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  • Open access
  • 26 Reads
Compliant Magnetic Sensor Technologies

We will review the recent progress in the field of shapeable magnetoelectronics allowing to realize not only mechanically imperceptible electronic skins, which enable perception of the geomagnetic field (e-skin compasses), but also enable sensitivities down to ultra-small fields of sub-50 nT. We demonstrate that e-skin compasses allow humans to orient with respect to earth’s magnetic field ubiquitously. The biomagnetic orientation enables novel interactive devices for virtual and augmented reality applications, which is showcased by realizing touchless control of virtual units in a game engine using omnidirectional magnetosensitive skins. This concept was further extended by demonstrating a compliant magnetic microelectromechanical platform (m-MEMS), which is able to transduce both tactile (via mechanical pressure) and touchless (via magnetic field) stimulations simultaneously and discriminate them in real time. Those devices are crucial for interactive electronics, human-machine interfaces, but also for the realization of smart soft robotics with highly compliant integrated feedback system as well as in medicine for physicians and surgeons.

  • Open access
  • 19 Reads
Effect of milling time on the sensing properties of fly ash zeolite composite thin films
Published: 17 May 2021 by MDPI in 8th International Symposium on Sensor Science session Physical Sensors

Thin films consisting of a sol-gel Nb2O5 matrix doped with zeolite Na-X synthesized from fly ash through ultrasonic-assisted double stage fusion-hydrothermal alkaline activation were deposited by the spin-coating method. In order to improve the optical quality and sensing properties of the thin films zeolites were wet-milled for 60, 120 and 540 seconds prior to incorporation in the film. The liquid adsorption ability of thin films were tested by measuring the reflectance spectra prior to and after exposure to liquid acetone and the change in the reflection coefficient ∆R of the films was calculated. The influence of milling time of zeolites on the sensing and optical properties of the films was studied.

  • Open access
  • 14 Reads
Study of the effect of bending deformation on the performance of flexible polymer layered humidity sensor
Katerina Lazarova, Silvia Bozhilova, Sijka Ivanova, Darinka Christova, Tsvetanka Babeva

Humidity-sensitive polymer, namely poly(vinyl alcohol-co-vinyl acetal) was deposited on a flexible poly(ethylene terephthalate) (PET) substrate pre-covered with sputtered Au:Pd thin layer in order to develop an optical flexible humidity sensor. Spin-coating method was applied for the thin polymer film deposition. The optical and sensing properties of the device were studied after repeated bending deformation in the range 25−1000 times. Transmittance measurements at different levels of relative humidity were conducted in order to examine the sensing properties of probed flexible sample. The influence of the number of bending deformations on performance of the sensor is studied and the possibility for its successful application is demonstrated and discussed.

  • Open access
  • 6 Reads
New Potentiometric Surfactant Sensor for Anionic Surfactants Determination in Real System Containing Amphoteric Surfactants
Nikola Sakač, Dubravka Madunić-Čačić, Dean Marković, Marija Jozanović
Published: 17 May 2021 by MDPI in 8th International Symposium on Sensor Science session Chemical Sensors

Surfactants are used for washing, cleaning and disinfection in many every-day products like detergents, cleaning agents, cosmetics, but also in a broad spectra of industry (detergents, pharma, oil exploitations, textile, etc.). Surfactants are divided into four groups: anionic, cationic, nonionic and amphoteric. On the global scale, the demands for surfactants are constantly growing (CAGR of 4.5%. from 2020 to 2025) mainly because of the population growth and life-standard increase. This will make an additional pressure on surfactant pollution of waters. For this reason, it is important to establish fast and sensitive analytical tools for surfactant quantification in water, but also as a quality control tools in production processes. New ion-pair 1,3-dihexadecyl-1H-benzo[d]imidazol-3-ium-tetraphenylborate (DHBI-TPB) was used as an ionophore for fabrication of PVC-based potentiometric surfactant sensor for quantification of anionic surfactants in real samples. Direct potentiometric response measurements showed excellent response characteristics with a Nernstian slope in the linear response region for all investigated surfactants. Developed surfactant sensor was used for potentiometric titrations of anionic surfactants in model and real samples containing amphoteric surfactants betaine or amine oxide, and showed excellent performances and good recoveries. The sensor showed high stability, reproducibility and long-lifetime.

  • Open access
  • 29 Reads
Cost-effective multiplex real-time PCR chip system using open platform camera

This paper proposes a cost-effective real-time multiplex polymerase chain reaction (PCR) chip system for point-of-care (POC) testing. In the proposed system, nucleic acid amplification is performed in a reaction chamber built on a printed-circuit-board (PCB) substrate with a PCB pattern heater and thermistor. Fluorescence can be detected through the transparent plastic on the other side of the substrate. Open platform cameras were used for miniaturization and cost effectiveness. We also used a simple and cost-effective oblique lighting to stimulate fluorescence. Response performance was investigated by observing the change in the average brightness of the chamber images with various reference dye concentrations. In addition, we investigated the interference properties between different colors by measuring the fluorescence response for each dye concentration mixed with the maximum concentration of the different dyes. Quantitative performance was validated using standard DNA solutions. Experimental results show that the proposed system is suitable for POC real-time multi-PCR system.

