kPa Pressure Research Articles

Preparation of fast-swelling porous superabsorbent hydrogels with high saline water absorbency under pressure by foaming and post surface crosslinking

Superabsorbent hydrogels have wide applications in many fields because of their unique water absorbing performance. In spite of decades of research about superabsorbent hydrogels, high water absorbency under pressure and fast-swelling are still challenging and highly desired for their applications in hygienic products and others. Here, we report preparation of fast-swelling porous starch-g-poly(acrylic acid)/poly(vinyl alcohol) superabsorbent hydrogels with high saline water absorbency under pressure by foaming and post surface crosslinking. 2,2′-Azobis(2-amidinopropane) dihydrochloride (AIBA) was used as a new porogen instead of conventional porogens like NaHCO3. Post surface crosslinking of the hydrogel was achieved using glycerol via the esterification reaction. AIBA is a better porogen than NaHCO3 regarding porosity and swelling performance of the hydrogels, and its content has great influences on structure and swelling performance of the hydrogels including water absorbency and swelling rate. Also, the surface crosslinking using glycerol can significantly enhance the saline water absorbency under pressure (2 kPa) but at the sacrifice of the swelling rate. Consequently, the hydrogels show high water absorbencies for deionized water (560 g/g), 0.9 wt% NaCl solution (58 g/g), 0.9 wt% NaCl solution under 2 kPa pressure (28 g/g) and fast-swelling (31 s to achieve a highly swelling state).

Overcurrent Test of High-Temperature Superconducting Coils With Liquid Hydrogen Immersion Cooling

The operating temperature of a high-temperature superconducting (HTS) coil is desired to be 15-40 K from the viewpoint of specific heat of the material and the operating current. Development of relatively small-capacity coils with gas helium cooling or refrigerator cooling in this temperature range is underway. Here, refrigerant cooling is desirable for large-capacity coils and liquid hydrogen, which has 20.7 K atmospheric pressure saturation temperature, is a candidate refrigerant. However, due to the difficulty of handling hydrogen, there have been few studies on the HTS coil cooled by liquid hydrogen. And in the HTS coil, the heat generated in the normal conducting region causes a chain of temperature rise and decrease of the critical current, which leads to an irreversible increase in coil temperature beyond the balance with the cooling conditions, and so-called thermal runaway is a problem. In this study, we report on the observation of thermal runaway phenomena in Bi2223 coils under liquid hydrogen immersion cooling. The coils were energized twice at saturated condition of 950 kPa pressure and 30 K temperature. We observed thermal runaway in both energizations and the coil tap voltage before thermal runaway was several tens of mV. From this test, it could be said that the liquid hydrogen cooling has a potential to protect HTS coils.

Study on Bioresponsive Gelatin-Hyaluronic Acid-Genipin Hydrogel for High Cell-Density 3D Bioprinting.

The Development of bioresponsive extrudable hydrogels for 3D bioprinting is imperative to address the growing demand for scaffold design as well as efficient and reliable methods of tissue engineering and regenerative medicine. This study proposed genipin (5 mg) cross-linked gelatin (1 to 1.5 g)-hyaluronic acid (0.3 g) hydrogel bioink (20 mL) tailored for 3D bioprinting. The focus is on high cell loading and a less artificial extra-cellular matrix (ECM) effect, as well as exploring their potential applications in tissue engineering. The bioresponsiveness of these hydrogel scaffolds was successfully evaluated at 37 °C and room temperature (at pH 2.5, 7.4, and 9). The rheological and mechanical properties (more than three times) increased with the increase in gelatin content in the hydrogel; however, the hydrogel with the least amount of gelatin showed the best extrusion capability. This optimized hydrogel's high extrusion ability and post-printing shape fidelity were evident from 3D and four-axis printing of complex structures such as hollow tubes, stars, pyramids, and zigzag porous tubular (four-axis) scaffolds (printed at 90 kPa pressure, 70 mm/s speed, 22G needle, fourth axis rotation of 4 rpm). 3 million/mL MC3T3-E1 mouse osteoblast cells were used in preparing 3D bioprinted samples. The in vitro cell culture studies have been carried out in a CO2 incubator (at 37 °C, 5% CO2). In the cytocompatibility study, almost three times more cell viability was observed in 3 days compared to day 1 control, proving the non-toxicity and cell-supportiveness of these hydrogels. High cell viability and cell-to-cell interactions observed at the end of day 3 using this moderately stable hydrogel in 3D bioprinting exhibit high potential for precise cell delivery modes in tissue engineering as well as regenerative medicine.

