Micro-opto-electro-mechanical Systems Research Articles

Photonic Crystals Fabricated by Two-Photon Polymerization with Mechanical Defects

One-dimensional photonic crystals have been used in sensing applications for decades, due to their ability to induce highly reflective photonic bandgaps. In this study, one-dimensional photonic crystals with alternating low- and high-density layers were fabricated from a single photosensitive polymer (IP-Dip) by two-photon polymerization. The photonic crystals were modified to include a central defect layer with different elastic properties compared to the surrounding layers, for the first time. It was observed that the defect mode resonance can be controlled by compressive force. Very good agreement was found between the experimentally measured spectra and the model data. The mechanical properties of the flexure design used in the defect layer were calculated. The calculated spring constant is of similar magnitude to those reported for microsprings fabricated on this scale using two-photon polymerization. The results of this study demonstrate the successful control of a defect resonance in one-dimensional photonic crystals fabricated by two-photon polymerization by mechanical stimuli, for the first time. Such a structure could have applications in fields, such as micro-robotics, and in micro-opto–electro–mechanical systems (MOEMSs), where optical sensing of mechanical fluctuations is desired.

All Optical Integrated MOEMS Optical Coherence Tomography System

Integrating all optical components of an optical coherence tomography (OCT) device into a single chip is non-trivial and a challenging job. The design and development of such a lab-on-a chip is possible only via Micro-Opto-Electro-Mechanical System (MOEMS) technology. The reproducible and integrated optical device fabrication would reduce cost and size many folds as compared to bulk or fiber optic OCT system. A miniaturized OCT of size less than 5mm2 area is designed, simulated, and optimized. The successful fabrication of this device would help in point-of-contact devices as well as embedded biomedical sensor applications. Also, the design promises the possibility of fabrication of all optical components of OCT integrated into a single chip.

Design and Development of a MOEMS Accelerometer Using SOI Technology.

The micro-electromechanical system (MEMS) sensors are suitable devices for vibrational analysis in complex systems. The Fabry-Pérot interferometer (FPI) is used due to its high sensitivity and immunity to electromagnetic interference (EMI). Here, we present the design, fabrication, and characterization of a silicon-on-insulator (SOI) MEMS device, which is embedded in a metallic package and connected to an optical fiber. This integrated micro-opto-electro-mechanical system (MOEMS) sensor contains a mass structure and handle layers coupled with four designed springs built on the device layer. An optical reading system using an FPI is used for displacement interrogation with a demodulation technique implemented in LabVIEW®. The results indicate that our designed MOEMS sensor exhibits a main resonant frequency of 1274 Hz with damping ratio of 0.0173 under running conditions up to 7 g, in agreement with the analytical model. Our experimental findings show that our designed and fabricated MOEMS sensor has the potential for engineering application to monitor vibrations under high-electromagnetic environmental conditions.

Highly Sensitive Micro-Opto-Electromechanical Systems Accelerometer Based on MIM Waveguide Wavelength Modulation

In this article, a novel micro-opto-electro- mechanical system (MOEMS) accelerometer sensor based on metal–insulator–metal (MIM) waveguide wavelength modulation is proposed. The device senses the vibration signal of external acceleration by the mechanical sensing system and uses the MIM waveguide in the optical sensing system to sense the displacement of the mechanical vibration component to cause the change of the light wavelength. The characteristics of the optical sensing system and the mechanical sensing system of the MOEMS accelerometer are analyzed by the finite-difference time-domain (FDTD) and finite-element analysis (FEA) methods, respectively. The simulation results show that the proposed accelerometer sensor has an optical system sensitivity of up to 7.827 in the wavelength modulation range of 1– <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$12~\mu \text{m}$ </tex-math></inline-formula> , a mechanical sensitivity of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.292963~\mu \text{m}$ </tex-math></inline-formula> /g, a natural frequency of 939.28 Hz, and a linear measurement range of ±4.4 g. Surprisingly, we obtained accelerometer sensitivity up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.293~\mu \text{m}$ </tex-math></inline-formula> /g and resolution up to 436.1 ng ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\delta \lambda ={1}$ </tex-math></inline-formula> pm). We also show the performance advantages of this accelerometer with high sensitivity and high resolution over the measurement range by comparing this MOEMS accelerometer sensor with previously reported work. Based on these performance characteristics, we expect this work to be widely used in high-precision measurements for inertial navigation.

