Many-particle charged-particle plasma simulations using spatial meshes for the electromagnetic field solutions, particle-in-cell (PIC) merged with Monte Carlo collision (MCC) calculations, are coming into wide use for application to partially ionized gases. The author emphasizes the development of PIC computer experiments since the 1950s starting with one-dimensional (1-D) charged-sheet models, the addition of the mesh, and fast direct Poisson equation solvers for 2-D and 3-D. Details are provided for adding the collisions between the charged particles and neutral atoms. The result is many-particle simulations with many of the features met in low-temperature collision plasmas; for example, with applications to plasma-assisted materials processing, but also related to warmer plasmas at the edges of magnetized fusion plasmas. >

Particle-in-Cell Charged Particle Simulations, plus Monte Carlo Collisions with Neutral Atoms, PIC-MCC

The etch rates for 317 combinations of 16 materials (single-crystal silicon, doped, and undoped polysilicon, several types of silicon dioxide, stoichiometric and silicon-rich silicon nitride, aluminum, tungsten, titanium, Ti/W alloy, and two brands of positive photoresist) used in the fabrication of microelectromechanical systems and integrated circuits in 28 wet, plasma, and plasmaless-gas-phase etches (several HF solutions, H/sub 3/PO/sub 4/, HNO/sub 3/+H/sub 2/O+NH/sub 4/F, KOH, Type A aluminum etchant, H/sub 2/O+H/sub 2/O/sub 2/+HF, H/sub 2/O/sub 2/, piranha, acetone, HF vapor, XeF/sub 2/, and various combinations of SF/sub 6/, CF/sub 4/, CHF/sub 3/, Cl/sub 2/, O/sub 2/, N/sub 2/, and He in plasmas) were measured and are tabulated. Etch preparation, use, and chemical reactions (from the technical literature) are given. Sample preparation and MEMS applications are described for the materials.

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Etch rates for micromachining processing

Because of their small size, passive nature, immunity to electromagnetic interference, and capability to directly measure physical parameters such as temperature and strain, fiber Bragg grating sensors have developed beyond a laboratory curiosity and are becoming a mainstream sensing technology. Recently, high temperature stable gratings based on regeneration techniques and femtosecond infrared laser processing have shown promise for use in extreme environments such as high temperature, pressure or ionizing radiation. Such gratings are ideally suited for energy production applications where there is a requirement for advanced energy system instrumentation and controls that are operable in harsh environments. This paper will present a review of some of the more recent developments.

https://www.mdpi.com/1424-8220/12/2/1898/pdf

Fiber Bragg grating sensors for harsh environments.

Any device which senses information such as shape, texture, softness, temperature, vibration or shear and normal forces, by physical contact or touch, can be termed a tactile sensor. The importance of tactile sensor technology was recognized in the 1980s, along with a realization of the importance of computers and robotics. Despite this awareness, tactile sensors failed to be strongly adopted in industrial or consumer markets. In this paper, previous expectations of tactile sensors have been reviewed and the reasons for their failure to meet these expectations are discussed. The evolution of different tactile transduction principles, state of art designs and fabrication methods, and their pros and cons, are analyzed. From current development trends, new application areas for tactile sensors have been proposed. Literature from the last few decades has been revisited, and areas which are not appropriate for the use of tactile sensors have been identified. Similarly, the challenges that this technology needs to overcome in order to find its place in the market have been highlighted.

/pdf/a-review-of-tactile-sensing-technologies-with-applications-12ul5smpoy.pdf

A review of tactile sensing technologies with applications in biomedical engineering

Gas sensors fabricated with nanowires as the detecting elements are powerful due to their many improved characteristics such as high surface-to-volume ratios, ultrasensitivity, higher selectivity, low power consumption, and fast response. This paper gives an overview on the recent process of the development of nanotechnology and nanowire-based gas sensors. The two basic approaches, top-down and bottom-up, for synthesizing nanowires are compared. The conduction mechanisms, sensing performances, configurations, and sensing principles of different nanowire gas sensors and arrays are summarized and discussed. Meanwhile, an emerging nanowires fabrication method and a self-powered nanowire pH sensor are highlighted. The scientific and technological challenges in the field are discussed at the end of the review. © 2012 Elsevier B.V. All rights reserved.

