Impact of nanoparticle shape on thermohydraulic performance of a nanofluid in an enhanced microchannel heat sink for utilization in cooling of electronic components

In this article,the thermal–hydraulic efficacy of a boehmite nanofluid with various particle shapes is evaluated inside a microchannel heat sink.The study is done for particle shapes of platelet,cylinder,blade,brick,and oblate spheroid at Reynolds numbers(Re)of 300,800,1300,and 1800.The particle volume fraction is assumed invariant for all of the nanoparticle shapes.The heat transfer coefficient(h),flow irregularities,pressure loss,and pumping power heighten by the elevation of the Re for all of the nanoparticle shapes.Also,the nanofluid having the platelet-shaped nanoparticles leads to the greatest h,and the nanofluid having the oblate spheroid particles has the lowest h and smallest pressure loss.In contrast,the nanofluid having the platelet-shaped nanoparticles leads to the highest pressure loss.The mean temperature of the bottom surface,thermal resistance,and temperature distribution uniformity decrease by the rise in the Reynolds number for all of the particle shapes.Also,the best distribution of the temperature and the lowest thermal resistance are observed for the suspension containing the platelet particles.Thereby,the thermal resistance of the nanofluid with the platelet particles shows a 9.5%decrement compared to that with the oblate spheroid particles at Re=300.For all the nanoparticle shapes,the figure of merit(FoM)uplifts by elevating the Re,while the nanofluids containing the brickand oblate spheroid-shaped nanoparticles demonstrate the highest FoM values.

Influence of Nanoparticle Shapes of Boehmite Alumina on the Thermal Performance of a Straight Microchannel Printed Circuit Heat Exchanger

The efficiency and irreversibility defined based on the second law of thermodynamics provide a new path for heat exchangers design and make performance analysis more straightforward and elegant.The second law of thermodynamics is applied in a Straight Microchannel Printed Circuit heat exchanger to determine the thermal performance of different shapes of Boehmite Alumina compared to Al2O3 aluminum oxide.The various forms of non-spherical Boehmite Alumina are characterized dynamically and thermodynamically through dynamic viscosity and thermal conductivity,using empirical coefficients.The non-spherical shape includes platelet,cylindrical,blades,and bricks forms.Graphical results are presented for thermal efficiency,thermal irreversibility,heat transfer rate,and nanofluid exit temperature.The non-spherical shapes of Boehmite Alumina show different thermal characteristics concerning the spherical shape when there are variations in fluid flow rates and the nanoparticles fraction.Furthermore,it was theoretically demonstrated that non-spherical particles have higher heat transfer rates than spherical particles,emphasizing platelets and cylindrical shapes for the low volume fraction of nanoparticles and bricks and blades for high volume fraction.

Orchestrating antigen delivery and presentation efficiency in lymph node by nanoparticle shape for immune response

Activating humoral and cellular immunity in lymph nodes(LNs)of nanoparticle-based vaccines is critical to controlling tumors.However,how the physical properties of nanovaccine carriers orchestrate antigen capture,lymphatic delivery,antigen presentation and immune response in LNs is largely unclear.Here,we manufactured gold nanoparticles(AuNPs)with the same size but different shapes(cages,rods,and stars),and loaded tumor antigen as nanovaccines to explore their disparate characters on above four areas.Results revealed that star-shaped AuNPs captured and retained more repetitive antigen epitopes.On lymphatic delivery,both rods and star-shaped nanovaccines mainly drain into the LN follicles region while cage-shaped showed stronger paracortex retention.A surprising finding is that the star-shaped nanovaccines elicited potent humoral immunity,which is mediated by CD4^(+)T helper cell and follicle B cell cooperation significantly preventing tumor growth in the prophylactic study.Interestingly,cage-shaped nanovaccines preferentially presented peptide-MHC I complexes to evoke robust CD8^(+)T cell immunity and showed the strongest therapeutic efficacy when combined with the PD-1 checkpoint inhibitor in established tumor study.These results highlight the importance of nanoparticle shape on antigen delivery and presentation for immune response in LNs,and our findings support the notion that different design strategies are required for prophylactic and therapeutic vaccines.

Shape Effect of Nanoparticles on Nanofluid Flow Containing Gyrotactic Microorganisms

In this paper,we discussed the effect of nanoparticles shape on bioconvection nanofluid flow over the vertical cone in a permeable medium.The nanofluid contains water,Al2O3 nanoparticles with sphere(spherical)and lamina(non-spherical)shapes and motile microorganisms.The phenomena of heat absorption/generation,Joule heating and thermal radiation with chemical reactions have been incorporated.The similarity transformations technique is used to transform a governing system of partial differential equations into ordinary differential equations.The numerical bvp4c MATLAB program is used to find the solution of ordinary differential equations.The interesting aspects of pertinent parameters on mass transfer,energy,concentration,and density of themotilemicroorganisms’profiles are computed and discussed.Our analysis depicts that the performance of sphere shape nanoparticles in the form of velocity distribution,temperature distribution,skin friction,Sherwood number and Motile density number is better than lamina(non-spherical)shapes nanoparticles.

