High Electrical Sensitivity Research Articles

Fabrication and Characterization of Thick Film Ceramics La0,9Ca0,1FeO3 for Ethanol Gas Sensor using Extraction of Fe2O3 from Yarosite Mineral

Fabrication of La0,9Ca0,1FeO3 thick film ceramics using Fe2O3 powder extracted from yarosite mineral as ethanol gas sensor has been successfully performed. Fe2O3 powder extracted from yarosite mineral as the basic material in this research can increase the added value yarosite mineral. Fe2O3 powder and 10% mol of CaO dissolved in HCl were mixed with LaCl3.7H2O powder dissolved in aquades.The solution of Fe2O3, LaCl3.7H2O and CaO mixed and then precipitate using NH4OH. The La0,9Ca0,1FeO3 precipitate was calcined at temperature 8000C for 2 hours to produce La0,9Ca0,1FeO3 powder. La0,9Ca0,1FeO3 powder was crushed and mixed with Organic Vehicle to produce a La0,9Ca0,1FeO3 paste. Using the screen printing technique, the La0,9Ca0,1FeO3 paste is coated on the alumina substrate and then fired at 600°C for 2 hours to produce the thick film ceramic La0,9Ca0,1FeO3. Based on XRD and SEM characterization data, the thick film ceramics La0,9Ca0,1FeO3 were made even though some of Fe2O3 did not react and the grain size is almost uniform, and there are many pores. Measurement of electrical characteristics shows a good response to the presence of ethanol gas, has high electrical sensitivity value and low optimum working temperature that is in the range 290°C - 295°C.

Double-tilt in situ TEM holder with ultra-high stability

A double tilting holder with high stability is essential for acquiring atomic-scale information by transmission electron microscopy (TEM), but the availability of such holders for in situ TEM studies under various external stimuli is limited. Here, we report a unique design of seal-bearing components that provides ultra-high stability and multifunctionality (including double tilting) in an in situ TEM holder. The seal-bearing subsystem provides superior vibration damping and electrical insulation while maintaining excellent vacuum sealing and small form factor. A wide variety of in situ TEM applications including electrical measurement, STM mapping, photovoltaic studies, and CL spectroscopy can be performed on this platform with high spatial resolution imaging and electrical sensitivity at the pA scale.

Novel Safeguarding Tactile e‐Skins for Monitoring Human Motion Based on SST/PDMS–AgNW–PET Hybrid Structures

AbstractA novel versatile electrical skin (e‐skin) with safeguarding and multisensing properties based on hybrid structures is developed by assembling Ag nanowires (AgNWs), polyester (PET) film with hybrid shear stiffening polymer/polydimethylsiloxane (SST/PDMS) matrix. The hybrid SST/PDMS polymer shows stable configuration. Storage modulus of the SST/PDMS increases from 5.5 kPa to 0.39 MPa when the shear frequency changes from 0.1 to 100 Hz, exhibiting typical rate‐dependent behavior. e‐Skin functions as a human‐monitoring device by detecting various motions such as gentle touching, stroking, elbow bending, as well as speaking. More importantly, due to the shear stiffening characteristic, e‐skin with high damping capacity exhibits safeguarding performance, which can dissipate impact force from 720 to 400 N and increase buffer time (from 0.9 to 2 ms). Meanwhile, distinguishable resistance values can reveal the level of harsh impact applied on the e‐skin. In addition, the visible thermosensation effect of e‐skin similar to chameleon epidermis is convenient for assessing environmental temperature. e‐Skin arrays can precisely map the dynamic impact location and pressure distribution. Finally, the high electrical sensitivity and shear stiffening performance are attributed to the disturbance of AgNW effective conductive paths and dynamic BO bonds, respectively.

Self-Healing Sensors Based on Dual Noncovalent Network Elastomer for Human Motion Monitoring.

