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Swelling elastomers are designed to swell when immersed into fluids like water, oil, or acid. The mechanism of swelling can be either diffusion or osmosis, initiating the imbibition of fluid inside the elastomer and progressively swelling it. Work presented here investigates diffusion as the swelling mechanism. Swelling experiments are conducted at two temperatures (room and 50°C) using water of different salinities (0.6% and 12%) as the swelling medium. Changes in volume, thickness, mass, and hardness are recorded. Measurements are taken before swelling and after 1, 2, 4, 7, 10, 16, 23, and 30 days of swelling. As expected, volume, thickness, and mass of the elastomer increase with increase in the number of swelling days, while hardness shows a decreasing trend. More variation is observed for all quantities in low-salinity brine as compared to high salinity, at both temperatures. However, density values are larger for high-salinity brine at both temperatures. Stokes–Einstein formula is used to determine the diffusion coefficients. Viscosity is measured using a Cannon–Fenske apparatus of size 50. Larger values of diffusion coefficient are found in low-salinity water at both temperatures, consistent with the higher amount of swelling and the faster swelling rate. These results and the diffusion-based approach will help in understanding the mechanics of swelling phenomenon. This work can aid in the development of new analytical and semi-analytical models that can predict seal pressure and other performance factors more accurately for applications in oil and gas wells.

Industrial gas turbine fueled by blended palm olein is a promising option for electricity generation in next generation of gas turbines. In order to evaluate combustion performance of palm olein and blended diesel in a combustion chamber, detailed experimental investigations were done to evaluate the combustion performance of diesel and palm olein blended fuels. The experimental studies were conducted for 100% diesel and blending diesel with 10, 20, 30, 40, 50 and 60% palm olein (PO). The combustion performances were evaluated for blended oil and compared with diesel. The emission of NO ranged from 30–55 ppm while the soot emissions were high for high blended fuel. A maximum blending ratio of 30% PO was recommended to be used in gas turbines in order to avoid any modification in the spray combustion system so that it can be utilized in existing gas turbine systems. The computational fluid dynamic modeling of the combustor was also done, and a comparison was made between the experimental and computational results. This can be helpful in future parametric studies of the combustor performance under different operating conditions. An acceptable level of comparison between numerical simulations and experimental findings was obtained as far as the flame structure is concerned. For high blended fuel, it was found out that increasing amount of soot particles can damage the blades of the turbine which ultimately requires early monitoring and maintenance scheduling.

A highly sensitive body motion sensor has been fabricated based on a composite active layer of zinc stannate (ZnSnO3) nano-cubes and poly(vinylidene fluoride) (PVDF) polymer. The thin film-based active layer was deposited on polyethylene terephthalate flexible substrate through D-bar coating technique. Electrical and morphological characterizations of the films and sensors were carried out to discover the physical characteristics and the output response of the devices. The synergistic effect between piezoelectric ZnSnO3 nanocubes and β phase PVDF provides the composite with a desirable electrical conductivity, remarkable bend sensitivity, and excellent stability, ideal for the fabrication of a motion sensor. The recorded resistance of the sensor towards the bending angles of −150° to 0° to 150° changed from 20 MΩ to 55 MΩ to 100 MΩ, respectively, showing the composite to be a very good candidate for motion sensing applications.

Conductive polymer poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) is being considered as an alternate material for metallic thin-film conductors in numerous biomedical sensing applications. This study investigates the electromechanical response of delaminating thin films of this conductive polymer (PEDOT/PSS) on a highly compliant elastomeric substrate called polydimethylsiloxane. The value of Young’s modulus for the substrate was tuned to remain between 120 kPa and140 kPa, while its thickness was at a submillimeter level. The films were fabricated using a non-vacuum, scalable, and cost-effective method of rod coating. The films were intentionally fabricated in a way, so that when the tensile strain is applied, the films are only loaded through interfacial shear, which results in delamination of the films instead of cracking. The experiments indicate an onset of delamination at an average value of 13.3% strain with continuous increase in resistance up to an average of 26% strain for the as-fabricated laminate. The study presents simple mathematical models relating the variation of electrical resistance with the applied strain which can be of potential use in predicting the response of such a polymer–elastomer laminate in areas like flexible and stretchable electronic sensing.

Mechanical performance of nanoparticle-based thin films depends on the method of fabrication and the properties of the underlying substrate. This study presents experimental results of electromechanical response of micrometer-thick dip-coated silver nanoparticle-based films on rough and highly compliant (Young’s modulus between 120 and 130 kPa) polydimethylsiloxane substrate having random micro-bumpy surface. The experimental results demonstrate stretchability of 13% and flexibility of 3.43% for the as-fabricated metal–polymer laminate. The entire process being amenable to mass production suggests a cost-effective and high-throughput route toward the fabrication of stretchable/flexible electronic devices and thin film sensors.

