Ajay Beniwal
@gla.ac.uk
Marie Curie Fellow (Electronic & Nanoscale Engineering)
University of Glasgow, UK
EDUCATION
Doctor of Philosophy (PhD)
RESEARCH, TEACHING, or OTHER INTERESTS
Electrical and Electronic Engineering, Surfaces, Coatings and Films, Multidisciplinary, Materials Science
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Ajay Beniwal and Chong Li
IEEE
Temperature sensors with excellent disposability, biocompatibility, flexibility, and a facile fabrication process are strongly desirable for real-world applications in the realm of wearable healthcare. In this paper, we demonstrate poly(3,4ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS)based temperature sensor that has a PEDOT:PSS sensing layer and drop casted on graphene carbon ink based interdigitated electrodes (IDEs), screen printed on a paper substrate. The temperature sensing characteristics were examined in the range of $25^{\\circ}\\mathrm{C}$ to $60^{\\circ}\\mathrm{C}$. The results show that the sensors have a substantial sensitivity of -0.486 %$/^{\\circ}\\mathrm{C}$ in the considered range and exhibit an excellent linear fit with a Adj. R-Square value of 0.96412. Other imperative characteristics like hysteresis analysis (4.08 %), response/recovery time, repeatability (3-cyclic), reproducibility etc. were also studied and discussed. The results show that the sensor is an excellent candidate for temperature sensing in the healthcare sector particularly for monitoring wound healing temperature via smart bandages.
Ajay Beniwal, Priyanka Ganguly, Rahul Gond, Brajesh Rawat, and Chong Li
Institute of Electrical and Electronics Engineers (IEEE)
This work presents a flexible and disposable nitrogen dioxide (NO2) gas sensor based on Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), operating at room temperature (RT). The gas sensing layer, composed of PEDOT:PSS, is deposited on interdigitated electrodes (IDEs) made from graphene–carbon ink, which are screen printed onto a paper substrate using the drop casting method. The Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses are carried out to understand the successful deposition and surface morphology analysis of the sensing layer. The NO2 sensing properties are explored in the range 0.5–50 ppm at RT (27 °C ± 2 °C). The sensor displays significant % response viz., 0.79%–12.97% in the measured range 0.5–50 ppm. Other important sensing characteristics, such as response and recovery times (210 s / 60 s at 0.5 ppm), repeatability, and reproducibility along with sensing mechanism are also presented. The findings of this letter suggest that the developed sensor holds promise for various application areas.
Deepan Kumar Neethipathi, Ajay Beniwal, Adrian M. Bass, Marian Scott, and Ravinder Dahiya
Institute of Electrical and Electronics Engineers (IEEE)
Heavy metal ions (HMI), such as Cu<inline-formula> <tex-math notation="LaTeX">$^{{2}+}$ </tex-math></inline-formula>, are harmful to the environment and our health. Such ions are typically measured using glassy carbon electrode (GCE)-based electrochemical sensors developed on rigid substrates. However, several emerging applications require such sensors on flexible, and even disposable, substrates. Herein, we present a molybdenum disulfide (MoS2)-modified screen-printed carbon electrode (SPCE)-based flexible electrochemical sensor for the detection of copper ions in the water. The sensor exhibits excellent response with a limit of detection (LOD) of <inline-formula> <tex-math notation="LaTeX">$5.43 \\mu \\text{M}$ </tex-math></inline-formula> for Cu ions in the range of <inline-formula> <tex-math notation="LaTeX">$5 \\mu \\text{M}$ </tex-math></inline-formula> - 5 mM. The developed sensor is compared with MoS2-modified conventional GCE using electrochemical impedance spectroscopy (EIS). The comparative studies show better linearity (<inline-formula> <tex-math notation="LaTeX">${R}^{{2}}$ </tex-math></inline-formula> value <inline-formula> <tex-math notation="LaTeX">$\\sim $ </tex-math></inline-formula>0.99) for SPCE-based sensor and underline how easily they can detect Cu ions. The interference study, i.e., detection of copper ions in the presence of other HMI-based analytes, also shows the excellent response of SPCE-based flexible electrochemical sensor—thus, demonstrating their practical application is the detection of Cu in water.
