| NSF Org: |
DMR Division Of Materials Research |
| Recipient: |
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| Initial Amendment Date: | July 31, 2019 |
| Latest Amendment Date: | July 31, 2019 |
| Award Number: | 1905527 |
| Award Instrument: | Standard Grant |
| Program Manager: |
Birgit Schwenzer
bschwenz@nsf.gov (703)292-4771 DMR Division Of Materials Research MPS Directorate for Mathematical and Physical Sciences |
| Start Date: | September 1, 2019 |
| End Date: | August 31, 2024 (Estimated) |
| Total Intended Award Amount: | $496,544.00 |
| Total Awarded Amount to Date: | $496,544.00 |
| Funds Obligated to Date: |
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| History of Investigator: |
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| Recipient Sponsored Research Office: |
300 TURNER ST NW BLACKSBURG VA US 24060-3359 (540)231-5281 |
| Sponsor Congressional District: |
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| Primary Place of Performance: |
VA US 24061-0001 |
| Primary Place of
Performance Congressional District: |
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| Unique Entity Identifier (UEI): |
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| Parent UEI: |
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| NSF Program(s): | SOLID STATE & MATERIALS CHEMIS |
| Primary Program Source: |
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| Program Reference Code(s): |
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| Program Element Code(s): |
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| Award Agency Code: | 4900 |
| Fund Agency Code: | 4900 |
| Assistance Listing Number(s): | 47.049 |
ABSTRACT
PART 1: NON-TECHNICAL SUMMARY
Self-assembly -the spontaneous formation of well-defined ordered structures from simpler components- is a key mechanism that enables living organism to develop and grow in size and complexity. If self-assembly could be fully applied to technological problems, it would make it possible to create materials and devices that are well beyond the reach of other fabrication techniques, potentially revolutionizing many areas of materials science, electrical and chemical engineering, and other fields. One of the barriers preventing this is the difficulty in making starting components of sufficient complexity of the required quality for efficient self-assembly to take place. This project, which is supported by the Solid State and Materials Chemistry program at NSF, implements a new technique for making such particles. The particles are between a few hundred nanometers and a few micrometers in size and possess surface properties that can be patterned in nearly any configuration. These so-called "patchy particles" are excellent candidates for self-assembly starting components. The technique researchers at Virginia Polytechnic Institute and State University employ uses light to pattern spherical particles that are suspended in liquid, and it has very few restrictions of the distribution and configuration of the pattern fabricated on the spheres. On the level of basic science, this new route to patchy particles permits a more thorough exploration of self-assembly, which helps unravel the principles underlying this complex and only partially understood phenomenon. Because the same pattern can straightforwardly be projected onto any number of particles, it potentially makes the technique amenable to future production of patchy particle on an industrial scale. Thereby, this research may impact a wide range of fields, but some of the project's initial target structures may be particularly useful in the areas of flexible solar cells and in microrobotics. In addition to the scientific and potential technological advances described, students are benefitting from this research either by direct involvement in the project and mentoring, or through the insights it adds to the course curriculum of the new Nanoscience program at Virginia Polytechnic Institute and State University.
PART 2: TECHNICAL SUMMARY
With this project, supported by the Solid State and Materials Chemistry program at NSF, researchers at Virginia Polytechnic Institute and State University develop a new paradigm for synthesizing patchy particles with a patch distribution that can be chosen with nearly complete freedom, and to demonstrate the self-assembly of these particles into well-defined structures, includes some that are not readily achievable with existing patchy particle fabrication techniques. The project applies an optical imaging technique to project identical patterns on any number of dielectric nanospheres and/or microspheres, where functionalization with ligands containing photocleavable protecting groups (PPGs) ensure that the optical patterns are transferred into functional groups such as amines, thiols, carboxyls, etc., which can then be modified further to produce patches with desired functionality. With functionalizations containing optically orthogonal PPGs (including o-nitrobenzyl, aminocoumarin, and BODIPY groups), multiple patch types with distinct properties can be produced through a single exposure, which is required for full implementation of the patchy particle concept. The basic building blocks for self-assembly are titania micro- and nanospheres for which a number of ligands are developed to suit the needs of the project, using phosphonic acid anchors to form stable bonds with the surface. Titania spheres are particularly useful for applications beneficial to society, such as photonic crystals for high efficiency dye-sensitized solar cells. Other potential applications include TiO2/Pt light-controlled micromotors, or their photocatalytic properties could be used to directly assist in the surface patch formation. As part of this project one or more patch-patch interactions (such as hydrophobic attraction, electrostatic binding, biotin-avidin binding etc.) are used to achieve several target structures ranging from relatively simple (linear chains, tetrahedra) to more challenging but previously demonstrated (Kagome lattices, pentapods) to structures of high interest that have yet to be assembled (icosahedra, diamond-structure colloidal crystals.) The patterning can be applied to particles in a bulk suspension and is therefore potentially scalable.
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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