Micromechanical Switch Research Articles

Snap-induced flow in a closed channel

Snap-through is a buckling instability that allows slender objects, including those in plant and biological systems, to generate rapid motion that would be impossible if they were to use their internal forces exclusively. In microfluidic devices, such as micromechanical switches and pumps, this phenomenon has practical applications for manipulating fluids at small scales. The onset of this elastic instability often drives the surrounding fluid into motion – a process known as snap-induced flow. To analyse the complex dynamics resulting from the interaction between a sheet and a fluid, we develop a prototypical model of a thin sheet that is compressed between the two sides of a closed channel filled with an inviscid fluid. At first, the sheet bends towards the upstream direction and the system is at rest. However, once the pressure difference in the channel exceeds a critical value, the sheet snaps to the opposite side and drives the fluid dynamics. We formulate an analytical model that combines the elasticity of thin sheets with the hydrodynamics of inviscid fluids to explore how external pressure differences, material properties and geometric factors influence the system's behaviour. To analyse the early stages of the evolution, we perform a linear stability analysis and obtain the growth rate and the critical pressure difference for the onset of the instability. A weakly nonlinear analysis suggests that the system can exhibit a pressure spike in the vicinity of the inverted configuration.

Finite Element Mode-ling of Damping of a Squeeze Gas Film in High-Frequency Microelectromechanical Switches with Capacitive Contact

The damping effects of a squeeze gas film are one of the main components of damping and naturally arise in the designs of dynamic micromechanical devices, in particular, in high-frequency micromechanical switches with an electrostatic activation mechanism, in which the electrostatic drive consists of a fixed electrode in the form of a plate and a movable electrode in the form of a movable plate suspended on elastic suspensions for the case of capacitive contact. In the static mode of the device, a thin film of gas consisting of air molecules or other inert gas surrounding the device is located and held between the electrodes of the electrostatic drive. This article presents a mathematical model based on the obtained linear inhomogeneous Reynolds differential equation and performs finite element modeling of the pressure distribution in the plate of a suspended movable electrode during compression of a gas film during electrostatic activation of micromechanical switches with a capacitive contact and parallel arrangement of the electrodes of an electrostatic drive depending on the magnitude of the coefficient of this component of damping in a three-dimensional coordinate system, the dependences between the damping force and the elastic force of the compressible gas film on the value of the damping coefficient are also presented. The presented results are applicable to assess the effect of isothermal damping of a squeeze gas film on the dynamics of micromechanical devices, in particular, on the dynamic characteristics of high-frequency micromechanical switches with an electrostatic activation mechanism and a capacitive contact.

Design Guideline for a Cantilever-Type MEMS Switch with High Contact Force

Micromechanical switches are of significant interest for advanced radio frequency and microwave systems, but their practical implementation is limited by low reliability. Electrodes of a microscopic size develop weak contact force that leads to high and unstable contact resistance. The force is typically increased by using a sophisticated switch design with extended lateral dimensions, although a simple and compact cantilever is more preferable. The paper describes for the first time a comprehensive approach to enhance the force of an electrostatically actuated switch. The strategy is applied to a miniature device based on a 50 µm long cantilever. The contact force is increased from 10 to 112 µN, making the switch strong enough to achieve low and stable contact resistance. The restoring force is also enhanced in order to ensure reliable de-actuation. The growth of forces is accompanied by a reduction in the pull-in voltage. Connecting several cantilevers in parallel and manipulating the number and position of contact bumps additionally improves the force and mechanical stability of the switch. An optimal design contains a triple cantilever with two bumps. It provides 50% higher force per contact compared to the single-cantilever switch at the same pull-in voltage and keeps the advantages of a miniature device. The proposed design strategy may be used for building reliable MEMS switches.

