2,261 research outputs found
Field effect transistor based wearable biosensors for healthcare monitoring
No full textThe rapid advancement of wearable biosensors has revolutionized healthcare monitoring by screening in a non-invasive and continuous manner. Among various sensing techniques, field-effect transistor (FET)-based wearable biosensors attract increasing attention due to their advantages such as label-free detection, fast response, easy operation, and capability of integration. This review explores the innovative developments and applications of FET-based wearable biosensors for healthcare monitoring. Beginning with an introduction to the significance of wearable biosensors, the paper gives an overview of structural and operational principles of FETs, providing insights into their diverse classifications. Next, the paper discusses the fabrication methods, semiconductor surface modification techniques and gate surface functionalization strategies. This background lays the foundation for exploring specific FET-based biosensor designs, including enzyme, antibody and nanobody, aptamer, as well as ion-sensitive membrane sensors. Subsequently, the paper investigates the incorporation of FET-based biosensors in monitoring biomarkers present in physiological fluids such as sweat, tears, saliva, and skin interstitial fluid (ISF). Finally, we address challenges, technical issues, and opportunities related to FET-based biosensor applications. This comprehensive review underscores the transformative potential of FET-based wearable biosensors in healthcare monitoring. By offering a multidimensional perspective on device design, fabrication, functionalization and applications, this paper aims to serve as a valuable resource for researchers in the field of biosensing technology and personalized healthcare.Full Tex
Enhancing Electron Transfer and Stability of Screen-Printed Carbon Electrodes Modified with AgNP-Reduced Graphene Oxide Nanocomposite
No full textThis paper presents a reliable solution to enhance the electron transfer and stability of screen-printed carbon electrodes (SPCEs) for the direct detection of pathogenic bacteria. A nanocomposite of silver nanoparticles (AgNPs) and reduced graphene oxide (rGO) was used to modify the SPCEs. Herein, the nanocomposite was synthesized via a hydrothermal method and then characterized by physicochemical methods. The electron transfer rate and electrochemical properties of the AgNP-rGO nanocomposite-modified SPCEs were investigated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy. Measurements were performed for the detection of Salmonella bacteria without any labels. Results showed that the nanocomposite firmly adhered to the surfaces of the SPCEs, led to an increase of approximately 160% in the peak current, and decreased the charge transfer resistance to 0.45 kΩ. Electrochemical stability was found in 30 CV cycles. The modified SPCEs could detect Salmonella bacteria directly at concentrations of 10–105 CFU/mL, with a limit of detection (LoD) of as low as 22 CFU/mL. A possible mechanism was proposed to explain the enhanced electron transfer on the surface and the stability of the AgNP-rGO nanocomposite-modified SPCEs. The biosensor showed high stability, cost-effectiveness, and simplicity for the direct detection of pathogenic bacteria. Graphical Abstract: [Figure not available: see fulltext.
Engineering Stress in Thin Films: An Innovative Pathway Toward 3D Micro and Nanosystems
No full textTransformation of conventional 2D platforms into unusual 3D configurations provides exciting opportunities for sensors, electronics, optical devices, and biological systems. Engineering material properties or controlling and modulating stresses in thin films to pop-up 3D structures out of standard planar surfaces has been a highly active research topic over the last decade. Implementation of 3D micro and nanoarchitectures enables unprecedented functionalities including multiplexed, monolithic mechanical sensors, vertical integration of electronics components, and recording of neuron activities in 3D organoids. This paper provides an overview on stress engineering approaches to developing 3D functional microsystems. The paper systematically presents the origin of stresses generated in thin films and methods to transform a 2D design into an out-of-plane configuration. Different types of 3D micro and nanostructures, along with their applications in several areas are discussed. The paper concludes with current technical challenges and potential approaches and applications of this fast-growing research direction.No Full Tex
Nanodielectrics for machine insulation
