Dr. Regina Ragan Profile

Dr. Regina Ragan

Professor at Univ of California Irvine

SPIE Involvement:

Author

Proceedings Article | 9 September 2019 Presentation

Illuminating bacterial communities with plasmonic nanoantennas (Conference Presentation)

Regina Ragan, William Thrift, Antony Cabuslay , Allon Hochbaum

Proceedings Volume 11082, 110821B (2019) https://doi.org/10.1117/12.2535513

KEYWORDS: Plasmonics, Nanoantennas, Molecular self-assembly, Machine learning, Statistical analysis, Nanolithography, Control systems, Chemical analysis, Data acquisition, Bacteria

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While availability of nanoscale fabrication tools has uncovered a rich area of physical phenomena with applications including sensing, energy, and imaging - scalable nanomanufacturing techniques allowing for technological impact still remain elusive. Self-assembly of nanoarchitectured systems, with control on atomic and molecular length scales, not only hold promise for device fabrication but offer new functionality for probing and interacting with molecular systems. For example, understanding hierarchical driving forces in assembly of nanospheres from colloid enables arranging 2D ‘metamolecule’ building blocks where the geometry of resultant oligomers, gap spacing, and dielectric environment provide additional degrees of freedom for tuning electromagnetic response. I will present metasurface geometries exhibiting magnetic fields at optical frequency and billon-fold electric field enhancements in nanogaps. The reproducibility offered by controlling nanogap spacing with chemical crosslinkers allows for acquisition of large data sets needed for machine learning analysis. Our group has recently demonstrated that plasmonic nanoantennas enhance surface enhanced Raman scattering (SERS) signals sufficiently for continuously monitoring metabolites produced by bacteria. Multivariate statistical analysis of SERS data from nanogaps incorporated in microfluidic devices shows bacterial metabolite concentration can be quantified across five orders of magnitude and detected in supernatant from Pseudomonas aeruginosa cultures as early as three hours after innoculation. Bacteria exposed to a bactericidal antibiotic were differentially less susceptible after 10 h of growth, indicating that these devices may be useful for early intervention of bacterial infections. Analysis with artificial neural networks pushes quantification down to the femtomolar regime offering the promise of quantification down to the single molecule limit. We will also show results demonstrating the ability to discriminate antibiotic resistance to rifampicin and susceptibility to carbenicillin in Psuedomonas Aeruginosa through SERS analysis of metabolites in cellular lysate. Discrimination accuracies greater than 99% are achieved using big data machine learning techniques like convolutional neural networks. Yet these techniques require large quantities of labeled data, which is extraordinarily expensive to acquire for medical diagnostics due to the need for experts to culture and analyse bacterial samples. Thus we have also introduced few shot and semi-supervised machine learning techniques in the analysis of SERS spectra to greatly reduce the amount of labeled data. We have demonstrated an increase in one shot classification of over 10% through the use of a semi-supervised variational autoencoder and a spike timing plasticity dependent model designed for few shot learning. These results demonstrate that SERS is a fast, accurate, and facile method for identification of pathogenic states by analysis of unknown metabolites. The ability of clinicians to quickly determine the susceptibility of an infection to antibiotic therapy is critical to limit the spread of antibiotic resistant bacterial strains.

Proceedings Article | 3 September 2019 Paper

Improved regressions with convolutional neural networks for surface enhanced Raman scattering sensing of metabolite biomarkers

William Thrift, Cuong Nguyen, Junlin Wang, Jason Kahn, Ruijun Dong, Andrew Laird, Regina Ragan

Proceedings Volume 11089, 1108907 (2019) https://doi.org/10.1117/12.2535410

KEYWORDS: Raman spectroscopy, Surface enhanced Raman spectroscopy, Raman scattering, Convolutional neural networks, Molecules, Sensors, Nanoparticles, Biosensing, Nanolithography, Particles

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Proceedings Article | 17 September 2018 Presentation

Quantitative single molecule SERS sensing enabled by machine learning (Conference Presentation)

Regina Ragan, William Thrift

Proceedings Volume 10728, 107280C (2018) https://doi.org/10.1117/12.2320297

KEYWORDS: Molecules, Surface enhanced Raman spectroscopy, Molecular self-assembly, Biosensing, Machine learning, Sensors, Molecular spectroscopy, Complex systems, Convolutional neural networks, Neural networks

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Proceedings Article | 19 September 2017 Paper

Robust SERS spectral analysis for quantitative detection of pyocyanin in biological fluids

Cuong Nguyen, Will Thrift, Arunima Bhattacharjee, Katrine Whiteson, Allon Hochbaum, Regina Ragan

Proceedings Volume 10352, 1035205 (2017) https://doi.org/10.1117/12.2267958

KEYWORDS: Surface enhanced Raman spectroscopy, Machine learning, Gold, Raman scattering, Molecules, Nanoparticles, Chemistry, Chemical analysis, Polymethylmethacrylate, Silicon