Glass Package and Through Glass Via (TGV) for MEMS

Menlo Microsystems has introduced a glass-based MEMS switch that utilizes through glass via (TGV) technology. Created in the R&D labs at GE, these MEMS solutions combined with utilization of glass packaging, has enabled the creation of the highly reliable Ideal Switch™. It is the world’s smallest, most reliable, and efficient micro-mechanical switch that can be used for numerous applications, including power. Several advantages are gained by taking advantage of the low electrical loss of glass and hermetic TGV. The TGV technology enables >60% smaller package size relative to wirebond. Parasitics are reduced by >75% and devices have a wide operational bandwidth from DC to > 50 GHz. Devices can have dozens of switches in a small form factor that give reliable performance over billions of cycles. Leading up to the volume production of these devices, Menlo has helped drive the glass supply chain to an increased level of maturity. In this talk we will provide an overview of Menlo’s glass package for the Ideal Switch™ technology as well as discuss the growing maturity and emerging capabilities in the glass/TGV supply chain.

Research of Electromagnetic Parameters of the Radio-Frequency Micromechanical Switch Designed for Operation in 5G Transceiver Systems

This article presents the results of an experimental study of the electromagnetic parameters (scattering parameters) of a manufactured experimental sample of a capacitive single-pole single-throw radio-frequency micromechanical switch with an electrostatic activation mechanism designed to operate in the transceiver radio-modules of 5G mobile networks in the frequency range NR FR1, namely at a central resonant electrical frequency of 3,6 GHz. The effective operating frequency range of the developed and manufactured experimental sample of a radio-frequency micromechanical switch is the S-frequency range. The basis for the development of the presented experimental sample is the developed methodology for designing capacitive radio-frequency micromechanical switches with an electrostatic activation mechanism.

MEMS Switching Voltage Regulator Using a Normally-On Electret Relay

We report on a DC/DC step-down switching regulator using a microelectromechanical systems (MEMS) switch for the first time. The output voltage developed in a storage capacitor is used as a feedback control voltage for the electrostatic actuator that drives a micromechanical contact switch inserted between the rectifier and the capacitor. The switch is configured to be normally-on owing to the electrostatic potential remaining in the electret film on the electrodes. When the output voltage exceeds and the feedback control voltage cancels the built-in potential of the electret, the differential voltage acting on the actuator becomes small and the contact is opened, thereby decoupling the rectifier from the storage capacitor. When the output voltage becomes low, on the other hand, the net differential voltage becomes large and the contact is closed again, thereby reconnecting the rectifier to the capacitor and recovering the voltage. Fast repetition of this sequence maintains the DC voltage of the storage capacitor at a constant level. For demonstration, an electret film that is pre-charted to 240 V is used to regulate the output voltage in a range between 12 V and 14 V. Different from the switching regulators using transistors, the MEMS regulator does not require any bias current for operation, being suitable as a low-power voltage regulator for environmental energy harvesters. [2021-0220]

Single Electrode Bidirectional Switching of Latchable Prestressed Bistable Micromechanical Beams

Electrostatically actuated, bistable, curved micromechanical beams can exhibit latching, wherein the beams remain in two distinct stable states without an applied voltage. These structures could serve as building blocks in a variety of applications such as micromechanical logic elements, switches, non-volatile memories, and low power consumption sensors. However, the design of such devices is challenging since such structures are prone to symmetry breaking, which consequently inhibits latching. Generally, asymmetric responses may be circumvented by introducing a tailored axial compressive prestress. In this work we explore, both theoretically and experimentally, the influence of prestress on the single electrode, bidirectional dynamic switching of curved, latchable, single crystal Si <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 1000 \;\mu \text{m}$ </tex-math></inline-formula> long and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\approx 3.5\;\mu \text{m}$ </tex-math></inline-formula> wide beams. We use Joule heating to apply the necessary prestress required to eliminate symmetry breaking and ensure latching. In accordance with reduced-order model predictions, our experimental findings show that prestress plays a key role in the dynamic response of the beam. Our results demonstrate bidirectional operation using a single electrode, fostering a compact footprint device for tailoring the axial stress and dynamic conditions.

