Basic Sensor Parameters Research Articles

Magneto-Optical Indicator Films: Fabrication, Principles of Operation, Calibration, and Applications.

Magneto-optical indicator films (MOIFs) are a very useful tool for direct studies of the spatial distribution of magnetic fields and the magnetization processes in magnetic materials and industrial devices such as magnetic sensors, microelectronic components, micro-electromechanical systems (MEMS), and others. The ease of application and the possibility for direct quantitative measurements in combination with a straightforward calibration approach make them an indispensable tool for a wide spectrum of magnetic measurements. The basic sensor parameters of MOIFs, such as a high spatial resolution down to below 1 μm combined with a large spatial imaging range of up to several cm and a wide dynamic range from 10 μT to over 100 mT, also foster their application in various areas of scientific research and industry. The history of MOIF development totals approximately 30 years, and only recently have the underlying physics been completely described and detailed calibration approaches been developed. The present review first summarizes the history of MOIF development and applications and then presents the recent advances in MOIF measurement techniques, including the theoretical developments and traceable calibration methods. The latter make MOIFs a quantitative tool capable of measuring the complete vectorial value of a stray field. Furthermore, various scientific and industrial application areas of MOIFs are described in detail.

Fiber optic humidity sensor based on silk fibroin interference films

The article presents an inexpensive and simple method of fiber optic interference relative humidity (RH) sensors based on silk fibroin (SF) films. The sensors were made on standard multimode telecommunications optical fibers using dip-coating method and examined using broadband light sources. The measuring stand at which the basic sensor parameters were measured and the measured parameters were presented. Full Text: PDF ReferencesY.-G. Han, "Relative Humidity Sensors Based on Microfiber Knot Resonators—A Review", Sensors, 19(23), 5196 (2019) CrossRef L.D. Koh, Y. Cheng, C. P. Teng, Y. W. Khin, X. J. Loh, S. Y. Tee, et al., "Structures, mechanical properties and applications of silk fibroin materials", Prog. Polim. Sci. 46, 86-110 (2015) CrossRef H. Tao, D. L. Kaplan, F. G. Omenetto, "Silk Materials – A Road to Sustainable High Technology", Adv. Mater., 24, 2824-2837 (2012), CrossRef Q. Li, N. Qi, Y. Peng, Y. Zhang, L. Shi, X. Zhang, et al., "Sub-micron silk fibroin film with high humidity sensibility through color changing", RSC Adv. 7(29), 17889-17897 (2017) CrossRef S.K. Hwan, H.C. Sung, B. Roy, S. Kim, Y.H. Ahn, "Humidity sensing using THz metamaterial with silk protein fibroin", Opt. Express 26(26), 33575-33581 (2018) CrossRef M. Procek, Z. Opilski, A. M. Maqueda, X. M. Berbel, S. D. Aznar-Cervantes, J. L. Cenis, C. D. Horna, "Silk fibroin thin films for optical humidity sensing", Proc. SPIE , 11204, 0277-786X, (2019). CrossRef Y. Luo, Y. Pei, X. Feng, B. Lu, L. Wang, "Silk fibroin based transparent and wearable humidity sensor for ultra-sensitive respiration monitoring", Mater. Lett., 260, 126945 (2020) CrossRef E. Maciak, "Low-Coherence Interferometric Fiber Optic Sensor for Humidity Monitoring Based on Nafion® Thin Film†", Sensors 19(3), 629 (2019) CrossRef

