contrast, at high scan speeds, the spectra exhibit sidebands centered around the excitation harmonics and separated from them by the scanner's eigenfrequency. Exploiting this phenomenon, a scanner dynamics-based method is proposed to reconstruct the surface topography, and, thereby, to reduce the oscillation-induced image artifacts. The method is proven for a variety of sample surfaces at very high scan rates up to 59.2 Hz (corresponding to a linear speed of 4.74 mm/s) upon scanning over a 40 μm × 40 μm area and is successfully demonstrated to be able to virtually eliminate any image artifacts. A nearly ten-fold increase in the scan rate is demonstrated using even a legacy scanner, with no changes required to the hardware.

Investigation of the Photothermal Excited Microcantilevers Based on Modified Couple Stress Theory

In microscale and sub-micron scale, scale effect highlights and the classical continuum mechanics cannot describe microstructure-dependent size effects. So many non-classical theories were put forward. The modified couple stress theory was established by introducing a material parameter to characterize the scale effect. In this paper, the dynamic responses of microcantilever under photothermal excitation are studied using the modified couple stress theory. The microcantilever deflection governing equation was given, and deflections were obtained numerically using relaxation method. Comparison was made between numerical results with that obtained with experimental measurement and showed a good agreement. According to the numerical results, the scale effect becomes remarkable as the ratio of thickness to the material parameter changes from zero to one. Also, the results showed that this ratio has prominent effect on the resonant frequency of microcantilever.

Design of AFM automatically feeding probe system

A set of automatically feeding probe system which can operate independently is designed. It can be widely used in the independent development of most atomic force microscope scanning system. In the approximation process, by VB serial communication, the command is send to control ARM to collect AFM micro-cantilever deflection signal, which is transmitted to the computer for display and analysis, real-time monitor the force between the probe and the sample, and ultimately realize the automatic approximation of probe. The system can be used in combination with various related atomic force microscopy devices, and achieve the goal of personalized multi-function detection.

Role of photostriction and photothemal effects in photon induced deflection of Si microcantilevers

Laser beam (He-Ne – 6328 A0) induced deflection in uncoated, Au, and Al coated Si microcantilevers (MCs) of various dimensions was studied, using an AFM head, to examine the induced stress contribution from photothermal and photostriction phenomenon. The laser beam was made to incident sequentially on front and back surfaces of the MC, by flipping it, and results were compared in terms of deflection magnitude, direction of bending and response time. In case of uncoated MCs, it was observed that the induced deflection was always in the direction of the incident laser beam with a fast response. In contrast, in metal (Au, Al) coated MCs, deflection direction was found to be dependent on laser beam exposure side with two orders of enhanced deflection sensitivity and slow response time. The former is attributed to photostriction effect while the latter is explained on the basis of photothermal effect in bimetallic MCs. Flipping experiments on bimettalic MCs, further revealed that stress contribution from these two source mechanisms crucially depends on MC dimensions and direction of laser exposure.

Thermomechanical Response of a Representative Porin for Biomimetics.

The thermomechanical response of Omp2a, a representative porin used for the fabrication of smart biomimetic nanomembranes, has been characterized using microcantilever technology and compared with standard proteins. For this purpose, thermally induced transitions involving the conversion of stable trimers to bigger aggregates, local reorganizations based on the strengthening or weakening of intermolecular interactions, and protein denaturation have been detected by the microcantilever resonance frequency and deflection as a function of the temperature. Measurements have been carried out on arrays of 8-microcantilevers functionalized with proteins (Omp2a, lysozyme and bovine serum albumin). To interpret the measured nanofeatures, the response of proteins to temperature has been also examined using other characterization techniques, including real time wide angle X-ray diffraction. Results not only demonstrate the complex behavior of porins, which exhibit multiple local thermal transitions before undergoing denaturation at temperatures higher than 105 °C, but also suggest a posttreatment to control the orientation of immobilized Omp2a molecules in functionalized biomimetic nanomembranes and, thus, increase their efficacy in ion transport.