Cantilever Array Research Articles

Wind energy harvesting from a magnetically coupled piezoelectric bimorph cantilever array based on a dynamic magneto-piezo-elastic structure

This paper presents a novel wind energy harvester based on a magneto-piezo-elastic structure using a magnetically coupled piezoelectric bimorph cantilever. The harvester consists of a power-generating stator for the piezoelectrics and a wind-powered rotor and Savonius blades. A permanent magnet on the free-end-tip mass of the vertically aligned piezoelectric bimorph cantilever interacts with a rotating counterpart permanent magnet affixed onto the top disk plate of the Savonius rotor. Its operating principle provides a better understanding of the magneto-piezo-elastic energy conversion. A good arrangement of permanent magnets was demonstrated to be effective for a reduction of the resistance torque to approximately 94.6 mN∙m. The dynamic behavior of the magnetically coupled piezoelectric bimorph cantilever was also investigated according to the output voltage signal pattern in relation to the deflection dependent on the wind speed. As the wind speed was increased from 2.5 m/s to 6.5 m/s, the deflection and output power of the single piezoelectric bimorph cantilever tended to increase linearly. The highest output power of 24.95 mW, which corresponds to 2.10 mW/cm3, was obtained at a wind speed of 6.5 m/s for the parallel-connected piezoelectric bimorph cantilever array, implying better performance compared to those reported previously.

An investigation to the design of high-precision wind sensing device based on piezoelectric array

A new wind sensing device based on bimorphs array is designed for apperceiving wind direction and velocity, whose structure is an L-shaped cantilevers array. A coupling model of the array is proposed to predict the response voltage stimulated by wind. By extracting the response voltage ([Formula: see text]) on each bimorph cantilever, the values of wind direction ([Formula: see text]) and velocity ([Formula: see text]) can be calculated in terms of the geometric relation. Further, the relations among wind errors, array amounts ( m) and array radius ( r) are acquired, and m & r can be utilized to decreasing angle error [Formula: see text] and velocity error [Formula: see text] of wind. The calculated and experimental results show that, increasing m initially yields decreasing these two errors, then it begins to increase the errors when m is larger than 6. The minimal wind angle and velocity errors of the array are 0.14° and 0.34%, respectively, at actual wind of 13.4 m/s, m = 6 and r = 20 mm. Meanwhile, increasing r can decrease [Formula: see text] and [Formula: see text], Besides, for calculating 20 random incidence wind angles, respectively, the range of wind velocity error is from 0.34% to 0.87%, the range of wind angle error is from 0.12°to 0.38°, and the response time is 10 ms.

Performance Analysis of Cantilever Beam for Tunable Fabry Perot Filter

The design and simulation of the cantilever beam for tunable fabry perot filter is discussed in this paper. The fabry perot filter is tuned to operate in three frequency ranges namely short wave Infrared (SWIR), mid wave Infrared (MWIR) and long wave Infrared (LWIR) are operated in the frequency range of 1.6–2.5 μm, 3–5 μm and 8–12 μm respectively. The light that is emitted from the array of vertical cavity surface emitting laser (VCSEL) is tuned to the desired wavelength using this fabry perot filter. The fabry perot cavity length is varied using the MEMS cantilever. By applying the reflective coating to the arms of the cantilever, the fabry perot cavity is formed. The actuation given to the MEMS cantilever is electrostatic actuation. The potential difference between the two arms of the cantilever creates the electrostatic force, which attracts the free end of the cantilever. Due to the impact of the electrostatic force the arms get pulled in, as a result the separation between the mirrors varies, which in turn filters the desired wavelength. The array of cantilever is also simulated to get a desired pattern of the wavelength. The fabrication process flow for the simulated cantilever is explained. The fixed-free beam approach leads to the analysis of capacitance, stress, strain and displacement.

Temperature effect on pull-off force for gold cantilevers array

This paper focuses on revealing the length influence of a group of gold cantilevers on the mechanical behaviour (i.e. bending stiffness, Young modulus, pull-off force) on the one hand and on the investigation of the temperature influence on the pull-off force of thermally actuated microcantilevers, on the other hand. The length was ranged between 200 μm and 350 μm while the temperature was ranged between 20 °C to 100 °C. The tests were performed using an atomic force microscope. The results obtained in the study are important to enhance the design of MEMS devices and to increase their reliability and their lifetime.

