Microelectromechanical System Cantilever Research Articles

Microcontact printing fabrication of diamond MEMS cantilevers on silicon substrate

Diamond shows great potentials as an ultimate material candidate for application in microelectromechanical systems (MEMS). In this work, we report microcontact printing (μCP) transfer as a facile technique to fabricate diamond MEMS cantilever arrays. We started from the Deryaguin–Landau–Verwey–Overbeek (DLVO) principles and formulated a colloidal “ink” that contains nanodiamonds (NDs) seeds well dispersed in polymethyl methacrylate/acetone. The NDs seeds were then transfer printed onto a silicon (100) substrate by using a flexible polydimethylsiloxane (PDMS) stamp with predefined pattern. The densely packed NDs pattern (∼109 cm−2) enables facile and selected-area growth of diamond with microwave plasma chemical vapor deposition (MPCVD) technique. A diamond film with minimal graphite contaminants and low residual stresses was obtained after growth at 1118 K for 3 h. The diamond cantilevers were released from the substrate by wet chemical etching using KOH (40 % wt.) and isopropyl alcohol (10 % vol.). An examination of the vibrational kinetics indicates that the diamond film has a high Young's modulus (∼795 GPa) and the cantilevers exhibit consistently distributed resonant frequencies and high quality factors in ambient air. The method opens the door for large-scale, cost-effective production of uniform diamond MEMS devices for sensor and quantum applications.

Needle‐type pressure sensor with silicone oil and parylene membrane inside for minimally invasive measurement

AbstractThis paper addresses a pressure sensor for body pressure measurement. Many pressure sensors have been developed for disease treatment in the medical field. However, these sensors require inserting electronic components and other sensor elements via surgical operations, so the measurement physically burdens patients. Hence, we proposed a needle‐type pressure sensor using MEMS (Micro Electro Mechanical Systems) cantilever. The sensor has a needle part with a thin membrane on the tip and is filled with incompressible fluid inside. The fractional resistance of the built‐in piezoresistive cantilever varies according to the pressure change applied to the needle tip. We can measure body fluid pressure with minimal surgery by inserting a simple needle into the target organ. Because the fabricated sensor responded to pseudo‐body pressure changes, it was suggested that the fabricated needle‐type pressure sensor could detect pressure inside the body.

Characterization of Residual Stress in SOI Wafers by Using MEMS Cantilever Beams.

Silicon-on-insulator (SOI) wafers are crucial raw materials in the manufacturing process of microelectromechanical systems (MEMS). Residual stresses generated inside the wafers during the fabrication process can seriously affect the performance, reliability, and yield of MEMS devices. In this paper, a low-cost method based on mechanical modeling is proposed to characterize the residual stresses in SOI wafers in order to calculate the residual stress values based on the deformation of the beams. Based on this method, the residual strain of the MEMS beam, and thus the residual stress in the SOI wafer, were experimentally determined. The results were also compared with the residual stress results calculated from the deflection of the rotating beam to demonstrate the validity of the results obtained by this method. This method provides valuable theoretical reference and data support for the design and optimization of devices based on SOI-MEMS technology. It provides a lower-cost solution for the residual stress measurement technique, making it available for a wide range of applications.

Polymer‐Based MEMS Sensor for Label‐Free Chikungunya Virus Detection

AbstractPiezoelectric MEMS (Micro‐Electro‐Mechanical Systems) Cantilevers have successfully been used in a wide variety of applications in recent years. This paper is a simulation‐based study on Micro‐cantilever based Piezoelectric MEMS biosensors for Chikungunya Virus (CHIKV) detection. In addition to providing early detection, the proposed method is label‐free, faster, and more reliable. The proposed biosensor detects CHIKV E2 protein via MEMS Sensor. The basic principle involves using piezoelectric material on a micro‐cantilever for biomaterial detection. A piezoelectric MEMS cantilever is simulated in COMSOL Multiphysics and compared for voltage, stress, and displacement for three materials (silicon, gold, and PDMS). Analytical equations are derived. Post‐processing for biosensor design is done in SIMULINK. Simulated voltage, stress, and displacement show a linear relationship with the viral load. PDMS also provided the highest voltage and displacement among the three materials used for MEMS simulation. The graphs show the comparison between simulated and analytical values. Simulation results are also compared to clinical results to prove the biosensor's validity. MEMS Biosensor performance matches with the RT‐PCR results, with the added advantage of faster results. Diagnostic tests in the medical field can be performed using the proposed biosensor.