  • Open access
  • 50 Reads
ZnO/RGO Heterojunction based near Room temperature Alcohol Sensor with Improved Efficiency
Sanghamitra Ghosal, Partha Bhattacharyya
Published: 17 May 2021 by MDPI in 8th International Symposium on Sensor Science session Chemical Sensors

Systematic optimization of surface engineering (dimensionality) indeed plays a crucial role for achieving efficient vapor sensing performance. Among various semiconducting metal oxides, owing to some of its unique features and advantages, ZnO has attracted worldwide researchers for application in various fields including chemical sensors. Concomitant optimization of the surface attributes (varying different dimensions) of ZnO became a sensation for the entire research family. Moreover, the small thickness and extremely large surface of exfoliated 2D nanosheets render the gas sensing material as an ideal candidate, for achieving strong coupling with different gas molecules. However, temperature is a crucial factor in the field of chemical sensing. Recently, graphene-based gas sensors have attracted attention due to their variety of structures, unique sensing performances and room temperature working conditions. In this work, highly sensitive and fast responsive low temperature (60 ºC) based ethanol sensor, based on RGO/2D ZnO nanosheets hybrid structure, is reported. After detailed characterizations, vapor sensing potentiality of such sensor was tested for the detection of ethanol. The ethanol sensor offered the response magnitude of 89% (100 ppm concentration) with response and recovery time of 12 s/29 s respectively. Due to excessively high number of active sites for VOC interaction, with high yield synthesis process and appreciably high carrier mobility, paved the path for developing future generation, miniaturized and flexible (wearable) vapor sensor devices meeting the multidimensional requirements for traditional and upcoming (health/medical sector) applications. Underlying mechanistic framework for vapor sensing, through such hybrid junction, was explained with the Energy Band Diagram.

  • Open access
  • 16 Reads
Multiple Camera Fluorescence Detection for Real Time PCR

The general polymerase chain reaction (PCR) amplifies DNA and analyzes the amplification results of the quantified DNA. Recently, real-time PCR has been developed to detect DNA amplification in various ways. The conventional camera-based system is too expensive and difficult to reduce device size. In this paper, we propose a low-cost, compact fluorescence detection system for real-time PCR systems using open platforms camera. To simplify the optics, four low-cost small cameras were fixedly placed and entire tube was divided into four quadrants to minimize the field of view. In addition, an effective image processing method was used to compensate. The proposed system measured the fluorescence detection performance on the basis of the amount of DNA using various fluorescent substances.

  • Open access
  • 43 Reads
Flexible SERS Sensors based on Carbon Nanomaterials-Supported Au Nanostructures

Surface-enhanced Raman scattering (SERS) is a powerful technique to detect analytes in a label-free and non-destructive way at extremely low concentrations, even down to the single-molecule level. In the present study, a series of anisotropic Au nanostructures are integrated onto the platforms of carbon nanomaterials, mainly carbon nanotubes (CNT) and graphene, in order to fabricate high-performance flexible SERS sensors. Sizes, dimensions and shapes of Au nanostructures can be well controlled through this strategy, based on which Au nanowires, nanoribbons, nanoplates, nanobelts, and nanoframes are successfully deposited onto CNT and graphene templates, respectively. Significantly enhanced plasmonic activity originates from these Au nanocrystals, which provide increased SERS signals of the analytes by many orders of magnitude, while CNT films or graphene substrates offer the superior flexibility and accessibility. For instance, A flexible SERS sensor made of graphene supported Au nanoframes can detect the analyte R6G at the concentration as low as 10-9 M. The mechanism for the sensitivity enhancement could be attributed to the homogenous distribution of Au nanoframes on the graphene support as well as the strong molecule adsorption to the graphene nanoporous network.

  • Open access
  • 16 Reads
LATE-PCR for LoC molecular diagnostics devices and its application to the sensitive detection of SARS-CoV-2

The emergence of the novel coronavirus, SARS-CoV-2, has highlighted the need for rapid, accurate, and point-of-care diagnostic testing. Lab-on-a-Chip (LoC) devices offer the possibility to run such tests at a low cost while at the same time permitting the multiplexed detection of several viruses when coupled with microarray detection of the amplified products. Herein, we report the development of a protocol for the qualitative detection of SARS-CoV-2 through the design of appropriate primers that target evolutionary conserved regions of the virus. The proposed protocol relies on .an improved version of asymmetric RT-PCR, the Linear-After-The-Exponential (LATE)-PCR that uses primers that are deliberately designed for use at unequal concentrations. As a result, LATE-PCR exhibits similar efficiency to symmetric PCR while promoting accumulation of single-stranded products that can subsequently hybridize to a single strand DNA probe-spotted microarray. The performance of the developed LATE-PCR protocol was compared to that of symmetric RT-PCR and validated with the use of artificial viral RNA and nasopharyngeal swabs samples from real patients. Furthermore, and in order to illustrate its potential for integration into a biosensor platform, the amplicons were allowed to hybridize with probes covalently immobilized onto commercially-available functionalized glass, without the need of heat denaturation.

  • Open access
  • 13 Reads
Development of enzymatic biosensors to detect biocides disinfectants to strengthen self-monitoring in industry
Published: 17 May 2021 by MDPI in 8th International Symposium on Sensor Science session Chemical Sensors

Biocides disinfectants are used in agro-food industries in order to limit the development of pathogens present in environment or on surfaces in contact with food for human or animal consumption. Biocides residues remaining on food surfaces may constitute a toxicological risk for the consumer. Very little feedback from the field on the rates of biocides residues in the industry exist due to a lack of simple, fast and responsive self-checking methods. The development of biosensors for the detection of biocides disinfectants represent a promising way to explore but most of this research remains limited.