A selection of sensing techniques for mapping soil hydraulic properties

Data on soil hydraulic properties are needed as input for many models, such as models to predict unsaturated water movement and crop growth, and models to predict leaching of nutrients and pesticides to groundwater. The soil physics database of the Netherlands shows several lacunae, and a substantial part of the data were collected more than thirty years ago and thus might not represent actual soil hydraulic conditions

Passive direct methanol fuel cells acting as fully autonomous electrochemical biosensors: Application to sarcosine detection

This work describes an innovative electrochemical biosensor that advances its autonomy toward an equipment-free design. The biosensor is powered by a passive direct methanol fuel cell (DMFC) and signals the response via an electrochromic display. Briefly, the anode side of the DMFC power source was modified with a biosensor layer developed using molecularly imprinted polymer (MIP) technology to detect sarcosine (an amino acid derivative that is a potential cancer biomarker). The biosensor layer was anchored on the surface of the anode carbon electrode (carbon black with Pt/Ru, 40:20). This was done by bulk radical polymerization with acrylamide, bis-acrylamide, and vinyl phosphonic acid. This layer selectively interacted with sarcosine when integrated into the passive DMFC (single or multiple, in a stack of 4), which acted as a transducer element in a concentration-dependent process. Serial assembly of a stack of hybrid DMFC/biosensor devices triggered an external electrochromic cell (EC) that produced a colour change. Calibrations showed a concentration-dependent sarcosine response from 3.2 to 2000 µM, which is compatible with the concentration of sarcosine in the blood of prostate cancer patients. The final DMFC/biosensor-EC platform showed a colour change perceptible to the naked eye in the presence of increasing sarcosine concentrations. This colour change was controlled by the DMFC operation, making this approach a self-controlled and self-signalling device. Overall, this approach is a proof-of-concept for a fully autonomous biosensor powered by a chemical fuel. This simple and low-cost approach offers the potential to be deployed anywhere and is particularly suitable for point-of-care (POC) analysis.The authors acknowledge the financial support of EU-Horizon 2020 (Symbiotic, FET-Open, GA665046), and from national funds from FCT - Fundação para a Ciência e a Tecnologia, I.P., in the scope of the projects LA/P/0037/2020, UIDP/50025/2020, UIDB/50025/2020 and UID/EMS/00532/2019. Nádia Ferreira (SFRH/BD/122955/2016), Liliana Carneiro (SFRH/BD/122954/2016), and Ana Carolina Marques (SFRH/BD/115173/2016) acknowledge Fundação para a Ciência e Tecnologia (FCT) for financial support.info:eu-repo/semantics/publishedVersio

Development of a capacitive bioimpedance measurement system

Bioelectrical impedance spectroscopy (BIS) is a well-established and non-invasive method to determine and monitor body composition. Commercially available bioelectrical impedance systems use coated hydrogel-aluminium electrodes, where the hydrogel acts as an adhesive and as an electrolytic medium. The gel/adhesive is physiologically inert over short periods. However, when used over longer periods, hydrogel-aluminium electrodes present limitations, which capacitive electrodes may overcome. First measurements using capacitive electrodes have shown that commercial devices are not designed to work with these kind of electrodes. The presented high impedance, specially at low frequencies (e.g. 5kHz), presents a challenge for the current injection and therefore for the design of the current source. Within this project, a bioimpedance spectroscopy (BIS) system to perform measurements using capacitive electrodes has been developed. The system has been tested in the critical frequency range, namely in the lower frequency range (5 kHz - 43 kHz). Measurements have been performed using dummy electrical models, which simulate di erent values of skin and electrode impedance. The results obtained show the better performance of the device in comparison to a commercial device (Xitron Hydra 4200, Xitron Technologies) for that frequency range. An important item in this thesis has been the design of a multi-frequency current source able to perform measurements using capacitive electrodes

Recent advances in chemical sensors for soil analysis: a review

The continuously rising interest in chemical sensors' applications in environmental monitoring, for soil analysis in particular, is owed to the sufficient sensitivity and selectivity of these analytical devices, their low costs, their simple measurement setups, and the possibility to perform online and in-field analyses with them. In this review the recent advances in chemical sensors for soil analysis are summarized. The working principles of chemical sensors involved in soil analysis; their benefits and drawbacks; and select applications of both the single selective sensors and multisensor systems for assessments of main plant nutrition components, pollutants, and other important soil parameters (pH, moisture content, salinity, exhaled gases, etc.) of the past two decades with a focus on the last 5 years (from 2017 to 2021) are overviewed