Nowadays, it is still a challenge to prepare flexible sensors with great mechanical strength, stretchability, high sensitivities, and excellent self-healing (SH) abilities. Herein, a nanostructured supramolecular elastomer is reported with a dual noncovalent network of hydrogen bonding interactions and metal-ligand coordination. The resultant flexible sensor presents ultrafast (30 s), autonomous, and repeatable SH ability with high healing efficiency (80% after the 3rd healing process), as well as enhanced mechanical properties. Benefitting from the 3D conductive network, the sensor exhibits high electrical sensitivity and very low detection limit (0.2% strain). As a result, the flexible sensor is capable of precisely monitoring small strains of human motions (such as vocal-cord vibration), and exhibits reproducible and recognizable current signals after cutting-healing process. The dual noncovalent network design proposed here opens up a new opportunity for scalable fabrication of high performance SH sensors and other electronic devices.

A rapid and easy procedure of conductive 3D nanofibrous structure induced by nanosecond laser processing of Si wafer coated by Au thin-film

Many biomedical sensing applications require high electrical sensitivity as well as a method to control and implement them into biological applications. This requires a material to have both conductive and biocompatible properties. Many conductive materials fail in these applications due to their lack of biocompatibility, and many biocompatible materials have very low conductivity. A method to control the conductivity of fibrous silicon through the laser processing of silicon covered with a thin film of gold (1μm) is detailed in this article. An Nd:YAG pulsed nanosecond laser was utilized to process the thin film at a line spacing of 0.025mm at different overlaps (number of laser beams scanning through the same path), for increasing the surface to volume ratio and biocompatibility of the single crystalline silicon. The biocompatibility assessment has shown positive results with traces of the elements necessary for the formation of hydroxyapatite. Samples processed at a lower power showed higher concentrations of these trace elements, suggesting an increase in biocompatibility. Overall, this research offers preliminary findings as to the direction and future work that can be done with porous silicon to offer a cost effective and efficient method of enhancing the conductivity and biocompatibility for biomedical sensing and conductive tissue engineering applications.

Design and optimization of a doubly clamped piezoresistive acceleration sensor with an integrated silicon nanowire piezoresistor

Piezoresistive acceleration sensors have found a wide range of applications for the last four decades. However, in recent times, high performance piezoresistive acceleration sensors with lower footprint are in demand, especially in the fields of consumer electronics and biomedical engineering. The design of such sensors remains a challenging task due to the competing requirements of high electrical sensitivity (∆R/R) and resonant frequency (f 0 ) along with low device footprint. In this paper, we elaborate the design and optimization of a highly miniaturized doubly clamped acceleration sensor with an integrated silicon nanowire as a piezoresistor. The diminutive size of the silicon nanowire helps in reducing the device foot print. The design is performed using two methods: (1) electrical approach and (2) mechanical approach. In the electrical approach, the conventional bulk silicon diffused piezoresistors are replaced with a silicon nanowire without changing the dimensions of the original structure. It is shown that compared to the conventional design, a silicon nanowire based sensor exhibits 2.51 times better performance in terms of electrical sensitivity. One of the major constraints with miniaturized high performance acceleration sensors is reduced resonant frequency. Therefore, in the mechanical approach we have devised a geometrical optimization technique to miniaturize the sensor geometry by keeping its resonant frequency constant. Numerical simulations are performed to validate the proposed miniaturized sensor with an integrated silicon nanowire as the piezoresistor. The sensor performance is evaluated with a new performance factor given as $${{\left( {{{\Delta R} \mathord{\left/ {\vphantom {{\Delta R} R}} \right. \kern-0pt} R}} \right)f_{0}^{2} } \mathord{\left/ {\vphantom {{\left( {{{\Delta R} \mathord{\left/ {\vphantom {{\Delta R} R}} \right. \kern-0pt} R}} \right)f_{0}^{2} } {Diesize}}} \right. \kern-0pt} {Diesize}}$$ , which takes into account the electrical sensitivity, the resonant frequency and the die size of the sensor. Results show that the proposed sensor design with an integrated silicon nanowire has 48.2 times better performance factor than a bulk piezoresistor based conventional acceleration sensor.