Nanowire-based gas sensors

Fiber Bragg grating (FBG) temperature sensor and sensor arrays were applied widespread particularly in harsh environments. Although FBGs are often referring to permanent refractive index modulation in the fiber core, exposure to high-temperature environments usually results in the bleach of the refractive index modulation. The maximum temperature reported for the conventional FBG temperature sensor is around 600 degC due to its weak bonds of germanium and oxygen. In this paper, we report design and development of a novel high-temperature resistance FBG temperature sensor, based on the hydrogen-loaded germanium-doped FBG. The refractive index modulation in the FBG is induced by the molecular water. The results of our experiments have shown that the stability of the device is substantially increased at high temperature range. Due to the high bonds energy of hydroxyl and the low diffusivity of the molecular water, the thermal testing results of this temperature sensor show the thermal stability of hydrogen-loaded FBG can be increased by using annealing treatment; moreover, the highest erasing temperature for the device could reach to 1100 degC or more. The reflectivity of this new FBG depends on the concentration of Si-OH and indirectly related to the reflectivity of hydrogen-loaded FBG. Furthermore, the experimental results have provided a better understanding of the formation of the hydrogen-loaded FBGs and the chemical transfers at elevated temperatures in the fiber core

High-Temperature Resistance Fiber Bragg Grating Temperature Sensor Fabrication

This paper aimed to develop a miniaturized tactile sensor capable of measuring force and force position in minimally invasive surgery. The in situ measurement of tactile information is a step forward toward restoring the loss of the sense of touch that has occurred due to shift from traditional to minimally invasive surgeries. The sensor was designed such that it can sense low forces which could be comparable to those produced by pulsating delicate arteries, yet can withstand high forces comparable to grasping forces. The influence of some hidden anatomical features, such as lumps, voids, and arteries, on the stress distribution at the grasping surface was studied. In this paper, the capability of the sensor to determine and locate any point load was also investigated. The proposed sensor was designed and manufactured to be highly sensitive, using polyvinylidene fluoride (PVDF). The microfabrication procedure of the sensor, including corner compensation for toothlike projections and patterning of PVDF film, was discussed. The micromachined sensor was tested, and the experimental results were compared with the results of 3-D finite element modeling.

PVDF-Based Microfabricated Tactile Sensor for Minimally Invasive Surgery

Hillocks on etched Si{100} surfaces produced by anisotropic etching are a common irritant in the creation of micromachined devices. Close inspection of typical pyramidal hillock shapes reveals that they are usually bounded by convex -directed edges and {111} or near-{111} planes. Underetch experiments at varying TMAH etchant composition confirm that the etch rates of {101} planes and {100} planes vary with etchant conditions. Hillocks are suppressed when {101} etches faster than {100}, which occurs when the TMAH concentration is low. A simple model involving kinks and ledges is proposed and allows direct relation of hillock features to etch anisotropy. Hillocks are hypothesized to be stable due to a lower etch rate for ledges adjacent to the etched surface. The apex of the pyramids may be protected by impurities or defects. Re-etch experiments indicate that hillock-producing conditions are quite sensitive to etchant conditions.

On hillocks generated during anisotropic etching of Si in TMAH

Freestanding gold nanowires (AuNW) were incorporated to fabricate a miniaturized gas ionization sensor. The device exhibited improved sensitivity in sub-Torr pressure (P) regime compared to similar devices reported earlier, since the room temperature breakdown voltage (Vb) was further reduced in low gas pressures or concentrations (N). Also excellent selectivity was achieved for pressures up to 10 Torr, while Vb remained almost unaffected by pressure. In the Vb–P characteristic below 1 Torr, Vb was less when the AuNWs was configured as cathode, and it started to decline until a Paschen-like (Vb)min was observed at very low pressures (0.3

A novel miniature gas ionization sensor based on freestanding gold nanowires

In recent researches, fiber Bragg grating (FBG) is proven the most promising fiber optic strain sensor upon its elaborate strain sensibility. Numerous efforts have been done in realizing practical FBG strain gage systems, either mounted on the surface, or integrated within the structure. Fiber reinforced composite materials are always regarded as the nominated candidate to embed FBG sensors upon the fact that, fiber reinforced filamentary topology enables the integration and effectively protects sensors from hostile attack, therefore a fiber optic smart structure is achievable. However, one must recognize that embedded FBG fibers are foreign entities to host structures, mechanical mismatches may eventually lead to alteration on sensors’ responsive behaviours, and measurand interpretation becomes complicated. This work reports a set of experiments on an orthogonal FBG array embedded in graphite/epoxy composite structures. Recurring to corresponding surface mounted resistance strain gages, the authors tend to provide a comprehensive investigation on strain-optic behaviours of embedded FBG sensors, and a quantitative discussion on inevitable deviations of the sensors when used as buried strain gages.

Mojtaba Kahrizi

Papers

High-Temperature Resistance Fiber Bragg Grating Temperature Sensor Fabrication

PVDF-Based Microfabricated Tactile Sensor for Minimally Invasive Surgery

On hillocks generated during anisotropic etching of Si in TMAH

A novel miniature gas ionization sensor based on freestanding gold nanowires

Characterization of a FBG strain gage array embedded in composite structure