Integration of Gold Nanoparticle-Carbon Nanotube Composite for Enhanced Contact Lifetime of Microelectromechanical Switches with Very Low Contact Resistance.

Electrical circuits require ideal switches with low power consumption for future electronic applications. However, transistors, the most developed electrical switches available currently, have certain fundamental limitations such as increased leakage current and limited subthreshold swing. To overcome these limitations, micromechanical switches have been extensively studied; however, it is challenging to develop micromechanical switches with high endurance and low contact resistance. This study demonstrates highly reliable microelectromechanical switches using nanocomposites. Nanocomposites consisting of gold nanoparticles (Au NPs) and carbon nanotubes (CNTs) are coated on contact electrodes as contact surfaces through a scalable and solution-based fabrication process. While deformable CNTs in the nanocomposite increase the effective contact area under mechanical loads, highly conductive Au NPs provide current paths with low contact resistance between CNTs. Given these advantages, the switches exhibit robust switching operations over 5 × 106 cycles under hot-switching conditions in air. The switches also show low contact resistance without subthreshold region, an extremely small leakage current, and a high on/off ratio.

Micromechanical Switch-Based Zero-Power Chemical Detectors for Plant Health Monitoring

In this paper, for the first time we demonstrate zero-power volatile-organic-chemical (VOC) detectors based on micromechanical switches suitable for plant health monitoring. Differently from state-of-the-art active chemical sensors, the device presented here exploits a completely passive, chemically-sensitive switch based on a bimaterial micro-cantilever and a passive switch-based readout mechanism to detect VOCs exceeding a pre-determined concentration released by unhealthy plants. When exposed to target VOCs, the polymer/metal bimaterial beam bends downward and trigger the switch due to the stress induced from the absorption of chemicals in the polymer layer. Here we show experimental demonstrations of detecting toluene, hexenol (cis-3-Hexen-1-ol, a chemical released from plants under attack by pests) and ethanol, respectively, with our fabricated prototypes. The demonstrated high sensitivity to ethanol (~8 nm/ppm ) and hexenol (~3.3 nm/ppm ) was achieved by the optimization of device geometries showing a great promise of the proposed technology to ultimately achieve 10s ppm detection limit (with a sub-micron contact gap and voltage bias) which is required for the device operation in close proximity to a plant in an open environment. [2020-0190]

Review on Switches for Power Applications: Macro to Micro

Background: Switches are important component in electrical system. The switches needs to have the advantages of low ON-state resistance, very high OFF-state resistance, high isolation, no leakage current, less power loss, fast switching, high linearity, small size, arcless and low cost in bulk production. Also these switches have to be reliable and environmental friendly. Methods: In this paper, macro and microswitches for power applications are extensively reviewed and summarized. Various types of switches such as mechanical, solid-state, hybrid and micromechanical switches have been used for power applications are reviewed. The importance and challenge in achieving arcless switching is presented. Results: The use of micromechanical switches for power applications, actuation techniques, switching modes, reliability and lifetime are also reviewed. The modeling and design challenges are also reviewed. Conclusion: The applications of micromechanical switches shows that the switches can reduce the leakage current in battery operated systems and reduce the size of the system considerably.

Modeling and Analysis of Scalable Arcless Micromechanical Switch for Battery Powered Electrical System

Modeling and Analysis of Scalable Arcless Micromechanical Switch for Battery Powered Electrical System

Micromechanical simulation of ferroelectric domain processes at crack tips

The electromechanical loading situation at cracks in ferroelectric ceramics is essentially affected by domain switching. Under high electrical and/or mechanical external fields, the state of polarization and remanent strains is substantially changed at the crack tip. These irreversible dissipative processes influence the fracture toughness of the cracked ferroelectric material. In the present paper, the micromechanical domain switching processes at the crack tip are studied by numerical simulation and compared with the in situ experimental results obtained by Jones et al. (Acta Mater 55(16):5538–5548, 2007) using X-ray diffraction analyses in synchrotron. Main attention is payed to the spatial distribution of preferred domain orientation in a mechanically loaded compact tension specimen made of a soft tetragonal lead zirconate titanate ceramics. It is found that the mechanically induced favored domain orientation distribution depends on position within the plane of the CT specimen and correlates with projected deviatoric stresses and strains. Some issues concerning shortcomings in the experimental and simulation results are raised and discussed. The outcome of this type of simulations forms the basis for more realistic fracture mechanical evaluations in future.