Microfluidic devices for photo-and spectroelectrochemical applications

The review presents recent developments in electrochemical devices for photo- and spectroelectrochemical investigations, with the emphasis on miniaturization (i.e., nanointerdigitated complementary metal-oxide-semiconductor devices, micro- and nano-porous silicon membranes or microoptoelectromechanical systems), silica glass/microreactors (i.e., plasmonic, Raman spectroscopy or optical microcavities) or polymer-based devices (i.e., 3D-printed, laser-engraved channels). Furthermore, we have evaluated inter alia the efficiency of various fabrication approaches for bioelectrochemical systems, biocatalysis, photochemical synthesis, or single nanoparticle spectroelectrochemistry. We envisioned the miniaturization of applied techniques such as cathodoluminescence, surface plasmon resonance, surface-enhanced Raman spectroscopy, voltametric and amperometric methods in the spectroelectrochemical microdevices. The research challenges and development perspectives of microfluidic, and spectroelectrochemical devices were also elaborated on.

A Thermal and Electro-Magnetic Hybrid MOEMS Microscanner With Integrated Spatial Light Modulation and Metalens for Resolution Enhancement of Infrared Imaging Systems

This article describes the development of a novel integrated thermal and electromagnetic hybrid microoptoelectro mechanical system (MOEMS)-based scanning actuator. Determining the optical architecture and components used for scanning are significant points of the study. A metalens and a coded mask, both of which can be produced by microfabrication methods, are used in the optical part of the actuator. In this context, a metalens consisting of nanoholes was designed and fabricated as the first alternative. Second, a specific coded mask was designed and applied to the center of the MOEMS structure for obtaining spatial light modulation. Captured scene images including the coded mask are processed and reconstructed by using the compressive sensing image processing algorithms. Silicon-on-insulator (SOI) is the substrate of structure and deep reactive ion and wet etching methods were used to fabricate the integrated actuator. To increase the optical transmission, the optically transmissive coded mask zone was coated with antireflective coating at the midwave infrared band. The magnetic field for obtaining Lorentz force on the actuators was achieved by using the neodymium permanent magnet located beneath the structure.

Design and Fabrication of a Differential MOEMS Accelerometer Based on Fabry–Pérot Micro-Cavities

In this paper, a differential MOEMS accelerometer based on the Fabry-Perot (FP) micro-cavities is presented. The optical system of the device consists of two FP cavities and the mechanical system is composed of a proof mass that is suspended by four springs. The applied acceleration tends to move the PM from its resting position. This mechanical displacement can be measured by the FP interferometer formed between the proof mass cross-section and the optical fiber end face. The proposed sensor is fabricated on a silicon on insulator (SOI) wafer using the bulk micromachining method. The results of the sensor characterization show that the accelerometer has a linear response in the range of 1g. Also, the optical sensitivity and resolution of the sensor in the static characterization are 6.52 nm/g and 153ug. The sensor sensitivity in the power measurement is 49.6 mV/g and its resonant is at 1372 Hz. Using the differential measurement method increases the sensitivity of the accelerometer. Based on experimental data, the sensor sensitivity is two times as high as that of a similar MOEMS accelerometer with one FP cavity.

A High-Speed Chip-Scale Rotary Polygon Optical Scanner Based on a Micromotor Integrated With a Micro-Polyhedron Mirror

Micro-opto-electro-mechanical systems (MOEMS) based mirrors with a suitable actuation range are often used for optical beam scanning applications. While several MOEMS scanners have been reported, they often have limitations with respect to their range of motion, field of view, mass, size and fabrication cost. In this work, we present a rotary micro-polygon scanner based on an electrostatic variable capacitance micromotor for laser beam steering applications. The miniaturized scanner consists of a hollow micro-polyhedron mirror with a base radius of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$200 {\mu }\text{m}$ </tex-math></inline-formula> and a height of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$400 {\mu }\text{m}$ </tex-math></inline-formula> . It is mounted on the rotor of a variable capacitance micromotor using an epoxy-based adhesive. The rotor has a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$600 {\mu }\text{m}$ </tex-math></inline-formula> and is <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$2.5 {\mu }\text{m}$ </tex-math></inline-formula> thick. The micromotor was fabricated using a commercial three-layer polysilicon surface micro-machining process (PolyMUMPs) and the micro-polyhedrons were fabricated using a commercial bulk micro-machining process (PiezeoMUMPs). After fabrication of the components, the micro-scanner was assembled and operated under atmospheric conditions using a three-phase square wave excitation ranging from 0 V to 200 V and achieved rotational speeds of up to 2100 rpm. An optical laser beam with a wavelength of 632 nm was reflected off the sidewall of the rotating micro-polyhedron, achieving an experimentally measured scanning angular range of 57.88°, an angular scan rate of 220 radians per second and a scan speed of 25,200 lines per minute or 420 lines per second with a 12 sided micro-mirror. The ratio of the output power over the input optical power is measured over a scanning range of 22°, which is limited by the size of the photo-detector, yielding a ratio spanning from 0.18 to 0.22. This rotary micro-scanner can provide high scanning speeds and a wide scanning field of view with a footprint of 1.25 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and a thickness of 0.83 mm, which is suitable to implement chip-level high-performance micro-beam steering systems for various applications. [2022-0020]