Saw-tooth type piezoelectric multi-modal energy harvester

The paper presents results of numerical and experimental investigations of a new design piezoelectric energy harvester based on a saw-tooth type cantilever array. The proposed energy harvester has multi-modal operation principle and allows to harvest mechanical vibrations energy in narrow frequency range. Moreover, the multi-modal operation principle of the harvester enable summation of bending strains of several cantilevers and allows to improve efficiency of the harvester. The proposed multi-modal energy harvester consist of four cantilevers that are connected rigidly to each other at 30° angles. Cross-sections of the cantilevers were modified by cylindrical gaps in order to increase bending strain. Seismic masses were placed at each corner of the harvester in order to reduce values of natural frequencies and to create additional rotation moment. Numerical investigation revealed that the energy harvester has five resonance frequencies in the range from 20 Hz to 135 Hz. The numerical investigation of electrical characteristics showed that voltage density of 48.39mV/mm3 and energy density of 61.25μJ/mm3 was obtained. Experimental investigations confirmed the results of numerical investigation and showed that voltage and energy densities reached 55.65mV/mm3and 52.56μJ/mm3, respectively.

Quantitative Identification Scheme for Multiple Analytes With a Mode-Localized Cantilever Array

This work proposes an identification scheme for two different analytes using a coupled three-cantilever array. In this scheme, for the first time, we put forward two key parameters including the localization degree $\text{X}_{\mathrm {k}}$ and norm of normalized eigenmode shifts $\vert \Delta u\vert $ to make qualitative and quantitative identification of mixed target analytes, respectively. Theoretical results, which have been verified by numerous simulations, indicate that the linear range (i.e., localization degree with respect to mass ratio) of this mass identification can reach approximately two orders of degree. Besides, we also studied the effect of the coupling factor on the resonance frequency and also proposed that the coupling factor possessed a lower limit to guarantee the resolution of mass sensing in either low vacuum environment or ambient pressure. Last but not least, this scheme could extend to identify analytes as many as possible in a confined space or certain sorts of analytes with a structure as simple as possible, which contributes to the application of gas sensors.

Fully automated high-throughput cardiac toxicity screening platform using interlocking-structured 192 SU-8 cantilever arrays

This paper proposes a high-throughput drug-screening platform integrated with 48 well plates containing 192 SU-8 cantilevers that assess cardiac toxicity levels by measuring changes in the contractile force of cardiomyocytes in vitro environment. To improve the reliability and reproducibility of the measured data, four interlocking-structured cantilevers were employed in each well and the displacement changes were measured at the nanometer scale using a laser-based sensor. The use of the mean value of the cantilever displacement in each well greatly improved the accuracy of the drug toxicity results. In addition, microgrooves patterned onto the SU-8 cantilevers greatly enhanced the alignment of cardiomyocytes, resulting in an increase in the contraction force by approximately 2.4 times. After the preliminary experiment, the contractile behaviors of cardiomyocytes on the surface-patterned SU-8 cantilevers were measured under various drugs, namely, Bay K8644, Verapamil, Isoproterenol, Quinidine, Lidocaine, E-4031, and Astemizole. In the case of Bay K8644, Verapamil, and Isoproterenol, the contractile force of cardiomyocytes was increased or decreased by 30%, 50%, and 20%, respectively, at the value of IC50. However, Quinidine only increased the half-value duration (HaVD) by approximately 22%, even though it did not affect the contractile force at IC50. Potassium-channel inhibitors E-4031 and Astemizole also showed no change in contractile force at low concentrations. However, the HaVD increased by approximately 3.4 times and abnormal peaks were observed at higher drug concentrations. The fully automated high-throughput screening capability of the proposed platform has immense potential as a preliminary drug-screening system in the next generation.

Multimodal atomic force microscopy with optimized higher eigenmode sensitivity using on-chip piezoelectric actuation and sensing

Atomic force microscope (AFM) cantilevers with integrated actuation and sensing provide several distinct advantages over conventional cantilever instrumentation. These include clean frequency responses, the possibility of down-scaling and parallelization to cantilever arrays as well as the absence of optical interference. While cantilever microfabrication technology has continuously advanced over the years, the overall design has remained largely unchanged; a passive rectangular shaped cantilever design has been adopted as the industry wide standard. In this article, we demonstrate multimode AFM imaging on higher eigenmodes as well as bimodal AFM imaging with cantilevers using fully integrated piezoelectric actuation and sensing. The cantilever design maximizes the higher eigenmode deflection sensitivity by optimizing the transducer layout according to the strain mode shape. Without the need for feedthrough cancellation, the read-out method achieves close to zero actuator/sensor feedthrough and the sensitivity is sufficient to resolve the cantilever Brownian motion.

