MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

Nonlinear Optical Responsive Molecular Switches

Nonlinear optical (NLO) materials have gained much attention during the last two decades owing to their potentiality in the field of optical data storage, optical information processing, optical switching, and telecommunication. NLO responsive macroscopic devices possess extensive applications in our day to day life. Such devices are considered as assemblies of several macroscopic components designed to achieve specific functions. The extension of this concept to the molecular level forms the basis of molecular devices. In this context, the design of NLO switches, that is, molecules characterized by their ability to alternate between two or more chemical forms displaying contrasts in one of their NLO properties, has motivated many experimental and theoretical works. Thus, this chapter focuses on the rational design of molecular NLO switches based on stimuli and materials with extensive examples reported in the literature. The factors affecting the efficiency of optical switches are discussed. The device fabrication of optical switches and their efficiency based on the optical switch, internal architecture, and substrate materials are described. In the end, applications of switches and future prospectus of designing new molecules with references are suitably discussed

Parylene Based Flexible Multifunctional Biomedical Probes And Their Applications

MEMS (Micro Electro Mechanical System) based flexible devices have been studied for decades, and they are rapidly being incorporated into modern society in various forms such as flexible electronics and wearable devices. Especially in neuroscience, flexible interfaces provide tremendous possibilities and opportunities to produce reliable, scalable and biocompatible instruments for better exploring neurotransmission and neurological disorders. Of all the types of biomedical instruments such as electroencephalography (EEG) and electrocorticography (ECoG), MEMS-based needle-shape probes have been actively studied in recent years due to their better spatial resolution, selectivity, and sensitivity in chronical invasive physiology monitoring. In order to address the inherent issue of invasiveness that causes tissue damage, research has been made on biocompatible materials, implanting methods and probe structural design. In this dissertation, different types of microfabricated probes for various applications are reviewed. General methods for some key fabrication steps include photolithography patterning, chemical vapor deposition, metal deposition and dry etching are covered in detail. Likewise, three major achievements, which aim to the tagets of flexibility, functionality and mechanical property are introduced and described in detail from chapter 3 to 5. The essential fabrication processes based on XeF2 isotropic silicon etching and parylene conformal deposition are covered in detail, and a set of characterization is summarized

Parylene Based Flexible Multifunctional Biomedical Probes And Their Applications

MEMS (Micro Electro Mechanical System) based flexible devices have been studied for decades, and they are rapidly being incorporated into modern society in various forms such as flexible electronics and wearable devices. Especially in neuroscience, flexible interfaces provide tremendous possibilities and opportunities to produce reliable, scalable and biocompatible instruments for better exploring neurotransmission and neurological disorders. Of all the types of biomedical instruments such as electroencephalography (EEG) and electrocorticography (ECoG), MEMS-based needle-shape probes have been actively studied in recent years due to their better spatial resolution, selectivity, and sensitivity in chronical invasive physiology monitoring. In order to address the inherent issue of invasiveness that causes tissue damage, research has been made on biocompatible materials, implanting methods and probe structural design. In this dissertation, different types of microfabricated probes for various applications are reviewed. General methods for some key fabrication steps include photolithography patterning, chemical vapor deposition, metal deposition and dry etching are covered in detail. Likewise, three major achievements, which aim to the tagets of flexibility, functionality and mechanical property are introduced and described in detail from chapter 3 to 5. The essential fabrication processes based on XeF2 isotropic silicon etching and parylene conformal deposition are covered in detail, and a set of characterization is summarized

Glassy Materials Based Microdevices

Microtechnology has changed our world since the last century, when silicon microelectronics revolutionized sensor, control and communication areas, with applications extending from domotics to automotive, and from security to biomedicine. The present century, however, is also seeing an accelerating pace of innovation in glassy materials; as an example, glass-ceramics, which successfully combine the properties of an amorphous matrix with those of micro- or nano-crystals, offer a very high flexibility of design to chemists, physicists and engineers, who can conceive and implement advanced microdevices. In a very similar way, the synthesis of glassy polymers in a very wide range of chemical structures offers unprecedented potential of applications. The contemporary availability of microfabrication technologies, such as direct laser writing or 3D printing, which add to the most common processes (deposition, lithography and etching), facilitates the development of novel or advanced microdevices based on glassy materials. Biochemical and biomedical sensors, especially with the lab-on-a-chip target, are one of the most evident proofs of the success of this material platform. Other applications have also emerged in environment, food, and chemical industries. The present Special Issue of Micromachines aims at reviewing the current state-of-the-art and presenting perspectives of further development. Contributions related to the technologies, glassy materials, design and fabrication processes, characterization, and, eventually, applications are welcome