Ajay Beniwal, Dina Anna John, and Ravinder Dahiya
Institute of Electrical and Electronics Engineers (IEEE)
This letter presents a flexible and disposable humidity sensor based on Poly(3,4-ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS). The sensing layer is developed by drop casting PEDOT:PSS on screen printed graphene-carbon-ink-based interdigitated electrodes (IDEs) on paper substrate. The humidity sensing properties are investigated in a wide humidity range (25%RH–90%RH) at room temperature (RT; 27 °C ± 2 °C). The sensor exhibits substantial % response (118.5% at 90%RH) in the considered range with response/recovery time as 70/30 s. The applicability of the sensor has been demonstrated for skin moisture/humidity monitoring under normal and moist conditions. A read-out circuit is designed for demonstrating the real-time monitoring of skin moisture level. The obtained results indicate the suitability of the developed sensor for skin moisture monitoring, environmental humidity monitoring, and noncontact switching in areas such as healthcare and agriculture.
Xenofon Karagiorgis, Gaurav Khandelwal, Ajay Beniwal, Radu Chirila, Peter J. Skabara, and Ravinder Dahiya
Wiley
Highly sensitive pressure sensors, with a wide operating range, are needed in applications such as wearables, prostheses, and haptic‐based interactive systems. Herein, fully 3D printed capacitive pressure sensors comprising polydimethylsiloxane (PDMS) foam‐based dielectric layer, sandwiched between the poly(3,4‐ethylenedioxythiophene):polystyrene sulfonate and silver nanowire‐based electrodes, are presented. The printed electrodes exhibit excellent electrical properties (1.6 Ω sq−1, 20.35 kS m−1) and bendability. Various ratios of PDMS to ammonium bicarbonate (NH4HCO3) are evaluated to obtain dielectric layer with optimum pore sizes for better performance and ease of fabrication. The device with a PDMS:NH4HCO3 ratio of 4:0.8 exhibits a linear response with a sensitivity of 0.0055 kPa−1 in the tested pressure range of 5–170 kPa. The fully 3D printed sensors also show excellent repeatability over 500 cycles with an average hysteresis of 1.53%, and fast response and recovery times of 89 and 195 ms, respectively. The superiority of the presented 3D printed foam‐based device is confirmed by 30% higher sensitivity in comparison with PDMS‐based sensors. Finally, as a proof‐of‐concept, the pressure sensors presented in this study are assessed for their suitability in underwater environments and touch‐based object recognition.
Ajay Beniwal and Ravinder Dahiya
IEEE
This paper presents a flexible and disposable humidity sensor based on Poly(3,4ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). The sensing layer is developed by drop casting PEDOT:PSS on screen printed graphene-carbon (G-C) based interdigitated electrodes (IDEs) on paper substrate. The humidity sensing properties are investigated in a wide humidity range $(25 \\% \\mathbf{R H}$ - $90 \\% \\mathrm{RH})$ at room temperature (RT; $\\left.27^{\\circ} \\mathrm{C} \\pm 2{}^{\\circ} \\mathrm{C}\\right)$. The sensor exhibits substantial % response $(118.5 \\%$ at $90 \\% \\mathrm{RH})$ in the considered range with response/recovery time as $70 / 30$ seconds (sec.). The applicability of the sensor has been demonstrated for skin moisture/humidity monitoring under normal and moist conditions. The obtained results indicate the suitability of the developed sensor for applications such as skin moisture analysis, environmental monitoring, agriculture, healthcare, non-contact switching and industrial applications.
Xenofon Karagiorgis, Ajay Beniwal, Peter Skabara, and Ravinder Dahiya
IEEE
This paper presents a degradable nanofibers-based sensor for underwater pressure monitoring applications. The presented capacitive pressure sensor uses polyhydroxy butyrate (PHB) nanofibers as the dielectric material. The sensor is encapsulated in polyimide (PI) to prevent moisture permeation during the operation. The fabricated device is tested in air and water ambient under dynamic and static conditions. The sensor showed a sensitivity of 3.87 $\\mathrm{k}\\mathrm{P}\\mathrm{a}^{-1}$ with excellent linearity (99.8%) and stability, and low hysteresis of 1.3 %. The fabrication process used here could also be replicated to develop flexible pressure sensors for underwater wearables.