Fines Classification Based on Sensitivity to Pore-Fluid Chemistry

AbstractThe 75-μm particle size is used to discriminate between fine and coarse grains. Further analysis of fine grains is typically based on the plasticity chart. Whereas pore-fluid-chemistry-dependent soil response is a salient and distinguishing characteristic of fine grains, pore-fluid chemistry is not addressed in current classification systems. Liquid limits obtained with electrically contrasting pore fluids (deionized water, 2-M NaCl brine, and kerosene) are combined to define the soil “electrical sensitivity.” Liquid limit and electrical sensitivity can be effectively used to classify fine grains according to their fluid-soil response into no-, low-, intermediate-, or high-plasticity fine grains of low, intermediate, or high electrical sensitivity. The proposed methodology benefits from the accumulated experience with liquid limit in the field and addresses the needs of a broader range of geotechnical engineering problems.

Optimization of particle size for high birefringence and fast switching time in electro-optical switching of graphene oxide dispersions.

In order to use graphene oxide (GO) dispersions for electro-optical applications, both a high GO concentration and a high electrical sensitivity are essential; however, these have not been achieved to date. Here, we report that by optimizing the mean size of GO particles to approximately 0.5 μm, one can obtain a high GO concentration of up to 2 wt% and high electrical sensitivity simultaneously. By reducing the mean GO-particle size, the interparticle interaction and the rotational viscosity can be significantly reduced, and a high-concentration isotropic phase can be obtained. As a result, the maximum birefringence increases and the dynamic response becomes faster. However, further decrease of the mean size below 0.1 μm causes a decrease in the anisotropy of electrical polarizability, resulting in the reduction of the electrical sensitivity of GO dispersions.

High electrical sensitivity of polyurethane/carbon nanotube composites to tensile strain

Carbon nanotube/polyurethane (CNT/PU) composites were prepared by using an in-situ polymerization method, and their electrical sensitivity to tensile strain was investigated. The addition of CNTs can remarkably enhance both the mechanical strength and electrical conductivity of the composite. The CNT/PU composite exhibits a high sensitivity of electrical resistance to changes in tensile strain. The electrical resistance of the CNT/PU composite increases by six orders of magnitude in the elongation range 0–200%, which can be attributed to the decrease of CNT volume fraction, expansion of total volume, and changes in the CNT-network structure under the high strain. The dependence of electrical resistivity of the composites on tensile strain can be well explained by a percolation threshold theory. The high electrical sensitivity of the CNT/PU composites to tensile strain can be used as an intelligent material and strain sensors in the field of construction safety. [New Carbon Materials 2013, 28(2): 88–93]

Research on a haptic sensor made using MCF conductive rubber

To provide a new composite material having a high electrical sensitivity in thefields of robotics and sensing, a magnetic rubber having network-like magneticclusters was developed by utilizing a magnetic compound fluid (MCF). MCFrubber with small deformations can provide an effective sensor. In this paper, wereport many experiments in which changes of the MCF rubber’s resistance wereobserved when the rubber was compressed and a deformation was generated; we thenmade a trial haptic sensor using the MCF conductive rubber and performed manyexperiments to observe changes of the electrical resistance of the sensor. The resultsof experiments showed that the proposed sensor made with MCF conductiverubber is useful for sensing small amounts of pressure or small deformations.

Modeling and design of a novel high-sensitivity electric field silicon-on-insulator sensor based on a whispering-gallery-mode resonator

In this paper, we present the modeling and design of a new approach to a miniaturized electric field sensor, based on a whispering-gallery-mode resonator coupled with a Fabry-Perot cavity in silicon-on-insulator technology. The sensing element consists of a metal oxide semiconductor capacitor, optimized to achieve high electrical sensitivity and low optical losses. The theoretical model of the whole sensor architecture includes the influence of all electrical and optical parameters, including thin oxide thickness, silicon and polysilicon doping concentration, optical losses due to propagation, absorption and scattering, wavelength and amplitude characteristics of the architecture, charge accumulation effects in the capacitor, and thermal effects. The very high sensitivity of this device, demonstrated by simulations, is due to the simultaneous influence of the two coupled resonators and the metal oxide semiconductor structure.

