Particle Fabrication and Assembly Strategies for Optical Applications

Open Access
- Author:
- Famularo, Nicole
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- July 23, 2020
- Committee Members:
- Christine Dolan Keating, Dissertation Advisor/Co-Advisor
Christine Dolan Keating, Committee Chair/Co-Chair
Raymond Edward Schaak, Committee Member
Ayusman Sen, Committee Member
Douglas Henry Werner, Outside Member
Philip C Bevilacqua, Program Head/Chair - Keywords:
- Particle Assembly
Electric Fields
3D Printing
Directed Self Assembly
Electrodeposition
Nanofabrication
Metamaterials
Optical Metamaterials
Segmented
Dielectrophoresis
Chirality
Metamaterial absorber
Particle Fabrication
Perfect absorber
Additive manufacturing
Nanoscribe
Partially Etched Nanowires - Abstract:
- From naturally-occurring structural color that gives blue morpho butterflies brilliantly colored wings to laboratory-developed optical metamaterial devices like optical cloaks and negative refractive index materials, developing the ability to selectively manipulate optical phenomena has driven the study and advancement of materials with favorable light-matter interactions. As optical devices continue to trend towards miniaturization, it is becoming increasingly important to maximize the potential functionality of a device while retaining a compact size. One particularly promising way to do this is to use particle assembly to make reconfigurable structures where altering the organization of particles within the assembly tunes the output functional response. While this goal of on-chip platforms often inspires studies of particle assemblies, there are relatively few examples of particle-based reconfigurable optical devices in the literature. Part of the reason for this is because of a lack of fabrication methods for particles that are akin to optical metamaterial components and the further lack of understanding the assembly behavior of such a particle. The focus of this thesis is to develop fabrication methods, characterize the assembly behavior, and measure the optical response of particles which can ultimately be used to create reconfigurable particle-based optical devices. Since reconfigurability is such a prominent motivator for this work, a major focus of this dissertation is understanding the alternating current (AC) electric field assembly behavior of various particle systems. AC electric fields are well-suited for this because particles and their suspending medium readily respond to changes in field frequency and voltage, offering a means for real-time tunability. Chapter 2 of this dissertation specifically focuses on the assembly behavior of segmented metal-dielectric particles driven by dielectrophoresis (DEP) in AC fields. The particles are synthesized by templated electrodeposition which allows for different segmentation patterns to be fabricated based on the sequential deposition of metal salt solutions. The observed DEP behavior is shown to be dependent on segmentation pattern, and a mathematical model was developed to describe this relationship. The observed trends and model are used to develop binary assemblies of multicomponent particles with different segmentation patterns that can be reconfigurably mixed or controllably separated by altering the applied electric field, which is a feat that has not yet been achieved in the DEP literature. The Appendix of this thesis further explores this concept while introducing the use of fluorescent tagging to more easily differentiate each of the particle populations. The fluorescently tagged segmented particles are assembled into different configurations by incorporating templated electrodes in a vertical assembly setup. Two-photon polymerization (TPP)-based 3D printing is frequently used throughout this dissertation as a fabrication method of choice because it can be used to print rationally designed microscale structures that inherently have desired light-matter interactions. For example, Chapter 3 examines the linear and nonlinear optical properties of both metal-coated and uncoated dielectric 3D printed micro-helices. The coated and uncoated micro-helices demonstrate large circular dichroism, or the preferential absorption of one handedness of circularly polarized light over the other. In addition, 3D printing is used again in Chapter 5 to fabricate a 3D metamaterial absorber which operates in the mid-infrared (MIR) region. This chapter predominantly focuses on characterizing the MIR optical response of the absorber as a function of changing the polarization and incident angle of light. The metamaterial absorber is polarization-independent, and simulations suggest it could retain ≥80% absorbance at large incident angles. Simulations have also shown that it demonstrates potential to be used for sensing applications. Chapter 4 is an exploratory study regarding how TPP-based 3D printing can be used to assist particle assembly—a direction which is promising for particle assembly thanks to the highly reproducible and customizable nature of printed structures and a new frontier for microscale 3D printing. The use of 3D printing to enhance particle assembly is illustrated in two distinct approaches. The first approach uses 3D printing at the individual particle level, where particles can be rationally designed for their light-matter interactions (as demonstrated in Chapter 3 and Chapter 5). The electric field-directed assembly behavior of the gold-coated helices (first introduced in Chapter 3) is explored in this chapter. The second approach is to 3D print larger topographical features that can template the assembly of smaller non-printed particles. Using this approach, the spatial location of particles can either be driven into ridges in the microstructure of the 3D printed templates or directed around the template according to its overall macroscale design. This chapter concludes with some insights on the advantages and disadvantages of each approach and proposes different use cases where each is promising. The collective work in this thesis provides insight into how particle fabrication and rational assembly design can be used to close the gap between fundamental particle assembly and practical applications. In Chapter 6, advice is offered regarding the next steps required to ultimately realize particle assembly-based optical devices with tunable properties.