Nanoelectromechanical Sensors based on Suspended 2D Materials

The unique properties and atomic thickness of two-dimensional (2D) materials enable smaller and better nanoelectromechanical sensors with novel functionalities. During the last decade, many studies have successfully shown the feasibility of using suspended membranes of 2D materials in pressure sensors, microphones, accelerometers, and mass and gas sensors. In this review, we explain the different sensing concepts and give an overview of the relevant material properties, fabrication routes, and device operation principles. Finally, we discuss sensor readout and integration methods and provide comparisons against the state of the art to show both the challenges and promises of 2D material-based nanoelectromechanical sensing.Comment: Review pape

Membrane Platforms for Sensors

AbstractIn the past half century the IC technology could produce an unprecedented growth and penetration into all segments of our daily life due to the achieved extreme productivity and reliability by using well established and continuously refined processing platforms. This uninterrupted trend continued also with the advent of the More than Moore-type MEMS technology allowing the combination of the signal processing capability of the mature IC technology with the exploitation of mechanical, thermal, optical properties of the materials used in IC technology in different sensing and actuation purposes. Mass producibility by monolithic integration required here also the development of appropriate unified set of techniques for the various applications, i.e. sort of standardised platforms to explore.In this paper we focus on the development of bulk micromachined membrane platforms, being exploited in such applications. At the same time this summary also offers a “case study”, a retrospective review of the development of integrable sensors from pressure measurement to nanopore-type, label-free biosensing at the Institute of Technical Physics & Materials Science - MFA, Budapest

A COMPREHENSIVE OVERVIEW OF RECENT DEVELOPMENTS IN RF-MEMS TECHNOLOGY-BASED HIGH-PERFORMANCE PASSIVE COMPONENTS FOR APPLICATIONS IN THE 5G AND FUTURE TELECOMMUNICATIONS SCENARIOS

The goal of this work is to provide an overview about the current development of radio-frequency microelectromechanical systems technology, with special attention towards those passive components bearing significant application potential in the currently developing 5G paradigm. Due to the required capabilities of such communication standard in terms of high data rates, extended allocated spectrum, use of massive MIMO (Multiple-Input-Multiple-Output) systems, beam steering and beam forming, the focus will be on devices like switches, phase shifters, attenuators, filters, and their packaging/integration. For each of the previous topics, several valuable contributions appeared in the last decade, underlining the improvements produced in the state of the art and the chance for RF-MEMS technology to play a prominent role in the actual implementation of the 5G infrastructure

Geometrical Considerations for the Design of Liquid-phase Biochemical Sensors Using a Cantilever\u27s Fundamental In-plane Mode

The influence of the beam geometry on the quality factor and resonance frequency of resonant silicon cantilever beams vibrating in their fundamental in-plane flexural mode in water has been investigated. Compared to cantilevers vibrating in their first out-of-plane flexural mode, utilizing the in-plane mode results in reduced damping and reduced mass loading by the surrounding fluid. Quality factors as high as 86 have been measured in water for cantilevers with a 20 μm thick silicon layer. Based on the experimental data, design guidelines are established for beam dimensions that ensure maximal Q-factors and minimal mass loading by the surrounding fluid, thus improving the limit-of-detection of mass-sensitive biochemical sensors. Elementary theory is also presented to help explain the observed trends. Additional discussion focuses on the tradeoffs that exist in designing liquid-phase biochemical sensors using in-plane cantilevers

Doctor of Philosophy

dissertationThis thesis presents the design, fabrication and characterization of a microelectromechanical system (MEMS) based complete wireless microsystem for brain interfacing, with very high quality factor and low power consumption. Components of the neuron sensing system include TiW fixed-fixed bridge resonator, MEMS oscillator based action-potential-to-RF module, and high-efficiency RF coil link for power and data transmissions. First, TiW fixed-fixed bridge resonator on glass substrate was fabricated and characterized, with resonance frequency of 100 - 500 kHz, and a quality factor up to 2,000 inside 10 mT vacuum. The effect of surface conditions on resonator's quality factor was studied with 10s of nm Al2O3 layer deposition with ALD (atomic layer deposition). It was found that MEMS resonator's quality factor decreased with increasing surface roughness. Second, action-potential-to-RF module was realized with MEMS oscillator based on TiW bridge resonator. Oscillation signal with frequency of 442 kHz and phase noise of -84.75 dBc/Hz at 1 kHz offset was obtained. DC biasing of the MEMS oscillator was modulated with neural signal so that the output RF waveform carries the neural signal information. Third, high-efficiency RF coil link for power and data communications was designed and realized. Based on the coupled mode theory (CMT), intermediate resonance coil was introduced and increased voltage transfer efficiency by up to 5 times. Finally, a complete neural interfacing system was demonstrated with board-level integration. The system consists of both internal and external systems, with wireless powering, wireless data transfer, artificial neuron signal generation, neural signal modulation and demodulation, and computer interface displaying restored neuron signal