Breathers and other time-periodic solutions in an array of cantilevers decorated with magnets

In this article, the existence, stability and bifurcation structure of time-periodic solutions (including ones that also have the property of spatial localization, i.e., breathers) are studied in an array of cantilevers that have magnetic tips. The repelling magnetic tips are responsible for the intersite nonlinearity of the system, whereas the cantilevers are responsible for the onsite (potentially nonlinear) force. The relevant model is of the mixed Fermi-Pasta-Ulam-Tsingou and Klein-Gordon type with both damping and driving. In the case of base excitation, we provide experimental results to validate the model. In particular, we identify regions of bistability in the model and in the experiment, which agree with minimal tuning of the system parameters. We carry out additional numerical explorations in order to contrast the base excitation problem with the boundary excitation problem and the problem with a single mass defect. We find that the base excitation problem is more stable than the boundary excitation problem and that breathers are possible in the defect system. The effect of an onsite nonlinearity is also considered, where it is shown that bistability is possible for both softening and hardening cubic nonlinearities.

A Low Frequency Vibration Energy Harvester Using ZnO Nanowires on Elastic Interdigitated Electrodes.

This paper presents a low frequency piezoelectric vibration energy harvester using ZnO nanowires on elastic interdigitated electrodes. The interdigitated electrodes are formed using electroplated Ni and have suspended parts at the edges that are elastic and deformable by applying external force. A spherical Ni ball is used as a proof mass, which transforms a low frequency mechanical vibration into the force applied to deform the elastic electrodes. The ZnO nanowires are grown selectively on the electrodes and can generate a piezoelectric potential when the elastic electrodes are deformed by the proof mass activated by the external mechanical vibration. The proposed operation concept is demonstrated using two different types of energy harvesters, which have simple suspended part and cantilever array structures added to the electrodes, respectively. The output voltage of the fabricated harvesters is measured using a vibration exciter at 6 Hz sinusoidal vibration with an acceleration of 0.5 g. Maximum output power of 12.8 pW and 18.8 pW was generated with a load resistance of 1 MΩ for the harvesters using the simple suspended structure and cantilever array, respectively.

Localized trio cantilevers for identifying different mass perturbations

This paper demonstrates a method based on mode localization which, for the first time, verifies the possibility of identifying two kinds of mass perturbations with a coupled three-cantilever array theoretically, analytically and experimentally. In the light of mode shapes in certain resonance modes, the proportion of mass perturbations on the side and center cantilever can be qualitatively determined. A combination of the 1st and 3rd mode shape was selected for discriminating different situations including one single mass perturbation and mixed mass perturbations. On the one hand, the proposed method simplifies the structure of the present 15 or 5 cantilever array sensors used for mass positioning. On the other hand, it provides a simple and efficient way to the pre-warning of those multiple toxic substances in some public places.

Modified cantilever arrays improve sensitivity and reproducibility of nanomechanical sensing in living cells

Mechanical signaling involved in molecular interactions lies at the heart of materials science and biological systems, but the mechanisms involved are poorly understood. Here we use nanomechanical sensors and intact human cells to provide unique insights into the signaling pathways of connectivity networks, which deliver the ability to probe cells to produce biologically relevant, quantifiable and reproducible signals. We quantify the mechanical signals from malignant cancer cells, with 10 cells per ml in 1000-fold excess of non-neoplastic human epithelial cells. Moreover, we demonstrate that a direct link between cells and molecules creates a continuous connectivity which acts like a percolating network to propagate mechanical forces over both short and long length-scales. The findings provide mechanistic insights into how cancer cells interact with one another and with their microenvironments, enabling them to invade the surrounding tissues. Further, with this system it is possible to understand how cancer clusters are able to co-ordinate their migration through narrow blood capillaries.

