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

In this paper we discuss the fundamental principles of the Kelvin probe apparatus; in particular, first, we find an analytical relation for the sensitivity of vibrating capacitors, so that the advantages of integration can be quantitatively estimated; second, we describe an equivalent electric circuit for vibrating capacitors, thus allowing to simulate a complete Kelvin probe with a standard electronic circuit simulator; third, we illustrate the most important issues of the electronic interface. A fundamental part of the research and technological work reported by this paper deals with the fabrication process of micromachined gold–palladium vibrating capacitors fully integrated on silicon, for hydrogen sensing applications. The relevant technological fabrication steps are explained. Preliminary experimental results of the first capacitor prototypes testing are reported as static C–V (capacitance–voltage) curves and as measurement in air of the gold–palladium work–function difference.

A micromachined gold–palladium Kelvin probe for hydrogen sensing

Micro-Electro-Mechanical System (MEMS) RF switches have been one of the most interesting areas for research and development in the last years. It has been shown that they have an excellent performance in the RF and microwave frequency range and a great effort has been dedicated in designing suitable geometries and structures best suited for switching application. In parallel other devices useful for the construction of complex RF circuits have been proposed and studied. Among these tuneable capacitors are of high interest for a variety of applications. In this paper we present a new electromechanical design for a tuneable capacitor with a totally different shape from usual designs. In particular we try to exploit the effect of the small in-plane force that develops during the polarization of a parallel plate capacitor with partially overlapping plates. First prototype realizations are discussed and analyzed and as the first realization showed some problems an improved design is presented.

Novel design of a RF-MEMS tuneable capacitor based on electrostatically induced torsion

We propose the design of a reconfigurable impedance matching network for the lower RF frequency band, based on a developed RF-MEMS technology. The circuit is composed of RF-MEMS ohmic relays, metal-insulatormetal (MIM) capacitors and suspended spiral inductors, all integrated on a high resistivity Silicon substrate. The presented circuit is well-suited for all applications requiring adaptive impedance matching between two in principle unknown cascaded RF-circuits. The fabrication and testing of a monolithic integrated prototype in RFMEMS technology from ITC-irst is currently underway.

https://hal.archives-ouvertes.fr/hal-00257653/document

A reconfigurable impedance matching network employing rf-mems switches

In this paper we report the realization and characterization of low-loss, capacitive RF MEMS switches that utilize folded serpentine spring suspensions with large area actuation electrodes. The surface micromachined switches with 1.7 /spl mu/m thick electroplated gold beams are implemented in standard 50 ohm CPW configuration. The electromechanical characterization indicates the measured actuation voltages in the range of 8 - 15 volts. The RF measurements of devices give insertion loss of 0.24 dB and isolation better than 21 dB at 20 GHz.

Micromachined low actuation voltage RF MEMS capacitive switches, technology and characterization

A low-cost integrated microsensor for biomedical applications is proposed. It is composed by an antenna-coupled microbolometer as detector, which is coupled to a specifically designed integrated circuit for biasing and readout. The main features are fast response to radiation, device level reference sensor, and electronic time-correlation for pulsed sources. The detector and the integrated circuits have been fabricated in a custom MEMS technology and a standard CMOS technology, respectively. First electrical measurements show properly operating devices.

Benno Margesin

Papers

A micromachined gold–palladium Kelvin probe for hydrogen sensing

Novel design of a RF-MEMS tuneable capacitor based on electrostatically induced torsion

A reconfigurable impedance matching network employing rf-mems switches

Micromachined low actuation voltage RF MEMS capacitive switches, technology and characterization

Terahertz microsensor for biomedical applications