Thermal Microelectromechanical Systems Research Articles

Analysis of Thermal Characteristics of MEMS Sensors for Measuring the Rolling Period of Maritime Autonomous Surface Ships

Recently, with the emergence of maritime autonomous surface ships (MASS), ensuring seaworthiness has increased with the operation of MASS. Ship stability is important for safety, and technical methods for controlling a ship’s motion are required to evaluate the stability. A ship’s rolling period is estimated using microelectromechanical systems (MEMS) sensors to measure the ship’s metacentric height. However, weather changes (e.g., temperature) are drastic due to various marine environments in the sea. Hence, it is necessary to analyze MEMS sensors’ thermal characteristics for applying them to MASS. This study aims to analyze the thermal characteristics of a siX-axis MEMS sensor for its application in MASS. The experiments analyzed measurement errors and noise at six steps in the range of 25–75 °C in which the MEMS sensor can be operated. The experimental results showed that the gyroscope’s thermal error and MEMS sensor’s noise level were much larger than those of the accelerometer and the respective thermal error values along the Z-axis of the accelerometer and gyroscope were the most stable compared to those along the other axes. The findings can be applied to a measurement method of the stability of MASS employing MEMS sensors in navigation equipment.

Numerical analysis and RSM modeling of microthermal flowmeter performance

Thermal MEMS (micro-electro-mechanical system) flowmeter is one of the recent most popular flowmeters, in which its sensitivity to flow rate variations could be improved by various methods. This work aims at examining the effects of the microchannel (height (hc) and width (Wc)) and micro-heater serpentines (number (ns) and width (Ws)) dimensions on power consumption and sensitivity of micro-thermoresistive flowmeters by two numerical approaches. For the first time, a mathematical correlation has been introduced by response surface methodology (RSM) to compute the flowmeter sensitivity and power consumption in terms of geometrical parameters. Based on computational fluid dynamics (CFD) and RSM results, ns and hc have the most and the least impact on the sensitivity, respectively. Furthermore, the simultaneous influences of hc and Wc illustrated that the flowmeter saturation occurs at a specific quantity of Wc under different hc values. A reduction in hc, Wc, ns, and Ws prompt a maximum increment of 28%, 41%, 80%, and maximum decrement of 33% in sensitivity, respectively. Increment of Wc and ns have the most influence on the power consumption with a maximum reduction of 50% and 85%. Finally, two configurations with 5-day and 8-day battery life were introduced by results’ optimization.

A monolithic three-dimensional thermal convective acoustic vector sensor with acoustic-transparent heat sink.

An acoustic vector sensor can directly detect acoustic particle velocity based on the measured temperature difference between closely spaced heated wires. For the detection of velocity in three dimensions, an integrated three-dimensional (3 D) sensor is desired, but it remains challenging in MEMS (Micro-Electro-Mechanical System) manufacturing. Here, a novel monolithic 3 D acoustic vector sensor is proposed, which is constructed using in-plane distributed wires assembled with acoustically transparent heat sink. The planar MEMS structure of the proposed sensor makes it easy to be fabricated and packaged. This work offers a new method for the design of acoustic vector sensors and other thermal convection-based MEMS sensors.

Comparative Study on Modeling Approaches of V-Shaped MEMS Temperature Sensors

Thermal microelectromechanical system (MEMS) devices have gained immensely in popularity due to their good performances, relatively simple fabrication process, and to the availability of modeling tools. In this paper, the modeling results of several models were compared and the ability of each to reliably assess the performances of V-shaped thermal MEMS devices was investigated. The results of several models, in which the governing equations of motion were directly solved, were compared to those obtained from nonlinear large-deflection 3-D finite element analysis that was verified experimentally. The models were modified by including the temperature-dependent properties of the material of the device. In addition, a numerical iterative force control solution scheme was developed and used to predict the performances of V-shaped devices. Important parameters of V-shaped devices, such as apex deflection, stiffness, and output force, were evaluated in terms of the applied temperature and device geometry. In addition, the feasibility of capacitive sensing was demonstrated and high signal-to-noise ratio was calculated. Finally, the influence of microfabrication tolerances and internal stress on the performances of the devices were studied. Therefore, this paper will help future researchers and designers to assess the reliability of models of thermal MEMS devices and better evaluate device performance.

Analysis of a Chevron Beam Thermal Actuator

Thermal MEMS (Micro-Electro-Mechanical Systems) actuators and sensors have a wide range of applications. The chevron type thermal actuators comparatively show superior performance over other existing electrostatic and thermal actuators. This paper describes the design and analysis of chevron type thermal actuator. Here standard design of Chevron type thermal actuator is considered which comprises of proof mass at center and array of six beams of a uniform cross section of 3 3 microns and an initial angle of 5°. The thermal actuator was designed and analyzed using analytical and finite element method and the results were compared. The model was also analyzed for initial angles of 2.5° and 7.5°, and the results were compared with FEA model. The cross section of the beam was varied and the finite element analysis of all three models was compared to suggest the best suitable thermal actuator structure.