Broadband self-calibrating micromachined microphones with integrated optical displacement detection

An optical displacement detection method for micromachined microphones is described and experimental results are presented. The microphone membrane is fabricated on a transparent substrate and the back electrode is patterned in the form of diffraction fingers. This structure forms a phase sensitive diffraction grating, providing the displacement sensitivity of an optical interferometer. The diffraction fingers are also used for electrostatic actuation, providing sensitivity adjustment and self-calibration capabilities. Optically semitransparent coatings are also employed to create Fabry–Perot resonant cavities that enhance the optical detection sensitivity by an order of 10 dB. The high electrical sensitivity provided by optical displacement detection relaxes requirements on mechanical sensitivity, and small microphone membranes on the order of 200 μm with vacuum-sealed and air-sealed cavities are used to fabricate microphones with a flat response from dc to over 200 kHz. The optical detection and electrostatic actuation capabilities are demonstrated on fully integrated devices with aluminum microphone membranes micromachined on quartz substrates and bonded to microfabricated silicon photodiodes. [Work supported by DARPA.]

Surface reactivity of nanostructured tin oxide and Pt-doped tin oxide as studied by EPR and XPS spectroscopies

Nanostructured (3–6 nm) thin films (80 nm) of SnO 2 and Pt-doped SnO 2 were obtained by a new sol–gel route using tetra( tert-butoxy)tin(IV) and bis(acetylacetonato)platinum(II) as precursors. EPR and XPS investigations, performed on thin films after interaction with CO, demonstrated that singly ionized oxygen vacancies (V o ) fully transferred their electrons to the noble metal and reduced Pt(IV) to Pt(II). Contact with air at room temperature led to the reduction of O 2 to O 2 −, therefore, re-oxidizing metal centers. The reaction mechanism concords with the high electrical sensitivity of this material.

Electroreceptor mechanisms of the ampullae of lorenzini in skates

Responses of the receptor epithelium of single electrically isolated ampullae of Lorenzini and spike responses of nerve fibers connected to them to electrical stimulation under voltage clamping conditions were studied in experiments on the Black Sea skateRaja clavata. The preparations had an input resistance of 200–800 KΩ, a transepithelial resting potential of between 0 and −2 mV, and the usual spontaneous spike activity in their afferent fibers. Thresholds of the electroreceptors were 2–10 µV (current about 10−11 A). Within the working range of the electroreceptors (up to ±500 µV, current up to 1 nA) the current-voltage characteristic curve of the epithelium was linear without any evidence of spike or wave activity of the receptor cells. With negative currents of over 1–10 nA a regenerative spike appeared on the epithelium and was accompanied by an uncharacteristic pattern of spike discharge of the nerve fiber. It is concluded that, contrary to Bennett's hypothesis, spike or oscillatory activity bears no relationship to normal working of electroreceptors. It is postulated that "secondarily sensitive" receptor cells share a common functional organization, which is based on a chemical synapse with high electrical sensitivity.

Ionic compositions of the media across the sensory epithelium in the ampullae of Lorenzini of the marine catfish,Plotosus

1. In an electroreceptor, ampullae of Lorenzini of the marine catfishPlotosus, the jelly in the ampullary ducts was studied in order to determine the ionic composition of the microenvironment over the sensory epithelium of the electroreceptor. In comparison, the blood plasma of the fish and the sea water were similarly analysed. 2. The ionic composition of the plasma, Na 194, K 4.0, Ca 2.9, Mg 1.5 and Cl 169 (in mM/l), was similar to those in other marine teleosts despite the species difference. 3. The ampullary jelly was approximately isotonic to sea water, but contained much more K (62.6±22.0 mM/l, 580% of sea water), with Na, Ca and Mg all lower than those in sea water. The K concentration was higher in the proximal half of the ampullary duct than in the distal half, suggesting a secretion of the jelly from the ampulla. 4. The high electrical sensitivity of thePlotosus ampulla is maintained by a steady bias current which flows inwards through the apical and outwards through the basal membranes of the receptor cells in the sensory epithelium. It is suggested that this bias current is carried by K.