RF-MEMS for high-performance and widely reconfigurable passive components – A review with focus on future telecommunications, Internet of Things (IoT) and 5G applications

Abstract Since its first discussions in literature during late '90s, RF-MEMS technology (i.e. Radio Frequency MicroElectroMechanical-Systems) has been showing uncommon potential in the realisation of high-performance and widely reconfigurable RF passives for radio and telecommunication systems. Nevertheless, against the most confident forecasts sparkling around the successful exploitation of RF-MEMS technology in mass-market applications, with the mobile phone segment first in line, already commencing from the earliest years of the 2000s, the first design wins for MEMS-based RF passives have started to be announced just in late 2014. Beyond the disappointment of all the most flattering market forecasts and, on the other hand, the effective employment of RF-MEMS in niche applications (like in very specific space and defence scenarios), there were crucial aspects, not fully considered since the beginning, that impaired the success of such a technology in large-market and consumer applications. Quite unexpectedly, the context has changed rather significantly in recent years. The smartphones market segment started to generate a factual need for highly reconfigurable and high-performance RF passive networks, and this circumstance is increasing the momentum of RF-MEMS technology that was expected to take place more than one decade ago. On a broader landscape, the Internet of Things (IoT) and the even wider paradigm of the Internet of Everything (IoE) seem to be potential fields of exploitation for high-performance and highly reconfigurable passive components in RF-MEMS technology. This work frames the current state of RF-MEMS market exploitation, analysing the main reasons impairing in past years the proper employment of Microsystem technology based RF passive components. Moreover, highlights on further expansion of RF-MEMS solutions in mobile and telecommunication systems will be briefly provided and discussed

Single Substrate Electromagnetic Actuator

A microvalve which utilizes a low temperature ( <300° C.) fabrication process on a single substrate. The valve uses buckling and an electromagnetic actuator to provide a relatively large closing force and lower power consumption. A buckling technique of the membrane is used to provide two stable positions for the membrane, and to reduce the power consumption and the overall size of the microvalve. The use of a permanent magnet is an alternative to the buckled membrane, or it can be used in combination with the buckled membrane, or two sets of micro-coils can be used in order to open and close the valve, providing the capability for the valve to operate under normally opened or normally closed conditions. Magnetic analysis using ANSYS 5.7 shows that the addition of Orthonol between the coils increases the electromagnetic force by more than 1.5 times. At a flow rate of 1 mL/m, the pressure drop is < 100 Pa. The maximum pressure tested was 57 kPa and the time to open or close the valve in air is under 100 ms. This results in an estimated power consumption of 0.1 mW.Georgia Tech Research Corp

Influence Of Environmental Conditions On The Response Of MEMS Resonators

Micro-electro-mechanical-system (MEMS) devices are increasingly employed in physical systems to fill the growing demand for fast, small, cheap sensors. And with MEMS devices rapidly becoming miniaturized to increase accuracy and reduce response time, analysis of their reliability in different environments is increasingly needed. Furthermore, new sensor designs for applications such as temperature, humidity and pressure sensors, that directly utilize the MEMS interactions within their environments, are growing in demand. In this work, a comprehensive study of the response of MEMS cantilever and clamped-clamped resonators under various environmental conditions is performed in both the linear and nonlinear regimes. The study shows a consistent reduction of the natural frequency of cantilever and clamped-clamped MEMS devices due to the increase of humidity under fixed pressure and temperature as a result of decreasing the dynamic viscosity of air. This change is greater at high temperatures and is further increased when thermal stresses build up within the MEMS device or when the device is operated nonlinearly. Moreover, the study presents a possibility to correct for the effects of temperature and humidity due to the linearity around the primary resonance. Finally, this study demonstrates the viability of uncoated sensors for temperature, humidity and pressure sensing. Advisor: Fadi Alsalee