CAREER: Near-field Optical Forces

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AbstractECCS-0747560Kenneth Crozier, Harvard UniversityResearch In the first section of this proposal, the PI outlines a plan to realize a completely new optical tweezer technology based on metallic nanostructures known as optical antennas. The PI will demonstrate the trapping of nanoparticles with radii ranging from 10-500 nm using the fabricated optical antenna tweezer devices. The PI will demonstrate Brownian motors, in which thermal noise will assist in directed motion by providing a mechanism for overcoming energy barriers. Education In the second section of the proposal, the PI outlines his educational initiatives at the K12, undergraduate and graduate levels. At the K-12 level, the PI is committed to supporting science education in the Cambridge Public Schools system through seminars for interested teachers and students. Under the PI?s supervision, undergraduate students will construct a conventional optical tweezer system. This will be an important part of the research program, as the performance of the conventional system will be compared to that of the newly-constructed near-field optical tweezers. The PI will introduce a new Special Topics course in the Biophysics Program at Harvard. In this course, lectures will be given on the recent advances in nanophotonics that have applications in the biological sciences. Intellectual Merit A significant obstacle to the adoption of optical tweezers in microfluidic systems for the sorting of nanoparticles are the high laser powers needed with conventional optical tweezers. The proposed optical tweezer technology will reduce considerably the laser power required for the stable trapping of nanoparticles. The proposed Brownian motor will demonstrate that thermal motion combined with an asymmetric, time-varying optical potential can be used to exercise control over nanoscale systems. The PI?s education initiatives will translate the excitement of his research laboratory to the K-12, undergraduate and graduate levels. The PI?s K12 educational outreach plan is based on his experiences as a graduate student, in which he tutored at an after-school science program for elementary and middle school children. This left him with an appreciation such programs can be very effective at increasing students? enthusiasm for math and science. Broader Impact The proposed research will enable nanoparticles to be manipulated with compact, low power laser sources. The fact that the optical traps are produced by lithography makes them compatible with microsystem technology, and enables them to be placed at arbitrary locations on a chip. It is anticipated that the demonstration of thermal ratchets with surface plasmon nanostructures will contribute to our understanding of other examples of Brownian motors, for example in biology. The proposed education plan will help attract and retain students to science and engineering. The PI?s educational outreach program to K12 will support science teaching in the Cambridge Public Schools system, with a student body almost completely comprised of underrepresented groups in science and engineering. The PI has designed a specific research project that will be carried out by undergraduate students under the proposed program.