Spring 2017 – Fall 2018
I transformed a Ram Promaster cargo van into my personal camping vehicle and off-grid mobile home. Furniture was designed in SketchUp and built at IsGood Woodworks in Seattle, WA. I also outfitted the van with adjustable lights, a dry flush toilet, a refrigerator, a fan, running water, and a stove/oven combination. All electricity is powered by the solar system that I installed.
Silicone peripheral nerve interface for bi-directional prosthesis control
May 2013 – December 2014
Advisors: Professor Hugh Herr, MIT Media Lab; Dr. Bryan McLaughlin, Charles Stark Draper Laboratory
In the quickly-advancing world of prosthetics, bi-directional control with truly natural sensory feedback, as opposed to a buzzing sensation, is still yet to be achieved. This project aimed to create a peripheral nerve implant to enable native motor control and sensation between a prosthesis and its human user. The approach was to create a microchannel array implant, to be placed in series with a peripheral nerve during amputation surgery, that would both selectively record motor neuron activity to be transmitted to the prosthetic limb and selectively stimulate sensory neurons using data from sensors on the prosthetic limb. As the first graduate student on this project, I designed and fabricated a stacked PDMS (silicone) microchannel array with platinum electrodes. One technical challenge was that the optimal geometries to simultaneously achieve both selective nerve recording/stimulation and high signal fidelity were pushing the upper size limit of conventional microfabrication processes but also pushing the lower size limit of “macro”-scale machine shop processes. To overcome such challenges, I developed a process flow that mixed work in the cleanroom, machine shop, and bio labs, ultimately creating prototypes that could be implanted into rats for evaluation.
Near-infrared quantum dot LEDs with record-high efficiencies
October 2011 – May 2013
Advisor: Professor Vladimir Bulovic, MIT Organic and Nanostructured Electronics Laboratory
QD-LEDs offer the benefits of tunability, high brightness, and solution-processability, but especially in near-infrared wavelengths, their performance lags behind their conventional LED counterparts. Our approach was to enhance the quantum efficiency of QD-LEDs by designing devices that utilized “core-shell” quantum dots – 4.0nm-diameter PbS “cores” cladded by CdS “shell” – based on the theory that a wide bandgap shell could act as a barrier for the photoluminescence quenching. of the PbS core. Using PbS-CdS core-shell quantum dots that the Bawendi Lab at MIT synthesized, Geoffrey and I designed, fabricated, and characterized the light-emitting devices, demonstrating up a 100-fold increase in external quantum efficiency over PbS core-only QD-LEDs.
Electrophoretic deposition for electroluminescent quantum-dot films
August 2011-March 2013
Advisor: Professor Vladimir Bulovic, MIT Organic and Nanostructured Electronics Laboratory
Quantum dot films for QD-LEDs are traditionally hand-spun or printed in the laboratory, and depositing large-area films that preserve their electroluminescent properties is a challenge that must be overcome to enable scalable quantum dot optoelectronics. Electrophoretic deposition (EPD) is an attractive manufacturing technique in that it minimizes wastage of quantum dot solution, allows for parallel processing, and enables deposition of films onto electrodes of arbitrary size, shape, and texture. In collaboration with Dr. Ronny Costi, I developed an EPD process that preserved the luminescent properties of the deposited quantum dots and could controllably result in films thin enough to fabricate light emitting devices. We demonstrated QD-LEDs fabricated with electrophoretically-deposited films of CdSe-ZnS quantum dots for the first time. The characteristics of the devices were comparable to those of QD-LEDs fabricated using spun-cast quantum dot films under otherwise identical conditions, suggesting that our method could be a viable alternative to spin-casting in the fabrication of quantum dot optoelectronic structures.