Effects of temperature and relative humidity on resonant frequency of mems cantilever resonators under atmospheric pressure

In this study, the effects of temperature and relative humidity on the resonant frequency of a micro-electro-mechanical system (MEMS) cantilever resonator under atmospheric pressure (p=101325 Pa) are discussed. The squeeze film damping (SFD) problem of MEMS cantilever resonators is modeled by solving the modified molecular gas lubrication (MMGL) equation, the equation of motion of micro-cantilever, and their appropriate boundary conditions, simultaneously in the eigen-value problem. The effective viscosity (µeff(RH, T)) of moist air is utilized to modify the MMGL equation to consider the effects of temperature and relative humidity under atmospheric pressure. Thus, the effects of temperature (T) and relative humidity (RH) on the resonant frequency of MEMS cantilever resonators over a wide range of gap thicknesses and under atmospheric pressure are discussed. The results showed that the frequency shift increases as the relative humidity and temperature increase. The influence of relative humidity on the resonant frequency becomes more significant under conditions of higher temperature and smaller gap thickness.

Design and Fabrication of Millimeter-Wave Frequency-Tunable Metamaterial Absorber Using MEMS Cantilever Actuators.

In this paper, a MEMS (Micro Electro Mechanical Systems)-based frequency-tunable metamaterial absorber for millimeter-wave application was demonstrated. To achieve the resonant-frequency tunability of the absorber, the unit cell of the proposed metamaterial was designed to be a symmetric split-ring resonator with a stress-induced MEMS cantilever array having initial out-of-plane deflections, and the cantilevers were electrostatically actuated to generate a capacitance change. The dimensional parameters of the absorber were determined via impedance matching using a full electromagnetic simulation. The designed absorber was fabricated on a glass wafer with surface micromachining processes using a photoresist sacrificial layer and the oxygen-plasma-ashing process to release the cantilevers. The performance of the fabricated absorber was experimentally validated using a waveguide measurement setup. The absorption frequency shifted down according to the applied DC (direct current) bias voltage from 28 GHz in the initial off state to 25.5 GHz in the pull-down state with the applied voltage of 15 V. The measured reflection coefficients at those frequencies were −5.68 dB and −33.60 dB, corresponding to the peak absorptivity rates of 72.9 and 99.9%, respectively.

Compensation of the Stress Gradient in Physical Vapor Deposited Al1-xScxN Films for Microelectromechanical Systems with Low Out-of-Plane Bending.

Thin film through-thickness stress gradients produce out-of-plane bending in released microelectromechanical systems (MEMS) structures. We study the stress and stress gradient of Al0.68Sc0.32N thin films deposited directly on Si. We show that Al0.68Sc0.32N cantilever structures realized in films with low average film stress have significant out-of-plane bending when the Al1−xScxN material is deposited under constant sputtering conditions. We demonstrate a method where the total process gas flow is varied during the deposition to compensate for the native through-thickness stress gradient in sputtered Al1−xScxN thin films. This method is utilized to reduce the out-of-plane bending of 200 µm long, 500 nm thick Al0.68Sc0.32N MEMS cantilevers from greater than 128 µm to less than 3 µm.

MEMS cantilever–controlled plasmonic colors for sustainable optical displays

Conventional optical displays using indium tin oxide and liquid crystal materials present challenges for long-term sustainability. We show here a cost-effective and complementary metal-oxide semiconductor (CMOS)–compatible fast and full-range electrically controlled RGB color display. This is achieved by combining transmission-based plasmonic metasurfaces with MEMS (microelectromechanical systems) technology, using only two common materials: aluminum and silicon oxide. White light is filtered into RGB components by plasmonic metasurfaces made of aluminum nanohole arrays. The transmission through each color filter is modulated by MEMS miniaturized cantilevers fabricated with aluminum and silicon oxide on top of the color filters. We show that the relative transmission of a color subpixel can be freely modulated from 35 to 100%. The pixels can also operate well above 800 Hz for future ultrafast displays. Our work provides a road to future circular economic goals by exploiting advances in structural colors and MEMS technologies to innovate optical displays.

A survey of MEMS cantilever applications in determining volatile organic compounds

Recently, microelectromechanical system (MEMS) cantilevers have received significant interest in the domain of Volatile Organic Compounds (VOCs). An analysis of MEMS cantilevers in VOCs is presented in this Review. It examines the different forms of sensors used to detect VOCs. It goes into the conditions that influence MEMS and the strategies used for VOC sensing. It examines research on MEMS cantilevers and other VOC sensing and detection techniques. It shows how MEMS can be used to detect VOCs. Moreover, it presents a comparative study based on the objectives, types of sensors employed, merits, and shortcomings of existing works. This Review intends to explore MEMS cantilevers in VOCs for supporting further research and applications.