Modal characteristics of a scaling stratospheric airship in still air

As one of the most crucial and intrinsic characteristics of structural systems, modal analysis has received considerable attention in aerospace, mechanical, and civil engineering. A traditional approach of modal identification involves linear perturbation of the solid structure alone. However, the modal behaviors of flexible stratospheric airships are greatly influenced by surrounding air and prestress, and the accurate modal identification remains a challenge. In this paper, the modal characteristics of a scaling stratospheric airship in still air are thoroughly investigated by experimental and numerical methods. The 3D testing comprehensively revealed the full-field modal characteristics, while the 1D testing served as a supplement and validation for the frequency results. The global vibration contours stitched by four regions indicate that the first four modes of the airship under 2∼10 kPa pressure are all breathing modes. Furthermore, a refined fluid-structure interaction (FSI) model based on the potential fluid theory was built with ADINA software. It is found that the numerical model can give satisfactory results for the first mode with a 1.05% error, but errors for higher-order modes may exceed 10%. Besides, the air domain significantly decreases the modal frequency of the airship. The maximum error of the first-order frequency neglecting the air amounts to 32.25%.

Oil absorption stability of modified cellulose porous materials with super compressive strength in the complex environment

AbstractThe occurrence of oil spills has severe damage upon both the environment and human health. Hence, the development of a green, recyclable, complex environment resistant, and efficient oil–water separation aerogel is required in order to effectively absorb marine or industrial oil. In this study, modified cellulose/N,N'-methylenebisacrylamide/tannin (PCMT) composite porous materials were prepared utilizing the sol–gel method and were modified with tertbutyl acrylate. PCMT possesses a three-dimensional interpenetrating porous structure, exhibiting remarkable oil–water separation performance and excellent compressive strength (PCMT can capable of bearing 7000 times its own weight; PCMT can endure 290.3 kPa pressure at 80% strain when the amount of tannin is 0.2 g). The unique pore structure of PCMT engenders differential oil adsorption capacities (PCMT0, PCMT0.05, PCMT0.1, and PCMT0.2 evince higher adsorption capacities for petroleum ether and dichloromethane, n-hexane and dichloromethane, toluene, and toluene and dichloromethane, respectively). Of critical import, PCMT demonstrates exceptional adaptability to complex environments, wherein the porous materials maintain good hydrophobicity and oil absorption capacity under conditions of vigorous stirring, a wide pH range (1–14), a wide temperature range (4–160 °C), ultraviolet irradiation (8 h), and tape peeling (10 times). Moreover, the porous materials may be employed for the recovery of oil through simple mechanical extrusion, thus demonstrating certain economic significance and the application potential in the treatment of oil spills.

Magnetohydrodynamics analysis of magnetorheological fluid damper

A key feature of magnetorheological fluid is its variability of rheological properties in which upon exposing this fluid, the viscosity of the fluid changes accordingly. Hence this nature can be implemented in various engineering applications. To understand its influence in a magnetorheological (MR) damper, it is essential to study the flow behaviour using computational and numerical methods. The main objective of this work is to estimate the influence of the external magnetic field on the fluid flow velocity inside the damper using magnetohydrodynamic analysis. Finite element analysis, magnetostatic analysis, and magnetohydrodynamic (MHD) analysis have been carried out to investigate the change in the shape of the velocity profile across the flow gap of the monotube MR damper under the various magnitude of magnetic force using the MHD module of ANSYS fluent software. The simulation is conducted by considering laminar, steady-state, and incompressible fluid flow. In finite element analysis, the magnitude of magnetic flux density (MFD) ‘B’ was evaluated at various direct currents. Later, obtained MFD has been applied perpendicular direction to the flow of MR fluid. The effective length of the fluid exposed to the MFD is taken as 2 mm to 28 mm in an overall flow length of 30 mm. The extracted results have shown that the fluid flow velocity reduces with an increase in the magnetic flux density. It has been observed that 10.42 % reduction in velocity upon increasing the magnetic flux density from 0.25 T to 1 T at 75 kPa pressure. The reason for a reduction in velocity is because of variation in the rheological properties of the fluid under the magnetic field, which is very much essential to produce a good damping effect in the MR damper.

