Microelectromechanical Research Articles

BioIn-Tacto: A compliant multi-modal tactile sensing module for robotic tasks

We present the open-source design and fabrication of a compliant multimodal tactile sensing module. The sensing module design presented here enables robotic end-effectors to sense contact properties like pressure and vibration and estimate a quaternion that represents the deformation due to contact. We elaborated the module’s compliant structure fabrication process to use only 3D printed molds and a vacuum chamber, making it accessible to a broad range of roboticists. The process also allows production batches of up to five modules and easy deployment to robotic hands. The repository associated contains packages that support the Robot Operating System (ROS) to perform data collection and visualization. All hardware Computer-Aided Design (CAD) files and software source codes have been released and can be easily assembled and modified. The sensing module proposed in this paper uses off-the-shelf Microelectromechanical (MEMs) barometers and Magnetic, Angular Rate and Gravity (MARG) systems. Those components may be replaced by alternatives depending on the sensor’s availability, constraints related to the module’s size, or robotic application without prejudice to sensor functionality.

Voltage Divider based on Switched Capacitors for MEM Generators

Simulation results of the operation of voltage dividers based on switched capacitors with diode and transistor-diode switching for microelectromechanical (MEM) generators are presented. It has been established that for a divider with diode-switched capacitors, the voltage division factor doesn't remain when the load resistance changes, and for higher load resistances, the value of the load voltage asymptotically approaches to V0, but not to V0/N. At the same time, a divider with transistor-diode switching of capacitors at higher load resistances makes it possible to obtain an output voltage Vl, which is N times lower than the voltage of the primary power source V0. Analytical expressions have been obtained for estimating the parameters of dividers with diode switching, which allow calculating the characteristics of the divider at the stage of preliminary design of MEM generators with diode-capacitor voltage dividers. It is shown that the simulation of the operation of a diode-capacitor voltage divider must be carried out taking into account the dynamic current-voltage characteristic of diodes. It is established that when using a bipolar transistor as a charging switch, the ripple coefficient of the output voltage is less than when using a reed relay

Experimental Demonstration of Coupled Sub-Harmonic Injection Locked Oscillation in Micro-Electro-Mechanical Relays

The voltage dependence of DC-driven self-sustaining oscillation behavior of a micro-electro-mechanical (MEM) relay makes it possible to influence the phase of oscillation by coupling the gate or body, source and/or drain electrodes to other voltage signals. In this work, sub-harmonic injection locking and synchronized oscillation of electrically coupled MEM relays are experimentally demonstrated, representing a significant milestone toward achieving a MEM-oscillator-based Ising machine that can solve combinatorial optimization problems much more efficiently than conventional computer architectures.

Diode-capacitor voltage divider for electrostatic microelectromechanical generator

The simulation results of the voltage divider operation based on switchable capacitors with diode switching for electrostatic microelectromechanical (MEM) generators are presented. It has been established that for the divider with diode-switched capacitors, the voltage dividing coefficient is not remain the same when the load resistance changes, and for higher load resistances, the load voltage asymptotically approaches the value of the power source. Analytical expressions have been obtained for estimating the parameters of the divider with diode switching, which allow evaluating its characteristics at the preliminary stage of the MEM generator design. It has been shown that the simulation of the diode-capacitor voltage divider operation has to be carried out taking into account the dynamic volt-ampere characteristics of diodes.

Digital twin and IOT technology for secure manufacturing systems

The Digital Twin (DT) method offers new concepts for choosing the context of information technologies and smart production systems. This research focuses on low-price, extremely effective defect diagnosis methods, low-efficiency, high-cost devices to obtain timely feedback and accurate fault detection results, and secure manufacturing systems. The data structure, control plane, and output units are the three components of the manufacturing system that creates a data link between the virtual model using Micro-Electro-Mechanical (MEM) devices and the Zigbee wireless transmission system in the database layer. This study acquired DT information from the control plane using the Internet of Things (IoT) through sensors for secure manufacturing information. It separates and calls the pertinent data by the attribute processor and transfers it to the outcome units. To produce the classification and outcomes of work build features information, the evaluation method analysis the output nodes that split the test set and learning group using a dynamic database. The hybrid IoT with DT technology to examine the consequences of defects detected efficiently predicted and secures the manufacturing system.

