Surface engineering of the PLA films for fabricating dexterous humidity sensors (original) (raw)
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Characterization and Comparison of Biodegradable Printed Capacitive Humidity Sensors
Sensors, 2021
Flexible and biodegradable sensors are advantageous for their versatility in a range of areas from smart packaging to agriculture. In this work, we characterize and compare the performance of interdigitated electrode (IDE) humidity sensors printed on different biodegradable substrates. In these IDE capacitive devices, the substrate acts as the sensing layer. The dielectric constant of the substrate increases as the material absorbs water from the atmosphere. Consequently, the capacitance across the electrodes is a function of environmental relative humidity. Here, the performance of polylactide (PLA), glossy paper, and potato starch as a sensing layer is compared to that of nonbiodegradable polyethylene terephthalate (PET). The capacitance across inkjet-printed silver electrodes is measured in environmental conditions ranging from 15 to 90% relative humidity. The sensitivity, response time, hysteresis, and temperature dependency are compared for the sensors. The relationship between...
Capacitive Humidity Sensor Based on Polymer Composite Thin Film
2018
Nowadays humidity sensors are used in every industry, such as in food, pharmaceuticals [1], medicine, [2] and agriculture [3, 4]. These commercial humidity sensors are quite expensive, complicated in operation, and have low sensitivity and stability because of the materials used as a sensing element [5]. It is difficult to maintain their operational cost, power losses, sensitivity and stability [4]. Therefore, it is essential for a sensor to have high sensitivity and stability, low cost, small hysteresis, wide linear range, simple operation, short response, and short recovery time [5, 6]. Electrical conduction is affected significantly by dipoles of water molecules, which makes it important for researchers to investigate the magnitude of change in impedance and capacitance of the samples with respect to varying relative humidity. The investigation becomes more important for composite materials due to the contribution of properties by two or more ingredients. Changing the constitutin...
2014
The humidity sensing characteristics of different sensing materials are important properties in order to monitor different products or events in a wide range of industrial sectors, research and development laboratories as well as daily life. The primary aim of this study is to compare the sensing characteristics, including impedance or resistance, capacitance, hysteresis, recovery and response times, and stability with respect to relative humidity, frequency, and temperature, of different materials. Various materials, including ceramics, semiconductors, and polymers, used for sensing relative humidity have been reviewed. Correlations of the different electrical characteristics of different doped sensor materials as the most unique feature of a material have been noted. The electrical properties of different sensor materials are found to change significantly with the morphological changes, doping concentration of different materials and film thickness of the substrate. Various applications and scopes are pointed out in the review article. We extensively reviewed almost all main kinds of relative humidity sensors and how their electrical characteristics vary with different doping concentrations, film thickness and basic sensing materials. Based on statistical tests, the zinc oxide-based sensing material is best for humidity sensor design since it shows extremely low hysteresis loss, minimum response and recovery times and excellent stability.
The humidity sensing characteristics of different sensing materials are important properties in order to monitor different products or events in a wide range of industrial sectors, research and development laboratories as well as daily life. The primary aim of this study is to compare the sensing characteristics, including impedance or resistance, capacitance, hysteresis, recovery and response times, and stability with respect to relative humidity, frequency, and temperature, of different materials. Various materials, including ceramics, semiconductors, and polymers, used for sensing relative humidity have been reviewed. Correlations of the different electrical characteristics of different doped sensor materials as the most unique feature of a material have been noted. The electrical properties of different sensor materials are found to change significantly with the morphological changes, doping concentration of different materials and film thickness of the substrate. Various applications and scopes are pointed out in the review article. We extensively reviewed almost all main kinds of relative humidity sensors and how their electrical characteristics vary with different doping concentrations, film thickness and basic sensing materials. Based on statistical tests, the zinc oxide-based sensing material is best for humidity sensor design since it shows extremely low hysteresis loss, minimum response and recovery times and excellent stability.
Synthesis and characterization of polymer based humidity sensor
INTERNATIONAL SCIENTIFIC AND PRACTICAL CONFERENCE “TECHNOLOGY IN AGRICULTURE, ENERGY AND ECOLOGY” (TAEE2022)
The Humidity Polymer sensors are of great interest for the scientific communities depending on their properties and applications such as alarm clocks, smart watches and flexible wearable electronic devices. In this paper, humidity sensors have been prepared using mixture of poly (vinyl alcohol) (PVA), poly (4-styrenesulfonic acid) (PSSA) and silver nitrate (AgNO3) using solvent casting method. The ratio of PVA/PSSA is kept constant and different concentrations of AgNO3 is mixed with it. Variations in the properties was analyzed using the impedance analyser and humidity analyser was used to analyse the relative humidity. The relative humidity was measured in range of (68% to 21%) at temperature range of (25 °C to 65°C). This paper concludes that on addition of 0.6gm of AgNO3 , best results of dielectric properties and the conductivity was seen. Relevant parameter like conductivity of the membranes and relative humidity was highly affected by AgNO3 content. Incresase in conductivity of membrane was observed at low frequency and after 10 4 Hz it start decreasing as frequency increases. Highest dielectric constant of the membrane increased from 10 4 to 10 7. Decrease in relative humidity was observed with increase in temperature.