Graphene-coated nylon nonwoven for pressure sensing application

Graphene-coated textiles have attracted great interest in recent years for the development of advanced piezo-resistive materials. In this work, rGO (reduced graphene oxide) treated nylon nonwoven is prepared by the dip coating method. The influence of treatment parameters viz. graphene oxide (GO) concentration, sodium dithionite (Na2S2O4) concentration, and, pH of GO dispersion on rGO add-on and electrical conductivity is analysed and optimized by using Box–Behnken response surface design to prepare electroconductive nylon nonwoven for pressure sensing application. An rGO add-on of 9.12% and surface resistivity of 3.62 kΩ sq−1 have been achieved after two dippings at the optimized dipping condition viz. 0.6% GO concentration, 2 pH, and 15 mM Na2S2O4 concentration. Surface resistivity of 3.62 kΩ sq −1 is achieved after two dippings at the optimized dipping condition with the rGO add-on of 9.12%. The piezoresistive properties of this fabric are investigated. Resistance and thickness of rGO-coated nylon nonwoven treated fabric show a strong negative correlation with the applied pressure. A maximum gauge factor of 2.56 is observed which is in line with pure compression-based pressure sensors. A high-pressure sensitivity of − 0.34 kPa −1 is observed at 2 kPa pressure with a recovery time of 1.2 s implying that it can be used for pressure sensing. After rGO dipping, bending rigidity, bending modulus, and breaking strength of nylon nonwoven are increased whereas the breaking elongation decreased. Bending rigidity, bending modulus, and breaking strength of nylon nonwoven increase after rGO dipping, while breaking elongation decreases. Surface resistivity and rGO add-on of treated nylon nonwoven remain unchanged even after multiple washing, rubbing, and atmospheric ageing. Nylon nonwovens are characterised by FT-IR, XRD, Raman, FESEM, and LEICA image analyser analysis are used to characterise the developed nonwovens.

Behaviour of nickel coatings made by brush plating technology in conditions of cavitation erosion and corrosion

The basic hypothesis of the research was that the structure of the coating, i.e. the type of defects, affects the mechanical and electrochemical properties, as well as the resistance to cavitation erosion and corrosion. For this purpose, nickel coatings produced by brush-plating technology using two different electrolytes and deposited on X20Cr13 steel were tested. The electrolytes affected the structure and properties of the coatings: one coating had a network of cracks, and the second one had a “cauliflower-like” structure. The hardness and Young's modulus of both coatings were investigated under multi-cycle loading modes. Cavitation erosion resistance was tested in a cavitation tunnel equipped with a barricade system at an inlet pressure of 600 kPa and outlet pressure of 120 kPa. Both nickel coatings protected the substrate against cavitation erosion. The lowest rate of cavitation erosion had a coating with a network of cracks and high hardness. Microscopic examinations showed no influence of the net of cracks on the degradation process. Electrochemical tests confirmed the better corrosion resistance of the compact coating. The compact coating had about an order of magnitude lower corrosion potential and about 100 mV higher corrosion current density than that of the agglomerate coating. The agglomerate coating had electrochemical parameters comparable to the substrate.

Hot‐Pressing/Salt‐Leaching Method Assisted by Boronic Ester Dynamic Bond to Prepare Vitrimer Foams with Ultra‐Low Relative Permittivity and Superhydrophobic Performance