Monolithic Integrated Micro-Opto-Electromechanical Accelerometer Based On Michelson Interferometer Structure

In this paper, we design a monolithic integrated micro-opto-electromechanical system(MOEMS) accelerometer based on the Michelson interferometer structure. The accelerometer realizes the on-chip integration of the mode spot converter, the sensing optical path, the phase modulator and the photonic crystal reflector, and it senses the external acceleration through a “three-beam” structure which is composed of a central support beam and two tiny beams. The push-pull structure eliminates the coupling crosstalk caused by paraxial acceleration. Accurate results are demonstrated as follows: an accelerometer mechanical sensitivity of 3.638 nm/g, with a resonance frequency of 1742.2 Hz and a linear measurement range of ± 500 g, corresponding to a foot print of the core part with 960 μm×600 μm. With its high precision, large measurement range, and small size, the proposed accelerometer may pave the way for the applications in civil, industrial and military fields.

Micro-opto-electro-mechanical systems accelerometer based on the Talbot effect of double-layer diffraction gratings.

In this paper, we present the design, fabrication, and test of a micro-opto-electro-mechanical systems (MOEMS) accelerometer based on the Talbot effect of double-layer diffraction gratings. The detection of acceleration is realized by using the highly sensitive displacement characteristic of Talbot imaging of near-field diffraction with double-layer gratings. For the purpose of obtaining optimal contrast of the optical interferometric detection, the parameters of the gratings are optimized by the finite-difference time-domain (FDTD) simulation. The experimental results indicate that this MOEMS accelerometer with the proposed design can achieve a resolution of 246 µg, sensitivity of 6.1 V/g, and bias stability of 0.02 mg. The proposed accelerometer can be operated at higher accelerations (∼80g), which shows significant potential for being used in applications that require detection of strong and fast vibrations, especially in vibration sensing of vehicles and geophysical seismic sensing in real time.

Closed-loop MOEMS accelerometer.

In this paper, a closed-loop micro-opto-electro-mechanical system (MOEMS) accelerometer based on the Fabry-Pérot (FP) interferometer is presented. The FP cavity is formed between the end of a cleaved single-mode optical fiber and the cross-section of a proof mass (PM) which is suspended by four U-shaped springs. The applied acceleration tends to move the PM in the opposite direction. The arrays of fixed and movable comb fingers produce an electrostatic force which keeps the PM in its resting position. The voltage that can provide this electrostatic force is considered as the output of the sensor. Using a closed-loop detection method it is possible to increase the measurement range without losing the resolution. The proposed sensor is fabricated on a silicon-on-insulator wafer using the bulk micromachining method. The results of the sensor characterization show that the accelerometer has a linear response in the range of ±5 g. In the closed-loop mode, the sensitivity and bias instability of the sensor are 1.16 V/g and 40 µg, respectively.

Miniaturized NIR Spectroscopy in Food Analysis and Quality Control: Promises, Challenges, and Perspectives.