Acetate Detection with a Living Biosensor – The Capability of Anodic Biofilms

Biosensors based on electroactive bacteria are one promising application of microbial electrochemical technologies (MET) beside, e.g., microbial fuels, electrolysis cells and desalination cells [1]. Here we present a microbial electrochemical sensor platform for online detection of acetate within the anaerobic digestion (AD) process. Despite its wide distribution and existing practical experiences, the anaerobic digestion process is still low automated compared to other industrial processes. Acetate as highly process-relevant volatile organic acid (VFA) in AD is nowadays measured off-line with gas- or liquid chromatography. To establish real time process monitoring and control especially for industrial biogas production (e.g. requiring flexible feeding regimes), an online measurement of process relevant VFA is needed. Online control of VFA and subsequent adaption the feeding rate could prevent process disturbances or process breakdown especially in high-throughput or flexible biogas production. Biosensors based on microbial fuel cells were already proposed for VFA quantification in anaerobic digestion [2–4]. By advancing the idea of a microbial electrochemical sensor we propose the application of a membrane less sensor with a three electrode transducer and a microbial anode as sensing element for online VFA measurement. Thereby the sensor housing allows an implementation into existing AD-reactors. The basic sensor parameters like measurement range and resolution, cross sensitivity and response time were examined in a non sterile, continuous stirred flow cell setup (100 mL, 1 ml min-1) using artificial wastewater as growth medium. The sensors measurement range for acetate could be determined with 0.5 to 5 mmol L-1 with a measurement resolution from 0.25 to 1 mmol L-1 acetate (see figure) [5]. Cross sensitivity was tested for propionate and butyrate and showed only a low signal for both VFA. To provide proof of concept for real process application first experiments in a semi continuous lab scale biogas fermenter (10 L) with maize silage and cow manure as substrate were carried out. Therefore, an external grown biosensor was introduced into an existing biogas reactor. The sensor signal followed to a typical intraday VFA concentration profile being confirmed by GC-FID measurements. So far, the achieved measurement range of the sensor is too low for application in AD. We discuss measures to pave the way to application, e.g., by optimized sensor architecture, tailored anode material´s or dilution of process fluids in a bypass. Figure: Biofilm current response on changing acetate concentrations. Data summarized from CA and CV measurements. The grey boxes correspond to the middle 50% of the data, whiskers (error bars) indicate minimum and maximum, n= 12 (6 for CA and 6 for CV) [5]. Literature: [1] U. Schröder, F. Harnisch, L.T. Angenent, Microbial electrochemistry and technology: terminology and classification, Energy Environ. Sci. 8 (2015) 513–519. doi:10.1039/C4EE03359K. [2] J.M. Tront, J.D. Fortner, M. Plötze, J.B. Hughes, A.M. Puzrin, Microbial fuel cell biosensor for in situ assessment of microbial activity, Biosens. Bioelectron. 24 (2008) 586–590. doi:10.1016/j.bios.2008.06.006. [3] A. Kaur, J.R. Kim, I. Michie, R.M. Dinsdale, A.J. Guwy, G.C. Premier, Microbial fuel cell type biosensor for specific volatile fatty acids using acclimated bacterial communities, Biosens. Bioelectron. 47 (2013) 50–55. doi:10.1016/j.bios.2013.02.033. [4] Z. Liu, J. Liu, B. Li, Y. Zhang, X.-H. Xing, Focusing on the process diagnosis of anaerobic fermentation by a novel sensor system combining microbial fuel cell, gas flow meter and pH meter, Int. J. Hydrog. Energy. 39 (2014) 13658–13664. doi:10.1016/j.ijhydene.2014.04.076. [5] J. Kretzschmar, L.F.M. Rosa, J. Zosel, M. Mertig, J. Liebetrau, F. Harnisch, A microbial biosensor platform for in-line quantification of acetate in anaerobic digestion: potential and challenges, Chem. Eng. Technol. accepted Figure 1

Electrochemical pesticide sensor based on Langmuir–Blodgett film of cobalt phthalocyanine-anthraquinone hybrid

A cathode active and selective pesticide electrochemical sensor based on Langmuir–Blodgett (LB) film of cobalt phthalocyanine-anthraquinone hybrid (CoPc-AQ) was constructed for the first time in this study. Cobalt-based, Pc ring-based, and anthraquinone-based reduction processes of CoPc-AQ indicated suitability of the complex as a possible electrochemical catalyst and sensor for detection of target species. LB film of CoPc-AQ on ITO (ITO/CoPc-AQ electrode) was titrated with eserine and carbofuran pesticides and interaction of the electrode with these pesticides was tested with square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS), and double potential step chronocoulometry (DPSCC) techniques. ITO/CoPc-AQ electrode selectively sensed carbofuran and eserine pesticides. While ITO/CoPc-AQ electrode senses carbofuran with the voltammetric responses recorded at anodic potentials (1.20 V), eserine sensing affected antraquinone based reduction peaks recorded at cathodic potentials (-0.80 V). Modification of ITO/CoPc-AQ electrode with nano-platinum and nano-gold particles (ITO/CoPc-AQ-n Pt and ITO/CoPc-AQ-n Au ) increased the sensitivity of the electrode. All basic sensor parameters of modified electrodes were derived with different measurement techniques and compared with each other. The lowest detection limit (2.30 × 10-9M) was recorded with EIS techniques on ITO/CoPc-AQ-n Pt electrode for sensing of eserine.