Technological challenges in the development of optogenetic closed-loop therapy approaches in epilepsy and related network disorders of the brain

Epilepsy is a chronic, neurological disorder affecting millions of people every year. The current available pharmacological and surgical treatments are lacking in overall efficacy and cause side-effects like cognitive impairment, depression, tremor, abnormal liver and kidney function. In recent years, the application of optogenetic implants have shown promise to target aberrant neuronal circuits in epilepsy with the advantage of both high spatial and temporal resolution and high cell-specificity, a feature that could tackle both the efficacy and side-effect problems in epilepsy treatment. Optrodes consist of electrodes to record local field potentials and an optical component to modulate neurons via activation of opsin expressed by these neurons. The goal of optogenetics in epilepsy is to interrupt seizure activity in its earliest state, providing a so-called closed-loop therapeutic intervention. The chronic implantation in vivo poses specific demands for the engineering of therapeutic optrodes. Enzymatic degradation and glial encapsulation of implants may compromise long-term recording and sufficient illumination of the opsin-expressing neural tissue. Engineering efforts for optimal optrode design have to be directed towards limitation of the foreign body reaction by reducing the implant’s elastic modulus and overall size, while still providing stable long-term recording and large-area illumination, and guaranteeing successful intracerebral implantation. This paper presents an overview of the challenges and recent advances in the field of electrode design, neural-tissue illumination, and neural-probe implantation, with the goal of identifying a suitable candidate to be incorporated in a therapeutic approach for long-term treatment of epilepsy patients

Optical MEMS

Optical microelectromechanical systems (MEMS), microoptoelectromechanical systems (MOEMS), or optical microsystems are devices or systems that interact with light through actuation or sensing at a micro- or millimeter scale. Optical MEMS have had enormous commercial success in projectors, displays, and fiberoptic communications. The best-known example is Texas Instruments’ digital micromirror devices (DMDs). The development of optical MEMS was impeded seriously by the Telecom Bubble in 2000. Fortunately, DMDs grew their market size even in that economy downturn. Meanwhile, in the last one and half decade, the optical MEMS market has been slowly but steadily recovering. During this time, the major technological change was the shift of thin-film polysilicon microstructures to single-crystal–silicon microsructures. Especially in the last few years, cloud data centers are demanding large-port optical cross connects (OXCs) and autonomous driving looks for miniature LiDAR, and virtual reality/augmented reality (VR/AR) demands tiny optical scanners. This is a new wave of opportunities for optical MEMS. Furthermore, several research institutes around the world have been developing MOEMS devices for extreme applications (very fine tailoring of light beam in terms of phase, intensity, or wavelength) and/or extreme environments (vacuum, cryogenic temperatures) for many years. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on (1) novel design, fabrication, control, and modeling of optical MEMS devices based on all kinds of actuation/sensing mechanisms; and (2) new developments of applying optical MEMS devices of any kind in consumer electronics, optical communications, industry, biology, medicine, agriculture, physics, astronomy, space, or defense

Application of [Ba. sub. 0.5][Sr. sub. 0.5] Ti [O. sub. 3](Bst) Film Doped with 0%, 2%, 4% and 6% Concentrations of Ru [O. sub. 2] as an Arduino Nano-Based Bad Breath Sensor

Ba0.5Sr0.5TiO3 (BST) film doped with variations in RuO2 concentration (0%, 2%, 4%, and 6%) has been successfully grown on a type-p silicon substrate (100) using the chemical solution deposition (CSD) method and spin-coating at a speed of 3000 rpm for 30 s. The film on the substrate was then heated at 850 °C for 15 h. The sensitivity of BST film + RuO2 variations as a gas sensor were characterized. The sensitivity characterization was assisted by various electronic circuitry with the purpose of producing a sensor that is very sensitive to gas. The responses from the BST film + RuO2 variation were varied, depending on the concentration of the RuO2 dope. BST film doped with 6% RuO2 had a very good response to halitosis gases; therefore, this film was applied as the Arduino-Nano-based bad-breath detecting sensor. Before it was integrated with the microcontroller, the voltage output of the BST film was amplified using an op-amp circuit to make the voltage output from the BST film readable to the microcontroller. The changes in the voltage response were then shown on the prototype display. If the voltage output was ≤12.9 mV, the display would read “bad breath”. If the voltage output >42.1 mV, the display would read “fragrant”. If 12.9 mV < voltage output ≤ 42.1 mV, the display would read “normal”

