Search

The amplification of weak molecular signals to visible output could provide a gateway to the macroscopic world. In this context, supramolecular interfaces were designed by depositing macrocyclic "host" molecules in a multilayer film that can be utilized to discriminate isomers by their fluid flow response upon "host-guest" molecular recognition.

In a viscoelastic environment, characterized by Deborah number (De), active droplets get deformed and perform zig-zag motion. This unique motion is inextricably linked to the swimming mode employed by them.

The release of those materials would be contained within the facility’sboundariese so that the impact on the public would be negligible. Hazardous facilities include oil refineries, micro-chip manufacturing,g, etc. Basic Facilities: The buildings not classified as safety-critical or essential/dangerous come under this category. This paper investigates the effect of the cylindrical charge aspect ratio on the spatial distribution of sufficient pressure induced by blast blasting on the face of a concrete element. A clear pattern of the spatial distribution of internal pressure can be seen in the graphical comparison of different aspect ratios. This may be attributed to the complex pressure wave patterns produced by the detonation of cylindrical explosives. Adequate pressure decreases as the aspect ratio of the cylindrical head increases. A 50% reduction in clean printing is observed when the aspect ratio varies between 1 and 2.

The study uses coupled finite or boundary element models expressed in terms of the axial wavenumber. It is found to be important to include the track in the model as this determines how the load is distributed at the soil’s surface, which significantly affects the insertion loss of the barrier. Calculations are presented for a range of typical layered grounds in which the depth of the upper soil layer is varied. Variations in the width and depth of the trench or barrier are also considered. The results show that in all ground conditions considered, the notional rectangular open trench performs best.

Fabrication and processing approaches that facilitate the ease of patterning and the integration of nanomaterials into sensor platforms are of significant utility and interest. In this work, we report the use of laser-induced thermal voxels (LITV) to fabricate microscale, planar gas sensors directly from solutions of metal salts. LITV offers a facile platform to directly integrate nanocrystalline metal oxide and mixed metal oxide materials onto heating platforms, with access to a wide variety of compositions and morphologies including many transition metals and noble metals. The unique patterning and synthesis flexibility of LITV enable the fabrication of chemically and spatially tailorable microscale sensing devices. We investigate the sensing performance of a representative set of n-type and p-type LITV-deposited metal oxides and their mixtures (CuO, NiO, CuO/ZnO, and Fe

Self-powered supramolecular micropumps could potentially provide a solution for powerless microfluidic devices where the fluid flow can be manipulated via modulating non-covalent interactions.

Despite the extensive developments of flexible capacitive pressure sensors, it is still elusive to simultaneously achieve excellent linearity over a broad pressure range, high sensitivity, and ultrahigh pressure resolution under large pressure preloads at low cost. This work presents a facile and low-cost fabrication method to integrate an ultrathin ionic layer with gradient microstructures with programmable profiles and heights created by a simple CO2 laser. The coupled electrical and mechanical simulations provide a route to optimize the design of iontronic pressure sensors based on the electric double layer to address the existing challenges for significantly improved pressure sensing performance. The resulting optimized sensor exhibits a high sensitivity of 33 kPa− 1 over an ultra-board linear sensing range of 1700 kPa, an ultralow detection limit of 0.36 Pa, and a pressure resolution of 0.00725% under ultrahigh pressure of 2000 kPa. Taken together with a rapid response/recovery time of 4/16 ms and excellent repeatability over 4,500 cycles, the sensor has been applied to subtle pulse detection from the fingertip, interactive control on the robotic hand, and a smart weight scale/chair with ultrahigh pressure resolution. The simple fabrication approaches and design toolkit from this work can also be leveraged to easily tune the pressure sensor performance for varying target applications and open up the opportunities to create other iontronic sensors for the next-generation flexible devices.