No full textThanks to the development of nanotechnology, epoxy nanocomposites have been expected to be potential candidates to replace the base resin, due to their superior properties. However, the effects of nano-fillers have been controversial, in both positive and negative ways. There are two main factors, comprising of stoichiometry and the nature of interfacial areas of nano-sized fillers, which are expected to contribute to the final properties of epoxy nanocomposites. The chosen stoichiometry is important in determining the nature of the polymer network that forms. A stoichiometric formulation with the optimal chemical balance between reactants will introduce good performance. However, incorporation of nano-fillers with large interfacial areas into epoxy matrices may modify the cure behaviour of the system, through introducing additional chemical reactions between moieties on the nano-filler surfaces and reactants, thereby altering the rate and sequence of the possible chemical reactions that occur during curing. These effects change the chemical balance of the original base resin system. As a result, the nature of the cross-linked network that forms may be altered.An investigation into the effects of stoichiometry and the nature of the interfacial surface of treated nanosilica particles of various sizes on properties of epoxy-based systems has been conducted, using the differential scanning calorimetry, space charge and ac breakdown measurements, and the dielectric spectroscopy. The introduction of nanosilica has induced changes in curing mechanisms and led to different impacts on systems of different resin stoichiometry. In addition, the investigation has revealed a key role of the characteristic interaction between the nanoparticle surface and the resin matrix in determining material properties, rather than the filler size. Weak interactions have produced negative impacts on material properties. The addition of nano-silica particles into conventional microcomposites has suggested the possible synergetic effects due to the presence of both nano and micro fillers.Furthermore, the long-term performance of the unfilled epoxy and its nanocomposites has been explored. Open branch trees with the faster propagation rate have been observed in nanocomposites, compared to the unfilled epoxy. The material degradation during partial discharge activities has also been evinced using the confocal Raman microprobe spectroscopy
A low-power RF direct-conversion receiver/transmitter for 2.4-GHZ band IEEE 802.15.4 standard in 0.18-mu m CMOS technology
No full textThis paper presents a low-power RF receiver/transmitter front-end for 2.4-GHz-band IEEE 802.15.4 standard in 0.18-mu m CMOS technology. An RF receiver comprises a single-ended low-noise amplifier, a quadrature passive mixer, and a transimpedance amplifier. A current-mode passive mixer showing a very good 1/f noise performance is adopted to convert an RF signal directly to a baseband signal. Moreover, this type of passive mixer shows high-linearity performance, leading to overall RF receiver linearity improvement. A low-power, high-linearity transmitter front-end is implemented by using a passive mixer and two-stage driver amplifier in which the first stage is a conventional cascode amplifier and the second stage uses a folded cascode one. The receiver front-end achieves 30-dB voltage conversion gain, 7.3-dB noise figure with 1/f noise corner frequency of 70 kHz, -8-dBm input third-order intercept point, and +40-dBm input second-order intercept point. The transmitter front-end shows 12-dB power conversion gain, 0-dBm output power with 10-dBm output third-order intercept point, and -30-dB local-oscilator suppression. The receiver and transmitter front-end dissipate 3.5 and 3 mA from a 1.8-V supply, respectively
Free Standing Stress Amplification Structure for Ultrasensitive 3C-SiC/Si Pressure Sensor
No full textThis paper presents an innovative stress amplification approach for enhancing the sensitivity of piezoresistive pressure sensors. The structure consists of two pillars raised from the membrane supporting a released 3C-SiC micro-beam which acts as the sensing element. The proposed design was demonstrated using a 3C-SiC/Si heterostructure. Experimental results found our device highly sensitive, with a high sensitivity of 0.1328 kPa-1. The sensitivity improvement was attributed to the stress-amplification phenomenon observed in our free-standing structure. Analytical and numerical methods confirmed that our device increases the stress/sensitivity by 750% over a traditional membrane structure.No Full Tex
Effect of starch and glycerol on the properties of alginate-microcapsules creating by phase separation coacervation method
No full textThe aim of our research was to prepare probiotic micro-capsules with alginate, starch, glycerol and to evaluate effect of different microcapsules formula on their properties. Lactobacillus acidophilus ATCC 4356 were encapsulated in alginate microcapsules by phase separation coacervation method. The mixture of 3% sodium alginate, 5% or 10% starch, 15% glycerol and cell biomass were dripped into 2% calcium chloride solution (all concentration were in % w/v) and the newly formed microcapsules were incubated for approximately 30 mins in order to obtain the rigid structure. After freeze-drying of the microcapsules, the more spherical shape and higher bacteria density were observed with the formula of alginate-starch-glycerol in compare to the formula without glycerol. The images from the scanning electron microscope (SEM) of cross section of those microcapsules with glycerol showed a uniform concentric circle inner layers, which was not seen in the formula without glycerol. Both starch and glycerol improved the survival of L. acidophilus after freeze-drying process and help to maintain low moisture of obtained microcapsules. After 3 months storage at 4°C, the viability of L. acidophilus in both types of microcapsules decreased but remained at 108 (cfu/g) colonies forming unit pergram. The highest bacteria density of 1.91×109 cfu/g were observed with the formula of alginate-glycerol-10% starch as well as the virtually constant low water activity (0.011).Full Tex
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