Bio-inspired optical components

Abstract

Guiding electro-magnetic radiation is fundamental to optics. Lenses, mirrors, and photonic crystals all accomplish this task by different routes. Understanding the interaction of light with materials is fundamental to improving and extending optical science and engineering as well as producing novel optical elements. Improvement in this understanding should not only include work to understand the interaction with traditional engineering materials but also should target the understanding of the interaction of electromagnetic radiation with biological structures as millions of years of evolution have sorted out numerous ways to modulate light (e.g. the fish eye or the skin of the octopus). The goal of this thesis work is to fabricate novel optical elements by taking cues from nature and extending the state of the art in light guiding behavior. Here, optical elements are defined as structured materials that guide or direct electromagnetic radiation in a predetermined manner. The work presented in this thesis encompasses biologically inspired tunable multilayer reflectors made from block copolymers and improvements to liquid filled lenses which mimic the human eye.In this thesis a poly(styrene)-poly(2-vinylpyridine) block copolymer was used to create a bio-mimetic, one-dimensional, multilayer reflector. The wavelengths of light reflected from this multilayer reflector or Bragg stack were tuned by the application of stimuli which included temperature, change in the solvent environment, pH, salt concentration in the solvent, and electrochemistry.

(cont.) A linear-shear rheometer was also built to investigate the mechanochromic color change brought about through the shearing of a one-dimensional, high molecular-weight, block-copolymer, photonic gel. Biologically inspired lenses were also studied through the construction of a finite element model which simulated the behavior of a liquid-filled lens. Several tunable parameters, such as the modulus, internal residual stress, and thickness of the membrane were studied for their influence on the shape of the lens membrane. Based on these findings, suggestions for the reduction of spherical aberration in a liquid filled lens were made. A gradient in the elastic modulus of the membrane was also investigated for use in the reduction of spherical aberration.