Simulation fabrication and characterization of micro-cantilever array based ozone sensor

Abstract Cantilever plays a significant role in sensing of gases with miniaturing technology replacing conventional sensors. In this paper, the micro-cantilever array was simulated using COMSOL Multiphysics 4.2 and Ansys environment to analyze the microcantilever array based on resonant frequency mechanism. From the simulation results, the fabrication of the micro-cantilever array on SOI wafer with gold layers coated on the surface was done. The microstructure of the fabricated microcantilever array was characterized using SEM and AFM. The fabricated cantilever array was tested by Laser Doppler Vibrometer on exposing it to ozone gas to find the resonant frequency of each cantilever in a micro-cantilver array. From the simulation and fabrication results, it was found that these results were well-matched and the design is best suited for sensing the ozone gas efficiently using micro-cantilever array. Of the three micro-cantilevers in a micro-cantilever array used in this investigation, cantilever-C has good sensitivity towards detecting ozone gas efficiently, due to the high structural stability.

Novel Process Development of Pyrolytic Carbon Devices

Sandia National Laboratories has developed novel approaches to integrate pyrolytic carbon as a viable alternative material in microelectronic devices. Our work demonstrates fabrication of simple single layer and multiple layer devices, targeting future microelectronic applications. We demonstrate a patterned photoresist on a silicon (Si) substrate, followed by a high temperature bake, and a xenon difluoride Si etch release process as a simple fabrication approach. Loading nanomaterials into the pre-pyrolized polymer establishes the capability to tune specific mechanical and electrical properties. Micromachining blanket carbon films using a dry etch process, allows for precise critical dimension control, and the ability to integrate carbon into complex multilevel device processing. Carbon is durable, adaptable, highly conductive, inexpensive, and easy to produce. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed in the article do not necessarily represent the views of the U.S. Department of Energy or the United States Government. Figure 1) SEM image of cantilever array dry etched and released in xenon difluoride. Figure 1

A hybrid piezoelectric and electromagnetic energy harvester for scavenging low frequency ambient vibrations

This work presents a hybrid type piezoelectric and electromagnetic multi-degree of freedom (MDOF) energy harvester for low-frequency ambient vibrations. The proposed device is designed with unique MDOF mechanical structure that helps to obtain multiple resonant modes operation of the harvester at low frequency range. The mechanical design comprises of a clamped-clamped beam as primary beam and four secondary beams as cantilever array. During external excitation, the secondary cantilever beams vibrate simultaneously along with the magnetic proof mass that causes mechanical strain to the piezoelectric elements as well as relative motion between magnets and coils placed underneath of it. A prototype of the hybrid MDOF energy harvester has been fabricated, simulated, and experimentally verified. The frequency response of the prototype implies that the proposed hybrid MDOF harvester has four resonant modes which concentrate around 12, 16, 17, and 21 Hz, respectively. On the other hand, a maximum of 218μW and 204µW peak powers have been obtained across the respective optimal load resistances from a single piezoelectric and electromagnetic generator of the array at 3rd resonance (17Hz) under 0.1g base acceleration.

Interdigitated cantilever array topology for low frequency MEMS vibration energy harvesting

Micro-fabricated vibration energy harvesters enable merits such as miniaturisation, economies of scale for manufacturing, and ease of integration with semiconductor IC technologies. However, the frequency range of ambient vibration is generally low (10’s Hz to 100’s Hz). Existing MEMS vibration energy harvesters that target these frequencies typically are in the centimetre scale range. This sacrifices the miniaturisation aspect as well as introducing new challenges in packaging and integration for the unconventionally large MEMS devices. This paper proposes a new interdigitated fork cantilever array topology, which allows for up to about a third reduction in resonant frequency compared to the classical cantilever topology, for the same design area and without compromising on power optimisation. Further resonant frequency reduction is also possible, but at the expense of power optimisation. This opens up design flexibility to achieve low frequency MEMS resonators that are more suitable to practically target ambient vibration, without sacrificing the aforementioned merits of MEMS technology.

Actuation of higher harmonics in large arrays of micromechanical cantilevers for expanded resonant peak separation.

