Advances in computational power over the last few decades have dramatically opened up the modeling capability of the typical researcher. Although laborious analysis and approximations of physical systems were quite the norm some decades ago, today complex problems can be simulated extensively before being built or committed to design. Today, the pursuit of computational experimentation has displaced, to a large extent, either laboratory experimentation or extensive theoretical analysis, especially in systems in which the governing equations are well developed. Indeed, in the field of electromagnetics (EM), where only select canonical problems are amenable to analytical solutions, computer simulations have allowed for great flexibility in searching for new applications to Maxwell’s equations. In light of this flexibility, however, one should not abandon completely either the approaches or models researchers have developed over the years.
The potential for the use of biological agents by terrorists is a real threat. Two approaches for antibody-based detection
of biological species are described in this paper: 1) The use of microbead arrays for multiplexed flow cytometry
detection of cytokines and botulinum neurotoxin simulant, and 2) a microfluidic platform for capture and separation of
different size superparamagnetic nanoparticles followed by on-chip fluorescence detection of the sandwich complex.
These approaches both involve the use of automated fluidic systems for trapping antibody-functionalized microbeads,
which allows sample, assay reagents, and wash solutions to be perfused over a micro-column of beads, resulting in faster
and more sensitive immunoassays. The automated fluidic approach resulted in up to five-fold improvements in
immunoassay sensitivity/speed as compared to identical immunoassays performed in a typical manual batch mode. A
second approach for implementing multiplexed bead-based immunoassays without using flow cytometry detection is
currently under development. The goal of the microfluidic-based approach is to achieve rapid (<20 minutes),
multiplexed (≥ 3 bioagents) detection using a simple and low-cost, integrated microfluidic/optical detection platform.
Using fiber-optic guided laser-induced fluorescence, assay detection limits were shown to be in the 100's of picomolar
range (10's of micrograms per liter) for botulinum neurotoxin simulant without any optimization of the microfluidic
device or optical detection approach.
At Pacific Northwest National Laboratory, wideband antenna arrays have been successfully used to
reconstruct three-dimensional images at microwave and millimeter-wave frequencies. Applications
of this technology have included portal monitoring, through-wall imaging, and weapons detection.
Fractal antennas have been shown to have wideband characteristics due to their self-similar nature
(that is, their geometry is replicated at different scales). They further have advantages in providing
good characteristics in a compact configuration. We discuss the application of fractal antennas for
holographic imaging. Simulation results will be presented.
Rectennas are a specific class of antennas in which a received signal drives a nonlinear junction and
is retransmitted at either a harmonic frequency or a demodulated frequency. Applications include
tagging and tracking objects with a uniquely-responding antenna. It is of interest to consider fractal
rectenna because the self-similarity of fractal antennas tends to make them have similar resonance
behavior at multiples of the primary resonance. Thus, fractal antennas can be suited for applications
in which a signal is reradiated at a harmonic frequency. Simulations will be discussed with this
application in mind.