Soft robotics focuses on mimicking natural systems to produce dexterous motion. Dielectric elastomer actuators (DEAs) are an attractive option due to their large strains, high efficiencies, lightweight design, and integrability, but require high electric fields. Conventional approaches to improve DEA performance by incorporating solid fillers in the polymer matrices can increase the dielectric constant but to the detriment of mechanical properties. In the present work, we draw inspiration from soft and deformable human skin, enabled by its unique structure, which consists of a fluid-filled membrane, to create self-enclosed liquid filler (SELF)-polymer composites by mixing an ionic liquid into the elastomeric matrix. Unlike hydrogels and ionogels, the SELF-polymer composites are made from immiscible liquid fillers, selected based on interfacial interaction with the elastomer matrix, and exist as dispersed globular phases. This combination of structure and filler selection unlocks synergetic improvements in electromechanical properties-doubling of dielectric constant, 100 times decrease in Young's modulus, and ∼5 times increase in stretchability. These composites show superior thermal stability to volatile losses, combined with excellent transparency. These ultrasoft high-k composites enable a significant improvement in the actuation performance of DEAs-longitudinal strain (5 times) and areal strain (8 times)-at low applied nominal electric fields (4 V/μm). They also enable high-sensitivity capacitive pressure sensors without the need of miniaturization and microstructuring. This class of self-enclosed ionic liquid polymer composites could impact the areas of soft robotics, shape morphing, flexible electronics, and optoelectronics. Ministry of Education (MOE) Accepted version The authors acknowledge funding from the Ministry of Education (MOE) Tier 1 grant (MOE2018-T1-002-179).

Thermal mixing behavior of shear-thinning fluids with the specified heat flux boundary condition at mixing zone walls is studied numerically to investigate the effect of Reynolds number (10 to 50),...

In the event of a nuclear reactor accident, large amount of radioactivity in the form of fission products may get released to the piping assembly of primary heat transport system. These fission products mostly in the form of aerosol particles get deposited on the inner surface of the piping system due to various depositional processes. The removal processes in the complex piping system are controlled to a large extent by the thermal-hydraulic conditions like temperature, pressure and flow rates. These parameters generally vary with time and therefore must be carefully monitored to predict the aerosol behavior in the piping system. Experimental determination of the deposition fraction, interpretation of the role of controlling parameters and development/validation of theoretical models are key areas gaining constant attention among researchers. In the present work, experiments were conducted in a piping assembly consisting of bends and horizontal-vertical orientation at two different carrier gas flow rates. Deposition fractions in the test assembly were estimated and the role of different dynamical processes (thermophoresis, gravitation and bend impaction) was interpreted. The computational fluid dynamics modeling approach is used for theoretical simulation in this work. Aerosol behavior in terms of number concentration, particle size distribution, and particle deposition in the piping system was simulated with the computational fluid dynamics software ANSYS Fluent 16.0 and the results were compared with experimental measurements (wherever applicable).

Branching T-channel is a very common element of a piping system for the transportation of liquids and gases. The brachesbranches of the T-channel can be inclined at different angles which affects the flow dynamics and heat transfer characteristics significantly. Thus, the present work focuses on the flow and thermal characteristics of the laminar forced convection of power-law fluids in a rectangular branching channel which have been numerically investigated over a wide range of parameters such as Reynolds number, 50 ≤ Re ≤ 300, Prandtl number, 10 ≤ Pr ≤ 50, inclination angle, 30° ≤ α ≤ 90° and power-law index, 0.2 ≤ n ≤ 1.4 (includes shear-thinning, n 1 and Newtonian, n = 1 fluids). This is perhaps the first systematic study which examines the role of power-law fluid behaviour and of branch inclination on momentum and heat transfer characteristics. New extensive results for the flow and temperature fields are presented in terms of streamline contours and separated-flow zones, pressure coefficient, recirculation length, critical Reynolds number, isotherm contours, temperature profiles and local Nusselt number. The pressure coefficient is found to be higher for shear-thickening fluids than that for the Newtonian and shear-thinning fluids while the inclination angle has only a weak effect. The recirculation length bears a positive dependence on the Reynolds number and inclination angle while an inverse relationship is observed with power-law index in both branches. The critical Reynolds number, at which the onset of flow recirculation is observed, is found to be lower for higher inclination angles and a strong influence of the power-law index is also seen on the critical Reynolds number in both branches. Also, the local Nusselt number is seen to be higher at lower Prandtl numbers, low power-law index values and high inclination angles for both branches. Overall, the inclination angle plays a significant role in determining the heat transfer characteristics.

A comparative study of the electrical and photodetection properties of ZnO and Cr doped ZnO thin films are being reported here. The films were deposited using magnetron sputtering. X-ray diffraction (XRD) revealed hexagonal crystal structure of the films with (002) preferred orientation. Pt/ZnO/Pt and Pt/Cr doped ZnO/Pt Schottky diodes were fabricated for photodetection studies. The Schottky barrier height was lowered for Cr doped ZnO film as compared to ZnO film. The ideality factor was improved upon Cr doping. Pt/ZnO/Pt diode was unresponsive to visible light, however, Pt/Cr doped ZnO/Pt diode showed response to visible light with short response and recovery times. The response of the Pt/Cr doped ZnO/Pt diodes to visible light is attributed to the reduction in band gap of the Cr doped ZnO thin film. Keywords: Chromium-doped Zinc oxide, Thin films, Sputtering, Schottky contact, Photodetectors

