Sharif Digital Repository

We analyze the process of electrowetting-induced jumping of droplets away from a substrate with a geometric heterogeneity in the form of a cone and compare the results with those of a flat substrate in different wettabilities and hydrophobicities. Our results reveal that the droplet dynamics can be enhanced through applying a topographic heterogeneity. However, increasing the height of the cones does not always provide a better condition for the jumping and there is an optimum value for the height of the cones. The enhancement is due to the fact that more liquid flowing affects the pressure gradient within the droplet leading to a higher jumping velocity. It is shown that for the flat... 

Mesoscopic hydrodynamic equations are solved to investigate the dynamics of nanodroplets positioned near a topographic step of the supporting substrate. Our results show that the dynamics depends on the characteristic length scales of the system given by the height of the step and the size of the nanodroplets as well as on the constituting substances of both the nanodroplets and the substrate. The lateral motion of nanodroplets far from the step can be described well in terms of a power law of the distance from the step. In general the direction of motion depends on the details of the effective laterally varying intermolecular forces. But for nanodroplets positioned far from the step it is... 

Employing a biharmonic boundary integral method with linear elements, coarsening dynamics of nanodroplets on topographical step heterogeneity is investigated. It is shown that the step height and droplet configuration have an influential effect on the dynamics. Increasing the step height slows down the process while locating the droplets close to the step boosts the coarsening rate. Considering a slip boundary condition enhances the dynamics and reveals a transition in the droplet migration direction. Our results reveal that increasing the surface wettability weakens the dynamics. Various types of the disjoining pressure over the step are also considered and their effects on the coarsening... 

In this study the effect of deposition temperature and thickness on the physical properties of carbon films deposited by magnetron sputtering PVD was investigated. The results of Raman spectra and grazing incidence XRD (GIXRD) patterns show that the graphitization increases by increasing the deposition temperature. There is a change in deposition mechanism at 400 °C from amorphous carbon deposition to nano-structured graphite deposition. Also by increasing substrate temperature the electrical resistance of carbon films reduces significantly up to 300 °C and then remains largely constant. High intrinsic compressive stress in low temperature deposited carbon films causes cracks and... 

Progress in tissue engineering and regenerative medicine necessitates the use of novel materials with promising bio-surface for biomedical applications. In this work, TixNy thin films are applied on biological TC4 substrates in a mixed atmosphere of Ar and N2 via magnetron sputtering system for the protection of TC4 alloy. The effects of N/Ti ratio on the phase structure, growth orientation, contact angle, and the mechanical and corrosion performances of thin films are discussed by implementation of composition-microstructure-property interrelationships. The phase structure of TixNy thin films is changed from amorphous-like to single phase Ti2N structure with increasing N/Ti ratio. In the...