Presenter: Jeff Perry
Authors: Jeff Perry, Roseanne Warren
Faculty Advisor: Roseanne Warren
Institution: University of Utah
Thin films, generally defined as nm-to-µm thick coatings deposited on a substrate of mm-thickness or above, have a variety of significant uses in many industries, some of which include semiconductors, optical coatings, light emitting diodes, medical devices, and others. Residual stress exists in many thin-film coatings and can lead to peeling, blistering, cracking, or buckling of the film post-deposition. Two-photon polymerization is a microfabrication method in which directed laser radiation causes a chemical reaction in a photoresist to deposit a polymer thin-film coating onto a substrate surface. The two-photon polymerization process results in residual stress in polymer films through temperature changes and other mechanisms, however the magnitude of the residual stresses in two-photon polymerized thin films is currently unknown. The objective of this research is to perform the first measurements of residual stress in two-photon polymerized films, and correlate these stresses with the polymerization conditions, including laser power and writing speed. This structural analysis will enable us to better understand the stresses existing in two-photon polymerized films post-deposition and see how these stresses affect devices and technologies made using two-photon polymerized thin film and ultimately improve the laser writing process to prevent these negative effects. In this work, we are carrying out an experiment wherein we create several films and perform a residual stress analysis on them using a Focused Ion Beam (FIB) drilling method and Digital Image Correlation (DIC) techniques. Finite element simulations in COMSOL Multiphysics are used to correlate theoretical with experimental results and ensure that we have selected proper experimental parameters for the FIB-DIC stress measurement. The end goal of the analysis is determining a range of process parameters for two photon polymerized thin films to ensure the stability and functionality of devices made with them.