AbstractUltra‐low dielectric foams (ULDFs) have found important use in antennas and wave transparent devices. However, the controlled preparation of ULDFs is still a big challenge. In this work, a boronic ester bond‐assisted hot‐pressing/salt‐leaching (BHS) method is proposed to generate interconnected pore structure with tunable porosity and performance. In detail, styrene resin vitrimer is prepared with boronic ester cross‐linked network (BESR) which possessed low dielectric constant of 2.70, high modulus of 385 MPa, and reprocessability. BESR vitrimer exhibited drastically enhanced processability at the temperature >Tv(160 °C). Thanks to this unique feature, BESR vitrimer foams can be fabricated by hot‐pressing with salt particles followed by salt leaching. Such vitrimer foams exhibited advantageous pore‐forming processability, fabrication efficiency, and pore stability over conventional polymeric foams. The low extreme of dielectric constant can reach 1.60. Furthermore, owing to interconnected pore structure, superhydrophobic foam (water contact angel (CA) ≈ 154°) is facilely fabricated on the basis of BESR to afford anti‐icing performance. The BESR foam can maintain its superhydrophobicity underwater flow impacting at 10 kPa pressure, showing advantageous high durability. BESR foams also have good recyclability and would be potentially applied in recyclable antennas.

Hybrid Piezo-Capacitive Multimodal Sensors Based on Polyurethane–Poly(vinylidene fluoride) Nanofibers for Wearable E-Textiles

Wearable textiles with integrated multimodal sensors have numerous uses in the healthcare, entertainment, fitness, and fashion industries. However, the majority of reported sensors use different measurement methods to measure different stimuli, i.e., strain, pressure, and temperature. Further, they lack repeatability and stretchability for multimodal sensing. We have solved these issues by fabricating hybrid piezoelectric-capacitive sensors based on the PVDF–PU blend. Though PVDF, being a piezoelectric polymer, can be used as a dielectric layer in a capacitive sensor, it shows a poor piezoelectric coefficient and is mechanically unstable to cyclic deformations. To overcome this problem, we have used a specific blend of PU with PVDF, which has both high stretchability and piezoelectric coefficient. PVDF79PU21 (with 21% PU) nanofiber capacitive sensors showed a multimodal response with an excellent sensitivity of 0.3 kPa–1 for up to 8 kPa pressure stimuli, a good gauge factor ranging between 0.5 and 0.75 for 0–40% cyclic strain, and high sensitivities of 0.8 and 2% °C–1 for 30–60 and 60–100 °C, respectively. They could be used for measuring the human body temperature in the range of 37–40 °C with a sensitivity of 0.9% °C–1. The prototypes of PVDF79PU21 nanofiber-based capacitive sensors were attached to different body parts to measure extension and flexion movements with high sensitivity, which showed its great potential as a wearable sensor.

A novel hybrid piezo-triboelectric sensor (PTS) based on the surface modification for monitoring the operating status of the moving component

Nowadays, industrial sensors based on piezo-triboelectric effects have been successfully applied for the detection of sophisticated devices. The current study proposes a novel hybrid piezo-triboelectric sensor (PTS) to detect the operating states of the moving component (MC) in the machine. Firstly, the PTS is designed as a hierarchical structure to achieve synchronous detection of two motion states of MCs. Secondly, the surface frosting and nanoparticle doping adds the friction coefficient of the sensor to improve charge transfer efficiency, so the voltage signals of the PTS are more than 39.05% higher than that of the sensor with smooth surfaces under 0.5 kPa ∼ 1.5 kPa pressure. In addition, the frosted surface reduces the impact of surface damage caused by impurities on the voltage signals compared with a smooth surface. Moreover, the direction sensing part within PTS contains 4 perceptual units to generate direction sensing signals that are correlated with state sensing signals to reflect the definite operating information of the MC. Meanwhile, the sensing properties of the PTS effectively demonstrate relative motion between the adjacent element and the MC in the actuator. With excellent performance, this work provides a new paradigm shift for the application of hybrid sensors in equipment detection.

Quality of the Ceramic and Ni-Cr Alloy Joint after Al2O3 Abrasive Blasting.