The ongoing miniaturization of spectrometers creates a perfect synergy with the common advantages of near-infrared (NIR) spectroscopy, which together provide particularly significant benefits in the field of food analysis. The combination of portability and direct onsite application with high throughput and a noninvasive way of analysis is a decisive advantage in the food industry, which features a diverse production and supply chain. A miniaturized NIR analytical framework is readily applicable to combat various food safety risks, where compromised quality may result from an accidental or intentional (i.e., food fraud) origin. In this review, the characteristics of miniaturized NIR sensors are discussed in comparison to benchtop laboratory spectrometers regarding their performance, applicability, and optimization of methodology. Miniaturized NIR spectrometers remarkably increase the flexibility of analysis; however, various factors affect the performance of these devices in different analytical scenarios. Currently, it is a focused research direction to perform systematic evaluation studies of the accuracy and reliability of various miniaturized spectrometers that are based on different technologies; e.g., Fourier transform (FT)-NIR, micro-optoelectro-mechanical system (MOEMS)-based Hadamard mask, or linear variable filter (LVF) coupled with an array detector, among others. Progressing technology has been accompanied by innovative data-analysis methods integrated into the package of a micro-NIR analytical framework to improve its accuracy, reliability, and applicability. Advanced calibration methods (e.g., artificial neural networks (ANN) and nonlinear regression) directly improve the performance of miniaturized instruments in challenging analyses, and balance the accuracy of these instruments toward laboratory spectrometers. The quantum-mechanical simulation of NIR spectra reveals the wavenumber regions where the best-correlated spectral information resides and unveils the interactions of the target analyte with the surrounding matrix, ultimately enhancing the information gathered from the NIR spectra. A data-fusion framework offers a combination of spectral information from sensors that operate in different wavelength regions and enables parallelization of spectral pretreatments. This set of methods enables the intelligent design of future NIR analyses using miniaturized instruments, which is critically important for samples with a complex matrix typical of food raw material and shelf products.

Integration of Multifocal Microlens Array on Silicon Microcantilever via Femtosecond-Laser-Assisted Etching Technology.

Micro-opto-electromechanical systems (MOEMSs) are a new class of integrated and miniaturized optical systems that have significant applications in modern optics. However, the integration of micro-optical elements with complex morphologies on existing micro-electromechanical systems is difficult. Herein, we propose a femtosecond-laser-assisted dry etching technology to realize the fabrication of silicon microlenses. The size of the microlens can be controlled by the femtosecond laser pulse energy and the number of pulses. To verify the applicability of this method, multifocal microlens arrays (focal lengths of 7–9 μm) were integrated into a silicon microcantilever using this method. The proposed technology would broaden the application scope of MOEMSs in three-dimensional imaging systems.

Review on Metasurfaces: An Alternative Approach to Advanced Devices and Instruments

This paper reviews the-state-of-the-art of electromagnetic (EM) metasurfaces and emergent applications in advanced integrated devices and instruments from the design method to physical implementation. The design method includes the analytical coupled mode theory model and commonly used building blocks to construct functional metasurfaces. The modeling approach creates a common design basis of metasurface devices for optical beam steering, focusing, modulation, lasing, and detection. The proof of concept of metasurfaces has been established and is translating to practical applications. Previous studies demonstrated promising applications of metasurfaces including but not limited to optical imaging instruments, biochemical sensing devices, and multifunctional microoptoelectromechanical systems (MOEMS). Significant performance improvement of devices and instruments has been achieved due to the implementation of specially tailored metasurfaces. This review provides an alternative for researchers to step forward on the way of advancing devices and instruments by the deployment of metasurfaces.

A Comprehensive Review on the Optical Micro-Electromechanical Sensors for the Biomedical Application.

This study presented an overview of current developments in optical micro-electromechanical systems in biomedical applications. Optical micro-electromechanical system (MEMS) is a particular class of MEMS technology. It combines micro-optics, mechanical elements, and electronics, called the micro-opto electromechanical system (MOEMS). Optical MEMS comprises sensing and influencing optical signals on micron-level by incorporating mechanical, electrical, and optical systems. Optical MEMS devices are widely used in inertial navigation, accelerometers, gyroscope application, and many industrial and biomedical applications. Due to its miniaturised size, insensitivity to electromagnetic interference, affordability, and lightweight characteristic, it can be easily integrated into the human body with a suitable design. This study presented a comprehensive review of 140 research articles published on photonic MEMS in biomedical applications that used the qualitative method to find the recent advancement, challenges, and issues. The paper also identified the critical success factors applied to design the optimum photonic MEMS devices in biomedical applications. With the systematic literature review approach, the results showed that the key design factors could significantly impact design, application, and future scope of work. The literature of this paper suggested that due to the flexibility, accuracy, design factors efficiency of the Fibre Bragg Grating (FBG) sensors, the demand has been increasing for various photonic devices. Except for FBG sensing devices, other sensing systems such as optical ring resonator, Mach-Zehnder interferometer (MZI), and photonic crystals are used, which still show experimental stages in the application of biosensing. Due to the requirement of sophisticated fabrication facilities and integrated systems, it is a tough choice to consider the other photonic system. Miniaturisation of complete FBG device for biomedical applications is the future scope of work. Even though there is a lot of experimental work considered with an FBG sensing system, commercialisation of the final FBG device for a specific application has not been seen noticeable progress in the past.

