Review Dry and Non-Contact EEG Electrodes for 2010-2021 Years

The basis of the work of electroencephalography (EEG) is the registration of electrical impulses from the brain or some of its individual areas using a special sensor/electrode. This method is used for the treatment and diagnosis of various diseases. The use of wet electrodes in this case does not seem viable, for several well-known reasons. As a result of this, a detailed analysis of modern EEG sensors developed over the past few years is carried out, which will allow researchers to choose this type of sensor more carefully and, as a result, conduct their research more competently. Due to the absence of any standards in the production and testing of dry EEG sensors, the main moment of this manuscript is a detailed description of the necessary steps for testing a dry electrode, which will allow researchers to maximize the potential of the sensor in the various type of research.

pH Sensitivity Estimation in Potentiometric Metal Oxide pH Sensors Using the Principle of Invariance

A numerically solvable engineering model has been proposed that predicts the sensitivity of metal oxide- (MOX-) based potentiometric pH sensors. The proposed model takes into account the microstructure and crystalline structure of the MOX material. The predicted pH sensitivities are consistent with experimental results with the difference below 6% across three MOX (RuO2, TiO2, and Ta2O5) analysed. The model distinguishes the performance of different MOX phases by the appropriate choice of surface hydroxyl site densities and dielectric constants, making it possible to estimate the performance of MOX electrodes fabricated through different high-temperature and low-temperature annealing methods. It further addresses the problem, cited by theoreticians, of independently determining the C1 inner Helmholtz capacitance parameter while applying the triple-layer model to pH sensors. This is done by varying the C1 capacitance parameter until an invariant pH sensitivity across different electrolyte ionic strengths is obtained. This invariance point identifies the C1 capacitance. The corresponding pH sensitivity is the characteristic sensitivity of MOX. The model has been applied across different types of metal oxides, namely, expensive platinum group oxides (RuO2) and cheaper nonplatinum group MOX (TiO2 and Ta2O5). High temperature annealed, RuO2 produced a high pH sensitivity of 59.1082 mV/pH, while TiO2 and Ta2O5 produced sub-Nernstian sensitivities of 30.0011 and 34.6144 mV/pH, respectively. Low temperature annealed, TiO2 and Ta2O5 produced Nernstian sensitivities of 59.1050 and 59.1081 mV/pH, respectively, illustrating the potential of using cheaper nonplatinum group MOx as alternative sensor electrode materials. Separately, the usefulness of relatively less investigated, cheap, and readily available MOX, viz. Al2O3, as the electrode material was analysed. Low-temperature-annealed Al2O3 with a Nernstian sensitivity of 59.1050 mV/pH can be considered as a potential electrode material. The proposed engineering model can be used as a preliminary prediction mechanism for choosing potentially cheaper alternative sensor electrode materials.

A Robust Optimization for Zinc Oxide - Graphene Composite Sensor Electrode Utilization in Biodegradable Environment

In this paper, the emphasis is made on sensor electrodes using Zinc Oxide and Graphene based composites. A robust optimization for ZnO - Graphene composite sensor electrode and its possible application as sensor in the potential field of biodegradable environment is explored. It is explored that the Graphene conductivity dependence on the geometrical structure of nanotubes. The reaction time and decomposition rate along with other properties at low temperatures are discussed along with the result and analysis. These composite based sensor devices can be very useful in the potential field of harmful environment and its effective utilization are analyzed and characterized.

Fabrication of porous NiMn2O4 nanosheet arrays on nickel foam as an advanced sensor material for non-enzymatic glucose detection

In this work, porous NiMn2O4 nanosheet arrays on nickel foam (NiMn2O4 NSs@NF) was successfully fabricated by a simple hydrothermal step followed by a heat treatment. Porous NiMn2O4 NSs@NF is directly used as a sensor electrode for electrochemical detecting glucose. The NiMn2O4 nanosheet arrays are uniformly grown and packed on nickel foam to forming sensor electrode. The porous NiMn2O4 NSs@NF electrode not only provides the abundant accessible active sites and the effective ion-transport pathways, but also offers the efficient electron transport pathways for the electrochemical catalytic reaction by the high conductive nickel foam. This synergy effect endows porous NiMn2O4 NSs@NF with excellent electrochemical behaviors for glucose detection. The electrochemical measurements are used to investigate the performances of glucose detection. Porous NiMn2O4 NSs@NF for detecting glucose exhibits the high sensitivity of 12.2 mA mM−1 cm−2 at the window concentrations of 0.99–67.30 μM (correlation coefficient = 0.9982) and 12.3 mA mM−1 cm−2 at the window concentrations of 0.115–0.661 mM (correlation coefficient = 0.9908). In addition, porous NiMn2O4 NSs@NF also exhibits a fast response of 2 s and a low LOD of 0.24 µM. The combination of porous NiMn2O4 nanosheet arrays and nickel foam is a meaningful strategy to fabricate high performance non-enzymatic glucose sensor. These excellent properties reveal its potential application in the clinical detection of glucose.

Rancang Bangun Smart pH Meter Sebagai Alat Ukur Pemantau Larutan Nutrisi

ABSTRAKPotential of Hydrogen (pH) adalah salah satu parameter penting yang terdapat pada nutrisi tanaman hidroponik. Setiap tanaman memerlukan nutrisi dengan pH sesuai kebutuhannya, agar dapat tumbuh dengan baik. pH nutrisi akan berubah setiap saat, sehingga perlu sering dipantau. Terdapat kendala pada pH meter yang digunakan saat ini, misalnya perlu kalibrasi ulang jika digunakan lebih dari 24 Jam karena elektroda sensor pH rentan terhadap larutan yang diukurnya. Pada penelitian ini dirancang sebuah pH meter cerdas yang akan digunakan untuk mengukur nutrisi tanaman. Alat ukur ini mampu digunakan secara terus menerus selama lebih dari 24 jam. Sensor pH yang digunakan adalah FIT0348 dan ATMega8 sebagai unit kontrolernya. Proses pengujian terdiri dari 4 tahap. Berdasarkan hasil pengujian, disimpulkan bahwa koefisien determinasi pada rangkaian pengkondisi sinyal yang dirancang telah linier yaitu 0,9999 dengan persamaan regresi y=0,0065x+6,189. ΔpH dari pH meter yang dirancang adalah ±0,01 dengan menggunakan PH/EC-9853 sebagai alat ukur pembandingnya.Kata kunci: potensial of hydrogen, pH meter, hidroponik, nutrisi tanamanABSTRACTPotential of Hydrogen (pH) is one of the important parameters found in hydroponic plant nutrition. Every plant needs nutrients with pH according to their needs, so they can grow well. The pH of nutrients will change at any time, so it needs to be monitored frequently. There is a problem with the pH meter used today, for example, it needs recalibration if it is used more than 24 hours because the pH sensor electrode is susceptible to the solution it measures. In this study, a smart pH meter was designed to be used to measure plant nutrient. This measuring instrument can be used continuously for more than 24 hours. The pH sensor used is FIT0348 and ATMega8 as the controller unit. The testing process consists of 4 steps. Based on tests, it was concluded that the coefficient of determination in the signal conditioning circuit designed was equal to 0.9999 with the regression equation y = 0.0065x + 6.189. ΔpH from the pH meter designed is ± 0.01 by using PH/EC-9853 as a comparison measuring instrument.Keywords: potensial of hydrogen, pH meter, hydroponic, plant nutrition