1,721,382 research outputs found
Printed lab-on-a-chip sensors for environmental monitoring
No full textAdditive manufacturing techniques such as printed electronics are currently very popular due to the efficiencies and cost benefits they offer together with the added environmental benefits resulting from the minimisation of material wastage. The screen printing of sensors for example can greatly facilitate the production of low cost, robust, miniature sensors and in particular the production of sensor arrays suitable for a wide variety of application areas. This presentation focuses on the development of a variety of different screen printed sensor types, with particular attention being given to environmental sensor arrays. Examples will be given of sensor arrays that have been developed for subterranean and subaqueous deployment for measurement of multiple parameters such as pH, temperature, conductivity, oxygen concentration and redox potential.The same print technology can also be used to produce low cost, rugged electronic circuits that can be used with the sensor arrays to facilitate monitoring of the environment in remote locations, for example throughout a water catchment area in the monitoring of rivers, ditches, agricultural field run off etc. Examples will also be given where the sensors are buried in the ground to monitor the stability of earthworks such as railway embankments and cuttings.<br/
A novel thick-film electrical conductivity sensor suitable for liquid and soil conductivity measurements
Full text linkResults are reported from an initial evaluation of a novel conductivity sensor that could be incorporated onto a multi-element thick film (screen printed) sensor array designed for soil and water analysis. The new sensor exhibits a repeatable cell constant over a wide range of conductivities and is currently performing very well in an investigation of soil structural properties where its output is being correlated with soil water content in a study of different soil porosities.<br/
A screen-printed amperometric dissolved oxygen sensor utilising an immobilised electrolyte gel and membrane
No full textAn amperometric dissolved oxygen sensor based on potentiostatic operation has been designed and fabricated using thick film technology. Calibration of the sensor has shown a strong linear relationship with dissolved oxygen concentration. The devices have been bulk tested for long-term stability and good device to device repeatability has been observed within the batch. Results indicate that a repeatable response to dissolved oxygen levels can be obtained over a period of several months when intermittently powered. The device has been found to operate efficiently for at least 2 weeks when it is continuously powered in deionised water. Silver and copper deposits have been identified on the working electrode of such devices. It is shown that sensor failure occurs after 3 days when powered in tap water and that it is attributed to deposition on the membrane surface
Thick film chemical sensors
No full textThe development of thick film sensors is described from their early stages, where thick film technology was employed primarily for the fabrication of interface circuits and as a sensor support medium, through to their complete fabrication as screen printed sensor arrays.The concept of processing signal data from sensor arrays as a means of improving sensor performance is also introduced and examples given. These examples include the reduction of the effects of 1/f noise in thick film conductimetric sensors and the use of pattern recognition techniques applied to arrays of low specificity gas sensors to improve their selectivity to particular analyte gases.Examples of various thick film gas sensors are given and the fabrication methods and associated techniques for their use in the detection of a variety of toxic, flammable and environmental gases are described.Various sensors for liquids are described and, in particular, arrays of sensors for water quality determination. The investigation of useful lifetimes and operational performance of these devices is reported with particular reference to sensors for the measurement of temperature, conductivity, redox potential, pH and dissolved oxygen concentration in water
A picturesque representation of the manners, customs, and amusements of the Russians : in one hundred coloured plates; with an accurate explanation of each plate in English and French
No full textby John Augustus Atkinson, and James Walke
Thick film silver-silver chloride reference electrodes
No full textThe fabrication of prototype thick film silver-silver chloride electrochemical reference electrodes is described. Combinations of commercially available and proprietary thick film pastes have been used in their construction in a multi-layer planar configuration modelled upon the structure of the classic single junction silver-silver chloride reference electrode cell. Several variations in the basic electrode design were fabricated, involving combinations of one of three different paste formulations for the silver-silver chloride layer coupled with one of two combinations of paste formulation for the salt containment matrix. The relative performances of these different versions of reference electrode were evaluated in terms of their chloride ion sensitivity, hydration times required to achieve a stable potential and usable lifetime. It is shown that, depending on the processing methodology employed at certain stages in the fabrication of these devices, a large degree of variation in characteristics can be achieved and therefore exploited in the design of reference electrodes suitable for a range of specific applications
An evaluation and comparison of cross-sensitivities of various different types of screen printed Ag/AgCl reference electrodes
No full textDifferent types of thick film screen printed silver and silver-silver chloride (Ag/AgCl) electrodes have been evaluated for use as solid state alternatives to liquid electrolyte filled Ag/AgCl reference electrodes. The tested electrodes included those employing different types of binder (glass and polymer) for the Ag/AgCl layer, those consisting of a bare silver (pseudo reference) electrode and those with a bare silver electrode with an additional covering layer of a polymer bound KCl salt matrix. The cross-sensitivities of these different electrodes to several different ion species (e.g. chlorides, nitrates and phosphates) were examined by recording their electro potentials in varying ionic strength solutions.</p
An investigation into the viability of screen printed organic semiconductor compounds as gas sensors
No full textThick film sensors for soil measurements
No full textWater content has considerable influence on soilpore water pressure and shear strength, potentially leading tofailure in earthworks. This research aims to develop novelsensors (employing Thick-Film electrodes) intended to detectchanges in soil parameters such as resistivity, porosity andwater content and determine if these are indicative ofearthworks instability (potential slope failure). Using ThickFilm electrodes to measure parameters could be a cost effectivemethod for condition monitoring. The resistivity output of thesensors and how it relates to the soil water content needs to beunderstood, and a framework of working conditions for thissensing technology needs to be documented. In this study, thebehaviour of the Thick Film cell developed by the University ofSouthampton was tested for a particular soil particle size bysimulating heavy rainfall and rising of the water table within asoil column. Final results show a consistent response fromThick Film cell for the specific soil sample used, however, thedirection of infiltration has created a very interestingdifference in resistivity readings that need to be furtherinvestigated
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