Novel DC-40 GHz MEMS series-shunt switch for high isolation and high power applications

This paper presents the design, fabrication, and characterization of a lateral contact series-shunt ohmic RF microelectromechanical systems (MEMS) switch actuated by an electrothermal actuator. Since the proposed RF MEMS switch is actuated electrothermally, it can be operated at an extremely low operation voltage of 0.16V. In this switch, two series switches are cascaded by a quarter wavelength section of transmission line suspended over the trench of the substrate to form a series-shunt configuration according to the principle of impedance transforming. By using a single bidirectional thermal MEMS actuator to control the signal, the switch provides higher reliability when through high power microwave signal. The measured results show that an insertion loss of 1.2dB or better is achieved from DC-40GHz. The isolation is −50dB at 5GHz, −45dB at 20GHz and −60dB at 35GHz. What is more, this switch also exhibits high linearity, and high power handing for DC-40-GHz applications. In the switch OFF state, self-actuation does not happen up to the input power of 40dBm at 1GHz. In the switch ON state, no significant insertion loss variations or problems in the contacts, due to the RF power, can be observed below 31dBm input power.

Molecular Dynamics Simulation of Diffusion Behavior for Thermalplastic Fusion Bonding

As a convenient way for the assembly of thermal plastic MEMS (Micro Electro-Mechanical Systems) devices fusion bonding was studied in molecular level. The diffusion behavior of polymer molecular chains was simulated by molecular dynamics. Amorphous PMMA (poly methyl methacrylate) layer were constructed. The interaction of PMMA layers in heating and cooling stages were simulated in NPT ensemble. In the simulation the PMMA molecular chains spread across the interface and entangled with the chains in the other layers. The factors including pressure and temperature which play important role in fusion bonding were analyzed in molecular level. System deformation was recorded in heating and cooling progress. Diffusion depth and binding energy in the model which had experienced heating and cooling simulation were obtained to investigate fusion degree. Deformation and fusion degree increase with larger pressure and higher temperature imposed to the system. It is concluded that only considering the diffusion of molecular chains parameters of relatively small pressure and high temperature are necessary to obtain precise bonding for micro joint, which is significant in guiding the precise bonding for micro assembly.

Thermal-Fluid MEMS Devices: A Decade of Progress and Challenges Ahead

Microdevices are becoming more prevalent and important in current and future technologies. Over the past decade, countless studies have been conducted in developing thermal microdevices. This paper focuses on the progress of research made during the last decade regarding heat transfer and fluid flow in microheat sinks, micropumps, microturbines, microengines, micromixers, as well as microsensors. Recent experimental techniques in the thermal microelectromechanical systems (MEMS) field have also been presented. Although some thermal MEMS devices have penetrated the commercial market, the mass implementation of thermal MEMS devices in future technology is still quite far, and is highly desirable. During the next decade, vast amounts of research need to be conducted before other microdevices can infiltrate the mainstream. Possible future directions of research have also been provided.

The fabrication of micro-heaters with low-power consumption using SOI and trench structures

This paper presents the optimized design, fabrication and thermal characteristics of micro-heaters for thermal MEMS (micro electro mechanical system) applications using SOI and trench structures. The micro-heaters are based on a thermal measurement principle and contain thermal isolation regions of 10 μm-thick Si membranes consisting of oxide-filled trenches in the SOI membrane rim. The micro-heaters were fabricated with Pt-RTD on the same substrate via the MgO buffer layer between the Pt thin-film and SiO2 layer. The thermal characteristics of the micro-heaters with trench-free SOI membrane structure was 280°C at an input power of 0.9 W; in the presence of 10 trenches, it was 580°C due to the reduction of the external thermal loss. Therefore, a micro-heater with trenches in the SOI membrane rim structure provides a powerful and versatile alternative technology for enhancing the performance of micro-thermal sensors and actuators.

Microbeams with Electronically Controlled High Thermal Impedance

In some MEMS (Micro-Electro-Mechanical Systems) applications, a tradeoff much be reached between the mechanical strength of a suspended microstructure and the thermal losses through the support beams. This is typically the case of suspended thermal MEMS, a major domain of application of CMOS-compatible bulk-micromachining technologies. This paper illustrates how suspended MEMS can be strengthened by means of additional support beams which can have a very high thermal impedance, thus having a very small impact in the thermal behavior of the microstructure. The high thermal impedance of a support beam is achieved through self-heating: an electronic control monitors the temperature drop and heats up the beam to reduce the heat flow. The control electronics of a beam is implemented using a single high-gain stage with auto-zeroing. A High Thermal Impedance Beam (HTIB) can be considered as a new MEMS design cell. We illustrate the use of this cell in the design of an Electro-Thermal Converter with long time constant, requiring several HTIB cells which can share the same control electronics. A single low-frequency high-gain stage is used, achieving 60 dB DC gain and DC offset and broadband noise below 100 μV, which is suitable for the ETC application.