MEMS tunable infrared metamaterial and mechanical sensors

Sub-wavelength resonant structures open the path for fine controlling the near-field at the nanoscale dimension. They constitute into macroscopic “metamaterials” with macroscale properties such as transmission, reflection, and absorption being tailored to exhibit a particular electromagnetic response. The properties of the resonators are often fixed at the time of fabrication wherein the tunability is demanding to overcome fabrication tolerances and afford fast signal processing. Hybridizing dynamic components such as optically active medium into the device makes tunable devices. Microelectromechanical systems (MEMS) compatible integrated circuit fabrication process is a promising platform that can be merged with photonics or novel 2D materials. The prospect of enormous freedom in integrating nanophotonics, MEMS actuators and sensors, and microelectronics into a single platform has driven the rapid development of MEMS-based sensing devices. This thesis describes the design and development of four tunable plasmonic structures based on active media or MEMS, two graphene-based MEMS sensors and a novel tape-based cost-effective nanotransfer printing techniques. First of all, we present two tunable plasmonic devices with the use of two active medium, which are electrically controlled liquid crystals and temperature-responsive hydrogels, respectively. By incorporating a nematic liquid crystal layer into quasi-3D mushroom plasmonic nanostructures and thanks to the unique coupling between surface plasmon polariton and Rayleigh anomaly, we have achieved the electrical tuning of the properties of plasmonic crystal at a low operating electric field. We also present another tunable plasmonic device with the capability to sense environmental temperature variations. The device is bowtie nanoantenna arrays coated with a submicron-thick, thermos-responsive hydrogel. The favorable scaling of plasmonic dimers at the nanometer scale and ionic diffusion at the submicron scale is leveraged to achieve strong optical resonance and rapid hydrogel response, respectively. Secondly, we present two MEMS -based tunable near-to-mid infrared metamaterials on a silicon-on-insulator wafer via electrically and thermally actuating the freestanding nanocantilevers. The two devices are developed on the basis of the same fabrication process and are easy-to-implement. The electrostatically driven metamaterial affords ultrahigh mechanical modulation (several tens of MHz) of an optical signal while the thermo-mechanically tunable metamaterial provides up to 90% optical signal modulation at a wavelength of 3.6 õm. Next, we present MEMS graphene-based pressure and gas flow sensors realized by transferring a large area and few-layered graphene onto a suspended silicon nitride thin membrane perforated with micro-through-holes. Due to the increased strain in the through-holes, the pressure sensor exhibits a very high sensitivty outperformed than most existing MEMS-based pressure sensors using graphene, silicon, and carbon nanotubes. An air flow sensor is also demonstrated via patterning graphene sheets with flow-through microholes. The flow rate of the air is measured by converting the mechanically deflection of the membrane into the electrical readout due to the graphene piezeroresistors. Finally, we present a tape-based multifunctional nanotransfer printing process based on a simple stick-and-peel procedure. It affords fast production of large-area metallic and dielectric nanophotonic sensing devices and metamaterials using Scotch tape

Performance of Smart Materials-Based Instrumentation for Force Measurements in Biomedical Applications: A Methodological Review

The introduction of smart materials will become increasingly relevant as biomedical technologies progress. Smart materials sense and respond to external stimuli (e.g., chemical, electrical, mechanical, or magnetic signals) or environmental circumstances (e.g., temperature, illuminance, acidity, or humidity), and provide versatile platforms for studying various biological processes because of the numerous analogies between smart materials and biological systems. Several applications based on this class of materials are being developed using different sensing principles and fabrication technologies. In the biomedical field, force sensors are used to characterize tissues and cells, as feedback to develop smart surgical instruments in order to carry out minimally invasive surgery. In this regard, the present work provides an overview of the recent scientific literature regarding the developments in force measurement methods for biomedical applications involving smart materials. In particular, performance evaluation of the main methods proposed in the literature is reviewed on the basis of their results and applications, focusing on their metrological characteristics, such as measuring range, linearity, and measurement accuracy. Classification of smart materials-based force measurement methods is proposed according to their potential applications, highlighting advantages and disadvantages