Wideband MOEMS for the Calibration of Optical Readout Systems.

The paper proposes a technology based on UV-LIGA process for microoptoelectromechanical systems (MOEMS) manufacturing. We used the original combination of materials and technological steps, in which any of the materials does not enter chemical reactions with each other, while all of them are weakly sensitive to the effects of oxygen plasma. This made it suitable for long-term etching in the oxygen plasma at low discharge power with the complete preservation of the original geometry, including small parts. The micromembranes were formed by thermal evaporation of Al. This simplified the technique compared to the classic UV-LIGA and guaranteed high quality and uniformity of the resulting structure. To demonstrate the complete process, a test MOEMS with electrostatic control was manufactured. On one chip, a set of micromembranes was created with different stiffness from 10 nm/V to 100 nm/V and various working ranges from 100 to 300 nm. All membranes have a flat frequency response without resonant peaks in the frequency range 0–200 kHz. The proposed technology potentially enables the manufacture of wide low-height membranes of complex geometry to create microoptic fiber sensors.

Determination of technological process modes for surface formation of substrates for functional components of microoptoelectromechanical systems

Determination of technological process modes for surface formation of substrates for functional components of microoptoelectromechanical systems

Micro-opto-electro-mechanical gyroscope based on the Talbot effect of a single-layer near-field diffraction grating.

We demonstrate a novel, to the best of our knowledge, micro-opto-electro-mechanical system (MOEMS) gyroscope based on the Talbot effect of a single-layer near-field diffraction grating. The Talbot effect of an optical grating is studied both theoretically and experimentally. A structure of grating-mirror combination, fabricated by the micro-nano processing method, is used for out-of-plane structure detection. The detection of a weak Coriolis force is realized by using the highly sensitive displacement characteristic of Talbot imaging of near-field diffraction with a mirror mass block and single-layer grating. The experimental results show that, the micro-displacement detection sensitivity can reach up to 0.09%/nm, and the MOEMS gyroscope can be moved in the driven direction, with a resonant frequency of 7048 Hz and a quality factor of 700, which indicates great potential of the Talbot effect in developing novel high-performance micro-gyroscopes.

A Dual-Axis MOEMS Accelerometer

This paper is a report on the design and fabrication of a dual-axis micro-opto-electro-mechanical system (MOEMS) accelerometer. The device consists of a proof mass (PM) suspended by four L-shaped springs. Two Fabry-Perot (FP) cavities are formed between the cross-sections of the PM and the ends of two cleaved optical fibers in perpendicular directions (the X and Y axes). The acceleration causes the proof mass to move in the reverse direction relative to the applied acceleration. The sensor is fabricated by a silicon-on-insulator wafer. The fabricated sensor is characterized both by spectral monitoring and power measurements in the range of ±1 g. The results of spectral measurements show 3.23 nm/g (g = 9.81 m/s2: gravity constant) and 3.19 nm/g to the applied acceleration along the X and Y axes, respectively. Moreover, the obtained resolutions for the two directions of X and Y are $309~\mu \text{g}$ and $313~\mu \text{g}$ , respectively. Besides, the sensitivity of the sensor in power measurements is 550 mV/g and 528 mV/g in the X and Y directions, respectively. The sensor also possesses the resonant frequencies of 1382.5 Hz and 1398.6 Hz in the X and Y axes, respectively, in the range of ±1 g. The maximum cross-axis sensitivities obtained for this sensor are below 0.19% for each pair of X, Y, and Z axes. This value is fewer than the cross-axis sensitivity of most micro electro-mechanical systems without any post processing. This small value is a result of insensitivity of the FP spectrum to the lateral displacements of the PM.

Design and Modification of a High-Resolution Optical Interferometer Accelerometer.

The Micro-Opto-Electro-Mechanical Systems (MOEMS) accelerometer is a new type of accelerometer that combines the merits of optical measurement and Micro-Electro-Mechanical Systems (MEMS) to enable high precision, small volume, and anti-electromagnetism disturbance measurement of acceleration, which makes it a promising candidate for inertial navigation and seismic monitoring. This paper proposes a modified micro-grating-based accelerometer and introduces a new design method to characterize the grating interferometer. A MEMS sensor chip with high sensitivity was designed and fabricated, and the processing circuit was modified. The micro-grating interference measurement system was modeled, and the response sensitivity was analyzed. The accelerometer was then built and benchmarked with a commercial seismometer in detail. Compared to the previous prototype in the experiment, the results indicate that the noise floor has an ultra-low self-noise of 15 ng/Hz1/2.