Simulation of fatigue damage in ferroelectric polycrystals under mechanical/electrical loading

The reliability of smart-structures made of ferroelectric ceramics is essentially reduced by the formation of cracks under the action of external electrical and/or mechanical loading. In the current research a numerical model for low-cycle fatigue in ferroelectric mesostructures is proposed. In the finite element simulations a combination of two user element routines is utilized. The first one is used to model a micromechanical ferroelectric domain switching behavior inside the grains. The second one is used to simulate fatigue damage of grain boundaries by a cohesive zone model (EMCCZM) based on an electromechanical cyclic traction–separation law (TSL). For numerical simulations a scanning electron microscope image of the ceramic’s grain structure was digitalized and meshed. The response of this mesostructure to cyclic electrical or mechanical loading is systematically analyzed. As a result of the simulations, the distribution of electric potential, field, displacement and polarization as well as mechanical stresses and deformations inside the grains are obtained. At the grain boundaries, the formation and evolution of damage are analyzed until final failure and induced degradation of electric permittivity. It is found that the proposed model correctly mimics polycrystalline behavior during poling processes and progressive damage under cyclic electromechanical loading.To the authors’ knowledge, it is the first model and numerical analysis of ferroelectric polycrystals taking into account both domain reorientation and cohesive modeling of intergranular fracture. It can help to understand failure mechanisms taking place in ferroelectrics during fatigue processes.

Criterion for Optimization of the Micromechanical Switch for RF Band

Criterion for Optimization of the Micromechanical Switch for RF Band

Surface Condition Influence on the Nonlinear Response of MEMS CC-Beam Resoswitches

This letter characterizes the effect of surface conditions on the nonlinear responses of micromechanical resonant switches (aka “resoswitches”). In particular, a CMOS-MEMS clamped–clamped beam (CC-beam) resoswitch used as a testing vehicle exhibits variations in the magnitude of the frequency tapping bandwidth upon modification of the surface stiction force by salinization with (1H, 1H, 2H, 2H)-perfluorodecyltrichlorosilane (FDTS) and by altering the operating temperature of the resoswitch. The tapping bandwidth of the CC-beam resoswitch increases from 17.37 to 29.75 kHz after salinization and reduces from 36.75 to 26.06 kHz as the device temperature rises from 35 °C to 80 °C. The experiment of salinization, together with the theory prediction, verifies that FDTS coating would result in a lower surface energy and thus a lower attractive force between the contact surfaces. As a result, the resoswitch would exhibit a larger tapping bandwidth due to the reduction of the attractive force. In contrast, raising the temperature would induce an increase in the surface energy and in the contact asperity radius of curvature due to material softening, both of which cause the attractive force to increase. Understanding the surface condition dependence of the nonlinear tapping frequency response could pave the way toward applications not achieved by the existing technologies, such as in situ monitoring of the anti-stiction coating quality in MEMS motion sensors.

Internet of things: Sensing without power.

A thermally activated micromechanical switch delivers an electrical readout signal only when irradiated by a narrowband mid-infrared light, thanks to a metamaterial element that converts light into heat.

Low-voltage micromechanical RF switch based on a piezoelectric micro-cantilever integrated with a transmission line

This paper reports a class of compact low-voltage-actuated micromechanical radio-frequency (RF) switches with a piezoelectric micro-cantilever and a signal transmission line in an integrated form. Perovskite lead zirconate titanate (PZT) thin film was prepared by using a facile sol-gel process in a programmable manner. The proposed RF switch was demonstrated without significant structural deformation by optimization of both the structural design and batch fabrication with various micromachining techniques. The proposed compact RF switch was experimentally found to be actuated with an applied voltage as low as 2 V. The switch also showed high isolation and moderate insertion loss for frequencies up to 5 GHz.

