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We investigate the gas flows near to solid surfaces in terms of the local spatial variation in the molecular mean free path (MFP). Molecular dynamics (MD) is the appropriate scientific tool for obtaining molecularly-accurate dynamic information in micro and nano-scale gas flows, and has been used to evaluate the molecular mean free path of gases. In the calibration procedure, the viscosity of a gas in the homogeneous case can be recovered in our MD simulations and reach good agreement with the theoretical prediction and data from NIST. In surface-bounded gas flows, if the collisions between gas molecules and walls are counted, a spatially-varying mean free path is presented, and for the first time we have observed that the distribution of the free paths deviates from the exponential one and spikes appear in their distributions at larger Kn, i.e. in the transition flow regime. Based on elementary kinetic theory, the effective viscosity of the gas derived from the mean free path has been incorporated into the framework of the continuum-fluid dynamics equations, and micro-Couette flows are performed to demonstrate this potential application. [ABSTRACT FROM AUTHOR]

In this work, we evaluate the material properties of graphene and assess the potential application of graphene to replace copper wires in Back-End-Of-Line (BEOL) interconnects. Based on circuit and system-level simulations, high restrictions are imposed to graphene with respect to contact resistance and mean free path. Experimentally we evaluate single and multi-layer graphene wires and we measure carrier mean free paths (MFPs) above ~ 110 nm. However, contact engineering will be the key issue for integration of graphene as interconnect. [ABSTRACT FROM AUTHOR]

The thermal conductivity of a material or device is dependent on its characteristic dimension. When the characteristic dimension is commensurate to the mean free paths of thermal energy carriers, the thermal conductivity decreases. The precise relationship between characteristic size and thermal conductivity, which depends on the distribution of energy carrier mean free paths in the material, is not straightforward to determine experimentally. The utility of this relationship has led many researchers to study the mean free path dependent contributions of thermal energy carriers to the thermal conductivity of materials, known as the thermal conductivity accumulation function. This review highlights a number of recent experimental results and techniques used to study the thermal conductivity accumulation function, including transient thermal grating, time domain thermoreflectance, and broadband frequency domain thermoreflectance. In these techniques, nondiffusive thermal transport is induced (i.e., thermal gradients occur over length scales comparable to energy carrier mean free paths) and an effective thermal conductivity of the material is determined. We conclude with our outlook on future directions for the field focused on improved interpretations of the experiments and new materials with unique mean free path distributions. [ABSTRACT FROM AUTHOR]