Investigation of Electrical and Mechanical Reliability of Inkjet-Printed 4-Terminal Microelectromechanical Relays

We investigate the mechanical and electrical reliability of inkjet-printed 4-terminal (4T) microelectromechanical (MEM) relays in various failure modes. Since an inkjet-printed mechanical relay exhibits an extremely low on-resistance (~4 Ω), the endurance of MEM relays can be limited dominantly by Joule heating from the high current density at the contacting asperities, which eventually leads to welding-induced and electromigration failures. Therefore, high drain-source voltage can reduce the mean number of cycles to failure (MCTF). In addition, the endurance also depends on the structural fatigue of the floated beams, where the mechanical strain is concentrated near the junction area of the two floated beams. Thermal and mechanical stress distributions of the suggested printed 4T MEM relay are analyzed by 3-dimensional affected significantly by charging of the dielectric or oxidation of the contacting surface which can degrade a pull-in voltage and on-current, respectively.

A Normalized Model of a Microelectromechanical Relay Calibrated by Laser-Doppler Vibrometry.

This work presents a behavioral model for a microelectromechanical (MEM) relay for use in circuit simulation. Models require calibration, and other published relay models require over a dozen parameters for calibration, many of which are difficult to extract or are only available after finite element analysis. This model improves on prior work by taking advantage of model normalization, which often results in models that require fewer parameters than un-normalized models. This model only needs three parameters extracted from experiment and one dimension known from device fabrication to represent its non-contact behavior, and two additional extracted parameters to represent its behavior when in contact. The extracted parameters–quality factor, resonant frequency, and the pull-in voltage–can be found using laser Doppler vibrometry. The device dimension is the actuation gap size, which comes from process data. To demonstrate this extraction process, a series of velocity step responses were excited in MEM relays, the measured velocity responses were used to calibrate the model, and then then simulations of the model (implemented in Verilog-A) were compared against the measured data. The error in the simulated oscillation frequency and peak velocity, two values selected as figures of merit, is less than 10% across many operating voltages.

Doping of Al/CuO with microwave absorbing Ti3C2 MXene for improved ignition and combustion performance

Nanothermites have a wide application in many civil and defense applications, including propulsion and detonations systems, micro-electromechanical (MEMs) and other systems that require fast energy release rate and low ignition temperature. Traditional ignition methods are commonly based on surface excitation (spot ignition), possessing a risk of undesired ignition. Safe and selective microwave (MW)-based igniting systems can interact with an ignitable material (typically a thermite) over its full volume at once. Unfortunately, thermites have low susceptibility to MW due to the presence of Al2O3 oxide shell on Al particles, which would commonly require a high ignition power of MW radiation and long ignition delay times. In this work, Ti3C2 MXene was introduced as a MW susceptor into Al/CuO energetic nanocomposites. The samples were ignited using a MW probe, showing that the introduction of MXene into Al/CuO/MXene could significantly reduce the power required for its MW ignition, as well as shorten the ignition delay time versus the parent Al/CuO nanothermite. Besides, presence of MXene could modulate and control a heat release, gas production and combustion performance of the Al/CuO/MXene composites, substantially extending safety, flexibility and adaptability of new nanothermites to various operational requirements.

Frequency shifts and thermoelastic damping in distinct Micro-/Nano-scale piezothermoelastic fiber-reinforced composite beams under three heat conduction models

