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PhD Projects

Shown here are brief descriptions of select research projects I have worked on in recent years. There are a couple of projects that are currently in progress or under peer review and consequently have have some information withheld in order to maintain IP protection.

For a comprehensive summary of my PhD work, please see my thesis.


Light is massless, yet it carries momentum. What this means is that when light interacts with an object and is refracted/scattered/reflected, its momentum (think speed or direction of propagation) is changed. The change in momentum of the light is consequently imparted onto the interacting object as a force. Thus, it possible to move an object by shining light on that object. In fact, this idea has been proposed as a form of space propulsion (see: Solar sail).

However, the force imparted by a beam of light is generally very small; on the order of pico- to nano-Newtons. For reference, an average male (~180 lbs) experiences roughly 800 Newtons of gravitational force on Earth, or almost 1,000,000,000,000,000 times the force that light exerts on you. Still, the force exerted by light is large enough to affect the motion of small micro- and nanoparticles. In fact, when a laser is tightly focused to its diffraction limit, it is possible to trap micro- and nanoparticles in 3-dimensions at the focus. This is known as an optical trap, or laser tweezer.

However, the force imparted by a beam of light is generally very small; on the order of pico- to nano-Newtons. For reference, an average male (~180 lbs) experiences roughly 800 Newtons of gravitational force on Earth, or almost 1,000,000,000,000,000 times the force that light exerts on you. Still, the force exerted by light is large enough to affect the motion of small micro- and nanoparticles. In fact, when a laser is tightly focused to its diffraction limit, it is possible to trap micro- and nanoparticles in 3-dimensions at the focus. This is known as an optical trap, or laser tweezer.

In my previous research, we utilized a custom laser tweezer setup to trap nanoparticles that we have synthesized in the lab for various energy, medical, and optoelectronic applications. Furthermore, much of my research was centered around developing methods for analyzing voltage data from a position sensitive light detector (quadrant photodiode, or QPD) to determine information about the trapped nanoparticle; including the nanoparticle size, shape, and temperature.

Click here to learn more about the laser tweezer setup and experiments.


Understanding the absorption of light by nanoscale materials is crucial for a range of phenomena including: the modeling of atmospheric aerosols that have been implicated in global climate cycles, for the generation of electrical energy by nanoscale solar cell devices, during laser-thermal processing of semiconductor nanostructures, in the heating profiles of metallic nanoparticles used in biomedical therapies and diagnostics, for the soft ionization of biological macromolecules in mass spectrometry, for laser-assisted timed ionization events in atom-probe-tomography, for the characterization of nanoparticles with Raman spectroscopy, and more recently in the performance devices fabricated to achieve laser refrigeration.

In order to understand the optical heating of nanoparticles, we 1) developed a theoretical model to predict the temperature increase in laser-irradiated nanomaterials, and 2) performed experiments with a laser tweezer to test those predictions by measuring the temperature of optically trapped nanoparticles.

Click here to learn more about the theory of optically heated nanoparticles and how we devised methods to determine the temperature of optically trapped nanoparticles.


Diamond is the hardest known material in the world. Aerogels are some of the least dense materials ever synthesized. Thus, one can imagine that diamond aerogels would exhibit very unique material properties. In this project, we sought out to synthesize the first room temperature and pressure diamond aerogel.

The extreme physical and chemical properties as well as low toxicity of detonation nanodiamond (DND) materials have led to great interest recently in using DND materials for both therapeutic and diagnostic applications in medicine as well as for supercapacitors. Furthermore, negatively charged nitrogen-vacancy color centers can be used for bright biolabelling applications based on their highly efficient extended red emission.

These materials are of interest, since aerogels are lightweight, have high surface areas, and contain abundant open pores which can be readily loaded with drugs or other compounds to be used as an effective payload delivery vessel. Developing synthetic approaches to high surface area diamond would greatly increase availability and reduce cost for a range of applied and fundamental scientific applications.

Here I outline a rapid, low-cost method to making diamond aerogels by utilizing a sol-gel reaction between resorcinol and formaldehyde (RF) molecular precursors.


Potassium niobate (KNbO3) belongs to a unique class of materials with efficient nonlinear optical properties. That is, potassium niobate is able to convert low frequency/energy light to high frequency/energy light (for example, converting red light to blue light). Previous research has been done on using laser tweezers to trap potassium niobate nanowires to use those nanowires as optical probes for biological/cellular studies.

In this project, we synthesized potassium niobate nanowires and further explored their use and effectiveness as optical probes at the nanoscale in our laser tweezer setup.

