HUMIDITY SENSOR USING NIPAAm NANOGEL AS SENSING MEDIUM IN SAW DEVICES

In this paper we report poly N-isopropylacrylamide (NIPAAm) nanogel used as sensing medium in Rayleigh wave type surface acoustic wave (SAW) devices to measure relative humidity. NIPAAm is synthesized by single-step surfactant-free emulsion polymerization reaction method. The prepared nanogel particles have dimensions less than 180 nm. Dynamic light scattering (DLS) analysis of these particles shows increase in size of the particles up to 100% when dispersed in water at room temperature. In this work we have developed two types of relative humidity (RH) sensors. In the first type commercial SAW resonators with resonance frequency at 315 MHz from EPCOSTM were used in our experiment. The casings of two resonators were removed carefully and one of them was left as such to serve as the reference device. The other was coated with the NIPAAm nanogel and used as the sensor. In the second type of SAW-based humidity sensor aluminum interdigital transducers (IDT) are fabricated over YZ lithium niobate piezoelectric substrate using metallization and lithography techniques. The fabricated IDTs have the pitch length of 34 μm and a resonance frequency of 51.6 MHz. Response of sensor to RH is measured by measuring the scattering parameters of both the types of sensors and reference devices recorded using the network analyzer.

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A Robust Electrochemical Humidity Sensor for the Detection of Relative Humidity Using Room Temperature Ionic Liquid (RTIL) for Integration in Semiconductor IC's

ECS Journal of Solid State Science and Technology ◽

10.1149/2.0091807jss ◽

2018 ◽

Vol 7 (7) ◽

pp. Q3043-Q3048 ◽

Cited By ~ 9

Author(s):

Ashlesha Bhide ◽

Badrinath Jagannath ◽

Edward Graef ◽

Shalini Prasad

Keyword(s):

Ionic Liquid ◽

Relative Humidity ◽

Room Temperature ◽

Humidity Sensor ◽

Room Temperature Ionic Liquid

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Highly sensitive, room temperature operated gold nanowire-based humidity sensor: adoptable for breath sensing

RSC Advances ◽

10.1039/d1ra07510a ◽

2022 ◽

Vol 12 (2) ◽

pp. 1157-1164

Author(s):

Parag V. Adhyapak ◽

Aishwarya M. Kasabe ◽

Amruta D. Bang ◽

Jalindar Ambekar ◽

Sulabha K. Kulkarni

Keyword(s):

Relative Humidity ◽

Room Temperature ◽

Humidity Sensor ◽

Gold Nanowire ◽

Humidity Sensing ◽

Highly Sensitive ◽

Resistive Sensor ◽

Relative Humidity Range ◽

Humidity Range

A novel, highly sensitive gold nanowire (AuNW) resistive sensor is reported here for humidity sensing in the relative humidity range of 11% to 92% RH as well as for breath sensing.

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New Potential Biologically Active Compounds: Synthesis and Characterization of Urea and Thiourea Derivativpes Bearing 1,2,4-oxadiazole Ring

Current Organic Synthesis ◽

10.2174/1570179417666200417112106 ◽

2020 ◽

Vol 17 (7) ◽

pp. 525-534 ◽

Cited By ~ 1

Author(s):

Nevin Arıkan Ölmez ◽

Faryal Waseer

Keyword(s):

Microwave Irradiation ◽

Room Temperature ◽

Antimicrobial Activities ◽

Phenyl Isocyanate ◽

Single Step ◽

Biologically Active Compounds ◽

Biologically Active ◽

Active Compounds ◽

Thiourea Derivatives ◽

Acyl Chlorides

Background: Urea, thiourea, and 1,2,4-oxadiazole compounds are of great interest due to their different activities such as anti-inflammatory, antiviral, analgesic, fungicidal, herbicidal, diuretic, antihelminthic and antitumor along with antimicrobial activities. Objective: In this work, we provide a new series of potential biologically active compounds containing both 1,2,4-oxadiazole and urea/thiouprea moiety. Materials and Methods: Firstly, 5-chloromethyl-3-aryl-1,2,4-oxadiazoles (3a-j) were synthesized from the reaction of different substituted amidoximes (2a-j) and chloroacetyl chloride in the presence of pyridine by conventional and microwave-assisted methods. In the conventional method, 1,2,4-oxadiazoles were obtained in two steps. O-acylamidoximes obtained in the first step at room temperature were heated in toluene for an average of one hour to obtain 1,2,4-oxadiazoles. The yields varied from 70 to 96 %. 1,2,4-oxadiazoles were obtained under microwave irradiation in a single step in a 90-98 % yield at 160 °C in five minutes. 5-aminomethyl-3-aryl-1,2,4- oxadiazoles (5a-j) were obtained by Gabriel amine synthesis in two steps from corresponding 5-chloromethyl-3- aryl-1,2,4-oxadiazoles. Finally, twenty new urea (6a-j) and thiourea (7a-j) compounds bearing oxadiazole ring were synthesized by reacting 5-aminomethyl-3-aryl-1,2,4-oxadiazoles with phenyl isocyanate and isothiocyanate in tetrahydrofuran (THF) at room temperature with average yields (40-70%). Results and Discussions: An efficient and rapid method for the synthesis of 1,2,4-oxadiazoles from the reaction of amidoximes and acyl halides without using any coupling reagent under microwave irradiation has been developed, and twenty new urea/thiourea compounds bearing 1,2,4-oxadiazole ring have been synthesized and characterized. Conclusion: We have synthesized a new series of urea/thiourea derivatives bearing 1,2,4-oxadiazole ring. Also facile synthesis of 3,5-disubstituted 1,2,4-oxadiazoles from amidoximes and acyl chlorides under microwave irradiation was reported. The compounds were characterized using FTIR, 1H NMR, 13C NMR, and elemental analysis techniques.