The present work aims to fulfill two primary objectives. Firstly, to present the micro-mechanics model of piezothermoelastic fiber-reinforced composite (PTFRC) medium using analytical techniques, viz., Strength of Materials (SM) & Rule of Mixtures (RM) and graphically establish some of its electro-mechanical-thermal advantages over monolithic PT materials. Secondly, to analytically study the thermoelastic damping (TED) and frequency shift (FS) in micro-/nano-scale PTFRC beams. TED and FS are analyzed considering the linear Euler-Bernoulli theory when the beam is under four distinct boundary conditions, viz., clamped-clamped (CC), simply supported-simply supported (SS), clamped-free (CF), and clamped-simply supported (CS). The eigenvalues of each beam are calculated numerically with 20 iterations each using the Newton-Raphson technique, followed by the analysis of TED and FS considering the assumed boundaries. The Classical dynamical coupled (CL), Lord-Shulman (LS), and Green-Lindsay (GL) thermoelasticity theories are exclusively analyzed. The effects of thermal relaxation parameters, fiber volume fraction, micro and nano beam dimensions, and the first two modes (M1 & M2) on the TED and FS are graphically illustrated. The critical thickness (CrTh) and critical length (CrLt) of all four beams influenced by the existing parameters are scrupulously investigated. The robustness of the obtained results is validated by matching them with previous literature. For high Ωf, the PTFRC beam has superior electro-mechanical-thermal properties and greater Q-factors compared to monolithic beam. However, the Q-factor increases as Ωf decreases. This facilitates the choice of a suitable value of Ωf for designing and optimizing frequency-sensitive microelectromechanical (MEM) and nanoelectromechanical (NEM) PTFRC beams.

Effect of crystal orientation on liquid phase performance of piezoelectric-on-silicon elliptical plate resonators

Various microelectromechanical (MEM) resonator topologies have been proposed for liquid phase sensing applications. Low liquid phase motional resistance (Rm) and moderately high liquid phase quality factor (Q) are critical to the performance of oscillators based on these resonators for real-time frequency tracking in sensing applications. We recently described a new topology we call the elliptical plate resonator EPR that delivers the lowest Rm after normalizing for area (which impacts mass sensitivity as a tradeoff for lower Rm). In this work, we show that further significant gains in performance can be made by choice of device alignment to the silicon crystal axis (< 110 > direction vs. < 100 > direction). We compare the liquid phase performance between the two orientations for a range of geometrical ratios defining the ellipse of the device. We show that the orientation makes a notable difference on trends in liquid phase Q and Rm. By aligning the EPR to the < 110 > direction, we demonstrate a liquid phase Q of 310 and Rm of 2.5 kΩ. Normalizing for area (Rm×A) to express the tradeoff between mass sensitivity and electrical performance in relation to device area, we report an Rm×A of 0.25 kΩ.mm2. We also show that these gains in liquid phase Rm and Q translate into significant lowering of the Allan deviation when these devices are embedded in close loop to track their frequency in real time with water loaded on the device as expected in liquid phase sensing applications.

Breakdown and Healing of Tungsten-Oxide Films on Microelectromechanical Relay Contacts

This work discusses the electrical break down of tungsten oxide films that form on contacting surfaces of tungsten electrodes in micro-electro-mechanical (MEM) relays. Electrical tests were applied to the contacts of 27 devices to measure the voltage, current and charge required to break down the oxide films, and also to measure the change in current through the contacts as the film healed. The oxide breaks down when an average of 58 <inline-formula> <tex-math notation="LaTeX">$\mu \text{C}$ </tex-math></inline-formula> of electronic charge passes through the oxide, which usually requires applying 1&#x2013;2 V to drive 100 nA-<inline-formula> <tex-math notation="LaTeX">$10~\mu \text{A}$ </tex-math></inline-formula> of current through the contact. The tungsten oxide heals quickly in laboratory ambient conditions: applying 0.5 V to a contact immediately after breaking down an oxide results in a contact current greater than <inline-formula> <tex-math notation="LaTeX">$5~\mu \text{A}$ </tex-math></inline-formula>, but the same test only induces 1 nA of current 1&#x2013;5 minutes later. The reduction in contact current with time follows a power law, which is characteristic of charge relaxation in oxides. Additionally, Holm&#x2019;s experiment shows that current conduction through the contacts is dominated by tunneling through an oxide. These facts together suggest that the break down and healing are electrical processes related to trap accumulation and relaxation in the tungsten oxide. [2021-0161]

Design and Demonstration of MEM Relay-Based Arithmetic and Sequential Circuit Blocks

The Internet of Things (IoT) has become more prevalent in recent years and is an integral part of everyday life. Thus, the need for ultralow-power sensors and processing units has dramatically increased. The continuous scaling of CMOS transistors has resulted in more severe subthreshold leakage and high power density issues. In recent years, microelectromechanical (MEM) relays have attracted research interests. They are viewed as promising beyond-CMOS candidates due to their nonleaking property and abrupt switch ON/OFF characteristics. This article presents the design and characterization of a few core relay-based digital blocks, including an adder and a D-latch. While the mechanical movement of relays makes them inherently slower than transistors, we show that the scaled 32-bit relay adder offers 60 times less energy per operation than its CMOS counterpart in 40-nm technology. This makes the proposed relay circuits particularly appealing to applications with stringent demand on energy efficiency and moderate performance requirements, such as remote sensors, wearable accessories, and implantable biomedical devices.