Hybrid nanoscale-macroscale electronics for structural health monitoring
Spring 2010 – Spring 2011
Advisors: Professors Naveen Verma and Sigurd Wagner, Princeton University
A new electronic technology has become prominent: large-area electronics, or macro-electronics. Its most important application is flat panel display screens, which cover areas of square meters. Large-area electronics is completely different from conventional, integrated nanoscale CMOS circuits: the former is on the scale of humans, the latter is among the smallest things than humans can make; the former is slow, the latter is ultra-fast. The objective of this project was to combine the advantages of these two technologies to create a new breed of electronics and to demonstrate its application to large engineered structures. In particular, we explored a new scheme for structural health monitoring. Thousands of TFT sensors connected to flexible, large-area a-Si:H TFT- based circuits would cover a structure completely like wallpaper. The large-area circuits would continuously scan through data from the sensors and interface to a small number of nanoscale IC units that can then read and process the data.
I specifically focused on creating such interfacial “scanning” circuits of TFTs. We created a SPICE model to simulate the theoretical operation of such circuits, and I designed and developed the process to fabricate these circuits on glass and plastic. We were able to demonstrate the functionality of a six-unit scanning chain, setting the foundation for larger and more complex circuits.
Empirical modeling of organic solar cells
Advisor: Dr. Robert Street, Palo Alto Research Center (formerly Xerox PARC)
In this summer internship, I designed and executed low-level photoconductivity measurements of bulk heterojunction organic solar cells to derive their electronic structure. I also created and experimentally verified a model for the influence of series resistance on photocurrent analyses of organic solar cells.
Flexible amorphous silicon thin-film transistors
Jan 2009-May 2010
Advisor: Professor Sigurd Wagner, Princeton University
The flexibility of large-area thin-film circuits is largely limited by the stiffness of the most brittle layers of its devices; among these is the inorganic SiNx or SiOx gate dielectric that is conventionally used in amorphous silicon (a-Si) thin-film transistors (TFTs). Unfortunately, most organic materials, while much more flexible than their inorganic counterparts, do not have the electronic insulation and reliability characteristics needed to be a sufficient replacement. Shortly before I joined, Sigurd Wagner’s lab at Princeton University had developed a novel SiOx-silicone “hybrid” material to be used as OLED encapsulation and had recently also demonstrated that the material could be used as a gate dielectric for a-Si TFTs that in fact resulted in a doubling of effective electron mobility over TFTs made with a conventional SiNx dielectric. As an undergraduate researcher, my contribution was to set up and execute experiments to characterize the mechanical flexibility of the new TFTs. I created a simple bending setup using drill bits and small metal tubing that allowed me to measure the electrical performance of the TFTs before, during, and after determined amounts of compressive and tensile strain. We found that the TFTs were “ultraflexible” and could be bent down to a 0.5mm radius (5% strain) in tension and down to a 1mm radius (2.5% strain) in compression.
I went on to use the hybrid dielectric material in a top-gate staggered TFT architecture, which is a structure of particular interest for display applications in industry but one that traditionally results in poorer effective mobility. The TFTs that I designed and fabricated showed mobilities as high as twice that of top-gate staggered TFTs made with a conventional SiNx gate dielectric, reinforcing the value of our new dielectric material.
Homemaker’s hydrogen generator
Fall 2009 – Spring 2010
I was the team captain of Princeton University’s entry into the International Association for Hydrogen Energy’s inaugural 2010 Hydrogen Energy Design Competition. I was responsible for leading the design and characterization of our hydrogen generator. We designed a simple generator from low-cost, readily available items, dubbing our generator the “homemaker’s hydrogen generator.” The design and hydrogen-producing capabilities of our product won us first place in the competition. YouTube summary
Self-driving miniature car – ELE302 final project
In the final project for the capstone course for our department, my classmate, Mary Catherine Wen, and I transformed a miniature RC car into a self-driving platform. We stripped the electronics of the kit car and implemented our own hardware and software systems for PID speed control, PWM steering control, line-following, and obstacle detection/avoidance. We also implemented an extra feature whereby the car would drive over a metallic “organ” and play a musical tune (where each note was generated by the LC resonant circuit formed between the track and the car wheels).