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Single Step 2-Port Device De-Embedding Algorithm for Fixture-DUT-Fixture Network Assembly

Electronics ◽

10.3390/electronics10111275 ◽

2021 ◽

Vol 10 (11) ◽

pp. 1275

Author(s):

Simone Scafati ◽

Enza Pellegrino ◽

Francesco de Paulis ◽

Carlo Olivieri ◽

James Drewniak ◽

...

Keyword(s):

Standard Technique ◽

Single Step ◽

Scattering Parameters ◽

Linear Set ◽

S Parameter ◽

Parameter Conversion ◽

Before And After ◽

One Step ◽

Typical Measurement

The de-embedding of measurement fixtures is relevant for an accurate experimental characterization of radio frequency and digital electronic devices. The standard technique consists in removing the effects of the measurement fixtures by the calculation of the transfer scattering parameters (T-parameters) from the available measured (or simulated) global scattering parameters (S-parameters). The standard de-embedding is achieved by a multiple steps process, involving the S-to-T and subsequent T-to-S parameter conversion. In a typical measurement setup, two fixtures are usually placed before and after the device under test (DUT) allowing the connection of the device to the calibrated vector network analyzer coaxial ports. An alternative method is proposed in this paper: it is based on the newly developed multi-network cascading algorithm. The matrices involved in the fixture-DUT-fixture cascading gives rise to a non-linear set of equations that is in one step analytically solved in closed form, obtaining a unique solution. The method is shown to be effective and at least as accurate as the standard multi-step de-embedding one.

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Back protection of canvas paintings

Heritage Science ◽

10.1186/s40494-020-00435-7 ◽

2020 ◽

Vol 8 (1) ◽

Author(s):

Tim Padfield ◽

Nicolas Padfield ◽

Daniel Sang-Hoon Lee ◽

Anne Thøgersen ◽

Astrid Valbjørn Nielsen ◽

...

Keyword(s):

Fluid Dynamics ◽

Computational Fluid Dynamics ◽

Relative Humidity ◽

Temperature Variation ◽

Room Temperature ◽

Single Point ◽

Confined Space ◽

Constant Wall Temperature ◽

Back Plate ◽

Inner Surface

Abstract In this paper different scenarios for back protection of a canvas painting and their effect on the stability of the relative humidity behind the painting are tested. A painting on canvas, stretched on a wooden frame, was fitted with various styles of back protection and then exposed to a cycle of temperature variation at the back, with the front exposed to a constant room temperature. The painting was also exposed to a constant wall temperature and varying room temperature. The space between the canvas and the back board was fitted with temperature and relative humidity (RH) sensors. The sensors were used to provide the essential single-point data of temperature and RH at the given locations. For more comprehensive understanding of the rather confined space, further numerical simulation (computational fluid dynamics) was adopted as part of the investigation. The computational fluid dynamics was used to understand the natural convection within the microclimate through the depictions of temperature distribution, as well as the corresponding airflow. The unprotected painting suffered a large RH variation at its back, because of the varying canvas temperature interacting with the constant room air moisture content. Effective stabilisation of the RH behind the canvas against temperature variation was provided by a shiny aluminium alloy sheet sealed against the frame. The non-absorbent back board experienced a strong variation in RH, because of humidity buffering of the space by the painting canvas at a different temperature. Either a space or insulation between this back plate and the wall reduced the risk of condensation on the inner surface of the back plate. Insulation will however increase the risk of condensation on the wall surface behind the painting. An absorbent back board de-stabilised the RH at the painting canvas surface by providing a competing humidity buffer at a different temperature. To provide protection against moisture exchange with an unsuitable room RH, extra humidity buffer was placed 3 mm behind the painting canvas, kept close to the painting temperature by insulation between this buffer and the back board. This stabilised RH at the canvas surface but increased both the temperature and the RH variation at the back board and thus increased the risk of condensation on the inner surface of the back board. The RH and the temperature in the narrow spaces between the painting canvas and the wooden stretcher frame were always more nearly constant than in the open canvas area, which suggests an explanation for the widely observed better condition of the areas of canvas paintings which lie close over the support structure. Our conclusion is that a non-absorbent, impermeable back plate gives good RH stability against a changing temperature gradient between wall and canvas painting surface.