Analytical and experimental study of the dynamics of a micro-electromechanical resonator based digital-to-analog converter

In this paper, an analytical model of a micro-electromechanical (MEM) resonator used as a 4-bit digital-to-analog converter (DAC) is presented. First, we derive the dynamic equation of the 4-bit DAC device, and the nonlinear governing equation is solved by the Galerkin method combined with a shooting technique to simulate the static response, linear eigenvalue problem, and forced vibration response of the device for various electrostatic actuation cases. Also, we optimize the air gaps in the linear domain to ensure enhanced performance of the DAC. Further, to analyze the operation of the DAC in the nonlinear regime, two experimental samples powered by −2 dBm and −12 dBm AC inputs are examined. Forward and backward frequency sweeps are conducted experimentally and analytically. The proposed analytical results are validated by comparison with experimental data. The results indicate that the presented modeling, simulations, and optimization are effective tools for the design of MEM resonator-based circuits.

Active Chiral Plasmonics: Flexoelectric Control of Nanoscale Chirality

The ability to electrically control the optical properties of metamaterials is an essential capability required for technological innovation. The creation of dynamic electrically tunable metamaterials in the visible and near infrared regions is important for a range of imaging and fiber optic technologies. However, current approaches require complex nanofabrication processes which are incompatible for low‐cost device production. Herein, a novel simple approach is reported for electrical control of optical properties which uses a flexoelectric dielectric element to electromechanically manipulate the form factor of a chiral nanostructure. By altering the dimensions of the chiral nanostructure, the polarization properties of light are allowed to be electrically controlled. The flexoelectric element is part of a composite metafilm that is templated onto a nanostructured polymer substrate. As the flexoelectric element does not require in situ high temperature annealing, it can be readily combined with polymer‐based substrates produced by high throughput methods. This is not the case for piezoelectric elements, routinely used in microelectromechanical (MEM) devices which require high temperature processing. Consequently, combining amorphous flexoelectric dielectrics and low‐cost polymer‐based materials provides a route to the high throughput production of electrically responsive disposable metadevices.

Study of MEM Relay Contact Design and Body-Bias Effects on on-State Resistance Stability

Body-biased micro-electro-mechanical (MEM) relays previously have been demonstrated to be a promising alternative to transistors for ultra-low voltage digital logic applications. A basic requirement for reliable relay-based circuit operation is suitably low and stable relay ON-state resistance (RON). In this work, the effect of body biasing on RON is investigated for relays of different contact designs. It is found that a single direct contact design not only provides for the smallest hysteresis voltage but also the smallest RON, making it the most suitable for low voltage applications. Body-biased operation is found to degrade RON stability over many ON/OFF switching cycles, however, due to a reduction in contact velocity.

Capacitive Accelerometers with Beams Based on Alternated Segments of Different Widths

Microelectromechanical (MEM) Accelerometers measure the accelerations or vibrations experienced by objects due to inertial forces or mechanical excitations. To improve their proof mass displacement, several alternatives have been used, such as the design of different shapes of suspension beams. In this work, a new shape of beam is proposed based on alternated segments of different widths. To analyze its performance, one-quarter, middle and complete accelerometers were calculated and simulated; the results were compared with similar cases using conventional uniform-shaped beams. A notable improvement in the proof mass displacement was obtained in all cases, especially with the proposed symmetrical-shaped beam. Harmonic response and explicit dynamic analysis were also considered to discover performance when they are subjected to structural load. An improvement in amplitude displacement was also observed, as well as operation frequency reduction. From the explicit dynamic analysis, a faster performance of the accelerometer with uniform arms can be observed; however, it responds at a lower range of input velocities. A performance comparison of the proposed beam is presented considering the two reported accelerometers. Finally, from the variation in the width of the thinner segment of the symmetrical arms, it can be observed that it is possible to obtain an increment in the displacement of the proof mass of 39.57% and a decrement in natural frequency of 15.30%, with respect to the case of the uniform arm. Other advantages of the symmetric beam are the stress distribution, reducing its effect on the proof mass, as well as their low cross-axis sensitivity. Simulations were performed with ANSYS.

