My approach to research is focused on building versatile one-of-a-kind instruments for studying liquid crystal systems. There are significant benefits to developing and building one's own instruments from scratch: the machine is perfectly suited to the task and costs far less than a commercial tool. My approach is to guide students through the design, fabrication and automation of custom laboratory instruments. It is exactly this type of collaboration and instruction Cal Poly's student-focused approach enables. When the tasks of in-house instrument design, instrument fabrication, and instrument refinement are added to the conventional research components of measurement and analysis, a research project can be readily broken into senior-project sized pieces. By taking this approach, teamwork is required and meaningful collaboration thrives.

In this era of open-source code and inexpensive micro-controllers, physics students can build robots, automate their lives, and harvest piles of data from the world around them. When these projects are designed to demonstrate or test a physical idea, a student is given an opportunity to make something real, right out of her imagination. Not only do these trials and efforts drive a profound academic growth, but students love making things. And everyone loves it when physics is fun!

My research has focused on the material properties and electro-optic applications of liquid crystals. Liquid crystals are best imagined as molecular rods. In the simplest liquid crystalline phase, called the nematic phase, these rod-shaped molecules prefer to remain aligned with one another, and the phase is distinguished by orientational, but not positional, order. Liquid crystals flow like ordinary liquids, yet they demonstrate macroscopic anisotropy associated with their average alignment direction. While liquid crystals prefer to be aligned with one another, the direction of their alignment is arbitrary, so boundary forces play an essential role in determining the orientational behavior of the bulk phase. The bulk orientation is anchored in a preferred direction by the preparation alignment surface.

Few details are known about the anchoring interaction that determines the LC alignment direction, which makes surface properties of photoalignment an interesting area of active research. Mechanical confinement of liquid crystals is a simple concept, yet it has been the focus of only a few experimental efforts. Yet, mechanical confinement is a great tool for investigating photoalignment anchoring and the generation of novel defect structures on photo-aligned substrates. Further, I have investigated in-situ photoalignment to produce a well-defined orientation between an incident light source and the liquid crystal director as a means to improve standard liquid crystal material characterizations.

Specific topics: Nematic Anchoring Strength · Pancharatnam Phase Devices · Photo Alignment · Defect Loops · Interference Metrology · Director Simulation · Surface Defect Stuctures

Automatic fire-suppression sprinklers prevent property damage and save lives, but their widespread adoption comes with a significant unintended consequence: Industry-standard, glass-bulb sprinklers are delicate and prone to breaking due to accidents and sabatoge. On average, there are more than 120 non-fire sprinkler activations in the United States every day, causing millions of dollars in property damage and lost business. Our novel SMA-based sprinkler promises to deliver the required durability, performance and price point to become the new industry standard.

“Shape-memory” describes the ability of some materials to recover from a plastic deformation. Shape memory alloys (SMAs) are a class of active-materials that undergo a diffusionless solid-to-solid lattice distorting structural phase transformation that dramatically changes the mechanical characteristics of the material including its shape. The salient feature of this phase transition is a direct mapping of the constituent atoms from one crystalline phase—there isn't a random diffusion of the atomic constituents from one phase to another, but a correlated shift from one configuration to the next.

Machine Vision Optical Interference Measurement

In the course of my research I developed software implementing machine vision to optically measure the thickness of my liquid crystal sample. Without user intervention, the final code was able to reliably identify the center of bullseye interference pattern produced in my experiment. Further, the radial intensity of the resulting pattern was then sampled and averaged, the extrema automatically detected. By combining data from many interference patterns, we made a dynamic measurement of the of the evolving bullseye patterns. The resulting points were then fit to a calculated model, such that the thickness of the optical medium could be reliably extracted. The result was a novel mechanism for measuring in-situ sample thickness.

Liquid Crystal Defect Image Analysis

My investigation of topological defects in nematic liquid crystals led to the development of a machine-vision application for detecting and measuring defect loops. Using the software, I measured the evolution of defect loop's area and perimeter from high definition video clips captured during experimental observation.

Adaptive 3D Director Simulation

I took a novel approach to developing a finite-difference numeric simulation for determining three dimensional liquid crystal director configurations. While the director relaxation is calculated by a program written in C, I exploited the symbolic manipulation of Mathematica to generate arbitrarily complicated C-syntax update equations. Using Mathematica, simulation parameters, including the core free-energy expression, can be inputted in familiar human-readable mathematical notation. My Mathematica code also allowed for external forces, periodic, weak or strong boundary conditions, irregular computational meshes (curved boundaries), and arbitrary coordinate systems and natural variables. By using Mathematica to generate the update equations for the C mother-code, the conditions of the simulation can be easily and drastically changed without the need for lengthy hand calculations or the tedious transcription of update equations character-by-character into lines of C-code. Further, the computationally-intensive relaxation mother-code was optimized for performance leveraging the speed advantages of C, free from the computational overhead of Mathematica at runtime.

Simulation: Other Areas of Experience

• Monte Carlo molecular dynamics and phase behavior
• Numerics in C
  • Solving ODEs
  • Dataset manipulation and curve fitting
• FTDT electrodynamics
• 4x4 Matrix-based optical simulation in anisotropic materials
• Sytem Modeling using Matlab and Modelica-based Wolfram System Modeler
  • Circuit Analysis
  • Motor Characterization
  • Electro-optical characterization of liquid crystal displays
  • Multibody dynamics

Automation: Other Areas of Experience

• Arduino data capture, motor control, and system interfacing
• Labview-based data collection for introductory physics undergraduate laboratory exercises
• Extensive G-Code programming, automated code generation and fabrication workflow development for computer-controlled milling machines