Electrode modification based on “click electrochemistry” between terminal-alkynyl substituted cobalt phthalocyanine and 4-azidoaniline

A new electrochemical sensor electrode was constructed with a new electrode modification technique, “click electrochemistry” (CEC) based on a functional cobalt phthalocyanine. In this newly constructed modified electrode (GCE/PANI-N3/TA-CoPc (CEC)), a terminal-alkynyl (TA) substituted cobalt phthalocyanine (CoPc-TA) was electrochemically bonded to the azido end of electro-polymerized 4-azidoaniline (PANI-N3), which was electropolymerized on the GCE electrochemically previously. GCE/PANI-N3/TA-CoPc (CEC) electrode was characterized with voltammetric, electrochemical impedance spectroscopy (EIS), UV–vis spectroscopy, and scanning electron microscopy (SEM) techniques. GCE/PANI-N3/TA-CoPc electrode gave three redox couples assigned to the CoPc and PANI in nonaqueous and aqueous electrolyte systems, which is a desired factor for the application of a modified electrode in various electrochemical applications such as electrocatalytic and electrosensing fields. Pesticide sensing responses of GCE/PANI-N3/TA-CoPc (CEC) electrode were tested with SWV method for usability as an electrochemical pesticide sensor for eserine. Basic sensor parameters, calibration lines, and detection limits (LOD) of GCE/PANI-N3/TA-CoPc (CEC) electrode were derived from SWV responses of the electrode. Amperometric sensing analyses of SVW responses of the electrode give a linear range between 1.56×10−7 and 2.45×10−6moldm−3 eserine with a sensitivity of 1.15Adm3mol−3 and LOD of 1.75×10−7moldm−3.

Novel cold chemical lamination bonding technique—A simple LTCC thermistor-based flow sensor

The LTCC technique enables fabrication of microfluidic devices. The structures consist of channels, chambers and screen-printed passives. The lamination is a quality-determining process in the manufacture of the fluidic modules. The commonly used bonding method is thermocompression. The tapes are joined together at high pressure (up to 30 MPa) and temperature (up to 80 °C) for 2–15 min. Although these parameters allow good LTCC module encapsulation, the quality of the chamber geometry is strongly affected by high pressure and temperature. The cold chemical lamination (CCL) technique presented in this paper, a solvent-based method, largely avoids these problems. A film of a special solvent is deposited on the green tape, and softens the surface. The tape layers are then stacked and compressed at low pressure, below 100 kPa, at room temperature. The fabrication of a simple LTCC thermistor-based flow sensor is presented here to compare both lamination methods. The test device consists of one buried thermistor screen printed on a bridge hanging in a gas/liquid channel. The basic sensor parameters (measurement range, working temperature, output signal, working pressure and measurement error) are analyzed.

Space and aircraft sensors

Metal oxide-based semiconducting sensors offer a promising solution for various measurement problems of practically all the small constituents in the atmospheres of the Earth and other planets. These sensors may be installed in various flying objects. The basic sensor parameters essential for these experiments are: sensitivity, rapid action and selectivity of data acquisition. The main advantage of these sensors is the possibility of making highly sensitive measurements of molecules (O 2, H 2, Cl 2, etc.) in the ground state and also of chemically active particles (free atoms: H, O, Cl, N, etc.; radicals: OH, CH 3, NH 2, etc.; vibrationally excited molecules: O v=1 2, N v=1 2, Cl v=1 2, H v=1 2 and their isotopes; electronically excited molecules: O 2 ( 1Δ g); metastable atoms of inert gases). The sensitivity of the sensors to free atoms and radicals is 10 6–10 8 cm t−3, that is two to three orders of magnitude higher than for excited molecules and three to six orders higher than for molecules in the ground state. In spite of the exciting solutions of some selectivity problems for the simplest particles (O and O 2, O and H, H and OH, O v=1 2, O 2 ( 1Δ g) and O), the problem of selectivity as a whole is far from being settled. A sensor system for O atoms installed in a meteorocket has been constructed and successfully examined in an experiment in the upper Earth's atmosphere.