Many everyday simple tasks involve moving objects, such as our cell phones and coffee mugs, from one position to another. However, when the objects become too small to be conveniently held by hand, new approaches are needed to handle such small objects. An elegant approach to manipulate microscopic objects is to use a focused light beam. Known as "optical tweezers", this technique was recognized with the 2018 Nobel prize in Physics and is widely used to manipulate cells to enable improved understanding of biological systems. However, because of the inherent inability to focus light to nanoscale (one-billionth of a meter) volumes, attempts to trap nanoscale objects with conventional optical tweezers have met significant challenges. To address these challenges and enable new capabilities for probing the nano-world, including nucleic acids that form the basis of our human genome and quantum dots that support technological advances in displays and solar cells, the PIs will develop optical nanostructures using silicon to squeeze light to very tiny, nanoscale volumes. The approach proposed by the PIs could enable the trapping of extremely small nanoscale objects with diameters that are at least ten thousand times smaller than the thickness of the human hair. Such a tool will equip scientists with new tools to probe the nano-world and potentially enable new scientific discoveries in application areas ranging from sensing to quantum computing. Faculty and graduate students will develop activities to promote STEM (science, technology, engineering, and mathematics) with middle and high school students in middle Tennessee.

The ability to trap and dynamically manipulate nanometer-scale objects is crucial to the advancement of nanotechnology. Optical trapping is widely used for stable trapping of microscale objects. However, attempts to translate them for use to handle nanometer scale objects have been met with challenges because of the inability to focus light to nanoscale volumes using free-space optics. While near-field nano-optical tweezers based on plasmonic nanoantennas have been developed within the last decade, the loss-induced heating effect presents a major challenge for handling delicate biological objects. The objective of this research is to demonstrate that it is possible to capture, rapidly transport, and stably trap sub-20 nm dielectric objects and quantum emitters with sub-milliwatt optical power using the extremely confined electromagnetic field in 2D dielectric bowtie photonic crystal cavities (PhCs). To achieve these objectives, 2D silicon bowtie PhCs with ultra-low mode volume and narrow resonance linewidth will be designed and fabricated. The intellectual significance of the proposed activities includes: (a) an understanding of the role of self-induced back-action force due to the position of the particle in the high-quality factor bowtie cavities on the optical trapping performance; (b) addressing the issue of low capture rate and diffusion-limited transport of nanometer scale objects towards the region of high energy density in the bowtie cavity; (c) an understanding of the role of thermophoretic force on the trapping performance; (d) the realization of long-range transport of nanometric objects between optical cavities, which has remained elusive. The project will expose students to different fields of research including nano-optics, nanofabrication, materials characterization, microfluidics and advanced Multiphysics modeling. Project members will engage in science and technology outreach targeting middle and high school students by participating in successful programs already well-established at Vanderbilt. Through these outreach and educational activities, the researchers expect to spark the interest of the younger generation and encourage them to pursue STEM-focused careers.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

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Vanderbilt University Medical Center
United States
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