|Alternative Title||Simulation design for the functional surfaces tuned by micro-forces|
|Place of Conferral||北京|
|Keyword||功能化表面 微观力 输运 自发集水 表面除湿|
Science has made a great revolution in the field of information technology, micro/nano machine, micro/nano electronics and optoelectronic devices which open the doors to the new dimensions of nanoscience world. The micro-force which is negligible in case of macroscale plays a dominant role in nanoscale and promotes our exploration regarding themicro-force and microcosm. In this paper, we focused on several nanoscale systems affected by micro-force, such as van der Waals' force, surface tension and capillary force. We studied the motion of nanoparticle and nanodroplet triggered by micro-force using molecular dynamics (MD) and further designed several functional surfaces that are capable of driving and separation of nanoparticles, water capturing and dewetting transition. Our work gives a novel idea for the design of new functional surfaces. The main work presented in the paper is given below as follows.
1. A new technique is proposed for the transportation and classification of different size nanoparticles based on van der Waals' forces. The effect of the nanoparticle size, slip velocity of sliding block and pre-tension of the graphene substrate on nanoparticle transportation is investigated, respectively. We found that the nanoparticles can be driven by the van der Waals' force between nanoparticle and sliding block. A pre-tensioned graphene substrate could influence the transportation mechanism and provide easier nanoparticle transportation relatively. The motion of the nanoparticle will be easier if the nanoparticles have small size and thickness, velocity of sliding block is slow along with the small viscous resistance. Based on such a new transportation mechanism, a novel nano-sieve can be designed, through which nanoparticles of different sizes can be screened and classified easily. This transportation technique could also help for the removal of fragments from the inside of carbon nanotubes.
2. The motion of droplet on a wedge-shaped wetting gradient surface was studied using MD simulation and theoretical analysis. The droplet volume and wedge-shaped angle were considered and several functional surfaces were designed. It was found that the droplet having smaller diameter moves faster but covers less distance, while the droplet on a smaller wedge-shaped angle moves smaller but covers long distance. An analytical model was developed to reveal the transport mechanism. Based on this transport mechanism, several functional surfaces were designed. On these surfaces, the droplets can be pinned, accelerated and forced to move on a nonlinear path. The conclusion of this study will provide ideas for manipulation of droplets.
3. Based on the wedge-shaped gradient surface, a multiple wedge-shaped gradient surface was designed to explore the spontaneous aggregation of droplets on solid surface. We designed the multiple wedge-shaped hydrophilic surface imbedded on a hydrophobic surface and studied the aggregation of droplets on the surface. The angle, symmetry and direction of the lateral branch were considered during study. It was found that aggregation of droplets will be easy if the angle of wedge-shaped lateral braches is small, the lateral branches on both side of main track are not symmetrical while the lateral branches and main track have same direction respectively. Based on this study, a multiple wedge-shaped gradient surfaces having large area could be designed for the aggregation of droplets on the surface.
4. The dewetting transportation of condensed droplet on a pillared surface is studied using MD simulation. In a moist ambient environment, droplets condense on the bottom of nanopillars and grow smoothly. A sudden dewetting transition phenomenon occurs while the droplet volume is large. We considered the effects of pillar height, diameter spacing and wettability of nanopillars. It was found that the dewetting transition can only be triggered if the relative volume of the droplet is larger than the critical volume of droplet. The relative critical volume decreases with the increase in pillar height and diameter, but increases with the increase of pillar spacing and wettability.
5. Combining with the work in our group, the interface energy densities of several face-centered cubic (FCC) metallic bilayers are also computed using MD simulation, the morphology and potential energy of atom in the interface is depicted. We found the periodic wrinkled atoms in the interface having distributed potential energy which is different from atoms inside the material. The Lagrange interface energy density and Euler interface energy density increases as the thickness of the bilayer increase, and both of them tend to the interface energy density of body material.
|王帅. 微观力调控的一类功能化表面的仿真设计[D]. 北京. 中国科学院大学,2018.|
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