Mass Fabrication Process Research Articles

A Power-Based Framework for Quantifying Parameter Uncertainties in Finite Vibroacoustic Metamaterial Plates.

Vibroacoustic metamaterials (VAMMs) are artificial materials that are specifically designed to control, direct, and manipulate sound waves by creating a frequency gap, known as the stop band, which blocks free wave propagation. In this paper, a new power-based approach that relies on the active structural intensity (STI) for predicting the stop band behavior of finite VAMM structures is presented. The proposed method quantifies the power loss in a locally resonant finite VAMM plate in terms of percentage, such as STI99% and STI90%, for stop band prediction. This allows for the quantitative analysis of the vibration attenuation capabilities of a VAMM structure. This study is presented in the context of a two-dimensional VAMM plate with 25 resonators mounted in the middle section of the plate. It has been demonstrated that this method can predict the stop band limits of a finite VAMM plate more accurately than using negative effective mass, unit cell dispersion analysis, or the frequency response function methods. The proposed approach is then implemented to establish a framework for investigating the influence of parameter uncertainties on the stop band behavior of the VAMM plate. Based on the STI99% method, which aims for significant vibration reduction, stricter tolerances in the mass fabrication process are required to ensure the robustness of VAMM. Conversely, the STI90% method suggests that larger fabrication tolerances can be leveraged to achieve a broader stop band range while still meeting the desired performance level, leading to cost savings in manufacturing.

Highly integrated, scalable manufacturing and stretchable conductive core/shell fibers for strain sensing and self-powered smart textiles

Although the research in triboelectric nanogenerator (TENG) textiles has seen a rapid development recently, their integrated and mass fabrication process is still challenging, which hinders its further applications for wearable sensors. Herein, highly integrated and scalable manufacturing conductive composite fibers for weaving TENGs are presented, which might overcome the major problems. The fibers possess liquid alloy/silicone rubber core/shell structures made by simultaneously injecting liquid alloy and silicone rubber into the separate input ports of a coaxial needle, followed by automatically assembled from the output. The liquid alloy/silicone rubber core/shell fiber (LCF) has both good pliability and high resistance-strain sensitivity, which is beneficial for serving as strain sensors directly, and for incorporating with woven for textile-TENGs (t-TENGs)-based self-powered sensoring application. As a result, the open-circuit voltage (Voc), short-circuit current (Isc), short-circuit transferred charge (Qsc) and maximum power density of 4 × 4 cm2 t-TENG are 175 V, 15 μA, 66 nC and 469 mW/m2, respectively. Additionally, the t-TENG is mechanically robust, chemically stable and easy-cleaning for daily use. The wearable t-TENG devices can be used to detect human motions. This work provides a novel method of scalable manufacturing LCFs for weaving wearable t-TENGs, contributing to the development of t-TENGs and wearable self-powered sensors.

Origination of free-form micro-optical elements using one- and two-photon grayscale laser lithography.

We discuss and describe the development of an origination process for planar free-form micro-optical elements from a given optical design. The targeted masters serve as origination structures for a roll-to-roll mass fabrication process. Specifically targeted are complex, optically smooth, surface relief structures with variable structure heights in the range of 1-20 µm, with typical lateral sizes of more than 5 µm. The area of the targeted masters is in the range of 1cm2. The main part of the paper is devoted to the description of a self-developed grayscale laser direct-write platform enabling one- and two-photon absorption lithography, also in combination on one and the same sample. In the following, we describe both methods and show that both lead to excellent structural quality of surface micro-relief structures. As a showcase of what the system can do in principle, we designed and fabricated free-form micro-optical elements to project light from an LED as a defined light pattern onto a wall. The proper optical functionality of the fabricated element was shown within a demonstrator setup.

Impact of Different Metals on the Performance of Slab Tamm Plasmon Resonators.

