Allen Taflove, Ph.D. - US grants

Contemporary high-frequency electromagnetic engineering problems can involve full-vector wave interactions with complex, electrically-large, three-dimensional structures. Numerical simulation of Maxwell's equations for such structures is of great importance since the classical analytical tools for electrodynamics cannot deal with vector near fields that may be almost arbitrarily complex. Two of the primary contemporary thrusts in numerically modeling such problems are: (1) the frequency-domain integro-differential equation approach with solution via the method of moments (MON); and (2) the time-domain partial differential equation approach with solution via the finite-difference time-domain (FD-TD) method. This research project will develop Connection Machine (CM) software for the latest versions of MOM and FD-TD, construct benchmarks relative to Cray-based versions, and develop scaling rules for CM processing of ultra-large near-field data bases. This project will also extend a new spatial decomposition (SD) technique to the latest combined-field surface integral equation versions of MOM. SD is very promising for reducing the dimensionality and ill-conditioning of large MOM problems, and may permit existing computers to process very large EM models.

9218494 Taflove This project seeks to develop novel three-dimensional time-domain algorithms for optical pulse propagation, scattering, and switching (including femtosecond pulses) using the full vector nonlinear time-domain Maxwell's equations, with specific applications of glass and semiconductor materials. Algorithms will be implemented on supercomputers of the class of the Cray C-90 or Cray T3D. One algorithm to be explored involves solving a time-domain system of ordinary differential equations for the bandgap physics of semiconductor materials concurrently with the time-domain vector Maxwell's equations. This algorithm could permit detailed modeling of the pulse dynamics of passive and active optical and electrooptic devices including switches and laser sources. A second approach of interest involves applying computational fluid dynamics techniques for tracking shock waves to model possible optical shock waves in nonlinear media. Overall, the project will develop and apply novel time-domain algorithms to explore the dynamics of a variety of optical wave species in nonlinear media in three dimensions, including "light bullets" and shocked-wave optical pulses. These may exhibit favorable properties with respect to all-optical switching at relatively low laser power levels because of unique properties arising form their temporal and spatial confinement or shocked carrier, respectively. There would exist potential engineering applications in the realization of novel ultra-fast sub-millimeter- size all-optical digital logic elements operation at low laser power levels. ***

Backman
0522639

This proposal seeks to experimentally demonstrate and characterize photonic nanojets. Nanojets are created through the local field enhancement of micro-spheres or micro-cylinders and greatly enhance the backscattering of small nanoparticles that are located within their extent. Rigorous FDTD calculations by the investigators have shown that the intensity and angular distribution of backscattered nanoparticles in the nanojets are highly dependent upon the particle size. A unique feature of the nanojets lies in the fact that they are neither diffracting nor evanescent. The investigators propose to use the nanojets as a new sorting method for nanoshells in order to obtain a uniform size distribution to obtain better spectral selectivity in imaging applications. Applications of the nanojets to sorting intracellular macromolecules are also proposed.

0960148
Backman

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).

The proposed instrument will allow cellular imaging at the nanoscale with resolution and sensitivity that are much higher than what is currently possible with optical microscopy. The instrument will combine the state-of-the-art confocal microscope and a partial wave spectroscopy module. The instrument will allow quantification of cellular nanoscale architecture with sensitivity up to a few nanometers, molecular as well as structural imaging in nearly real time. The instrument will work with live as well as fixed cells.
The instrumentation takes advantage of a novel optical technology, single-cell partial-wave spectroscopic microscopy. The instrument will provide information about cell nanoarchitecture and its relationship to molecular events, which has not been possible to obtain before. The proposed microscope will be a unique device that will open new directions for basic science as well as translational research including cell biology, bioengineering and development of novel diagnostic devices, nanotechnology, fundamental electromagnetics, tissue engineering, and macromolecular biophysics.

This project is at the interface of biophotonics, electronics and computational electrodynamics with applications to medicine. The main thrust is the development of a principally new disposable, low-cost, miniature fiber-optics probe technology that would enable minimally or non-invasive population screening for major cancers while being comfortable to patients, enabling a major improvement in diagnostic accuracy, and reducing health care costs.