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Proceedings Article | 11 September 2017 Paper

Templated electrokinetic directed chemical assembly for the fabrication of close-packed plasmonic metamolecules

W. Thrift, M. Darvishzadeh-Varcheie, F. Capolino, R. Ragan

Proceedings Volume 10346, 103461M (2017) https://doi.org/10.1117/12.2274554

KEYWORDS: Nanoparticles, Magnetism, Gold, Plasmonics, Nanolithography, Silicon, Resonators, Molecular self-assembly, Directed self assembly, Particles

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Proceedings Article | 30 September 2015 Paper

Field enhancement with plasmonic nano-antennas on silicon-based waveguides

M. Darvishzadeh-Varcheie, C. Guclu, R. Ragan, O. Boyraz, F. Capolino

Proceedings Volume 9547, 95473E (2015) https://doi.org/10.1117/12.2188603

KEYWORDS: Waveguides, Nano antennas, Plasmonics, Silicon, Spectroscopy, Raman scattering, Gold, Antennas, Glasses, Near field

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Proceedings Article | 31 August 2015 Paper

Surface enhanced Raman scattering for detection of Pseudomonas aeruginosa quorum sensing compounds

Will Thrift, Arunima Bhattacharjee, Mahsa Darvishzadeh-Varcheie, Ying Lu, Allon Hochbaum, Filippo Capolino, Katrine Whiteson, Regina Ragan

Proceedings Volume 9550, 95500B (2015) https://doi.org/10.1117/12.2188806

KEYWORDS: Surface enhanced Raman spectroscopy, Gold, Raman spectroscopy, Sensors, Molecules, Polymethylmethacrylate, Raman scattering, Resonance enhancement, Signal processing, Polymers

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Proceedings Article | 18 May 2015 Paper

Highly nonlinear sub-micron silicon nitride trench waveguide coated with gold nanoparticles

Yuewang Huang, Qiancheng Zhao, Nicholas Sharac, Regina Ragan, Ozdal Boyraz

Proceedings Volume 9503, 95030H (2015) https://doi.org/10.1117/12.2182290

KEYWORDS: Waveguides, Silicon, Nanoparticles, Gold, Refractive index, Semiconducting wafers, Wave propagation, Etching, Metals, Particles

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Proceedings Article | 11 September 2013 Paper

Tunable nano bead arrays on film for controlling propogation of light

Nicholas Sharac, Himanshu Sharma, Michelle Khine, Regina Ragan

Proceedings Volume 8809, 88091O (2013) https://doi.org/10.1117/12.2026143

KEYWORDS: Etching, Picosecond phenomena, Plasmonics, Nanostructures, Gold, Plasma etching, Surface enhanced Raman spectroscopy, Metals, Scanning electron microscopy, Atomic force microscopy

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Proceedings Article | 19 October 2006 Paper

Noble metal nanoparticle arrays: control of size, shape, and placement via chemical self-assembly

Ju Choi, George Saddiqi, Jere Wilson, Regina Ragan

Proceedings Volume 6370, 637010 (2006) https://doi.org/10.1117/12.688409

KEYWORDS: Nanoparticles, Polymethylmethacrylate, Thin films, Metals, Gold, Silver, Polymers, Scanning electron microscopy, Atomic force microscopy, Silicon

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Proceedings Article | 29 December 2004 Paper

Platinum and gold nanostructures on silicon via a self-assembled template

Regina Ragan, Sehun Kim, Yong Chen, Xuema Li, R. Stanley Williams

Proceedings Volume 5593, (2004) https://doi.org/10.1117/12.569439

KEYWORDS: Platinum, Scanning tunneling microscopy, Gold, Silicon, Reactive ion etching, Erbium, Nanostructures, Etching, Metals, Nanowires

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Proceedings Article | 15 November 2002 Paper

Structural transformations in self-assembled semiconductor quantum dots as inferred by transmission electron microscopy

Peter Mock, Yuanyuan Lei, Teya Topuria, Nigel Browning, Regina Ragan, Kyu Min, Harry Atwater

Proceedings Volume 4807, (2002) https://doi.org/10.1117/12.450998

KEYWORDS: Silicon, Tin, Transmission electron microscopy, Quantum dots, Scanning transmission electron microscopy, Semiconductors, Diffraction, Image resolution, Modulation, Interfaces

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Showing 5 of 12 publications

Conference Committee Involvement (3)

Nanosensing: Materials, Devices, and Systems III

11 September 2007 | Boston, MA, United States

Nanomaterial Synthesis and Integration for Sensors, Electronics, Photonics, and Electro-Optics

1 October 2006 | Boston, Massachusetts, United States

Nanosensing: Materials and Devices II

23 October 2005 | Boston, MA, United States

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