The significant self-heating effect severely restricts the performance and reliability of nano-electronic devices. Accordingly, it is very important to understand the process and mechanism of nano/microscale heat transfer for thermal management and thermal design of devices. In this work, we propose a new Lattice Boltzmann Method (LBM) scheme with effective correction of phonon mean free path (MFP) and relaxation time to study phonon heat transfer in silicon thin films and silicon medium with defects, where the correction factor is dependent on the lattice structure of LBM. The transformation analysis of phonon transfer mechanism at different scales shows that the size effect of cross-plane thermal conductivity is more remarkable than that of in-plane thermal conductivity. And the thermal conductivity of silicon medium with defects decreases exponentially as defect density increases. The proposed new LBM scheme can generate more accurate results than the traditional ones in the heat conduction simulations of different nano/microscale structures.

Controllable transport and size segregation of tiny particles following the Brownian motor mechanism are investigated with pseudo-particle modeling (PPM), a simplified molecular simulation approach, in which the liquid surrounding the Brownian particle is discretized into many pseudo particles and naturally introduces thermal noise by hard-sphere interaction between the pseudo particles. An asymmetric periodic potential is applied to the Brownian particles acting as a flashing ratchet model. The macroscopic directional motion of a single Brownian particle in external non-equilibrium fluctuation is reproduced well by the method. Illustratively, the PPM method is successfully employed to conduct the simulations of Brownian motor and testify the adaptability of the method. The segregation of different-sized particles is also studied by varying the size ratio and operation conditions, such as temperature. The simulations will help a quantitative design of Brownian motors and their application in particle transport, separation, and segregation.

No abstract