Hydrogen sensors are of increasing importance in connection with the development and expanded use of hydrogen gas as an energy carrier and as a chemical reactant. There are an immense number of sensors reported in the literature for hydrogen detection and in this work these sensors are classified into eight different operating principles. Characteristic performance parameters of these sensor types, such as measuring range, sensitivity, selectivity and response time are reviewed and the latest technology developments are reported. Testing and validation of sensor performance are described in relation to standardisation and use in potentially explosive atmospheres so as to identify the requirements on hydrogen sensors for practical applications.

Hydrogen Sensors - A review

Metal oxide semiconductor gas sensors are utilised in a variety of different roles and industries. They are relatively inexpensive compared to other sensing technologies, robust, lightweight, long lasting and benefit from high material sensitivity and quick response times. They have been used extensively to measure and monitor trace amounts of environmentally important gases such as carbon monoxide and nitrogen dioxide. In this review the nature of the gas response and how it is fundamentally linked to surface structure is explored. Synthetic routes to metal oxide semiconductor gas sensors are also discussed and related to their affect on surface structure. An overview of important contributions and recent advances are discussed for the use of metal oxide semiconductor sensors for the detection of a variety of gases—CO, NOx, NH3 and the particularly challenging case of CO2. Finally a description of recent advances in work completed at University College London is presented including the use of selective zeolites layers, new perovskite type materials and an innovative chemical vapour deposition approach to film deposition.

https://www.mdpi.com/1424-8220/10/6/5469/pdf

Metal Oxide Semi-Conductor Gas Sensors in Environmental Monitoring

The theoretical and experimental issues relevant to neutrinoless double beta decay are reviewed. The impact that a direct observation of this exotic process would have on elementary particle physics, nuclear physics, astrophysics, and cosmology is profound. Now that neutrinos are known to have mass and experiments are becoming more sensitive, even the nonobservation of neutrinoless double beta decay will be useful. If the process is actually observed, we will immediately learn much about the neutrino. The status and discovery potential of proposed experiments are reviewed in this context, with significant emphasis on proposals favored by recent panel reviews. The importance of and challenges in the calculation of nuclear matrix elements that govern the decay are considered in detail. The increasing sensitivity of experiments and improvements in nuclear theory make the future exciting for this field at the interface of nuclear and particle physics.

/pdf/double-beta-decay-majorana-neutrinos-and-neutrino-mass-2tfhqvhys8.pdf

Double Beta Decay, Majorana Neutrinos, and Neutrino Mass

An apparatus may include a semiconductor chip and a fluidics assembly. The semiconductor chip has an array of wells and an array of sensors and each sensor of the array of sensors is in fluid communication with a well of the array of wells. The fluidics assembly is located on top of the semiconductor chip and is configured to deliver fluids to the semiconductor chip. The fluidics assembly includes a flow expansion chamber configured to introduce the fluids, an outlet portion configured to pipe out the fluids, and a flow chamber portion. The flow chamber portion is configured to allow the fluids to flow from the flow expansion chamber to the outlet portion and to allow the fluids to interact along the way with material in the array of wells. The flow expansion chamber has a curved wall at the top or bottom so that the height of the flow expansion chamber at the center is less than at the walls that restrict the fluids to the left and right.

Methods and apparatus for measuring analytes using large scale fet arrays

Methods and apparatus relating to FET arrays including large FET arrays for monitoring chemical and/or biological reactions such as nucleic acid sequencing-by-synthesis reactions. Some methods provided herein relate to improving signal (and also signal to noise ratio) from released hydrogen ions during nucleic acid sequencing reactions.

Methods and apparatus for measuring analytes

The paper presents preliminary results on Au-Au and Ag-Ag thermocompression bonding at low temperature. For both materials, sample structures have been prepared and different bonding conditions experimented. Results are compared in order to evaluate Au and Ag bond strength and to establish the optimum parameters. Shear tests were performed to quantify the bond strength and after that SEM was employed to examine the bonded joints. Bond strength of Ag-Ag compare to Au-Au (at 300°C and under the pressure of 0.196 MPa) seems more promising.

Thermocompression bonding for 3D RF MEMS devices using gold and silver as intermediate layer

Self-assembling perforated microplates modeled and fabricated on silicon wafers by means of surface micromachining are presented. The structures consist of a single Cr/Au metal layer and are set into position by the residual tensile in-plane stress of the material; the geometry is designed to obtain a lifted microplate coplanar to the surface of the wafer. The structures are modeled both analytically and by finite element simulation to correlate the displacement with the strain of the structural material. Samples are fabricated using IC technology on standard 4-inch silicon wafers by surface micromachining; a photoresist is used as a sacrificial layer and electroplated gold is used as a structural layer on a chromium-gold PVD seedlayer. The fabricated structures exhibit a vertical displacement of 38 µm. The resulting estimated strain is 0.001 66, which corresponds to a tensile stress of 173 MPa and is consistent with thermal residual strain.

A single metal layer MEMS self-assembling coplanar structure

This paper presents the design, fabrication and first experimental results of a dual-band switchable band-pass filter structure for the selection of DCS 1800 and WLAN standards. The design approach makes use of intensive electromagnetic modelling and layout optimisation. The fabrication technology is based on bulk and surface silicon micromachining to manufacture lumped elements on high resistivity silicon bulk and dielectric membrane. Filter test structures were fabricated and their frequency responses are presented

Compact Lumped Elements Micromachined Band-Pass Filters with Discrete Switching for 1.8/5.2 GHZ Applications

This work presents the modeling of gold microbeams for characterizing Micro-electro-mechanical systems (MEMS) packages in terms of both strains induced to the MEMS devices and hermetic sealing capability. The proposed test structures are based on arrays of rectangular-shaped clamped-free and clamped–clamped beams, to be realized with a film of electroplated gold by surface micromachining technology. The resonant frequency of the microbeams is modeled by FEM simulations as a function of substrate deformations, which could be induced by the package. Clamped–clamped bridges show a linear change of the square of the resonant frequency in case of in-plane deformations, in fairly good agreement with an approximate analytical model. Cantilever beams are modeled as variable capacitors to detect out-of-plane deformations. Finally, an analytical model to study cantilever beams as resonators for detecting pressure changes is discussed and compared with preliminary experimental results, showing an impact on the quality factor in a range from 10−2 mbar to 1 bar.

Modeling of gold microbeams as strain and pressure sensors for characterizing MEMS packages

The system for monitoring the metabolic activity of living
cells (26) comprises: a cell (20) able to receive the cell
population (26) to be monitored; means for supplying to a
culture medium the cell (20), and means for detecting the pH
value determined by the catabolism of the cell population
(26) in the cell (20). This latter preferably comprises a
casing which encloses a membrane (22) on which the cell
population (26) can be fixed. In the casing there is formed
a channel (30) for the culture medium and a channel (28) for
supplying a solution containing the cell population (26).
The channels (28, 30) flow alongside the membrane (22) on
opposite sides and are separated from one another.

Benno Margesin

Papers

Thermocompression bonding for 3D RF MEMS devices using gold and silver as intermediate layer

A single metal layer MEMS self-assembling coplanar structure

Compact Lumped Elements Micromachined Band-Pass Filters with Discrete Switching for 1.8/5.2 GHZ Applications

Modeling of gold microbeams as strain and pressure sensors for characterizing MEMS packages

System for monitoring the metabolic activity of living cells