Diabetes mellitus is linked to both short-term and long-term health problems. Therefore, its detection at a very basic stage is of utmost importance. Research institutes and medical organizations are increasingly using cost-effective biosensors to monitor human biological processes and provide precise health diagnoses. Biosensors aid in accurate diabetes diagnosis and monitoring for efficient treatment and management. Recent attention to nanotechnology in the fast-evolving area of biosensing has facilitated the advancement of new sensors and sensing processes and improved the performance and sensitivity of current biosensors. Nanotechnology biosensors detect disease and track therapy response. Clinically efficient biosensors are user-friendly, efficient, cheap, and scalable in nanomaterial-based production processes and thus can transform diabetes outcomes. This article is more focused on biosensors and their substantial medical applications. The highlights of the article consist of the different types of biosensing units, the role of biosensors in diabetes, the evolution of glucose sensors, and printed biosensors and biosensing systems. Later on, we were engrossed in the glucose sensors based on biofluids, employing minimally invasive, invasive, and noninvasive technologies to find out the impact of nanotechnology on the biosensors to produce a novel device as a nano-biosensor. In this approach, this article documents major advances in nanotechnology-based biosensors for medical applications, as well as the hurdles they must overcome in clinical practice.

The capacitive sensors are widely used for liquid level measurement in different applications, but the contact type capacitive sensors suffer from frequent maintenance and drift of the sensor output. The present paper presents a simple noncontact IDT fringing field capacitance sensor for liquid level measurement. The sensor can be made using flexible /non-flexible substrate, and it can be used to measure the liquid level of the vessel for both planar and non-planar surfaces. Theory of level measurement using the sensor has been discussed. Four different IDT sensor (1-n-1) configurations such as 1-1-1, 1-3-1, 1-5-1 and 1-11-1 have been designed, analysed, simulated (finite element method), and fabricated to measure water and insulating transformer oil levels from 0 to 40 mm. The analytical expressions are derived for 1-n-1 configuration to estimate the value of the capacitance and the maximum field penetration depth of the sensors. The capacitance value of all the four sensors varies almost linearly with the variation of liquid levels. Experimental results show that the sensitivity of the 1-5-1 IDT sensor is 40 fF/mm. Performances of the sensors were compared with other capacitive sensors reported in the literature. The sensor is capable to detect the water level with a resolution of 0.1 mm.

A microcontroller-based digital hygrometer system using a low-cost moisture sensor in the range of 3.7-100 ppm has been developed. The sensor is of capacitive type and consists of nanoporous thin film of alumina (γ - Al ₂ O ₃ ) dip coated in between two parallel gold electrodes onto an alumina substrate. The behavior of the sensor has been modeled with an object to develop a signal processing circuit to convert capacitance change into frequency. The detection electronics circuit is based on a relaxation oscillator whose output is suitable for interfacing with a digital device. The sensor has been characterized with the circuit and then output frequency is calibrated in terms of ppm. The accuracy of the digital hygrometer when compared with the commercial dew point meter is found to be ±1 PPM.

This paper presents a low-cost interface circuit for lossy capacitive sensors. Most of the capacitive sensors are lossy in nature, where the resistance value of the sensor significantly varies along with the capacitance value. Accurate measurement of those values of a lossy capacitive sensor is a challenging task. This paper deals with the development of an electronic interface circuit for such a capacitive sensor. The circuit is based on the measurement of quadrature and in-phase components of the signal. To extract the actual value of the capacitance and the resistance, an average of the quadrature and the in-phase components of output is required. This is implemented using a microcontroller and provides flexibility in averaging (e.g., adjustable length of data to be processed). A PCB of the circuit has been fabricated and tested in the laboratory using capacitors and resistors with known values. The accuracy of the circuit was better than 0.6% and -2.2% for the measurement of capacitance and resistance, respectively. Also, the circuit is highly linear (FS nonlinearity of 0.32%) for a wide range of capacitance measurement (162 pF-3.680 nF). To confirm the effectiveness of the circuit, it was interfaced to a lossy capacitive humidity sensor and another capacitive transducer to measure the dielectric constants of edible oils. The results were compared with a precision impedance analyzer (Agilent 4294A); the maximum relative error was noted as ± 1.6% in the measurement of permittivity values of edible oil. The prototype developed has the option to easily adjust the sensitivity and operating range, depending on the application.

The main aim of this work is to establish a sensor MESH network using an ESP-MESH networking protocol with the ESP32 MCU (a Wi-Fi-enabled microcontroller) for indoor and outdoor air quality monitoring in real time. Each sensor node is deployed at a different location on the college campus and includes sensor arrays (CO₂, CO, and air quality) interfaced with the ESP32. The ESP-MESH networking protocol is a low-cost, easy-to-implement, medium-range, and low-power option. ESP32 microcontrollers are inexpensive and are used to establish the ESP-MESH network that allows numerous sensor nodes spread over a large physical area to be interconnected under the same wireless network to monitor air quality parameters accurately. The data of different air quality parameters (temperature, humidity, PM2.5, gas concentrations, etc.) is taken (every 2 min) from the indoor and outdoor nodes and continuously monitored for 72 min. A custom time-division multiple-access (TDMA) scheduling scheme for energy efficiency is applied to construct an appropriate transmission schedule that reduces the end-to-end transmission time from the sensor nodes to the router. The performance of the MESH network is estimated in terms of the package loss rate (PLR), package fault rate (PFR), and rate of packet delivery (RPD). The value of the RPD is more than 97%, and the value of the PMR and PER for each active node is less than 1.8%, which is under the limit. The results show that the ESP-MESH network protocol offers a considerably good quality of service, mainly for medium-area networks.

This paper deals with the development of a signal conditioning circuit, with microcontroller compatibility, for interfacing capacitive sensors suitable for a wide range of applications. The circuit comprises of a capacitive active bridge, along with a relaxation oscillator for converting capacitance changes into frequency directly. The design, analysis, and experimental results of the circuit and its application to a thin-film-based humidity sensor and a capacitive transducer for measurement of the dielectric constant of edible oil are reported. The experimental results confirm the theoretical values predicted. The frequency output of the circuit has been used to determine the response characteristics of the trace moisture sensor and the dielectric constants of the edible oils. Finally, the output frequency has been calibrated in terms of the trace moisture in parts per million (ppm), using commercial dew point meter (SHAW, U.K.). The accuracy of moisture measurement using custom designed capacitive sensor for the full-scale moisture range of 4-100 ppm, compared with the dew point meter (accuracy ±0.1%), is found to be nearly ±1% and the resolution is 1 ppm moisture. The circuit is less complex and is easy to integrate to application-specific integrated circuits in a standard CMOS technology with high sensitivity (selectable). It can be easily reproduced with the cheapest possible components, while achieving fairly good performance in terms of both accuracy and dynamic range.