Micromolding technology is widely used for the fabrication of polymer microneedles for transdermal and intradermal drug delivery applications. Geometric features of microneedles in molding are solely ...determined by geometry of the master mold template. Fabrication of master mold template usually involves costly and cumbersome technologies due to small feature sizes typical of microneedles. In this research, a novel molding platform is designed that is fabricated using low‐cost and simple techniques with flexibility of producing large number of microneedle geometries. The proposed molding platform eliminates need for developing multiple mold templates for fabrication of various geometries of polymer microneedles. Utility of this molding platform is demonstrated in polylactic acid‐based solid thermoplastic microneedles and polyacrylic acid‐based dissolvable microneedles with various aspect ratio settings. Various microneedles fabricated at heights differing with resolution of as low as 100 µm are successfully achieved using specified settings in the molding platform. The suitability of fabricated microneedles for drug delivery applications is evaluated by in vitro and in vivo testing.
Microneedle height adjustment using generic molding platform: Fabrication of polymeric microneedles with controlled aspect ratio using generic microneedle molding platform. Controlled rotary movement of central adjustment bolt with respect to 50 µm per division graduations on circular scale helps in precise adjustment. Successive rotary movements of 45° and 180° result in microneedles height resolution of 100 and 400 µm, respectively.
Residential district is the important space for people living and outdoor activities. Vegetation is proved to be effectively regulate microclimate. Living in Wuhan, residents have to suffer heat ...stress in summer and strong cold wind in winter simultaneously. It is necessary to dictate vegetation types and layout in residential area to get comfortable environment both in hot summer and cold winter. This study examined the vegetation influences of residential wind environment in hot and cold seasons by using the ENVI-met model V4. Field measurement validated the performance of ENVI-met model. The simulation was based on multi-story buildings representing the current primary form of residential area in Wuhan. 3 scenarios with three tree arrangements and 8 vegetation species were simulated. Height-to-distance ratio of trees (as “Aspect ratio of trees”, ART) was used to describe the tree distribution. Results showed that the impact of vegetation on both heat environment and ventilation depended on tree arrangement, LAI, crown width and tree height. The comparison of 3 tree distributions revealed that trees with an ART < 2 should be a priority to mitigate hot environments due to the large effects on PET reduction in summer. Evergreen species with an ART < 2 also effectively decreased wind speed in winter as well as blocked direct sunlight, resulting in negative effects on PET. Tall trees with a large LAI and canopy diameter should be a priority to improve the comfort of outdoor environments.
•Trees with an ART <2 should be a priority to mitigate hot environments due to the large effects on PET reduction in summer.•Evergreen species with an ART <2 also effectively decreased wind speed in winter as well as blocked direct sunlight.•Tall trees with a large LAI and canopy diameter should be a priority to improve the comfort of outdoor environments.
Free-standing nanofins or pillar meta-atoms are the most common constituent building blocks in metalenses and metasurfaces in general. Here, we present an alternative metasurface geometry based on ...high aspect ratio via-holes. We design and characterize metalenses comprising ultradeep via-holes in 5 μm thick free-standing silicon membranes with hole aspect ratios approaching 30:1. These metalenses focus incident infrared light into a diffraction-limited spot. Instead of shaping the metasurface optical phase profile alone, we engineer both transmitted phase and amplitude profiles simultaneously by inverse-designing the lens effective index profile. This approach improves the impedance match between the incident and transmitted waves, thereby increasing the focusing efficiency. The holey platform increases the accessible aspect ratio of optical nanostructures without sacrificing mechanical robustness. The high nanostructure aspect ratio also increases the chromatic group delay range attainable, paving the way for a generation of high aspect ratio ruggedized flat optics, including large-area broadband achromatic metalenses.
Self-assembly of two-dimensional patterned nanomembranes into three-dimensional micro-architectures has been considered a powerful approach for parallel and scalable manufacturing of the next ...generation of micro-electronic devices. However, the formation pathway towards the final geometry into which two-dimensional nanomembranes can transform depends on many available degrees of freedom and is plagued by structural inaccuracies. Especially for high-aspect-ratio nanomembranes, the potential energy landscape gives way to a manifold of complex pathways towards misassembly. Therefore, the self-assembly yield and device quality remain low and cannot compete with state-of-the art technologies. Here we present an alternative approach for the assembly of high-aspect-ratio nanomembranes into microelectronic devices with unprecedented control by remotely programming their assembly behavior under the influence of external magnetic fields. This form of magnetic Origami creates micro energy storage devices with excellent performance and high yield unleashing the full potential of magnetic field assisted assembly for on-chip manufacturing processes.