Deepan Kumar Neethipathi, Ajay Beniwal, Priyanka Ganguly, Adrian Bass, Marian Scott, and Ravinder Dahiya
IEEE
This work presents a 2-Dimensional (2D) Graphitic carbon nitride (g-C3N4) modified glassy carbon electrode (GCE)based electrochemical sensor for detection of F$\\mathrm{e}^{2+}$ ions in water. The 2Dg-C3N4 nanomaterial is prepared by dispersing, ultrasonification and then modifying the GCE using the drop-casting method. The structural and morphological characteristics of the prepared g-C3N4 are examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM). The performance of the sensor is analysed for different concentrations (from 0.9 mM to 5 mM) of iron content in the electrolyte using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The obtained results indicate excellent sensing performance towards target ions. Along with the concentration study, the accumulation study (with a scan speed of10 mV/s to 1000 mV/s in -0.6V to 0. SV region) and repeatability analysis (30 CV scans) are also carried out. Based on the obtained results, the 2Dg-C3N4 modified sensor work is a promising candidate for electrochemical detection of F$\\mathrm{e}^{2+}$ ions in water for a wide range of applications.
Ajay Beniwal, Priyanka Ganguly, Akshaya Kumar Aliyana, Gaurav Khandelwal, and Ravinder Dahiya
Elsevier BV
Akshaya Kumar Aliyana, Priyanka Ganguly, Ajay Beniwal, S. K. Naveen Kumar, and Ravinder Dahiya
Institute of Electrical and Electronics Engineers (IEEE)
The estimation of pH is vital to assess the biochemical and biological processes in a wide variety of applications ranging from water to soil, health, and environment monitoring. This work reports a screen-printed flexible and disposable pH sensor using the impedimetric method. The pH sensor was fabricated by screen printing graphene-carbon (G-C) modified zinc oxide (ZnO)-based active layer on a paper substrate and shows nearly three orders of change in impedance magnitude in the pH range of 2–9. The sensor was carefully designed using COMSOL Multiphysics software to understand the influence of electrode geometry and the electrical potential developed across the structure. The developed sensor was used for pH monitoring of soil and exhibited high sensitivity of 5.27 <inline-formula> <tex-math notation="LaTeX">$\\text{k}\\Omega $ </tex-math></inline-formula>/pH 2–8 with a correlation coefficient (<inline-formula> <tex-math notation="LaTeX">${R}^{{2}}$ </tex-math></inline-formula>) of 0.99. Finally, an IoT-enabled smart pH detection system was implemented for continuous pH monitoring for potential application in digital agriculture. The outcome demonstrates that the presented flexible and disposable pH sensor could open new opportunities for monitoring of water, product process, human health, and chemical (or bio) reactions even by using small volumes of samples.
Ajay Beniwal, Priyanka Ganguly, Deepan Kumar Neethipathi, and Ravinder Dahiya
IEEE
In this work, we present a screen-printed humidity sensor fabricated on a flexible polyvinyl chloride (PVC) substrate. A comparative analysis has been carried out for printed graphene-carbon electrode with and without Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) modification in the humidity sensing range of 25 - 90 %RH. The sensor modified with PEDOT:PSS demonstrated enhanced performance ( ~ 1 %/%RH versus ~ 0.8 %/%RH of unmodified sensor). Further, the enhancement in the performance of the modified sensor was found to be prominent in the low to moderate humidity range (≤60 %RH). The repeatability, response and recovery time were also analysed for both types of sensors and their applicability has been demonstrated for neonatal care by monitoring the humidity level of a wet baby diapers. This demonstration shows the potential application of presented humidity sensors in areas such as environmental monitoring, healthcare, industrial, and agriculture.
Deepan K. Neethipathi, Priyanka Ganguly, Ajay Beniwal, Marian Scott, Adrian Bass, and Ravinder Dahiya
IEEE
Monitoring of heavy metal ions in aquatic environment can be a tedious process, especially in harsh, logistically challenging field conditions. This work demonstrates the detection of copper ions in water using a low-cost screen printed 2D molybdenum disulfide (MoS2) nanoparticle based electrochemical sensor. To deal with the common field-testing challenges, an easily disposable, flexible, compact sized reliable sensor was fabricated using a screen-printing technique. The developed sensor shows an excellent performance with a linear range of 5 µM to 1000 µM, a low limits of detection (LOD) value of just 0.3125 µM, and high repeatability with standard deviation less than 0.5%. With this performance and attractive attributes such as flexible form factor, low-cost fabrication and disposability etc. the presented sensor shows a great potential for practical applications in soil and water monitoring.