The buckling and deflection studies of micro-electro-mechanical column and beam structures containing fixed-charges

A micro-electro-mechanical (MEM) beam and column structures are analysed in details in the present work containing fixed charge (+ve or −ve). The transverse deflection of this column, due to the presence of fixed-charge concentration and axial compressive force, is firstly studied (linear elastic and viscoelastic cases). An analytical solution of critical buckling load P supported by MEM column, with initial imperfections due to the presence of fixed-charge in the column (simply-supported), is derived. The variation of P with fixed-charge concentration is finally obtained. A pull-in instability of MEM beam is secondly studied under the influence of external electric field, and a critical voltage V without any instability is obtained varying fixed-charge concentration inside beam. All the presented formulations are extended incorporating finite deformation (von Kármán strain field) setting, as the beam rotation becomes significant at higher fixed-charge values. All the presented results are also verified with the published literature wherever it was possible. The presented work thus can be reasonably employed in the design of MEM micro-switches.

Thermomechanical-Noise-Limited Capacitive Transduction of Encapsulated MEM Resonators

The thermomechanical motion imposes the fundamental noise limit in room-temperature resonant sensors and oscillators. Due to the inherently low sensitivity of capacitive transduction in microelectromechanical (MEM) resonators, its effects are often masked by noise in the subsequent amplifier and measurement stages. In this work, we demonstrate a capacitive transduction scheme for measuring kHz-MHz frequency MEM resonators across 1 $\mu \text{m}$ capacitive gaps with 99.8% thermomechanical-noise-limited resolution. We delineate the transimpedance gain and noise of our custom off-chip differential transimpedance amplifier setup. The thermomechanical noise spectrum can provide estimates of the resonant frequency, quality factor, and electromechanical transduction factor comparable to the commonly used driven response, without the downsides of capacitive feedthrough or nonlinearity. [2019-0115]

Nanoscale Observation of Conformational Transformation of DNA Polymerase via In-Situ Liquid-Cell Transmission Electron Microscopy.

In recent years, liquid-cell transmission electron microscopy (LC-TEM) has been developed as in-situ, dynamic characterization of nanoscale materials in the liquid, although the state-of-art focus is heavy materials such as metals, and alloys. Herein we present a practical and stable liquid cell fabricated with standard micro-electro-mechanical (MEM) processes on silicon wafers. The liquid cell is universal for commonly used TEM holder, which may not only keep the liquid available for several weeks, and it has been also proven protective factor from electron beam damage when characterizing biomolecules such as proteins and DNAs, which are typical light-element molecules. DNA polymerase has been successfully characterized in the physiological state (unlabeled in PBS buffer), providing single molecular resolution, the dynamic structural evolution of the molecules and the complex interactions. Although more understandings of this technique has to be explored in the future, as we have pointed out in the manuscript, this work has illustrated that the LC-TEM can also become a potential and promising strategy, besides to the cryo-TEM technique, in the high-resolution characterization of biomolecules, which may benefit relative researches and industry, such as molecular and structural biology, ecology, pharmacology and environmental sciences.

Demonstration of a microelectromechanical tunable Fabry-Pérot cavity based on graphene-bonded fiber devices.

Taking advantage of the high thermal conductivity of graphene, this Letter demonstrates a microelectromechanical (MEM) tunable Fabry-Pérot (F-P) cavity, based on a graphene-bonded fiber device (GFD), which acts as a microheater. By increasing the electric current from 0 to 8mA in the heater, the temperature of the GFD can rise and approach a value of 760K theoretically. This high temperature will cause a deformation of the fiber, allowing the graphene-bonded fiber end to form a gap-adjustable F-P cavity with a cleaved single-mode fiber. The gap in the cavity can be reduced by increasing the current applied, leading the transmittance of the cavity to change. In this work, a highly sensitive current sensor (5.9×105 nm/A2) and a tunable mode-locked fiber laser (1.2×104 nm/A2) are created based on the MEM tunable F-P cavity.