A novel sensing concept utilizing targeted, complex, nonlinear MEMS dynamics

<p style='text-indent:20px;'>We present a case study of an active micro-electromechanical system (MEMS). The MEMS cantilever has integrated actuation and sensor mechanisms, which enable the active operation of the system. Our analysis is comprised of numerical continuation of equilibria and periodic orbits, which are briefly compared and discussed with initial experimental observations. In this case study, we consider the dynamic behaviour of two MEMS configurations, one excluding, and the other including a high-pass filter. With that we wish to study any differences between a dynamical system as typically analysed in the literature and the same system when investigated experimentally. We show that the MEMS' dynamic behaviour is significantly influenced by the experimental setup with different dominating dynamics associated with power electronics and filter properties. The dynamics of the MEMS cantilever is characterised by three key effects: the system is an actively operated system; it is a micro-scale system with amplitudes at nano-scale dimensions; and the integrated actuation physics introduces interesting complex dynamics. The MEMS cantilever with its integrated actuation and sensing abilities was developed for a commercial technology, thus, making our findings directly implementable and meaningful.</p>

Simulation & analysis of PZT/ P (VDF-TrFE) cantilever beams for health monitoring of building and structures

The design of a piezoelectric PZT/P(VDF-TrFE) based Microelectromechanical system cantilever beams for a very low frequency applications, using silicon bulk-micromachining technology is described in this paper. The natural frequencies of cantilever beams were calculated using the COMSOL software. For signal output, the cantilever-beam structure contains a layer of PZT/P(VDF-TrFE) as well as chrome-gold interdigitated electrodes. According to the simulation results, the cantilever-beam with dimensions of 10mmx3mmx5µm has a lowest resonant frequency of 95.56 Hz, implying that PZT/P(VDF-TrFE) is an appropriate piezoelectric material for really low frequency uses such as building and structure health monitoring.

Photon force microelectromechanical system cantilever combined with a fibre optic system as a measurement technique for optomechanical studies

In this paper we present a metrological measurement technique that is a combination of fibre optic interferometry and a microelectromechanical system (MEMS) sensor for photon force (PF) measurement with traceability via an electromagnetic method. The main advantage of the presented method is the reference to the current balance, which is the primary mass/force metrological standard. The MEMS cantilever transduces the PF to a deflection that can be compensated with the use of the Lorentz force. This movement is measured with the use of the interferometer and does not require any mechanical calibration. Combining the MEMS current balance system with interferometry is a unique and fully metrological solution. The resolution of the proposed measurement technique is calculated to be 4 pN Hz–0.5 (2% uncertainty). The PF–MEMS used for the investigation is a cantilever with a resolution of 46 fN Hz–0.5, which was calculated from the thermomechanical noise and is far below the resolution limit of the whole system. Because the whole construction is based on a fibre optic system, it does not require any complex adjustment procedure and may work as an optomechanical reference in any metrological laboratory.

A novel MEMS sensor concept to improve signal-to-noise ratios

Dynamic measuring concepts of sensors use a variety of different metrics. Some monitor the amplitude and/or phase, while others track resonance frequency or stability thresholds. Based on the underlying physics we further distinguish between quasi-static and dynamic, linear and nonlinear, passive and active, as well as coupled and decoupled concepts. While linear, passive concepts of single and/or decoupled oscillators are the state of the art and therefore widely used in technological applications today, the properties of nonlinear, active and/or coupled oscillators are far less implemented. In this work we theoretically investigate the amplification properties of an active micro-electromechanical system (MEMS) subject to an external dynamic load. Previously derived governing equations describe a real composite MEMS cantilever with integrated self-sensing and self-actuating mechanisms. A comprehensive dynamic analysis is presented to investigate the amplification properties of the active system in contrast to its passive counterpart, including equilibria, modal analysis, stability maps and bifurcation diagrams. New insights reveal compressive nonlinear amplification properties for the operation of the active system — similar to what can be observed by bio-sensor properties in the human cochlea. We conclude the work with a brief discussion on significantly increased noise-filtering properties for future signal processing technologies and how current limits of signal-to-noise ratio can be overcome.