Priyanka Ganguly, Deepan Kumar Neethipathi, Ajay Beniwal, and Ravinder Dahiya
IEEE
Screen printing is one of the widely used methods for printed sensors and electronics. The performance of these devices could vary with the printing parameters such as thickness of the printed layer, the squeeze length and pressure applied for printing etc. Whilst sensor design and the ink used for the printing of sensitive layers have been studied previously, the vital printing parameters has not attracted much attention. This paper reports the influence of thickness of printed sensor on their electrochemical sensing property. Carbon ink is used to print sensors with three-electrode geometry and their working electrode is modified with MoS2 to study the detection of ascorbic acid. The thicknesses of the sensitive layers varied from ~4 µm to 120 µm as the number of printed layers of ink increased from 1 to 5, 10 and 20. The cyclic voltammetry, differential pulse voltammetry and impedance spectroscopy are used to investigate the electrochemical performance. It was noted that the peak current indicating the oxidation of ascorbic acid at 0.04 V, increased with the increase in the thickness of electrode or the number of printed layers. The higher current values and lower series resistance was measured for layers 10 and 20, indicating the ideal printed thickness of sensors for low power operation and easy interfacing with read out electronics.
Ajay Beniwal and Sunny
Institute of Electrical and Electronics Engineers (IEEE)
In this work, a room temperature (RT) operated acetone (C3H6O) sensor having good sensing characteristics like good % response, fast response and recovery times, good selectivity, and substantial stability is developed using SnO2-polythiophene (PTh) nanocomposite. The electrospinning technique is used for depositing SnO2 nanofibers(diameter ~80–160 nm) followed by polymerization of thiophene to develop SnO2/PTh nanocomposite. X-ray diffraction (XRD), scanning electron microscopy (SEM), and Fourier-transform infrared spectroscopy (FTIR) results are used to examine the structural, morphological, and elemental analysis of the SnO2/PTh nanocomposite. The mean crystallite size of the nanocomposite is observed to be ~10.6 nm. The acetone sensing performance of the developed sensor is analyzed in concentration range of 0.5–20 ppm at RT (~27 °C) under ~45% relative humidity (RH) conditions. The sensor showed highly stable response with good sensing characteristics toward acetone detection having ~12.7% response for 0.5 ppm with fast response (10 s) and recovery (14 s) times. The response of the sensor reached up to ~131.1% for 20 ppm of acetone. Synergistic effect and p-n heterojunction formation at interface in SnO2/PTh nanocomposite are believed to be the major factors for achieving good sensing performance at RT.
Utkarsh Nirbhay, Ajay Beniwal, Suraj Kumar Lalwani, and Sunny
IEEE
Yttrium (Y) doped SnO2 nanofibers were successfully synthesized and used for detecting low ammonia concentrations at room temperature (RT). Electrospinning followed by calcination method was used to synthesize the Y doped SnO2 nanofibers for various Y concentrations, among which $5 wt$.% Y doped SnO2 nanofibers (average diameter ~90 nm) demonstrated the best response. To analyze the selectivity of the sensor, the sensing properties were also studied for other analytes like acetone, methanol and ethanol, along with ammonia. The% response was observed to be 237%under 10 ppm of ammonia, which is found to be 2.7, 5.3 and 6.6 times higher as compared to acetone (87.5%), ethanol (44.4%) and methanol (36%) responses at 10 ppm, respectively, defining the excellent selectivity of the sensor towards ammonia detection. The fabricated sensor manifests fast response and recovery times i.e. less than a minute. The structural and morphological characteristics of Y doped SnO2 nanofibers were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively.
Ajay Beniwal and Sunny
Royal Society of Chemistry (RSC)
An ultra-responsive room temperature operated dual sensing behavior novel SnO2–ZnO–Fe2O3tri-composite sensor for ammonia and ethanol detection at ppb level.
Suraj Kumar Lalwani, Ajay Beniwal, and Sunny
Springer Science and Business Media LLC
Ajay Beniwal and Sunny
IEEE
Ethanol sensing performance of the NiO sensor has been investigated from room temperature (RT) to optimum temperature (Topt.). A low cost sol-gel spin coating technique has been employed to develop the surfactant embellished NiO sensor for ethanol sensing. The scanning electron microscopy (SEM) results have evidenced the layer surface having cracks and voids, whereas, the lower mean crystallite size (~ 16.2 nm) has been verified by X-ray diffraction (XRD) results. The ethanol sensing characteristics at RT (27 °C) operation revealed the recovery problem. Therefore, the sensor is examined towards the Topt. (200 °C) of operation for removing the recovery problem along with obtaining enhanced ethanol sensing characteristics. The fabricated sensor has been investigated for low ethanol concentrations viz. 1-200 ppm.