The purpose of this in vitro study was to determine the effect of airborne-particle abrasion process parameters on the strength of the Ni-Cr alloy-ceramic bond. One hundred and forty-four Ni-Cr disks were airborne-particle abraded with 50, 110 and 250 µm Al2O3 at a pressure of 400 and 600 kPa. After treatment, the specimens were bonded to dental ceramics by firing. The strength of the metal-ceramic bond was determined using the shear strength test. The results were analyzed with three-way analysis of variance (ANOVA) and the Tukey honest significant difference (HSD) test (α = 0.05). The examination also considered the thermal loads (5000 cycles, 5-55 °C) to which the metal-ceramic joint is subjected during exploitation. There is a close correlation between the strength of the Ni-Cr alloy-dental ceramic joint and the alloy roughness parameters after abrasive blasting: Rpk (reduced peak height), Rsm (the mean spacing of irregularities), Rsk (skewness of the profile) and RPc (peak density). The highest strength of the Ni-Cr alloy surface bonding with dental ceramics under operating conditions is provided by abrasive blasting under 600 kPa pressure with 110 µm Al2O3 particles (p < 0.05). Both the abrasive blasting pressure and the particle size of the Al2O3 abrasive significantly affect the joint's strength (p < 0.05). The most optimal blasting parameters are 600 kPa pressure with 110 µm Al2O3 particles (p < 0.05). They allow the highest bond strength between the Ni-Cr alloy and dental ceramics to be achieved.

A review of nucleate pool-boiling heat transfer in different liquids and nanofluids

The goal of this review is to examine the current state of the art in nucleate pool boiling heat transfer in a variety of different fluids. The review is divided into many sections that discuss heat transfer in pool boiling, such as pool boiling of nanofluids, boiling behavior of water–glycerin combinations, and operational parameters. With the appropriate mixes of hydrocarbons and other commercial liquids, higher heat transfer coefficients may be produced. Coatings of nanoparticles with varying layer thicknesses applied to the heater surface may be optimized to improve heat transfer from the pool to the surrounding water. The heat transfer hypothesis elucidates the peculiarities of each pool’s boiling regime. It is also possible to expand it to flow boiling by combining pool boiling liquid motion with external mechanical force. Other phase transitions, such as condensation, solidification, and melting, can also be described using boiling heat flow processes. Pool boiling performance can be improved by making a variety of adjustments to the heating surfaces as well as by using pure liquids in the water. Improvements can be made to boiling parameters such as the heat flux, the critical heat flux, the heat transfer coefficient, bubble development and departure, and so forth. A nanoparticle addition to a pure liquid or a surface coating on a heating surface can improve heat transfer and boiling properties by increasing the surface area of the liquid. Pool boiling critical heat flux was enhanced with Al2O3-water nano fluid. Authors used three different powder sizes of Al2O3 which were 0.05, 0.3 and 1.0 μm. Addition of alumina particle in water increases the boiling heat flux. Critical heat flux (CHF) was significantly enhanced using Titania and Alumina nano particles in water as compared to pure water. Average size of nano particle used was 85 nm measured by scattering electron microscope. Enhancement in Critical heat flux is due to nano particle coating on heating surface. Characteristics of nucleate boiling are greatly affected by the operating pressure. Miniature flat heat pipe (MFHP) with evaporator having micro grooved heat transfer surface gives 50% increment in critical heat flux at atmosphere pressure whereas this value increases up to 150% at 7.4 kPa pressure. The addition of CNT (carbon nanotube) to the base liquid increases the critical heat flux. Transmission electron microscopy confirms the average size of a nanoparticle as 15 nm. Authors found that by decreasing pressure from atmosphere condition critical heat flux increases to 200% with CNT/water nano fluid as compared to deionized water. SiC-water nanofluids of 100 nm size were experimented with at volume concentrations of 0.001%, 0.001%, and 0.01%. The size of the nanoparticle was confirmed by a scattering electron microscope. Authors concluded that at 0.01% of nano particle enhances critical heat flux to 105%.

To what extent are objectively measured mammographic imaging techniques associated with compression outcomes

