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

Bioelectrochemical signal monitoring of in-vitro cultured cells by means of an automated microsystem based on solid state sensor-array.

A dedicated test chip has been designed and fabricated for assessing the compatibility of the ISFET (Ion Sensitive Field Effect Transistors) and CMNOS (Complementary Metal gate Nitride Oxide Semiconductor) technologies, in order to develop an ISFET/CMOS fabrication process The test chip contains three sets of test structures dedicated respectively to the evaluation of the sensor performances in terms of electro-chemical characteristics, to the extraction of the CMNOS process/design (eg SPICE) parameters, and to the characterisation of basic analogue integrated circuit blocks for the on chip interface electronics By using this technology single chemical sensors, arrays sensors and multi-sensors with on-chip signal conditioning for environmental and biomedical applications are currently under development in our laboratory

A test chip for ISFET/CMNOS technology development

This paper reports on a system for sampling atmospheric formaldehyde by dissolution in an aqueous solution followed by the monitoring of the aldehyde using an ion-sensitive field-effect transistor (ISFET) in conjunction with an enzyme specific for this pollutant. Formaldehyde dehydrogenase from Pseudomonas putida was chosen on the basis of its characteristics to be coupled to the ISFET transducer. This enzyme, using oxidized nicotinamide adenine dinucleoside (NAD) as cofactor, catalyses the oxidation of a molecule of formaldehyde with the parallel production of two protons, which are sensed by the ISFET. The working conditions were chosen to obtain a linear response of the sensor up to 200 μM formaldehyde. On the basis of the enrichment obtained by the sampling system, the detection limit of 10 μM formaldehyde in aqueous solution, achieved by the ISFET biosensor, corresponds to an atmospheric concentration of the formaldehyde in the ppb range.

Potentiometric detection of formaldehyde in air by an aldehyde dehydrogenase FET

In this work, the stress of electroplated gold films has been analyzed versus plating current density and bath temperature. Two different plating solutions have been adopted, one being based on cyanide-gold salt, the other on sulfite-gold. Gold surface quality was investigated in the experimented range of plating temperature and current density, in order to control the limit conditions for plating: surface roughness and non-uniformity appear whenever deposition parameters are brought to the limit (typically below 2 mA/cm/sup 2/ and above 5 mA/cm/sup 2/). Plated gold stress measurement was carried out by wafer curvature comparison, before and after deposition, using Stoney's formula for thin films/sup 1,2/. A current density range between 1.5 and 6 mA/cm/sup 2/ and temperature range between 50 and 70/spl deg/C was investigated. Stress analysis was also carried out on a Cr-Au multilayer, which actually is the structural layer employed for gold microstructures: the multilayer consists of a chromium adhesion layer, a PVD gold seed layer and a plated gold layer, with thickness respectively 10 nm, 150 nm and 1500 nm. A range of stress was obtained, varying from tensile to compressive: cyanide bath yielded stress from -30 MPa to about 0 MPa, and sulfite bath showed stress between -90 MPa and 110 MPa. Stress variation induced by thermal treatments after deposition was also investigated, by examining the effect of photoresist sacrificial etching on the internal stress of chromium-gold structural layers: the final stress was about 180 MPa tensile for all samples, regardless the as-deposited stress, with a variation ranging from about 80 MPa to more than 200 MPa.

Benno Margesin

Papers

Bioelectrochemical signal monitoring of in-vitro cultured cells by means of an automated microsystem based on solid state sensor-array.

A test chip for ISFET/CMNOS technology development

Potentiometric detection of formaldehyde in air by an aldehyde dehydrogenase FET

Stress characterization of electroplated gold layers for low temperature surface micromachining

A simple microfluidic system for patterning populations of neurons on silicon micromachined substrates.