A large array of elastically coupled micro cantilevers of variable length is studied experimentally and numerically. Full-scale finite element modal analysis is implemented to determine the spectral behavior of the array and to extract a global coupling matrix. A compact reduced order model is used for numerical investigation of the array's dynamic response. Our model results show that at a given excitation frequency within a propagation band, only a finite number of beams respond. Spectral characteristics of individual cantilevers, inertially excited by an external piezoelectric actuator, were measured in vacuum using laser interferometry. The theoretical and experimental results collectively show that the resonant peaks corresponding to individual beams are clearly separated when operating in vacuum at the 3rd harmonic. Distinct resonant peak separation, coupled with the spatially-confined modal response, make higher harmonic operation of tailored, variable-length cantilever arrays well suited for a variety of resonant based sensing applications.

Influences of W Content on the Phase Transformation Properties and the Associated Stress Change in Thin Film Substrate Combinations Studied by Fabrication and Characterization of Thin Film V1- xW xO2 Materials Libraries.

The mechanical stress change of VO2 film substrate combinations during their reversible phase transformation makes them promising for applications in micro/nanoactuators. V1- xW xO2 thin film libraries were fabricated by reactive combinatorial cosputtering to investigate the effects of the addition of W on mechanical and other transformation properties. High-throughput characterization methods were used to systematically determine the composition spread, crystalline structure, surface topography, as well as the temperature-dependent phase transformation properties, that is, the hysteresis curves of the resistance and stress change. The study indicates that as x in V1- xW xO2 increases from 0.007 to 0.044 the crystalline structure gradually shifts from the VO2 (M) phase to the VO2 (R) phase. The transformation temperature decreases by 15 K/at. % and the resistance change is reduced to 1 order of magnitude, accompanied by a wider transition range and a narrower hysteresis with a minimal value of 1.8 K. A V1- xW xO2 library deposited on a Si3N4/SiO2-coated Si cantilever array wafer was used to study simultaneously the temperature-dependent stress change σ( T) of films with different W content through the phase transformation. Compared with σ( T) of ∼700 MPa of a VO2 film, σ( T) in V1- xW xO2 films decreases to ∼250 MPa. Meanwhile, σ( T) becomes less abrupt and occurs over a wider temperature range with decreased transformation temperatures.

Utilization of a Two-Beam Cantilever Array for Enhanced Atomic Force Microscopy Sensitivity

An array of cantilevers offers an alternative approach to standard single beam measurement in the context of atomic force microscopy (AFM). In comparison to a single beam, a multi-degrees-of-freedom system offers a greater level of flexibility with regard to parameter selection and tuning. By utilizing changes in the system eigenmodes as a feedback signal, it is possible to enhance the sensitivity of AFM to changes in sample topography above what is achievable with standard single beam techniques. In this paper, we analyze a two-beam array operated in FM-AFM mode. The array consists of a single active cantilever that is excited with a 90 deg phase-shifted signal and interacts with the sample surface. The active beam is mechanically coupled to a passive beam, which acts to vary the response between synchronized and unsynchronized behavior. We use a recently developed mathematical model of the coupled cantilever array subjected to nonlinear tip forces to simulate the response of the described system with different levels of coupling. We show that the sensitivity of the frequency feedback signal can be increased significantly in comparison to the frequency feedback from a single beam. This is a novel application for an AFM array that is not present in the literature.

Multifunctional Microelectro-Opto-mechanical Platform Based on Phase-Transition Materials.

Along with the rapid development of hybrid electronic-photonic systems, multifunctional devices with dynamic responses have been widely investigated for improving many optoelectronic applications. For years, microelectro-opto-mechanical systems (MEOMS), one of the major approaches to realizing multifunctionality, have demonstrated profound reconfigurability and great reliability. However, modern MEOMS still suffer from limitations in modulation depth, actuation voltage, or miniaturization. Here, we demonstrate a new MEOMS multifunctional platform with greater than 50% optical modulation depth over a broad wavelength range. This platform is realized by a specially designed cantilever array, with each cantilever consisting of vanadium dioxide, chromium, and gold nanolayers. The abrupt structural phase transition of the embedded vanadium dioxide enables the reconfigurability of the platform. Diverse stimuli, such as temperature variation or electric current, can be utilized to control the platform, promising CMOS-compatible operating voltage. Multiple functionalities, including an active enhanced absorber and a reprogrammable electro-optic logic gate, are experimentally demonstrated to address the versatile applications of the MEOMS platform in fields such as communication, energy harvesting, and optical computing.