A numerical investigation of particle shape effects on fabric of granular packing is carried out using the three dimensional discrete element method with a superellipsoid model. A broad range of ...particle shapes controlled by two shape parameters (i.e., aspect ratio and blockiness) are taken into account. A series of random packing of non-cohesive, frictional monodisperse superellipsoids is conducted under gravitational forces in simulations. Fabric of a granular packing is quantified in terms of packing density, coordination number, distribution of particle orientations, anisotropy of three types of fabric vectors (i.e., particle orientation, contact normal and branch vector), and distribution of normalized contact forces. It is shown that the effects of particle shape on packing density and mean coordination number are in agreement with the reported in the literature. Moreover, ellipsoids show the lowest packing density in the family of superellipsoids. The distribution of particle orientations is much more sensitive to blockiness than aspect ratio. It is also found out that anisotropy of both particle orientations and contact normals shows a similar M-type relationship with aspect ratio, two times larger than that of branch vectors. Interestingly, particle shape has an insignificant effect on the probability distribution of normalized contact forces which shows a clear exponential distribution. Those findings would be useful for a better understanding of the initial fabric of granular packing, especially in granular mechanics and geomechanics.
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•We developed a super-ellipsoidal DEM model for random packing simulations.•A broad range of particle shapes controlled by aspect ratio and blockiness were considered.•Fabric of a granular packing was quantified with several measures.•Effects of particle shape on fabric of random packing were investigated.
•The mechanical behavior of steel fiber reinforced recycled fine aggregate concrete (RAC) was systematically studied.•The effect of steel fiber parameters on the fresh and hardened properties of RAC ...was investigated.•The high aspect ratio steel fibers significantly improved the toughness of the RAC.
In order to solve the problem of low toughness and easy cracking of recycled aggregate concrete, steel fibers were incorporated to recycled fine aggregate concrete (RAC) to prepare a sustainable fiber-reinforced concrete. Steel fibers of various contents (20, 35, 50 and 65 kg/m3) and aspect ratios (l/d = 40 and 55) were incorporated to the RAC, and their fresh properties, mechanical properties and microstructure were investigated. The results show that the slump of RAC decreases with increasing fiber aspect ratio and content. Meanwhile, incorporating a small amount of steel fibers (l/d = 40, 20 kg/m3) improves the 28-d compressive strength of RAC, but with further increase in fiber aspect ratio and content, the compressive strength of RAC decreases. The incorporation of steel fibers greatly improves the splitting tensile strength and flexural strength of RAC, and the steel fibers with high aspect ratio have a higher gain in strength. The 28-d flexural strength of concrete with 65 kg/m3 steel fibers (l/d = 40) increases by 148.11 % relative to plain RAC, while the 65 kg/m3 steel fibers with an aspect ratio of 55 makes RAC with increases by 243.78 %. The mass loss of fiber-reinforced RAC under abrasion is also lower than that of plain RAC, and the steel fiber with high aspect ratio performs better. For the load–deflection response, the incorporation of fibers increases the peak load, and also increases the flexural toughness and post-cracking toughness, with the greatest gain for high aspect ratio fibers.
•The influence of the particle morphology on the suspension viscosity was studied.•The effect of particle size, shape and aspect ratio on viscosity were obvious.•A new modified viscosity model of the ...suspension was obtained.•Prediction results of modified viscosity model showed agreed with experimental data.
Viscosity is the key factor affecting the flowability of molten coal slag in the entrained flow gasifier. The volume fraction and morphology of solid phase in slag are important factors affecting the slag viscosity. In this study, the malt syrup and the particles with different sizes and morphologies were chosen as the simulation medium to study the effect of particle morphology on the suspension viscosity. The influences of size, shape and aspect ratio of solid particles on the suspension viscosity were considered. It was concluded that the suspension viscosity increased with the decrease of the particle size. The suspension viscosity increased with the increase of the aspect ratio of the particles. This phenomenon was more obvious under the high volume fraction of solid phase. With the same size and aspect ratio, the non-spherical particles had greater effect on the suspension viscosity than spherical particles. A correction factor was used to modify the viscosity model with the consideration of particle size, shape and aspect ratio. The prediction results of new modified viscosity model of the suspension finally showed good agreement with the measured experimental data.