In the present study, the momentum and heat transfer aspects from an isothermally rotating cylinder immersed in a power-law fluid, confined symmetrically and asymmetrically between two parallel walls are considered. The governing equations are solved numerically for the rotational Reynolds number ( 10 − 3 ≤ R e ≤ 40 ) , Prandtl number ( 1 ≤ P r ≤ 100 ) , power-law index ( 0.02 ≤ n ≤ 1 ) , blockage ratio ( 10 − 3 ≤ β ≤ 0.9999 ) and asymmetry ratio ( 10 − 4 ≤ γ ≤ 1 ) to elucidate the role of these parameters on the momentum and heat transfer characteristics. The results reported herein pertain to the two dimensional, steady, incompressible power-law fluid in the laminar flow region. The numerical strategy and method used here are validated by comparing the present results with some of the available experimental and numerical studies, showing good agreements. As far as can be ascertained, it is the first systematic numerical study of a rotating cylinder immersed in power-law fluids elucidating the complex interplay between the rheological and kinematic parameters. The flow field is visualized by plotting the streamlines and, hydrodynamic forces and torque acting on the rotating cylinder are computed. The numerical results are supplemented by a lubrication approximation analysis relevant to highly confined cases, i.e., large values of β. In this case, when confinement increases, the asymptotic scaling of the torque is given by e − 1 / 2 where e denotes the non-dimensional gap between the cylinder surface and the nearest wall. The heat transfer characteristics are presented in terms of the isotherm contours, and the local and average Nusselt numbers as functions of the aforementioned governing parameters. The rate of heat transfer exhibits a positive dependence on the Reynolds number, Prandtl number, confinement and the degree of asymmetry while the shear-thinning behavior decreases the rate of heat transfer above the corresponding value in Newtonian fluids. Finally, the present results are consolidated by fitting them in the form of a predictive correlation for the average Nusselt number for different blockage ratios studied herein.

This study aims to analyze the stability of a gravity-driven thin film flow in the heated/cooled interior surface of a vertical hollow cylinder. The model development involves simplifying the flow and energy equations using the usual thin-film approximation, where the average film thickness is considered to be much smaller than the radius of cylinder. A dispersion relation is then derived to study the temporal stability of the system in order to quantify the effect of various non-dimensional parameters present in the model, such as the thermoviscous number, Marangoni number, Biot number, and Bond number. Another non-dimensional parameter is introduced by considering an opposing suction pressure in the annulus region. The thermocapillary stress and the thermoviscous effect are shown to strongly affect the temporal stability of the flow. It is shown that although the suction pressure affects the velocity profile of the flow, it does not affect the temporal stability results. The suction pressure is then shown to have some effect on the spatiotemporal stability. Critical condition is presented for the transition between absolutely and convectively unstable systems, and parameter regimes are presented to quantify the effect of the above-mentioned parameters.

In this study, a rotating cylinder is placed in a stream of shear-thinning fluids, flowing with a uniform velocity. Detailed investigations are performed for the following range of conditions: Reynolds number 100≤Re≤500, power-law index 0.2≤n≤1 and rotational velocity 0≤α≤5. Flow transitions are observed from steady to unsteady at critical values of the Reynolds number, the rotational velocity, and the power-law index. Critical values of the Reynolds number Rec have been obtained for varying levels of the rotational velocity, and the power-law index. Rec varies nonmonotonically with the rotational velocity. At a particular Reynolds number, an increase of the rotational velocity acts as a vortex suppression technique. For shear-thinning fluids considered here, the vortex suppression occurs at a larger value of the critical rotational velocity αc, relative to Newtonian fluids. For the unsteady flow, the lift coefficient versus time curve exhibits oscillatory behavior, and this has been used to delineate the flow regime as steady or unsteady flow. For unsteady flow regimes, both the amplitude of the lift coefficient and the Strouhal number increase with increasing Reynolds numbers. The results presented in this work for such high Reynolds numbers elucidate the possible complex interplay between the kinematic and rheological parameters of non-Newtonian fluids. This investigation also complements the currently available low Reynolds number results up to ∼ Re=140.

