Onsager principle is the variational principle proposed by Onsager in his celebrated paper on the reciprocal relation.The principle has been shown to be useful in deriving many evolution equations in soft matter physi...Onsager principle is the variational principle proposed by Onsager in his celebrated paper on the reciprocal relation.The principle has been shown to be useful in deriving many evolution equations in soft matter physics.Here the principle is shown to be useful in solving such equations approximately.Two examples are discussed:the diffusion dynamics and gel dynamics.Both examples show that the present method is novel and gives new results which capture the essential dynamics in the system.展开更多
A new variational method is proposed to investigate the dynamics of the thin film in a coating flow where a liquid is delivered through a fixed slot gap onto a moving substrate. A simplified ODE system has also been d...A new variational method is proposed to investigate the dynamics of the thin film in a coating flow where a liquid is delivered through a fixed slot gap onto a moving substrate. A simplified ODE system has also been derived for the evolution of the thin film whose thickness hf is asymptotically constant behind the coating front. We calculate the phase diagram as well as the film profiles and approximate the film thickness theoretically, and agreement with the well-known scaling law as Ca2/3 is found.展开更多
Capillary filling in small length scale is an important process in nanotechnology and microfabrication. When one end of the tube or channel is sealed, it is important to consider the escape of the trapped gas. We deve...Capillary filling in small length scale is an important process in nanotechnology and microfabrication. When one end of the tube or channel is sealed, it is important to consider the escape of the trapped gas. We develop a dynamic model on capillary filling in closed-end tubes, based on the diffusion-convection equation and Henry's law of gas dissolution. We systematically investigate the filling dynamics for various sets of parameters, and compare the results with a previous model which assumes a linear density profile of dissolved gas and neglect the convective term.展开更多
When a film of soft matter solutions is being dried, a skin layer often forms at its surface, which is a gel-like elastic phase made of concentrated soft matter solutions. We study the dynamics of this process by usin...When a film of soft matter solutions is being dried, a skin layer often forms at its surface, which is a gel-like elastic phase made of concentrated soft matter solutions. We study the dynamics of this process by using the solute based Lagrangian scheme which was proposed by us recently. In this scheme, the process of the gelation(i.e., the change from sol to gel) can be naturally incorporated in the diffusion equation. Effects of the elasticity of the skin phase, the evaporation rate of the solvents, and the initial concentration of the solutions are discussed. Moreover, the condition for the skin formation is provided.展开更多
Micro-droplets of soft matter solutions have different morphologies upon drying,and can become wrinkled,buckled or cavitated particles.We investigate the morphology evolution of a drying soft matter droplet in this wo...Micro-droplets of soft matter solutions have different morphologies upon drying,and can become wrinkled,buckled or cavitated particles.We investigate the morphology evolution of a drying soft matter droplet in this work:at the early stage of drying,wrinkling or cavitation instability can occur in the droplet,depending on the comparison between the critical wrinkling and cavitation pressure;at a later stage of drying,no wrinkles will appear if cavitation happens first,while cavitation can still occur if wrinkling happens first.A three-dimensional phase diagram in the space of elastic length,gel layer thickness and weight loss is provided to illustrate the drying pathways of a soft matter droplet.This diagram can help guide future fabrications of micro-particles with desired morphologies.展开更多
基金supported by Otto Moensted Foundation to give a lecture course on soft matter physics
文摘Onsager principle is the variational principle proposed by Onsager in his celebrated paper on the reciprocal relation.The principle has been shown to be useful in deriving many evolution equations in soft matter physics.Here the principle is shown to be useful in solving such equations approximately.Two examples are discussed:the diffusion dynamics and gel dynamics.Both examples show that the present method is novel and gives new results which capture the essential dynamics in the system.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.91630208,91641107,and 11771437)
文摘A new variational method is proposed to investigate the dynamics of the thin film in a coating flow where a liquid is delivered through a fixed slot gap onto a moving substrate. A simplified ODE system has also been derived for the evolution of the thin film whose thickness hf is asymptotically constant behind the coating front. We calculate the phase diagram as well as the film profiles and approximate the film thickness theoretically, and agreement with the well-known scaling law as Ca2/3 is found.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.21434001,21504004,and 21774004)
文摘Capillary filling in small length scale is an important process in nanotechnology and microfabrication. When one end of the tube or channel is sealed, it is important to consider the escape of the trapped gas. We develop a dynamic model on capillary filling in closed-end tubes, based on the diffusion-convection equation and Henry's law of gas dissolution. We systematically investigate the filling dynamics for various sets of parameters, and compare the results with a previous model which assumes a linear density profile of dissolved gas and neglect the convective term.
基金Project supported by the National Natural Science of China(Grant Nos.21434001,51561145002,and 11421110001)
文摘When a film of soft matter solutions is being dried, a skin layer often forms at its surface, which is a gel-like elastic phase made of concentrated soft matter solutions. We study the dynamics of this process by using the solute based Lagrangian scheme which was proposed by us recently. In this scheme, the process of the gelation(i.e., the change from sol to gel) can be naturally incorporated in the diffusion equation. Effects of the elasticity of the skin phase, the evaporation rate of the solvents, and the initial concentration of the solutions are discussed. Moreover, the condition for the skin formation is provided.
基金supports from Chinese Academy of Sciences(No.XDA17010504 and No.XDPB15)the National Natural Science Foundation of China(No.12047503)+1 种基金the support of the National Natural Science Foundation of China(Grant No.11774394)the Key Research Program of Frontier Sciences of Chinese Academy of Sciences(Grant No.QYZDB-SSW-SYS003)
文摘Micro-droplets of soft matter solutions have different morphologies upon drying,and can become wrinkled,buckled or cavitated particles.We investigate the morphology evolution of a drying soft matter droplet in this work:at the early stage of drying,wrinkling or cavitation instability can occur in the droplet,depending on the comparison between the critical wrinkling and cavitation pressure;at a later stage of drying,no wrinkles will appear if cavitation happens first,while cavitation can still occur if wrinkling happens first.A three-dimensional phase diagram in the space of elastic length,gel layer thickness and weight loss is provided to illustrate the drying pathways of a soft matter droplet.This diagram can help guide future fabrications of micro-particles with desired morphologies.