Intellectual Merit:
From the engineering perspective, the key areas of innovation are biophotonics and computational electromagnetics. The underlying biophotonics technology is Low-coherence Enhanced Backscattering Spectroscopy. The major technological advantages are miniaturization and the ability to depth-selectively quantify sub-diffractional (down to a few tens of nanometers) structure of live tissue, which is impossible with existing endoscopic or fiber-optic tools. In its application to cancer screening, the proposed approach takes advantage of the concept of field carcinogenesis, the notion that, initially, molecular/nanostructural alterations develop diffusely throughout an affected organ while further stochastic mutations lead to focal tumors. Thus, a cancer risk can be assessed by non-invasive analysis of tissue ultrastructure from an easily accessible surrogate site, such as the rectum for colon cancer, cheek mucosa for lung cancer, duodenal mucosa for pancreatic cancer, endocervix for ovarian cancer, etc. The project has three aims: (1) Development of a new paradigm for linking the ultrastructural and optical properties of tissue based on the Finite-Difference Time-Domain modeling of light-tissue interactions with nanoscale detail. Stochastic Finite-Difference Time-Domain simulation, a principally new approach to numerically solving Maxwell?s equations and modeling light transport in tissue of arbitrary complexity, will be developed. (2) Development of the miniature Low-coherence Enhanced Backscattering Spectroscopy probe. The design is a radical departure from other fiber-optics probes currently under development for biomedical applications, leveraging micro- and nano-fabrication technology and new sub-millimeter image sensors to produce an integrated device with unprecedented compactness capable of fully resolving the enhanced backscattering peak, and in turn, quantifying nanostructural changes in tissue. (3) Pilot human studies to demonstrate the potential clinical impact of the technology.

Broader Impact:
Although it is well accepted that cancer screening can dramatically decrease cancer mortality, no population screening exists for the majority of cancers. This is because existing techniques require examination of already formed cancerous or pre-cancerous lesions through interventional procedures (colonoscopy, endoscopy, bronchoscopy, etc.) and suffer from some of the following drawbacks: invasiveness, expense, low patient tolerance, or low sensitivity to curable lesions. The proposed technology may lead to a new paradigm in cancer screening that would be applicable to essentially any major cancer type and, due to its low-cost and high patient tolerance, can actually be used in the entire population. Furthermore, the implementation of the technology has the potential to dramatically reduce health care costs by identifying early preventable neoplastic lesions or early, readily treatable cancers. The project will also help increase the exposure of middle and high school students from underrepresented minority groups and inner-city schools to engineering, science and technology.

Retinal blindness, such as retinitis pigmentosa (RP), age-related macular degeneration (AMD), and glaucoma (POAG), is characterized by unrelenting neuronal death (photoreceptor loss in RP and AMD and ganglion cell loss in POAG). These prevalent blinding conditions account for a significant part of the estimated US$139 billion annual economic burden of vision disorders in the U.S. This group has, for the first time, shown that controlled microscale electromagnetic (EM) stimulation can lead to neuroprotective changes in the retina. The transformational vision of this project is to use non-invasive controlled electrical stimulation to induce genetic changes in the mammalian retina to slow down the progression of retinal blindness and perhaps even restore some level of the lost vision. The success of such an approach would spawn a whole new area in basic science, engineering, and medicine and in doing so develop new, innovative, cross-disciplinary educational programs critical to foster the next-generation of researchers of bioelectronic devices to affect protective genetic changes.


A number of mechanisms have been identified as to why neuronal death occurs in different retinal blinding disorders (e.g., genetic mutations in RP, lipid metabolism abnormalities and inflammation in AMD, and elevated intraocular pressure in POAG to name a few). This group has shown that controlled microscale electromagnetic (EM) stimulation can lead to epigenetic retinal changes with implications for neuroprotective changes. The hypothesis of this proposal is that neuroepigenetic and chromatin remodeling of the retina induced through controlled electrical stimulation is a key molecular determinant of neuroprotection and could prove to be pivotal for the treatment of certain retinal blindness conditions. The vision of this proposal is that the findings will demonstrate how stimulation using electromagnetic (EM) fields can be effectively adopted to slow or halt the progression of prevalent retinal diseases.

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.