Electro-sprayed PVA coating with texture-enriched surface morphology for augmented humidity sensing
Progress in Organic Coatings, 2018
This article reports the modified surface morphology of Poly-vinyl Alcohol (PVA) films using electro-spraying coating technique. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) were conducted to examine the surface structure of the prepared PVA films. Intriguingly, the novel micro-level developed surface, twisted by electro-spraying is very promising for humidity sensors. The resistivity of the humidity sensors was measured under controlled humidity levels. Owing to the unique surface assembly, the electro-sprayed humidity sensor showed superior performance as compared to the electro-spun PVA based humidity sensor.
Sensor Letters, 2010
In the current work, layer-by-layer self-assembled mica and cationic polyelectrolyte (poly(allylamine hydrochloride)) (PAH) or poly(diallyldimethylammonium chloride) (PDDA) were synthesized on a quartz-crystal microbalance (QCM) for low-humidity sensing applications. The surface characteristics of the thin films were studied for various assembly conditions. The thin films were characterized using QCM and by atomic force microscopy (AFM). The surface roughness and thickness of the mica/PDDA thin film both exceeded that of the mica/PAH thin film. The effects of the polycations type, polycations concentration and the number of layers on the low-humidity sensing properties (sensitivity) of the sensors were investigated. Additionally, other low-humidity sensing properties such as sensing linearity, response and recovery times and reproducibility were studied. The mica/PDDA multilayered thin film had the highest sensitivity (0.930-Hz/ ppm v at 42.9 ppm v and linearity and a short response time (12 s at 92.2 ppm v .
Characterization of capacitive humidity sensors based on doped poly(propargyl-alcohol)
Journal of Applied Electrochemistry - J APPL ELECTROCHEM, 2000
Films of poly(propargyl alcohol) (POHP), doped with both sulphuric acid and iron trichloride, were deposited on interdigitated gold electrodes. Their electrical properties were examined as a function of percentage relative humidity. The devices showed low-frequency capacitance linearly dependent on RH% with good response time, and are proposed as possible capacitive humidity sensors.
Layer-by-layer assembly of mica and polyelectrolyte for use in low-humidity sensor
Sensors and Actuators B: Chemical, 2009
Mica multilayer thin films were assembled layer-by-layer (LBL) from mica that was modified with carboxylic groups (COOH) and cationic polyelectrolyte (poly(allylamine hydrochloride)) (PAH) on a quartz-crystal microbalance (QCM) for low-humidity sensing applications. The surface characteristics of the thin films were studied for various assembly conditions of pH and ionic strength of modified mica solutions. The thin films were characterized using QCM and by atomic force microscopy (AFM). The thickness of mica-COOH/PAH multilayer thin films increased with assembly pH of modified mica solution. When salt was added, the multilayer films became thicker, smoother and grew more regularly. The mica-COOH/PAH multilayer films that were deposited from the mica-COOH solution with salt at pH 3 was coated on the gold electrode of the QCM exhibited excellent sensitivity (0.524 − Hz/ ppm v at 36.1 ppm v) and linearity and a short response time (13 s at 60.4 ppm v).
The Effect of SnO2 Mixture on a PVA-Based Thick Film Relative Humidity Sensor
International Journal on Advanced Science, Engineering and Information Technology
In this research, thick film technology has been used to design and fabricate relative humidity sensors with Polyvinyl Alcohol (PVA) as the sensing layer. The design was optimized to produce an ideal geometry according to the limitations of thick film technology. The sensor fabrication process used screen printing techniques on Alumina (Al2O3) substrate with Silver (Ag) as the electrode material. SnO2 was added to the PVA sensing layer with variations in the composition of 1:1 and 1:2. FTIR analysis showed that the addition of SnO2 did not affect the structure of the PVA, which indicated that there was no chemical reaction between PVA and SnO2. The deposition of the sensing layer was carried out using spin coating method, and the fabricated sensors were then tested by varying 5 humidity points inside a chamber with a hygrometer as a reference. Based on the test results, it was found that the sensors showed responses to humidity variation in the form of changes in resistance values. When the humidity in the chamber increased, the sensor resistance value decreased. The addition of SnO2 could reduce the relatively high resistance value of the PVA-based humidity sensor and also increase the sensor's time response to humidity variation. However, the humidity sensor's sensitivity decreased for the higher composition of SnO2. With this technique, a simple yet stable humidity sensor could be fabricated using thick-film technology with a wide range of potential applications.