Spotlight on Graduate Research

It is no secret that Caltech's graduate students have unparalleled research opportunities. Working closely with faculty advisers and colleagues in diverse fields across campus, their contributions are essential to the Institute's advances in science, engineering, and technology. For nearly two decades, the Everhart Lecture Series has provided a venue to highlight graduate student research at Caltech.

The annual series, named after Caltech president emeritus Tom Everhart, provides three carefully selected graduate students with an opportunity to present their work to an Institute-wide audience. The series was established with the goal of "encouraging interdisciplinary interaction and helping faculty and graduate students across campus to share ideas about recent research developments, problems and controversies, and to recognize the exemplary presentation and research abilities of Caltech's graduate students."

"Having the ability to demonstrate your work to the broader community—those outside of your own scientific area—is extremely important, and too often graduate students have very little experience with this," says graduate student Constantine Sideris, the 2014–15 chair of the Everhart Lecture Series committee, an interdisciplinary committee of graduate students that selects the three graduate student lecturers from a pool of more than a dozen applicants each fall.

"This series allows them to hone their presentation and dynamic speaking skills, and also their ability to explain difficult, technical concepts to a diverse audience," Sideris says.

This year's lecturers—Carissa Eisler (chemistry and chemical engineering), Roarke Horstmeyer (electrical engineering), and Peter Rapp (chemistry and chemical engineering)—gave talks on campus earlier this spring, and all three were invited to share their work with members of the Caltech community during the Institute's annual Seminar Day event in May. This year's lectures span a range of topics, from enhancing solar-cell efficiency, to improving microscope imaging, to understanding polymers. (Complete lecture descriptions from the students as well as links to podcasts of the recorded talks on iTunes U can be found below.)

"Research is only getting more interdisciplinary, so effectively communicating your work is an essential skill," says Eisler. "The lecture was really challenging, and I was very nervous, but it was incredibly rewarding, and I'm so glad that I did it."

Eisler and her colleagues noted that participating in the lectures provided valuable learning opportunities—by forcing them to synthesize and explain their work to individuals outside of their respective fields—and helped to build campus awareness for the breadth of research that's being done by graduate students.

"I work with a team of remarkable people, and I hope the lecture communicated that my project is just one among many exciting projects in our lab," Rapp says.  

Lecture Descriptions:

Building a Brighter Future: Spectrum-Splitting as a Pathway for 50% Efficiency Solar Cells
By Carissa Eisler
Lab: Harry Atwater, Howard Hughes Professor of Applied Physics and Materials Science and director of the Resnick Sustainability Institute

Although possible, ultra-high solar-cell efficiencies (>50 percent) have not been achieved because of limitations by current fabrication methods. Spectrum-splitting modules, or architectures that employ optical elements to divide the incident spectrum into different color bands, are promising because they can convert each photon more efficiently than traditional methods. This talk discusses our design and prototyping efforts to create such a spectrum-splitting module. We explore the spectrum-splitting optics and geometric optimizations in the context of high-efficiency designs. We show a design that achieves 50 percent efficiency with realistic device losses and geometric constraints. 

Listen to the lecture on iTunesU: https://itunes.apple.com/us/podcast/building-brighter-future-spectrum/id986954281?i=341029550&mt=2

Computational Microscopy: Turning Megapixels into Gigapixels
By Roarke Horstmeyer
Lab: Changhuei Yang, Professor of Electrical Engineering, Bioengineering, and Medical Engineering

Optical aberrations limit the size of current microscope images to tens of megapixels. This talk will present a method to boost a microscope's resolving power to one gigapixel using a technique termed Fourier ptychography. No moving parts or precision controls are needed for this resolution enhancement. The only required hardware is a standard microscope, which we outfit with a digital detector and an array of LEDs. An optimization algorithm does the rest of the work. Example applications of our new microscope include full-slide digital pathology imaging, wide-scale surface profile mapping of human blood, and achieving sub-wavelength resolution without needing oil immersion.

Listen to the lecture on iTunesU: https://itunes.apple.com/us/podcast/computational-microscopy-turning/id986954281?i=341030229&mt=2

Shaking Hands in a Crowded Room: How Sticky Polymers Travel through Viscoelastic Gels
By Peter Rapp
Lab: David Tirrell, Ross McCollum-William H. Corcoran Professor of Chemistry and Chemical Engineering; Director, Beckman Institute

What if you could give a polymer hands and feet and watch it move? We have developed biological approaches to synthesizing functional materials made from proteins, nature's flagship polymers. These approaches provide a set of tools for answering fundamental questions in polymer physics and for synthesizing dynamic materials that find applications in soft-tissue engineering and regenerative medicine. This talk will explore the dynamics of a model "sticky" polymer: an artificial protein engineered with associative endblocks that self-assembles into viscoelastic hydrogels. Fluorescence relaxation studies have demonstrated that polymer diffusion in these gels is controlled by endblock exchange, a process akin to a molecular handshake. Genetic approaches to modifying the endblock architecture enable tuning of polymer mobility over a wide range.

Listen to the lecture on iTunesU: https://itunes.apple.com/us/podcast/shaking-hands-in-crowded-room/id986954281?i=343195468&mt=2