We investigate the concept of slab Tamm plasmons (STP) in regard to their properties as resonant absorber or emitter structures in the mid-infrared spectral region. In particular, we compare the selective absorption characteristics resulting from different choices of absorbing material, namely Ag, W, Mo or highly doped Si. We devised a simplified optimization procedure using finite element simulations for the calculation of the absorption together with the application of micro-genetic algorithm (GA) optimization. As characteristic for plasmonic structures, the specific choice of the metallic absorber material strongly determines the achievable quality factor (Q). We show that STP absorbers are able to mitigate the degradation of Q for less reflective metals or even non-metals such as doped silicon as plasmonic absorber material. Moreover, our results strongly indicate that the maximum achievable plasmon-enhanced absorption does not depend on the choice of the plasmonic material presuming an optimized configuration is obtained via the GA process. As a result, absorptances in the order of 50–80% could be achieved for any absorber material depending on the slab thickness (up to 1.1 µm) and a target resonance wavelength of 4.26 µm (CO2 absorption line). The proposed structures are compatible with modern semiconductor mass fabrication processes. At the same time, the optimization procedure allows us to choose the best plasmonic material for the corresponding application of the STP structure. Therefore, we believe that our results represent crucial advances towards corresponding integrated resonant absorber and thermal emitter components.

A CMOS Compatible Pyroelectric Mid-Infrared Detector Based on Aluminium Nitride.

The detection of infrared radiation is of great interest for a wide range of applications, such as absorption sensing in the infrared spectral range. In this work, we present a CMOS compatible pyroelectric detector which was devised as a mid-infrared detector, comprising aluminium nitride (AlN) as the pyroelectric material and fabricated using semiconductor mass fabrication processes. To ensure thermal decoupling of the detector, the detectors are realized on a Si3N4/SiO2 membrane. The detectors have been tested at a wavelength close to the CO2 absorption region in the mid-infrared. Devices with various detector and membrane sizes were fabricated and the influence of these dimensions on the performance was investigated. The noise equivalent power of the first demonstrator devices connected to a readout circuit was measured to be as low as .

Characterization of Evanescent Field Gas Sensor Structures Based on Silicon Photonics

Photonic sensors that operate in the mid-infrared spectral range are an emerging field for photonic microsystems. In this paper, we present a photonic gas sensor concept based on silicon waveguides using infrared evanescent field absorption. The waveguides were specifically designed for CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> sensing at a wavelength of λ = 4.26μm as possible application for the proposed sensor platform. The waveguide cross section as well as the substructure were investigated using finite-element simulations and the devised structures were fabricated using mass fabrication processes exclusively. In order to evaluate the potential for long interaction path lengths using polysilicon strip waveguides, a study on the intrinsic losses of polysilicon waveguides was conducted. The lowest intrinsic damping that was obtained for polysilicon strip waveguides was 3.98 dB/cm. Furthermore, the sensing capability of the devised waveguides was tested with quantitative CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> measurements down to a concentration of 500 ppm CO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> . From the quantitative measurements, the evanescent field ratio was estimated and was in the range between η = 14%-16%.

Fast circuit breaker based on integration of Al/CuO nanothermites

Pyroswitches and circuit breakers play an important safety role in electrical systems. A miniature one-shot circuit breaker based on the violent reaction of a nanothermite is presented for safety application as protection against overcurrent, external perturbation and short circuit of a broad range of equipment and systems. This device consists of two circuits assembled together to define a cavity. An ignition chip is placed into this cavity and ignites, within less than 100 μs, a few milligrams of nanothermites powder. The resulting violent reaction interrupts a thick copper connection within 1 ms. After the presentation of the device design, fabrication and assembly, we demonstrate the good operation and reproducibility of the device (100% of success rate) with a response time much lower than that of classical mechanical circuit breakers, which are slow. The response time can be tuned from 1.02 ms to 0.57 ms just by adjusting the mass of nanothermites from 5.59 to 13.24 mg, i.e., adjusting the volumetric solid loadings from 5.6 to 19%. The nanothermites-based circuit breaker presented in this paper offers unprecedented advantages: it is built using only safe substances and is based on a low-cost mass fabrication process that is compatible with electronics. The proposed concept is generic and can be applied to a large number of applications (electrical storage, aerospace manufacturing, human safety, demolition parachute opening, road vehicles, battery powered machines…).