Actively logical modulation of MEMS-based terahertz metamaterial

The integration of micro-electro-mechanical system (MEMS) with metamaterial has provided a novel route to achieve programmability via its reconfigurable capabilities. Here, we propose and demonstrate a MEMS-based metadevice by using switchable winding-shaped cantilever metamaterial (WCM) for active logical modulation. WCM can be actuated by external driving voltage, and the logical modulation bit is performed by releasing MEMS cantilevers to represent “on” and “off” states. While the underneath substrate surface of a MEMS-based metadevice is rough after releasing the cantilevers, the metadevice is allowed to operate on the reconfigurable switching state and avoid the snapping down of the device when the system is overloaded. Such a reconfigurable and programmable MEMS-based metadevice exhibits multifunctional characteristics to simultaneously perform the logic operations of “OR” and “AND” gates. By exploiting the tuning mechanism of the MEMS-based metadevice, the arbitrary metamaterial configuration can be implanted into WCM. This opens a wide avenue to further enlarge the operating frequency range and applications in optoelectronic fields. These unique results provide various possibilities in multifunctional switching, active logical modulating, and optical computing applications.

Frequency–amplitude response of superharmonic resonance of second order of electrostatically actuated MEMS cantilever resonators

This paper deals with the frequency–amplitude response of superharmonic resonance of second order (order two) of electrostatically actuated Micro-Electro-Mechanical System (MEMS) cantilever resonators. The structure of MEMS resonators consists of a cantilever resonator over a parallel ground plate, with a given gap in between, and under AC voltage. This resonance results from hard excitations and AC voltage frequency near one-fourth of the natural frequency of the resonator. The forces acting on the resonator are the nonlinear electrostatic force to include fringe effect, and a linear damping force. In order to solve the dimensionless partial differential equation of motion along with boundary and initial conditions, two types of models are developed, namely Reduced Order Models (ROMs), and Boundary Value Problem (BVP) model. The BVP model is essentially a finite difference model with a discretization in time only. ROMs are developed using one through five modes of vibration. The Method of Multiple Scales (MMS), numerical integrations using MATLAB, as well as a continuation and bifurcation analysis are used to solve the ROMs. The BVP model, resulting from using finite differences for time derivatives, is also numerically integrated. Five modes of vibration ROM is found to make accurate predictions in all amplitudes. A softening effect of the response is predicted. The response consists of a bifurcation with a bifurcation point of amplitude one fourth of the gap, and a stable branch in larger frequencies with a pull-in instability end point at three fourths of the gap. The bifurcation point shifts to lower frequencies as the voltage and/or fringe effect increase, and/or damping decreases. If damping increases, the branches coalesce, peak amplitude decreases, and a linear behavior is experienced.

Development of algorithms in open-source Elmer FEM for frequency response and biased modal analysis of MEMS cantilever

The characteristic of the microelectromechanical systems (MEMS) structures can be determined by using static, modal and harmonic analyses implemented with finite element method (FEM) software packages. In the current study, two different algorithms for the open-source Elmer FEM are developed to analyze not only the biased modal analysis but also harmonic response. The proposed algorithms are implemented in Elmer FEM by using the design parameters of a MEMS structure already presented in the literature. Furthermore, as the same MEMS structure was also analyzed by using a commercial software, the simulation results of Elmer FEM are also checked with those of the commercial software. The result of Elmer FEM is almost consistent with the experimental value of the reported structure for the center frequency. Furthermore, the difference between the simulation results of Elmer FEM and those of commercial software for the same simulation conditions is almost in the range of 7% and 2.4% for the displacement and the resonance frequency, respectively. It is thought that the proposed algorithms can also be used to analyze more complex MEMS structures such as resonator and accelerometer for determining characteristic features.

Magnetophoresis-Assisted Capillary Assembly: A Versatile Approach for Fabricating Tailored 3D Magnetic Supercrystals.

The fabrication and integration of sub-millimeter magnetic materials into predefined circuits is of major importance for the realization of portable devices designed for telecommunications, automotive, biomedical, and space applications but remains highly challenging. We report here a versatile approach for the fabrication and direct integration of nanostructured magnetic materials of controlled shaped at specific locations onto silicon substrates. The magnetophoresis-assisted capillary assembly of magnetic nanoparticles, either spherical or anisotropic, leads to the fabrication of high-performance Co-based permanent magnets and Fe-based supercrystals. Integrated sub-millimeter magnets as well as millimeter self-standing magnets exhibiting magnetic properties competing with NdFeB-based composites were obtained through this cost- and time-efficient process. The proof-of-concept of electromagnetic actuation of a micro-electromechanical system cantilever by means of these supercrystals highlights their potentiality as efficient integrated magnetic materials within nomadic devices.