Impact of Contact Materials and Operating Conditions on Stability of Micromechanical Switches

Nano and micromechanical switches are of great interest in applications that require high speed, low-power consumption and high electrical isolation. There is strong evidence that airborne hydrocarbon accumulation on the contact surfaces of the switch is a key cause for device failure. Relatively unexplored contact materials such as RuO2 are of interest because they are believed to be less prone to hydrocarbon deposit accumulation than more commonly used materials such as Pt and Au. Here, we measure the reliability of RuO2 and Pt-coated microswitches in hydrocarbon-rich environments with N2 and N2:O2 background gases. The RuO2 material performs very poorly in contaminated N2, but very well in contaminated N2:O2. Furthermore, RuO2 performs much better than Pt in the contaminated N2:O2. It is demonstrated that the deposit, initially being an insulator, can be electrically broken-down, thereby substantially lowering switch resistance. It is further shown that the passage of electrical current through the contacts augments deposit accumulation.

Elastomer-Based Pneumatic Switch for Radio Frequency Microdevices

This paper reports the realization and characterization of a pneumatic microswitch integrated with a high-frequency radio frequency (RF) transmission line on an elastomer substrate. A process for the fabrication of low-loss RF coplanar transmission lines on flexible elastomeric polydimethylsiloxane (PDMS) substrates was developed, and devices realized using this process were used to determine the characteristics of PDMS as an RF substrate with uniform low loss and low dielectric constant being measured. To demonstrate the capabilities of this elastomer-based RF platform, a micromechanical switch exploiting a pneumatic membrane valve was integrated with the PDMS RF transmission line. Repeatable switching was observed with greater than 20-dB suppression in the “off” state and minimal degradation of the transmission line characteristics in the “on” state being achieved over a multioctave 2-20-GHz bandwidth. These valve-integrated transmission lines had an insertion loss of 0.16 dB·mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> at 20 GHz. This proof-of-concept device represents a novel combination of the areas of micropneumatics, flexible electronics, and broadband microwave devices with excellent RF properties, low interference, bias-free pneumatic switching, and relatively simple fabrication.

Fully parameterized model of a voltage-driven capacitive coupled micromachined ohmic contact switch for RF applications

A comprehensive and completely parameterized model is proposed to determine the related electrical and mechanical dynamic system response of a voltage-driven capacitive coupled micromechanical switch. As an advantage over existing parameterized models, the model presented in this paper returns within few seconds all relevant system quantities necessary to design the desired switching cycle. Moreover, a sophisticated and detailed guideline is given on how to engineer a MEMS switch. An analytical approach is used throughout the modelling, providing representative coefficients in a set of two coupled time-dependent differential equations. This paper uses an equivalent mass moving along the axis of acceleration and a momentum absorption coefficient. The model describes all the energies transferred: the energy dissipated in the series resistor that models the signal attenuation of the bias line, the energy dissipated in the squeezed film, the stored energy in the series capacitor that represents a fixed separation in the bias line and stops the dc power in the event of a short circuit between the RF and dc path, the energy stored in the spring mechanism, and the energy absorbed by mechanical interaction at the switch contacts. Further, the model determines the electrical power fed back to the bias line. The calculated switching dynamics are confirmed by the electrical characterization of the developed RF switch. The fabricated RF switch performs well, in good agreement with the modelled data, showing a transition time of 7 µs followed by a sequence of bounces. Moreover, the scattering parameters exhibit an isolation in the off-state of >8 dB and an insertion loss in the on-state of <0.6 dB up to frequencies of 50 GHz. The presented model is intended to be integrated into standard circuit simulation software, allowing circuit engineers to design the switch bias line, to minimize induced currents and cross actuation, as well as to find the mechanical structure dimensions necessary for the desired switching time and actuation voltage waveform. Moreover, process related design rules can be automatically verified.