Development of a bus armrest fabrication process with a high-vacuum, high-pressure die-casting process using the AM60 alloy

Abstract Recently, interest in light-weight vehicle research is spreading swiftly across the globe. This is part of efforts to reduce CO2 emissions in many countries of the world, including developed countries. Magnesium alloys represent light-weight, metallic materials with a density of 1.74 g/cc, the lowest of commercial metallic materials. Conventionally, magnesium alloy has a higher viscosity than aluminum alloy and its solidification velocity is remarkably fast. Thus, magnesium alloys can incur more casting defects than aluminum alloys. Traditionally, a die-casting process consists of filling the die cavity with the molten metal under high pressure. Thus mass fabrication process of magnesium alloys is die casting and machining process only, currently. In this study, we focus on the magnesium vacuum die-casting process for the AM60 material for automotive parts. This investigation includes the part design, solidification and structural simulation, mold making, vacuum die-casting process development, a mechanical property test, and a durability test.

Microelectromechanical reprogrammable logic device.

In modern computing, the Boolean logic operations are set by interconnect schemes between the transistors. As the miniaturization in the component level to enhance the computational power is rapidly approaching physical limits, alternative computing methods are vigorously pursued. One of the desired aspects in the future computing approaches is the provision for hardware reconfigurability at run time to allow enhanced functionality. Here we demonstrate a reprogrammable logic device based on the electrothermal frequency modulation scheme of a single microelectromechanical resonator, capable of performing all the fundamental 2-bit logic functions as well as n-bit logic operations. Logic functions are performed by actively tuning the linear resonance frequency of the resonator operated at room temperature and under modest vacuum conditions, reprogrammable by the a.c.-driving frequency. The device is fabricated using complementary metal oxide semiconductor compatible mass fabrication process, suitable for on-chip integration, and promises an alternative electromechanical computing scheme.

Selective Stiffening for Producing a Mass-Fabrication Compatible Motion Conversion Mechanism

We present a mechanism that converts in-plane to out-of-plane motions, which is fully compatible with mass-fabrication processes. By using selective stiffening, we induce coupling between in-plane and out-of-plane responses of the mechanism. The conversion ratio is constant (i.e., linear response), and it can be easily tailored by the number of stiffeners used in an otherwise unchanged design planform. The linearity of the motion conversion and the possibility to tailor it, are demonstrated experimentally using dedicated test devices. As a specific example of application, we use the motion conversion mechanism to achieve a parallel out-of-plane motion of a flat stage, which is driven by in-plane comb-drives. [2015-0154]

Mechanical Q-factor measurements on a test mass with a structured surface

We present mechanical Q-factors (quality factors) of a crystalline quartz test mass with a nano-structured surface, measured in the temperature regime from 5 to 300 K. The nano-structure was a grating with a period of 2 μm and a depth of about 0.1 μm. Comparative measurements were performed on the plain substrate and on the structured test mass with different numbers of SiO2/Ta2O5 coating layers. The measurements at different stages of the test mass fabrication process show that the surface distortion induced by the nanostructure does not severely lower the mechanical Q-factor of the substrate. Damping due to a multi-layer coating stack was found to be orders of magnitude higher. The results provide vital information concerning the potential usage of low-thermal noise nano-structured test masses in future generations of high-precision laser interferometers and in current attempts to measure quantum effects of macroscopic mirror oscillators.

Quantitative analysis of the molding of nanostructures

Mass fabrication processes such as injection molding and hot embossing are highly suitable for the replication of micro- and nanostructures. They require thermoplastic polymers with good molding properties at moderate process temperatures. We show a quantitative approach to the analysis of the molding properties of polymers in the nanorange in which the parameters are most important for achieving good replication fidelity. With this information we were able to fabricate high precision calibration chips for scanning probe microscopes.

Novel mass-fabrication of fibre couplers using arrayed fibre ribbons

To achieve high productivity and high density packaging of fibre couplers for practical systems, a novel mass-fabrication process using arrayed fibre ribbons has been developed. The fabricated arrayed-fibre coupler consists of four couplers which are all fabricated together from four-fibre ribbons. Each fibre coupler had 3 dB coupling ratio to within 49.3 ± 2.1%. It has been confirmed that plural fibre couplers with equal coupling ratio can be simultaneously fabricated by the mass-fabrication process.