Stochastic resonance induced performance enhancement of MEMS cantilever biosensors

This paper presents an application of stochastic resonance for improving the performance of micro-electromechanical system (MEMS) cantilever biosensors operating in liquid media. The hydrodynamic influences in liquid media that consist of added mass effect, viscous damping and squeeze film damping deteriorate the Q-factor of cantilever oscillator sensors so much that their operation under fluid-immersed conditions becomes impractical. The stochastic resonance can be produced by the addition of noise in two ways: one, by direct transfer of noise energy through some nonlinear interaction process with the oscillator; and second, by making intrinsic parameters of the oscillator noisy. In this work, we are concerned with the second approach where MEMS controlled feedback oscillator is the biosensor. The cantilever motion is modeled as a damped harmonic oscillator with its natural frequency and damping coefficient parameters made noisy for generating stochastic resonance. Both the frequency and the damping noises generate stochastic resonance in the oscillator amplitude; however, the damping noise generates an additional resonance effect in the oscillator phase. The latter creates the possibility for improving Q-factor against the detrimental influences of hydrodynamic loading. This is a novel feature, which we explore in this paper for maintaining self-sustained cantilever oscillations in a liquid medium and for enhancing biosensor performance. The biosensor model takes into account the circuit loading effect and the influence of cantilever noise in hydrodynamic environment as well. The analytical relations for mass sensitivity and limit of detection have been obtained. The limit of detection is found to be inversely proportional to where and denote cantilever amplitude and Q-factor, respectively. That means the phase stochastic resonance produced by the addition of damping noise lowers the limit of detection by enhancing both and . A prototype theoretical analysis with a Si-MEMS cantilever ( μm3 dimensions and 10 μm gap from boundary wall) oscillator sensor in aqueous medium shows 2 to 3 orders of magnitude enhancement in the Q-factor and 4 to 5 orders of magnitude improvement in the limit of mass detection.

Design and fabrication of PDMS‐based electrostatically actuated MEMS cantilever beam

Polymer microelectromechanical system (MEMS) devices emerge as the new class of sensor devices for bio-sensing applications exhibiting high mechanical deformability and sensitivity. In this work, the design and fabrication of electrostatically actuated polydimethylsiloxane (PDMS) MEMS cantilever on flexible PDMS substrate is presented. The physical parameters of the cantilever were analysed and optimised using Taguchi method coupled with COMSOL Multiphysics software. This work focusses on the development of a novel approach for the simple and cost-effective fabrication process of PDMS cantilevers and subsequently its arrays. The proposed device consists of a PDMS body with the metal bottom electrode, PDMS anchor, and PDMS cantilever beam as its top electrode and immobilization surface. The work presented is of the cracking phenomenon in the metal layer sputtered on the PDMS substrate. The novelty of the fabrication process is the use of low-cost processes, no need for sophisticated lithography tools or etching equipment. Also, the process allows the use of alternate material as base substrate (glass, silicon wafer etc.) wherein it is not consumed and is reusable. The fabricated device is then electrically characterised for its pull-in characteristics.

Design, fabrication and characterization of piezoelectric cantilever MEMS for underwater application

This work shows a preliminary microfabrication route for a novel directional hydrophone based on a cross-shaped design of piezoelectric cantilevers. A thin layer of aluminum nitride (AlN) using Molybdenum (Mo) thin film as electrodes will be exploited as piezoelectric functional layer for the microfabrication of a cantilever-based ultrasonic micro electro mechanical system (MEMS) hydrophone. A parameterized simulation based on length of these cantilevers between 100 and 1000 μm allowed to set the first resonant mode between 20 kHz and 200 kHz, the desired underwater ultrasonic acoustic range. The microsystem was designed with cantilevers facing each other in a cross configuration in order to have novel MEMS hydrophone with an omnidirectional response. In order to investigate the first resonance frequency mode and displacement measurements, a Laser Doppler Vibrometer was used and good agreement between simulations and experimental results was achieved. Responsivity and directionality measurements of the piezoelectric MEMS cantilevers were performed in water. Maximum sensitivity up to −153 dB with omnidirectional directivity pattern was achieved by fabricated MEMS sensor. • We show the microfabrication of a novel directional hydrophone based on a cross-shaped design of piezoelectric cantilevers. • Cantilevers facing each other in a cross configuration allow to have an omnidirectional response to underwater ultrasounds. • Aluminum nitride (AlN) using Molybdenum (Mo) thin film as electrodes is exploited as piezoelectric functional layer. • Maximum sensitivity underwater up to -153 dB with omnidirectional directivity pattern was achieved.