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Relative Humidity Sensor Based on Tilted Fiber Bragg Grating With Polyvinyl Alcohol Coating

IEEE Photonics Technology Letters ◽

10.1109/lpt.2009.2013185 ◽

2009 ◽

Vol 21 (7) ◽

pp. 441-443 ◽

Cited By ~ 98

Author(s):

Yinping Miao ◽

Bo Liu ◽

Hao Zhang ◽

Yuan Li ◽

Haibin Zhou ◽

...

Keyword(s):

Relative Humidity ◽

Polyvinyl Alcohol ◽

Fiber Bragg Grating ◽

Humidity Sensor ◽

Bragg Grating ◽

Relative Humidity Sensor

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CLAY-INORGANIC STUDIES. II. HYDROXY ALUMINUM PHOSPHATE–MONTMORILLONITE COMPLEX

Canadian Journal of Soil Science ◽

10.4141/cjss75-030 ◽

1975 ◽

Vol 55 (2) ◽

pp. 225-233 ◽

Cited By ~ 3

Author(s):

H. KODAMA ◽

M. D. WEBBER

Keyword(s):

Relative Humidity ◽

Room Temperature ◽

Aluminum Phosphate ◽

Silicate Layer ◽

Basal Spacing ◽

Minor Amount ◽

Chemical Compositions ◽

A Minor ◽

Positively Charged ◽

Water Contents

Two specimens of hydroxy aluminum phosphate interlayer materials in montmorillonite clay were prepared with 7.20 meq Al and 11.29 meq H3PO4/g clay and with 14.40 meq Al and 22.58 meq H3PO4/g clay, and the resulting complexes studied by chemical and mineralogical methods. Both interlayer materials were slightly positively charged and except for different water contents their chemical compositions were almost identical. They contained Al, PO4 and H2O and a minor amount of Ca and approximated hydrous AlPO4∙nH2O. The mole ratios of Al:Ca:PO4:OH were 1.00:0.08:0.92:0.24 and 1.00:0.05:0.91:0.24, respectively. The interlayer materials appeared to be loosely packed and distributed sparsely in interspaces of the montmorillonite. The degree of packing was greater for the preparation with the larger amount of interlayer material. The materials increased the montmorillonite basal spacing to 23.3 Å under air-dry condition (30–40% relative humidity) but did not affect the lateral dimensions. The basal spacing varied somewhat with relative humidity at room temperature and decreased markedly as water was driven off by heating. Heat treatments between room temperature and 300 C sharply reduced the d001 spacings to 16.7 Å which persisted up to 700 C. It is postulated that the large basal spacings occur because the hydrated interlayer materials have a framework structure with tunnels along the c-axis. This being so, changes in the spacings with different humidities might result from the movement of water molecules among interstitial spaces existing around and between the loosely distributed molecules of interlayer material. The 16.7 Å spacing for the dehydrated phase corresponds to the sum of 7.0 Å, the edge dimension of an orthorhombic anhydrous AlPO4 and 9.7 Å, the silicate layer thickness.

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Preparation and Characterization of Modified PVDF-g-PSSA Membrane

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.152-153.44 ◽

2010 ◽

Vol 152-153 ◽

pp. 44-50 ◽

Cited By ~ 2

Author(s):

Gui Bao Guo ◽

Er Ding Han ◽

Sheng Li An

Keyword(s):

Relative Humidity ◽

Sodium Silicate ◽

Room Temperature ◽

Proton Exchange Membrane ◽

Vinylidene Fluoride ◽

Proton Exchange ◽

Poly Vinylidene Fluoride ◽

Relative Humidity Range ◽

Exchange Membrane

A new method based on a solution graft technique was used to prepare poly (vinylidene fluoride) grafted polystyrene sulfonated acid (PVDF-g-PSSA) proton exchange membrane. Polystyrene is grafted into PVDF modified by plain sodium silicate (Na4SiO4). There is a linear relationship between the degree of grafting and the content of Na4SiO4. Fourier transform infrared spectroscopy is used to characterize changes of the membrane's microstructures after grafting and sulfonation. The morphology of the membrane's microstructures after grafting and sulfonation is studied by scanning electrolytic microscope (SEM). The effect of plain sodium silicate (Na4SiO4) concentration and relative humidity on the conductivity of the electrolyte was investigated by the impedance at room temperature. The results show that the styrene has been grafted into PVDF. The conductivity of PVDF-g-PSSA electrolyte doped 10% plain sodium silicate (Na4SiO4) is 0.016 S/cm at room temperature. The conductivity of the electrolyte changes slightly at a relative humidity range of 20%-70%. The weightlessness of PVDF-g-PSSA electrolyte heated to 40°C was less than 2%, which indicated that water capacity was good.

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