This study investigates the possibility of solving film problems using the phase-field lattice Boltzmann method (LBM). The mesoscopic nature of fluid interface makes the lattice Boltzmann method (LBM) a suitable tool to model two-phase systems. Experimental and theoretical observations for a film spreading on an inclined plane have been reproduced using LBM, justifying the use of LBM in film problems. We present a detailed analysis of the effect of the aspect ratio (the ratio of the film thickness far away from the contact point to the characteristic length), viscosity ratio, and surface wettability gradient. The study of the effect of the aspect ratio confirms that the dimensionless height of the tip of the ridge approaches unity exponentially as we move toward the thick film where lubrication approximation no longer holds. The ridge completely vanishes at a critical value of the aspect ratio [Formula: see text]. εc is found to be independent of the advancing contact angle, and increasing the aspect ratio beyond εc results in fluid protrusion ahead of the contact point. The film is more prone to instability in a more viscous surrounding where free-surface assumption is not valid. Furthermore, the study of the effect of the chemically induced wettability gradient on the solid substrate reveals that the contact point velocity and the interfacial profile depend on the local surface wettability.

This work aims to explore the T-channel momentum and heat transfer characteristics with the combined effect of Bingham plastic fluids (0.01 ≤ Bn ≤ 20) behavior and geometrical variation in terms of branching angle (30 deg ≤ α ≤ 90 deg). The problem has been solved over a wide range of Reynolds number (50 ≤ Re ≤ 300) and Prandtl number (10 ≤ Pr ≤ 50). For the momentum flow, qualitative and quantitative features are analyzed in terms of streamlines, structure of yielded/unyielded regions, shear rate contours, plug width and length variation, and local pressure coefficient. These features have been represented in terms of isotherm patterns, temperature profile, Nusselt number, and its asymptotic value for heat transfer characteristics. The recirculating flows have been presented here in the vicinity of T-junction, which promote mixing and heat transfer. Broadly, the size of this zone bears a positive dependence on Re and α. However, fluid yield stress tends to suppress it. The critical Reynolds and Bingham numbers were found to be strong functions of the pertinent parameters like α. The inclination angle exerts only a weak effect on the yielded/unyielded regions and on the recirculation length of main branch. Results show a strong relationship of the plug width and length with key parameters and branches. The Nusselt number exhibits a positive relationship with α, Bn, and Re but for lower Pr in the T-junction vicinity for both branches. Such length indicates the required optimum channel length for thermal mixing.

In this work, thermal mixing of shear-thinning (i.e. CMC solutions) and Newtonian fluids has been numerically investigated in a rectangular T-channel for a specified heat flux boundary condition at the mixing zone walls. The influence of the Reynolds number (10 ≤ Re ≤ 50), power-law index (0.6161 ≤ n ≤ 1), Nusselt number (a dimensionless form of convective heat transfer coefficient for external air flow, 103 ≤ Nuo ≤ 104), and ambient temperature (−2.7 ≤ θa ≤ 1.3) is studied on the mixing behaviour. The flow is assumed to be steady, laminar, and incompressible. The new results are presented in terms of isotherm contours, mixing index, and required channel length to achieve complete mixing. The mixing index decreases along channel length for both shear-thinning and Newtonian fluids. Better mixing is seen at high power-law index, ambient temperature, and Nusselt number and low Reynolds numbers. The length required to achieve the 95% of the ambient temperature or the exact ambient temperature is shorter for mildly shear-thinning fluids (high power-law index) and Nusselt number, and low Reynolds numbers. Also, for the case of heating (high ambient temperature), the complete mixing demands a shorter channel length than that in the case of cooling.

Gravity-driven flow of a liquid over an isothermal cylinder is unconditionally unstable. The flow of a thermoviscous fluid over a heated or cooled substrate shows interesting stability behavior. The relevant parameters in the model affect the spatiotemporal nature of the instability.

Soft robotics focuses on mimicking natural systems to produce dexterous motion. Dielectric elastomer actuators (DEAs) are an attractive option due to their large strains, high efficiencies, lightweight design, and integrability, but require high electric fields. Conventional approaches to improve DEA performance by incorporating solid fillers in the polymer matrices can increase the dielectric constant but to the detriment of mechanical properties. In the present work, we draw inspiration from soft and deformable human skin, enabled by its unique structure, which consists of a fluid-filled membrane, to create self-enclosed liquid filler (SELF)-polymer composites by mixing an ionic liquid into the elastomeric matrix. Unlike hydrogels and ionogels, the SELF-polymer composites are made from immiscible liquid fillers, selected based on interfacial interaction with the elastomer matrix, and exist as dispersed globular phases. This combination of structure and filler selection unlocks synergetic improvements in electromechanical properties-doubling of dielectric constant, 100 times decrease in Young's modulus, and ∼5 times increase in stretchability. These composites show superior thermal stability to volatile losses, combined with excellent transparency. These ultrasoft high