Pores and cracks have an important role in the evolution of fault rocks because they strongly influence the behavior of the fluids that promote rock alteration and trigger the mechanical instability ...of faults. We used rock physics model inversion of measured elastic wave velocity and porosity to estimate the grain elastic moduli and crack aspect ratios of a range of fault rocks (intact rocks, fractured rocks, transition rocks, and fault gouge) from the Median Tectonic Line in southwest Japan. Our results show distinct gaps in the evolutionary trends of crack aspect ratios and grain elastic moduli from intact rocks to fault rocks. Crack aspect ratios show a nonlinear trend from intact rock to fault gouge, and then these values in fault gouge were considerably higher than in fractured rock and transition rock. In contrast, grain elastic moduli decreased as fracture evolved with the development and subsequent extinction of shear planes and then increased markedly with the formation of fault gouge. Our results show that crack aspect ratios and grain elastic moduli are clearly related to the evolution of shear fabrics in faults. Therefore, they might be useful indicators of fault activity and maturity.
•Elastic wave velocity and porosity are closely related to fault rock evolution.•There is a strong relationship between crack aspect ratio and shear fabric.•Crack aspect ratios and grain elastic moduli are indicators of fault activity and maturity.
•A simple economic analysis was introduced for the calculation of nanofluid cost.•CVFEM can successfully solve natural convection issues.•The entropy generation number has a minimum for each angle of ...the magnetic field.•Entropy generation number increase when the shape factor increases.
Natural convected heat transportation attributes can be elaborated better using entropy generation analysis. In current framework, we scrutinized magnetized Al2O3-H2O nanomaterial natural convection based on entropy generation and L-shaped cavity. Non-dimensional forms of governing expressions are computed through Control Volume-based Finite Element Method (CVFEM). Entropy generation number is calculated. Features of active parameters e.g. Rayleigh number, nanoparticles volume-fraction, nanoparticle shape, Hartmann number, magnetic field angle and aspect ratio versus average heat transportation rate (Nusselt number) and the entropy generation number are investigated. For the first time, an economic analysis is introduced for evaluating the performance of the enclosure with consideration cost of nanofluid. Also, in order to assess the performance of the enclosure, six criteria are introduced which two of them are based on the cost of nanofluids. The results were compared with references and a good compromise was seen. According to the results, both the entropy generation number and average heat transportation rate rise when Rayleigh number upsurges. The average heat transportation rate rises with ascending the nanoparticle volume-fraction whereas the entropy generation number declines when nanoparticles concentration ascends. The entropy generation number decreases 15.14% and 8.15% for Ha=25 and Ha=75, respectively, when ϕ increases from 0 to 0.1.
Centrifugal buoyancy affects all rotating turbulent convection phenomena, but is conventionally ignored in rotating convection studies. Here, we include centrifugal buoyancy to investigate what we ...call Coriolis-centrifugal convection (C^{3}), characterizing two so far unexplored regimes, one where the flow is in quasicyclostrophic balance (QC regime) and another where the flow is in a triple balance between pressure gradient, Coriolis and centrifugal buoyancy forces (CC regime). The transition to centrifugally dominated dynamics occurs when the Froude number Fr equals the radius-to-height aspect ratio γ. Hence, turbulent convection experiments with small γ may encounter centrifugal effects at lower Fr than traditionally expected. Further, we show analytically that the direct effect of centrifugal buoyancy yields a reduction of the Nusselt number Nu. However, indirectly, it can cause a simultaneous increase of the viscous dissipation and thereby Nu through a change of the flow morphology. These direct and indirect effects yield a net Nu suppression in the CC regime and a net Nu enhancement in the QC regime. In addition, we demonstrate that C^{3} may provide a simplified, yet self-consistent, model system for tornadoes, hurricanes, and typhoons.
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