Date of Award

Spring 1-1-2018

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

First Advisor

Robert R. McLeod

Second Advisor

Devatha P. Nair

Third Advisor

Christopher N. Bowman

Fourth Advisor

Carol J. Cogswell

Fifth Advisor

Sean E. Shaheen

Abstract

The ability to exert three-dimensional control over the intrinsic mechanical and optical properties of a solid are desirable in the fields of diffractive optical elements, shape programmable materials, and regenerative medicine. Although volume photostructuring in two-stage polymers has demonstrated the ability to produce such features, quantitative metrology of the photostructured elements remains a significant obstacle towards the widespread adoption of this patterning technique. Current methods to characterize photostructured features provide only qualitative information or fail to capture the entire material response. This inadequate characterization impedes the broader adoption of photostructuring to fabricate complex mechanical and optical devices.

In this thesis, I overcome the problem of quantitative metrology in photostructuring by developing techniques to measure the resulting mechanical and optical features. To do this, I first categorize the photostructuring process into two distinct groups: 1) local reactions that are confined to the exposed region, and 2) reactions that induce mass transport through e.g. diffusion. For local reactions, I demonstrate the suitability of bulk metrology on uniform samples to characterize and infer the properties of in-situ photostructured elements. For reactions that induce mass transport, bulk metrology is no longer adequate, and in-situ metrology is required. To measure photostructuring in these materials, I develop a new technique using quantitative phase imaging and confocal reflection microscopy that provides complete characterization of the material response. The knowledge gained from these metrology techniques is then applied to fabricate novel mechanical and optical devices such as self-folding origami structures and high diffraction efficiency, large-aperture Fresnel lenses. Finally, by exploring a novel multiple-exposure method, I demonstrate how the presented metrology enables the development and understanding of new photostructuring techniques. This new patterning technique enhances the dynamic range of the photostructuring process beyond the single-exposure limit and extends the range of current photostructuring materials.

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