Organic electronics have earned great reputation in electronic industry yet they suffer technical challenges such as short lifetimes and low reliability because of their susceptibility to water vapor and oxygen which causes their fast degradation. This paper report on the rapid fabrication of Al 2 O 3 encapsulations through a unique roll-to-roll atmospheric atomic layer deposition technology (R2R-AALD) for the life time enhancement of organic poly (4-vinylphenol) (PVP) memristor devices. The devices were then categorized into two sets. One was processed with R2R-AALD Al 2 O 3 encapsulations at 50 °C and the other one was kept as un-encapsulated. The field-emission scanning electron microscopy (FESEM) results revealed that pin holes and other irregularities in PVP films with average arithmetic roughness ( R a ) of 9.66 nm have been effectively covered by Al 2 O 3 encapsulation having R a of 0.92 nm. The X-ray photoelectron spectroscopy XPS spectrum for PVP film showed peaks of C 1s and O 1s at the binding energies of 285 eV and 531 eV, respectively. The respective appearance of Al 2p, Al 2s, and O 1s peaks at the binding energies of 74 eV, 119 eV, and 531 eV, confirms the fabrication of Al 2 O 3 films. Electrical current–voltage ( I – V ) measurements confirmed that the Al 2 O 3 encapsulation has a huge influence on the performance, robustness and life time of memristor devices. The Al 2 O 3 encapsulated memristor performed with superior stability for four weeks whereas the un-encapsulated devices could only last for one week. The performance of encapsulated device had been promising after being subjected to bending test for 100 cycles and the variations in its stability were of minor concern confirming the mechanical robustness and flexibility of the devices.

This paper investigates the fabrication of Ag films through the electrospray deposition (ESD) technique on sub-millimeter-thick acid-etched rough polydimethylsiloxane (PDMS) substrates having both low and high modulus of elasticity. The main focus of the study is on the stretchable behavior of ESD-deposited Ag nanoparticles-based thin films on these substrates when subjected to axial strains. Experimental results suggest that the as-fabricated films on thin acid-etched rough low modulus PDMS has an average stretchability of 5.6% with an average increase in the resistance that is 23 times that of the initial resistance at electrical failure (complete rupture of the films). Comparatively, the stretchability of Ag films on the high modulus PDMS was found to be 3 times higher with 4.65 times increase in the resistance at electrical failure. Also, a high positive value of the piezoresistive coefficient for these films suggests that the resistivity changes during stretching, and thus deviation from the simplified models is inevitable. Based on these results, new models are presented that quantify the changes in resistance with strain.

This study investigates the resistive behavior of rod-coated micrometer thick films of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) on ultra-low modulus (120– 130 kPa) polydimethylsiloxane (PDMS) substrate having scratch or microtrench-type roughness patterns. On average, the films were found to remain electrically functional up to 23% axial strain with an average increase of three times in the value of the normalized resistance. The films were also found to remain conductive up to bending diameter of 4 mm with an average increase of 1.12 times their initial resistance. The rod-coated PEDOT:PSS films on ultra-low modulus PDMS having microtrench-type roughness were also found to remain functional even after 1000 bending cycles at a bending diameter of 4 mm and even smaller with an increase in resistance that was on average 1.15 times their initial resistance. The films were found to fail firstly by cracking and thereby debonding from the substrate under the application of axial strain. On the other hand, the films exhibit no delamination under bending strains. The results from this investigation suggest that the polymer–polymer laminate has potential applicability in stretchable and flexible electronics and related applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2015, 53, 226–233

Stretchability and resistive behavior of spin coated silver (Ag) nanoparticles films on polydimethylsiloxane (PDMS) substrates having random micro ridges has been studied under the application of axial strain. No deposition was observed on smooth PDMS substrates using spin coating, while the PDMS substrates having random micro ridges were found to assist the deposition of the ink through spin coating. The deposited films show minimal change (

Metallic tubes have been widely used as primary heat transfer elements in laminar convectors for domestic and aerospace heating purpose. This paper uses CFD tool to investigate the heat output and pressure drop of liquid sodium flowing inside a circular tube having a wavy profile throughout its length. The wavy tube can be utilized in laminar liquid metal convectors as basic heat transfer element. The effect of Reynolds number (500≤Re≤2000) wave pitch (25 mm≤λ≤100 mm) and wave amplitude (2 mm≤a≤6 mm) on the heat output and pressure drop has been numerically studied. Based on the CFD results important controlling parameters have been identified and it is concluded that the heat output from the wavy tube is affected by the wave pitch and the wave amplitude while the pressure drop is mostly affected by the Reynolds number and wave amplitude.

The resistive behaviour of silver (Ag) nanoparticle based thin films at different loading conditions (axial stretching, bending and repeated bending) has been studied on rough ultra-low modulus polydimethylsiloxane substrates with scratch or trench type roughness. These films have been fabricated using a non-vacuum and scalable thin film deposition technique, rod coating. The fabricated films showed minute changes in their resistance when stretched up to an average of almost 27% axial strain, and when bent on circular surfaces with diameters in the range 10–30 mm. The films were also found to remain conductive even after 1000 bending cycles. These results suggest that the as-fabricated silver nanoparticle films could be potentially useful in areas like stretchable, flexible and epidermal electronics.

A simple Couette flow velocity profile with an appropriate correlation for the free terminal rise velocity of a single bubble in a quiescent liquid can produce reliable results for the trajectories of small spherical air bubbles in a low-viscosity liquid (water) provided the liquid remains under uniform shear flow. Comparison of the model adopted in this paper with published results has been accomplished. Based on this study it has also been found that the lift coefficient in water is higher than its typical value in a high-viscosity liquid and therefore a modified correlation for the lift coefficient in a uniform shear flow of water within the regime of the Eötvös number 0.305≤Eo≤1.22 is also presented.