To describe the association between objectively measurable imaging techniques and the resulting compression thickness and dose. The study included 80,495 routine screens from the South-West London Breast Screening Service between March 2013 and July 2017. Average compression force, paddle tilt and dose were calculated. The Volpara® DensityTM algorithm was used to estimate pressure, breast volume and density.Linear regression models, using generalized estimating equations (GEEs) to account for clustering by practitioner, assessed the strength of the associations between the imaging compression outcomes, (thickness, dose) and imaging techniques (force, pressure and paddle tilt), adjusting for the subject's characteristics (age, ethnicity, breast volume and percent mammographic density). Fully adjusted linear regression models showed that compression thickness decreased by ~1 mm (~2% of mean thickness) for every 1daN increase in force and decreased by ~0.8 mm with an increase of 1 kPa of pressure (at median pressure). Increasing pressure above 15 kPa resulted in minimal reduction in thickness. Dose increased with increased force but decreased by ~1% of mean dose with every increase in 1 kPa of pressure. For 1o increase in paddle tilt, the compression thickness increased by ~1.5 mm (~2.5%) and dose increased by ~2.5%, (Pt <0.001 in all cases). Differences in imaging technique are associated with imaging outcome measures (thickness and dose). A better understanding of the association between objective image acquisition parameters and tumour conspicuity could lead to clearer guidelines for practitioners. Increased paddle tilt is associated with increased compression thickness and increased dose after adjustment for breast volume and force applied.

Superhydrophobicity and compressive stability of Salvinia surface: Mechanical analysis and structural design

The surface of Salvinia had superhydrophobicity and kept good compressive stability, which was mainly attributed to the dense microscopic eggbeater structure villi on the surface. By means of force equilibrium, a theoretical model was established to analyze the interface mechanical behaviors when a droplet infiltrates the microstructures. Based on the minimum energy principle, a theoretical model was presented to analyze the process of a droplet spreading on the surface of Salvinia reaching a steady state. Combined with numerical simulations, it was found that the superhydrophobicity and compressive stability of the Salvinia were dependent on the morphological and geometric parameters of the microstructure (edge angle φ, number of branching n, width W and spacing D, etc.). By adjusting these geometrical parameters, the surface of the biomimetic structure can maintain a stable Cassie state at 0.63 kPa pressure, and the apparent contact angle is controllable in the range of 121°−169.8°. The research results provide a theoretical foundation for the structural design of superhydrophobic surfaces with high stability and tunable wettability.

Reduce methane emission from rice paddies by man-made aerenchymatous tissues

Methane is the second most important greenhouse gas after carbon dioxide, and 8–11% is emitted from paddy fields. Methanogenic microbial processes in water-saturated soils can be alleviated through the oxygenation of soils, which may hamper methane production and emissions in paddies. Here, by mimicking O2 release from rice roots, we report the use of man-made (i.e., silicone tube-based) aerenchymatous tissues (MAT) to continuously release O2 to abate methane emission from paddies. High O2-releasing rates (such as 5 kg O2/ha/d) can be easily achieved by adjusting MAT density (e.g., 0.2 m2 tube/m2 soil) and its inner air pressure (e.g., 25 kPa). Following deployment, MAT significantly increased soil redox potential (from -150 mV to -88.6 mV) and induced active iron redox cycling. This decreased the availability of organic substrates of methanogens and therefore dramatically reduced their abundance (-25.1% active mcrA gene). We quantified the decrease in methane emission both in mesocosms and paddy field trials and found in both setups that ~ 50% of methane emission was reduced. Moreover, we showed that the performance of MAT can be further improved by simply increasing the air pressure in MAT (e.g., -74.2% methane emission at 200 kPa air pressure). This work provides a powerful and sustainable method for mitigating methane emission from rice paddies.Graphical

Flexible multi-modal sensors based on CNT hollow spheres/PDMS composites for human motion recognition and colloid concentration detection

Because flexible sensors with multi-modal responses are essential for applications in the complex environment of wearable products, a unique carbon nanotube (CNT) hollow-sphere scaffold is fabricated using self-assembling of microspheres and microwave irradiation to achieve flexible strain, pressure, and laser sensors. The CNT hollow-sphere scaffold comprising intertwined CNTs is featured with a sophisticated conductive network, large tensile and compressive deformability, intrinsic photothermoelectric nature, and good accommodation for polydimethylsiloxane (PDMS) matrix. Thus, the fabricated CNT hollow spheres/PDMS composite sensors showed good responses to the applied strain (a high gauge factor exceeding 55000 in the strain region of 95–107%, 27 ms response time, and over 20000 cycles durability at 40% strain), pressure (a gauge factor of 0.07–3.15 kPa−1 with a wide sensing range (up to 248 kPa pressure), and laser irradiation (0.066 s−1 at 5 s of 532 nm laser irradiation). Moreover, their uses in body movement detection, healthcare, tactile perception, and colloid concentration detection are demonstrated. It is believed that the CNT hollow spheres/PDMS composite sensors will pave the way for practical applications for future wearable electronic devices, which could recognize human motion as well as sense air quality and disease diagnosis.