In this project, we synthesized potassium niobate nanowires and further explored their use and effectiveness as optical probes at the nanoscale in our laser tweezer setup.


Despite decades of research and development into small molecule pharmaceuticals and advanced surgical methods, cancer remains one of the leading causes of death in industrialized societies. Nanoscale materials are known to exhibit a range of unique physical and chemical properties such as tunable sizes, high surface areas (~1000 m2/g), biocompatibility, singlet oxygen generation, and large optical absorption coefficients that have led many researchers across the globe to consider them in next-generation clinical trials.Hybrid nanomaterials, including gold-polymer structures, have also shown the ability to release a payload of chemotherapeutic small molecules due to a volumetric contraction following photothermal heating.

The purpose of this project section is to discuss photothermal heating fundamentals for several distinct material platforms with which I have conducted research. The fundamental physical mechanisms behind photothermal heating are discussed, followed by recent results from in vitro or in vivo trials reported in literature. Synergistic applications between photothermal heating and other diagnostic or therapeutic capabilities are also highlighted to provide a sense of contemporary cutting edge multimodal theranostic potential for these engineered nanomaterials.

Click here to learn more about photothermal cancer therapy and diagnostics.


The atom probe is a unique and powerful instrument that allows for the atom-by-atom reconstruction of a nanomaterial (atom probe tomography, APT). Historically, atom probes were restricted to metallic or conducting materials. However, this restriction was rectified with the addition of a laser pulse to assist in ion evaporation.

Currently, the understanding of how the laser heating of nanomaterials in a laser-assisted atom probe affects the ion evaporation events is lacking. For this research, we developed a theoretical model to predict the temperature evolution of a laser pulsed nanowire sample in order to help elucidate evaporation events in a laser-assisted atom probe.

Click here to learn more about the APT heating theory and see videos that show time-evolving silicon nanowire temperature distributions.


Quantum computing? Cool! The idea of quantum computing is that instead of performing calculations using a series of two states (1’s and 0’s, called ‘bits’), we can use quantum objects that can have a multiple states (more appropriately, a superposition of states, called ‘qubits’). Having this capability would allow for very fast computations on enormous datasets.

There are, in fact, many methods to making a quantum computer. One such type of quantum computer is called a topological quantum computer. This type of quantum computer works by utilizing theoretical predicted 2-dimensional quasiparticles called ‘anyons’.

The details of what these particles are and how they work in a topological quantum computer are complicated. However, my work at Harvard University in Professor Charles Marcus’ group was fabricating nanodevices and testing those devices to try and identify the experimentally elusive anyon.

Click here to learn more about the project.


Graphene is all over the place nowadays. It even won the 2010 Nobel Prize in Physics. However, it wasn’t all that long ago (2003) that graphene was first experimentally realized. Graphene is interesting because it is a single atomic layer thick and has astounding material properties.

In 2008, when I worked on graphene at Cornell University in Professor John Silcox’s research group, a single sheet of graphene had yet to be directly imaged in a high resolution electron microscope. I was tasked with developing a process to deposit graphene on a scanning transmission electron microscope (STEM) sample holder/grid and attempt to image the graphene in a state-of-the-are Nion UltraSTEM.

Click here to learn more about the project.


Loud noise, claustrophobia, and the ability to remain still or to hold a breath are all limitations to MRI techniques. It is because of these limitations that it is extremely important to be able to acquire an MRI as quickly as possible. Partial parallel imaging (PPI) has allowed for the possibility of rectify some of these problems. Some limitations that are typically addressed in research include faster signal acquisition and the patient motion suppression during MRI acquisition. The later of which is dealt with in this research.

Not only is it hard for some patients to stay still or hold a breath for a given period of time, but taking images of the cardiovascular region includes many veins and arteries that are continually beating and moving. In order to get rid of motion ‘ghosts’ and artifacts that result from motion during signal acquisition, motion correction algorithms have been created that are able to detect motion corruptions in k-space by using the redundant data left over from the multiple receiver coils of a PPI n-coil array.

One technique to correct motion corruption uses simultaneous acquisition of spatial harmonics (SMASH) to compare a given line in k-space to its neighboring line. Thus, as data is acquired line by line in the read-out direction, inconsistencies that result from motion corruption can be detected by comparing a predicted line to the actual line: a significant difference between the two would suggest some type of motion corruption.

In this research project, conducted in 2007 in Professor Jake Willig-Onwuachi’s lab at Grinnell College, a novel technique known as generalized autocalibrating partial parallel acquisitions (GRAPPA) was explored for its adaptability as a motion correction technique and compared the SMASH technique in hopes that it is a more robust method.

Click here to learn more about the project.