Sensor Array-Based Optical Portable Instrument For Determination Of Ph

A portable optical instrument is presented that makes it possible to determine pH with a colorimetric sensor array. The use of four membranes containing acid-base indicators makes it possible to cover the full range of pH using the H (hue) coordinate measurements of the HSV colour space. pH sensitive membranes were directly cast onto a plastic support to form a two-dimensional array, located between an OLED display as the programmable light source and a set of digital colour detectors. The resulting microcontroller-based system is immune to optical and electrical interferences. A complete optical and electrical characterization and optimization of the hand-held instrument was carried out. The instrument was used to determine pH using a simple algorithm to select the sensor output that was programmed in the microcontroller. The initial eleven candidate pH membranes were reduced to only four, which permit to obtain reliable pH values. The pH response of the selected four sensing elements was modelled, and calibration curves were applied to a validation set and real samples obtaining positive correlations between the real and predicted data.Ministerio de Ciencia e Innovación, Dirección General de Investigación y Gestión del Plan Nacional de I+D+i (Spain) (Projects CTQ2009-14428-C02-01 and CTQ2009-14428-C02-02)Junta de Andalucía (Proyecto de Excelencia P08-FQM-3535)Partially supported by European Regional Development Funds (ERDF

Wireless ion selective electrode autonomous sensing system

A paradigm shift in sensing methods and principles is required to meet the legislative demands for detecting hazardous substances in the molecular world. This will encompass the development of new sensing technologies capable of performing very selective and sensitive measurements at an acceptable cost, developed by multidisciplinary teams of chemists, engineers and computer scientists to harvest information from a multitude of molecular targets in health, food and the environment. In this study we present the successful implementation of a low-cost, wireless chemical sensing system that employs a minimum set of components for effective operation. Specifically, our efforts resulted in a wireless, tri-electrode, ISE pH sensor for use in environmental monitoring. Sensor calibration and validated insitu field trials have been carried out and are presented in this paper

Quasi-Digital Biosensor-Interface for a Portable Pen to Monitor Anaesthetics Delivery

Monitoring of patient response to the anaesthetic drugs is an attractive improvement for achieving a correct balance of sedation level, increasing the chance of success in the right procedure of anaesthesia. Nowadays, there are no commercial tools able to offer real-time monitoring of anaesthetics, indeed, there is still a lack in sensing technologies able to maintain high performances in long term monitoring within a portable miniaturised hardware system. To overcome these limitations, we are here presenting the innovative concept of a portable pen-device able to sense anaesthetic compounds over time. This study is based on an electrochemical sensor to be fully integrated into a complete pen-shaped point-of-care for the monitoringof anaesthesia delivery. The design of the system is based on a bio-inspired event-based approach that is guaranteeing low complexity, low power consumption and is therefore suitable to be scaled to fit the barrel of a pen. An exhaustive comparison between the proposed system and a lab instrument proves that the presented approach obtains comparable performances in terms of sensitivity and resolution with the ones obtained by expensive commercial instrumentation, meanwhile, the results show a 95 % power consumption reduction and a 92 % area decrease w.r.t. previously presented implementation

Electrical Impedance Spectroscopy (EIS) characterization of saline solutions with a low-cost portable measurement system

Electrical Impedance Spectroscopy (EIS), a powerful technique used for wide range of applications, is usually carried out by means of benchtop instrumentation (LCR meters and ìmpedance analyzers), not suited for in-the-field measurements performed outside a laboratory.In this paper a new portable electronic system for EIS on liquid and semi-liquid media is presented that is capable to produce an electrical fingerprint of the sample under investigation. The proposed system was used for the characterization of four different saline solutions (NaCl, Na2CO3, K2HPO4 and CuSO4). A multi-frequency approach, based on the measurement of maximum value of the impedance imaginary component and its corresponding frequency, was tested for the first time to discriminate different saline solutions. The results show that the proposed method is capable to discriminate the different solutions and to measure the concentration (R2 = 0.9965) independently of the type of saline solution. Keywords: Impedance Spectroscopy, Measurement, Frequency, Sensor, Portable syste

Bone Remodeling Monitor

The impact of bone loss due to different mechanical loadings in microgravity is a major concern for astronauts upon reintroduction to gravitational forces in exploration missions to the Moon and Mars. it has been shown that astronauts not only lose bone at differing rates, with levels up to 2% per month, but each astronaut will respond to bone loss treatments differently. Pre- and post-flight imaging techniques and frozen urine samples for post-flight laboratory immunoassays To develop a novel, non-invasive, highly . sensitive, portable, intuitive, and low-powered device to measure bone resorption levels in 'real time' to provide rapid and Individualized feedback to maximize the efficacy of bone loss countermeasures 1. Collect urine specimen and analyze the level of bone resorption marker, DPD (deoxypridinoline) excreted. 2. Antibodies specific to DPD conjugated with nanoshells and mixed with specimen, the change in absorbance from agglutination is measured by an optical device. 3. The concentration of DPD is displayed and recorded on a PD