Impact of nanoparticle shape on thermo-solutal buoyancy induced lid-driven-cavity with inclined magnetic-field

The aim of this paper is to numerically investigate the influence of nanoparticles shape on heat and mass transport phenomena in a moving lid cavity under the combined effect of thermo-solutal buoyancy force and magnetic force.The governing equations are transformed into velocity-vorticity form of equations and solved using Galerkin's weighted residual finite-element-technique.The analysis has been carried out with parameters like buoyancy ratio(−5≤N≤5),magnetic field inclination angle(0°≤ϕ≤90°)with four shapes of Al_(2)O_(3) nanoparticle like bricks,blades,platelets and cylinders.The results revealed that the shape factor on Nusselt number is significant depending upon the inclined magnetic field and buoyancy ratio whereas on mass transfer the shape effect is negligible.The diffusion mode of transport process is stronger than the convection mode at higher inclination angle of magnetic field.Based on a given value of N andϕ,blade and cylinder shows the best performance in Nusselt and Sherwood number respectively except the platelet shape that shows maximum frictional loss in terms of wall shear stress.

Influence of various shapes of nanoparticles on unsteady stagnation-point flow of Cu-H_(2)O nanofluid on a flat surface in a porous medium:A stability analysis

The nanofluid and porous medium together are able to fulfill the requirement of high cooling rate in many engineering problems.So,here the impact of various shapes of nanoparticles on unsteady stagnation-point flow of Cu-H_(2)O nanofluid on a flat surface in a porous medium is examined.Moreover,the thermal radiation and viscous dissipation effects are considered.The problem governing partial differential equations are converted into self-similar coupled ordinary differential equations and those are numerically solved by the shooting method.The computed results can reveal many vital findings of practical importance.Firstly,dual solutions exist for decelerating unsteady flow and for accelerating unsteady and steady flows,the solution is unique.The presence of nanoparticles affects the existence of dual solution in decelerating unsteady flow only when the medium of the flow is a porous medium.But different shapes of nanoparticles are not disturbing the dual solution existence range,though it has a considerable impact on thermal conductivity of the mixture.Different shapes of nanoparticles act differently to enhance the heat transfer characteristics of the base fluid,i.e.,the water here.On the other hand,the existence range of dual solutions becomes wider for a larger permeability parameter related to the porous medium.Regarding the cooling rate of the heated surface,it rises with the permeability parameter,shape factor(related to various shapes of Cu-nanoparticles),and radiation parameter.The surface drag force becomes stronger with the permeability parameter.Also,with growing values of nanoparticle volume fraction,the boundary layer thickness(BLT)increases and the thermal BLT becomes thicker with larger values of shape factor.For decelerating unsteady flow,the nanofluid velocity rises with permeability parameter in the case of upper branch solution and an opposite trend for the lower branch is witnessed.The thermal BLT is thicker with radiation parameter.Due to the existence of dual solutions,a linear stability analysis is made and it is concluded that the upper branch and unique solutions are stable solutions.

A Simple Approach to Control the Growth of Non-spherical Gold Nanoparticles

A simple method to prepare the non-spherical gold particles was developed. The result solution included trigonal, truncated trigonal, hexagonal layers, and a pseudo-pentagonal shaped gold nanocrystals. The key factor is to control the relative rates of nucleation and cluster growth in this method. These attributes make seeding growth method as a useful tool in the fabrication of colloidal metal materials. A longitudinal plasmon resonance of 866 nm was observed, which is in the near-IR spectral regions (600-1000 nm). The excellent optical properties as near-IR labels are used to develop highly sensitive analysis method.

In vitro and in vivo evaluation of cerium oxide nanoparticles in respiratory syncytial virus infection

