MIKE SHEEHY BEng
PhD Research Postgraduate (2005-2008)

e: michael.sheehy@ul.ie

t: +353-61-202471

Mike Sheehy graduated from the University of Limerick in 2005 with a first-class honours degree in Mechanical Engineering. He has been awarded an IRCSET postgraduate scholarship to study at Stokes.

PhD Project Title: Analysis of a Micro-Cantilever Beam under Impact Stimuli

Background: Many innovations are currently emerging from research into micro and sub-micron scale systems. Applications for this new field of engineering are broad and diverse: in the biological sciences, they include biochips, lab-on-a-chip, and micro dispensing; and in information technology, micro switches, micro energy storage and silicon microchannel cooling. A body of engineering science is required in order to enable the optimum design of these micro systems, and this is not presently available. The theme of this project, a micro-cantilever beam, is a fundamental geometry occurring within many micro-systems – for example, as a micro switch for ICT applications, or as a planar biosensor. The behaviour of micro-cantilever beams – in particular, their reliability under mechanical stimuli – is currently not well understood, and there is a clear need for verified models to predict their performance under static and dynamic conditions.

The objective of the research is to investigate the fundamental engineering science governing the structural behaviour of a micro-cantilever beam under impact stimuli. Test structures will be fabricated in polysilicon*, and incorporated into test vehicles to impose static and dynamic load conditions. Optical and electrical techniques will be used to measure surface strain, to determine deflection profiles under static loading, and to perform frequency and modal analysis for vibrational loads. High-G impact stimuli will be imposed using a modified drop table, and the response of the beam will be recorded using high-speed imaging. A subset of the beams will feature notch structures to precipitate failure. These sites of failure will be analysed, primarily using SEM, and some finite element modelling will also be performed. The anticipated outcome of the research will be a fundamental understanding of the structural behaviour of micro-cantilever beams under impact stimuli, and a simulation methodology to predict their performance. It is also expected that the research will lead directly to novel developments in devices based on micro-beam geometries.

This research is being conducted in collaboration with Prof Suresh Goyal, Distinguished Member of Technical Staff, Bell Laboratories.

Publications to date

Kelly, G., Sheehy, M., Rodgers, B., Punch, J. and Goyal, S., 2007, “Analysis of High Acceleration Shock Pulses Part I: Geometry of Incident Mass”, accepted for presentation at the Society of Experimental Mechanics Annual Conference & Exposition, Paper 95, Springfield, MA, USA, June 3-6.

Sheehy, M., Kelly, G., Rodgers, B., Punch, J. and Goyal, S., 2007, “Analysis of High Acceleration Shock Pulses Part II: Pulse Shaper Material”, accepted for presentation at the Society of Experimental Mechanics Annual Conference & Exposition, Paper 94, Springfield, MA, USA, June 3-6.

Kelly, G., Punch, J. and Goyal, S., 2006, “The Dynamics of a Small-Scale Portable Electronics Device Under Impact Stimuli”, Proceedings of the American Society of Mechanical Engineers International Mechanical Engineering Congress and Exposition, IMECE2006-14371, Chicago, IL, November.