Events

Graham L. W. Cross 'Physics meets fabrication: Material mechanics in nanomanufacturing'

Date: Tuesday 21 February 2012 12:00 - 13:00

Location: SEMS Seminar room

Graham L. W. Cross,
CRANN Institute and School of Physics, Trinity College, Dublin, Ireland

Physics meets fabrication: Material mechanics in nanomanufacturing

Mechanics-based fabrication methods now provide a comprehensive means to realize scalable nanoscale device fabrication. Functional elements of the mechanical assembly line required for the massively parallel production of nanoscale structures and devices, including mastering, replication and transfer, have been demonstrated and in some instances even commercialized.
As the efficiency and reliability of these methods is improved, an increasing penetration to more traditional fields of research is enabled, particularly in medicine.
The new fabrication techniques include top down mastering by scanned probe techniques, replication by imprinting and printing techniques, and bottom up
self-assembly and organization. For example, scanned probe methods
deliver high resolution inking and deformation for serial and parallel pattern mastering. Nanoimprint enables mass manufacture of nanoscale patterns over large areas by mechanical replication of a master pattern.
Nano-object assembly methods that exploit adhesive surface interactions or fluid flow can controllably pick, place and/or orient low-dimension objects.

My group seeks to make a connection between fundamental nanoscale materials physics and these emerging nanofabrication methods. In this talk, I will review our research into the mechanical generation of shape and organization of structure at the nanoscale, with an emphasis on the deformation of thin film polymers in flow fields that arise during thermal imprint. In nanoimprint, molecular scale squeeze flow presents significant challenges to understanding and controlling the mass transport necessary for high fidelity replication of patterned dies. We use a modified nanoindentation technique to measure glassy forging and viscous melt moulding flows in ultrathin polymer films, on 10, 100, and 1000 nm length scales. A surprising scaling of stress vs. strain relationships as system size is reduced to dimensions below the statistical size of the polymer molecule is revealed and its connection to chain network topology is discussed. A brief introduction to a novel mass transport mechanism for planar geometries arising from the deliberate injection of small amplitude oscillatory shear stress during forming will be given.