Ajay Beniwal and Sunny
IEEE
The effect of UV illumination (254 nm) has significantly improved the sensing parameters viz. response/recovery times and % response, of SnO2-polypyrrole (PPy) composite based ammonia sensor. A facile and cost-effective sol-gel spin coating technique followed by vapor phase polymerization is applied for developing the sensor for ultra-low ammonia concentration detection at room temperature (RT). Electrical characterization, topography, elemental analysis and surface morphology have been examined through current-voltage (I-V) measurement, atomic force microscopy (AFM), energy-dispersive X-ray spectroscopy (EDX) and scanning electron microscopy (SEM), respectively. The ammonia sensing characteristics of the post-UV treated sensor evidenced no recovery issue that existed in pre-UV treated sensor. Enhanced % response is also observed with rapid response and recovery times after UV treatment.
Ajay Beniwal and Sunny
Elsevier BV
Ajay Beniwal and Sunny
Springer Science and Business Media LLC
Ajay Beniwal and Sunny
Springer Science and Business Media LLC
Ajay Beniwal, Suraj Kumar, and Sunny
Institute of Electrical and Electronics Engineers (IEEE)
The present work investigates the baseline resistance stability with a novel Ag doped SnO2/ZnO nanocomposite for ethanol detection. A facile and cost effective sol-gel spin coating technique was used to fabricate a progression series of gas sensors using Ag (2%wt.) doping in each SnO2/ZnO composites viz. SnO2 (100% wt.)/ZnO (0%wt.), SnO2 (95%wt.)/ZnO (5%wt.), SnO2 (75% wt.)/ZnO (25%wt.), and SnO2 (50%wt.)/ZnO (50%wt.) compositions. Sol-gel spin coated samples were characterized by X-ray diffraction, energy-dispersive X-ray spectroscopy, and scanning electron microscopy to investigate the structural, elements composition, and morphological analysis, respectively. High resolution transmission electron microscopy was used for obtaining the detailed structural information of the nanocomposite. The ethanol sensing properties of the fabricated sensors were investigated in order to analyze the baseline stability along with observing the minimum (Tmin) and optimum (Topt) temperature of operation. Observed tradeoff between the % response and baseline stability improvement is explained on the basis of crystallite size and agglomeration of interwoven nanograins in the structure. Analyte sensing results revealed that Ag doped SnO2 (50%wt.)/ZnO (50%wt.) composite exhibited maximum baseline resistance stability along with appreciable % response, high selectivity and appreciable response/recovery time towards ethanol detection at low operating temperature.
Ajay Beniwal, Vibhu Srivastava, and Sunny
IOP Publishing
SnO2 nanostructured thin film based gas sensor is fabricated by sol-gel spin coating technique. The performance of the fabricated sensor has been investigated for analytes viz. ammonia (NH3) solution, acetone (C3H6O), methanol (CH3OH) and 2-propanol (C3H8O) at room temperature (RT) with humidity level ∼55% RH for concentration range 500 ppb-500 ppm. High response and good selectivity towards ammonia are observed with very fast response and recovery time at RT, for extreme low concentrations. Upon exposure to 500 ppb and 1 ppm of NH3, sensor manifests appreciable response ∼28% and ∼31.5%, respectively. High response of the sensor at RT is attributed due to porous nanograins (with average particle size ∼50 nm) based SnO2 thin film layer. Nanograins structure is obtained due to addition of glycerine in the sol solution, which also leads to porosity enhancement of the sensing layer. Good reproducibility and appreciable immunity to drift behavior are other attributes of the fabricated device. X-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and scanning electron microscopy (SEM) results are used to study the structural, chemical composition, topography and morphological characteristics of the prepared SnO2 thin film, respectively.
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CONSULTANCY
Project: DETECT: Disposable Sensor for Continuous Detection of Renal Disease
Role: Principal Investigator (PI)
Funded Value: £203,795
Funder: Horizon Europe Guarantee / UK Research and Innovation
Funded Period: 2 Years
Organisation: University of Glasgow
Department Name: School of Engineering