Dynamic elastomers based on bio‐derived crosslinker

AbstractPetroleum‐derived monomers are the most common building blocks for ester‐based thermosets. Bio‐derived thermoset elastomers are becoming viable alternatives to conventional thermosets. Herein, we developed a biobased vitrimer‐type thermoset elastomers using abundant and sustainable raspberry ketone as feedstock. We utilize raspberry ketone to create building blocks for dynamic oxime chemistry and crosslinked these through free radical polymerization with poly(ethylene glycol) methyl ether methacrylate as a comonomer. In contrast to other dynamic networks based on ester bonds, which need catalysts, this is undesirable since catalyst deactivation or leaching lowers its effect over time and may impair reuse. This network incorporates catalyst‐free bond exchange reactions in catalyst‐dependent polyester networks by substituting oxime‐esters for typical ester linkages. The elastomer exhibits stress relaxation, a low glass transition temperature (Tg) (−55 to −40.2°C) and tensile strength up to 5.2 ± 3.0 kPa. Furthermore, the dynamic oxime transesterification exchange mechanism allows elastomers to be reprocessed using a hot press at 160°C and 8 × 103 kPa pressure. After reprocessing, the tensile strength of elastomers can be recovered up to 78.1 ± 10.9%. This work integrates the principles of catalyst‐free dynamic exchange process and mechanical recycling coupled with biobased components to provide a rational solution towards conventional elastomers. In the future, these elastomers can be exploited for the development of hydrogels, recyclable elastomers, and commodity plastics.

Tangential microfiltration of lime and pineapple juices using inexpensive tubular ceramic membrane and analysis of fouling mechanism

A non-thermal tangential filtration of lime and pineapple juices using an indigenously elaborated inexpensive bentonite-based tubular ceramic membrane (96 $/m2) is discussed in the present work. The fabricated membrane exhibited a porosity of 37% with 0.11 µm pore size and possessed adequate flexural stability of 18 MPa. Microfiltration experiments were conducted for both centrifuged juice (CJ) and Enzymatic treated centrifuged juice (ETCJ) of lime and pineapple at various operating pressures (69 – 345 kPa) and crossflow rates (110 – 150 Lph) to evaluate their effects on the resulting permeate flux and clarified juice properties. The membrane provided a maximum permeate flux of both ETCJ of lime and pineapple juices as 2.22 × 10−5 m3/m2s and 1.31 × 10−5 m3/m2s, respectively, at operating conditions of 345 kPa pressure and 150 Lph flowrate. Enzymatic pretreatment considerably enhanced the permeate fluxes of both juices. Also, comparatively a high clarity and complete removal of alcohol-insoluble solids were observed for permeate streams of ETCJ. In all the cases, the desirable characteristics of citrus juices, including pH, total soluble solids, and citric acid content, were unaltered, ensuring the uniqueness of the membrane separation processes. Furthermore, fouling analysis was carried out using Hermia's models, revealing experimental data best fits into the cake filtration model for pineapple juice and intermediate pore blocking model for lime juice clarification are identified as dominant mechanisms, respectively.

Flexible and Wearable Capacitive Pressure Sensor for Monitoring Heart Parameters

The increase in global average life expectancy over the past century has been largely attributed to medical science developments. In this study, we demonstrate a polymer-based capacitive pressure sensor for measuring heart rate and pulse pressure signal. The fabricated sensor has been characterized to evaluate its performance and to verify its repeatability and precision. It is observed that the sensor works in the range of 0 – 8 kPa pressure range and is suitable for measuring the pulse pressure. This sensor has a high sensitivity of 7.11 kPa <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> in the low-pressure range of 0 to 8 kPa. Further, the sensor demonstrated a considerable amount of repeatability with an error less than 6% in consecutive measurements. Moreover, the sensor demonstrated the use of a wearable, flexible piezo-capacitive pressure sensor for pulse pressure monitoring. The wrist pulse was used as the stimulus for the experimental characterization of the sensor, and health markers related to the measured response were also discussed.