Microcantilevers modified by a monolayer of azobenzene molecules bend up and down periodically, switched by a 365 nm UV light, as a result of the conversion of the two configurations of azobenzene molecules in the monolayer.
Accompanied with the changing of coagulation time, the micro-structure of aerogel can be controlled by adding Polyacrylic acid (PAA) into sol system. We simulate the process of particles aggregation contains attracting molecular chains based on diffusion-limited cluster aggregation (DLCA). Compared with the normal coagulation system, the coagulation rate of the system that contains attracting chains are sped up first and then slowed down. The results of the stimulation point out that the interaction between particles and chains not only accelerates the motion of particles, but also separates the region and constrains the clusters’ motion. These two effects are coexisting but the attracting interaction play a dominant role in the early state while the volume of chains has a dramatic influence on cluster’s motion in late states.
As a convenient way for the assembly of thermal plastic MEMS (Micro Electro-Mechanical Systems) devices fusion bonding was studied in molecular level. The diffusion behavior of polymer molecular chains was simulated by molecular dynamics. Amorphous PMMA (poly methyl methacrylate) layer were constructed. The interaction of PMMA layers in heating and cooling stages were simulated in NPT ensemble. In the simulation the PMMA molecular chains spread across the interface and entangled with the chains in the other layers. The factors including pressure and temperature which play important role in fusion bonding were analyzed in molecular level. System deformation was recorded in heating and cooling progress. Diffusion depth and binding energy in the model which had experienced heating and cooling simulation were obtained to investigate fusion degree. Deformation and fusion degree increase with larger pressure and higher temperature imposed to the system. It is concluded that only considering the diffusion of molecular chains parameters of relatively small pressure and high temperature are necessary to obtain precise bonding for micro joint, which is significant in guiding the precise bonding for micro assembly.
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