Spatio-temporally controlled suppression of the coffee-ring phenomenon by cellulose nanofibers

A droplet with a small portion of cellulose nanofibers (CNFs) has low viscosity to be compatible with inkjet discharge, but CNFs form structural order to prevent the coffee-ring phenomenon at the last stage of drying of the sessile droplet.

Numerical study on thoracic aortic aneurysms : the aneurysms aggravation effects on the seconda rythme flows motion

It is Well know that there is a strong correlation between artery wall diseases and the flow structure disturbance. Aneurysms are enlargements situated at different but specifics parts of the vascular system; it is a silent diseas that evolves in time. The thoracic aortic aneurysms (T. A. A) remains relatively unstudied and therefore the present study aimis is to clarify the effects of the (T . A. A) evolution and the geometrical variations on both hydrodynamic instabilities inside the aortic bulge especially the vortex ring phenomenon and the secondary motion (Dean and lyne vortices) downsream the aneurysms. Two different cases of asymmetric enlargements in the ascending part of the aortic are studied for both newtonien and the shear-thinning model to mimic the blood rheology inside the aneurysms bulge in order to investigate both parameters impact on the vortex ring behavior. Results schowed that the blood rheoligy effects the propagation velocity while the aneurysms size influences the vortex ring rupture, the motion of the ring interaction with an inclined wall phenomenon. Results also showed that vortex ring disturbs the boundary layer and therefore the secondary motion in the rest of the aorta.

3D Nanoparticle Tracking Inside the Silver Nanofluid

Movement of nanoparticle was investigated at the vicinity of silver nanofluid by using a microscope equipped with 100X lens. It was observed that silver nanoparticles were constantly moving inside the nanofluid for the first time. To explore the silver nanoparticle movement, the silver nanofluid was mixed with fluorescent nanoparticles. The coated nanoparticles were tracked three-dimensionally using a Delta Vision Elite inverted optical microscope. It was found that Marangoni flow was a possible reason of the nanoparticle movement which was generated by a gradient of the surface tension at the vicinity of the triple line. A gradient of the surface tension was formed by the segregation of the surfactant from the base liquid at the vicinity of the triple line. The surfactant was separated from the base liquid inside the triple region, since they have different affinities for the substrate. It was also shown that ring phenomenon took place when nanoparticle movement was weak or negligible.

Deposit heterogeneity and the dynamics of the organic semiconductors P3HT and PCBM solution under evaporation

The formation of organic semiconductor layer is the key procedure in the manufacture of organic photovoltaic solar cell, in which the natural evaporation of the solvent from the polymer solution plays the essential role for the conversion efficiency. Here, poly(3-hexylthiophene) ( P3HT ) and fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester ( PCBM ), as two types of semiconductor polymers, were selected as the active layer to form the deposit by drying the blend solution drops on the substrate. We explored the influences of droplet size and solute concentration on the homogeneity of the deposit. Additionally, the spatial distribution of molecular chains and grains and the instability of the droplet morphology during the drying were investigated. The results showed that the "coffee-ring" phenomenon occurred forming an annular deposit at the outermost edge and the width of the annular ring increased linearly with the concentration of the P3HT solution, until a saturation plateau is approached. On the other hand, the PCBM deposition presented a circular disk at low concentration, but displayed a sudden instability for an irregular perimeter at a critical concentration and there existed a second critical concentration above which the deposit exhibited the return of the stable circular shape. The results have an instructive impact on the performance of the device and the formation of fine structures during the process of printing, film preparation and painting.