Respiratory syncytial virus(RSV)is the most common cause of viral bronchiolitis among children worldwide,yet there is no vaccine for RSV disease.This study investigates the potential of cube and sphere-shaped cerium oxide nanoparticles(CNP)to modulate reactive oxygen(ROS)and nitrogen(RNS)species and immune cell phenotypes in the presence of RSV infection in vitro and in vivo.Cube and sphere-shaped CNP were synthesized by hydrothermal and ultrasonication methods,respectively.Physico-chemical characterization confirmed the shape of sphere and cube CNP and effect of various parameters on their particle size distribution and zeta potential.In vitro results revealed that sphere and cube CNP differentially modulated ROS and RNS levels in J774 macrophages.Specifically,cube CNP significantly reduced RSV-induced ROS levels without affecting RNS levels while sphere CNP increased RSV-induced RNS levels with minimal effect on ROS levels.Cube CNP drove an M1 phenotype in RSV-infected macrophages in vitro by increasing macrophage surface expression of CD80 and CD86 with a concomitant increase in TNFαand IL-12p70,while simultaneously decreasing M2 CD206 expression.Intranasal administration of sphere and cube-CNP were well-tolerated with no observed toxicity in BALB/c mice.Notably,cube CNP preferentially accumulated in murine alveolar macrophages and induced their activation,avoiding enhanced uptake and activation of other inflammatory cells such as neutrophils,which are associated with RSV-mediated inflammation.In conclusion,we report that sphere and cube CNP modulate macrophage polarization and innate cellular responses during RSV infection.

Shaped gold and silver nanoparticles

Advance in the synthesis of shaped nanoparticles made of gold and silver is reviewed in this article. This review starts with a new angle by analyzing the relationship between the geometrical symmetry of a nanoparticle shape and its internal crystalline structures. According to the relationship, the nanoparticles with well-defined shapes are classified into three categories： nanoparticles with single crystallinity, nanoparticles with angular twins, and nanoparticles with parallel twins. Discussion and analysis on the classical methods for the synthesis of shaped nanoparticles in each category are also included and personal perspectives on the future research directions in the synthesis of shaped metal nanoparticles are briefly sum marized. This review is expected to provide a guideline in designing the strategy for the synthesis of shaped nanoparticles and analyzing the corresponding growth mechanism.

The in vitro and in vivo toxicity of gold nanoparticles

Gold nanoparticles,owing to their unique physicochemical and optical properties,well-established synthetic methods and easy modifications,have been widely used in biomedical science.Therefore,for their safe and efficient applications,much attention has been given to the toxicological evaluations of gold nanoparticles in biological systems.A large number of studies focusing on this problem have been carried out during the past years.However,the researches on gold nanoparticles toxicity still remain fragmentary and even contradictory with each other.This may be caused by the variety in experimental conditions.In this review,we aim to provide a better understanding about the in vitro and in vivo toxicity of gold nanoparticles by reviewing and describing the up to date literatures related to this problem and we mainly focused on these properties such as the particle size and shape,the surface charge and modification.Besides,we also summarized the adverse effect of gold nanoparticles on immune systems and analyzed the origin of the toxicity.

Thermal management of nanoliquid forced convective flow over heated blocks in channel by using double elliptic porous objects

Effects of using nanoliquid and double porous elliptic objects on the flow separation and convective heat transfer control for flow over multiple heated blocks in channel are numerically investigated by using finite element method.Spherical,brick,blade and cylindrical shaped alumina particles are used in water up to solid volume fraction of 2%.Impacts of Reynolds number(50≤Re≤500),permeability of the porous ellipses(10^(-5)≤D_(a1)≤5×10^(-2) and 10^(-5)≤D_(a2)≤5×10^(-2)),aspect ratio of the ellipses(0.25≤AR_(1)≤1.5,0.25≤AR_(2)≤1.5),distance between the ellipses(0.2H≤sx≤1.6H)and distance of the first ellipse from inlet(-H≤mx≤H)on the hydro-thermal performance are explored.The highest performance improvement is obtained by using the cylindrical shaped particles in the base heat transfer fluid at the highest solid volume fraction and the amount of heat transfer enhancement are 33%and 40.5%for hot blocks while negligible pressure drop is observed.Varying the aspect ratio of the ellipses in the perpendicular direction to the flow,up to 25%and 30%heat transfer increment are obtained for hot block with slight rise of pressure coefficient.However,when varying the horizontal location of the porous ellipses in the channel and permeability of them,there is considerable rise of pressure drop.Variation of the average heat transfer from the hot blocks with varying permeability of the ellipses are obtained as 32%and 25%.Successful hydro-thermal performance estimation results are achieved by using artificial neural networks with feed-forward network architecture of 1 hidden layer and 17 neurons.

Natural Convection of Fe_3O_4-Ethylene Glycol Nanofluid under the Impact of Electric Field in a Porous Enclosure

Free convection of FeaO4-Ethylene glycol nanofluid in existence of Coulomb forces is studied. Effect of thermal radiation is taken into account. Properties of nanofluid are varied with supplied voltage and shape of nanoparticles. The bottom wall is considered as positive electrode. Control Volume based Finite Element Method is used to obtain the results, which are the roles of Darcy number （Da）, radiation parameter （Rd）, Rayleigh number （Ra）, nanofluid volume fraction （qS）, and supplied voltage （△φ）. Results indicate that Nusselt number is an enhancing function of supplied voltage and Darcy number. Maximum values for temperature gradient are occurred for platelet shape nanoparticles.