This lecture was an introduction to Surface Plasmon Resonance (SPR) Sensors. It started out with an explanation of Coulomb's Law for the force between two charges. This lead to the concept of the electric field and with an applied electric field, a molecule becomes a polarized dipole. On a system for when measuring things on a sensor, an externally applied electric field is used. The dipole moment for one molecule becomes reversed. This means when an Electric field is applied to a group of dipoles, all of the internal charges cancel out, except for the surface molecules. A secondary electric field is also produced. However, for this to occur it must be in a dielectric medium. The SPR Sensor can then characterize how easily the molecule is polarized by the electric field. All biomolecules have the 1/e > H2O, so the optical biosensors take advantage of this property. It doesn't measure the mass directly. It measure the changes in the dielectric permittivity due to the presence of biomolecules on the sensor surface. In order to do this it needs a way to project the Electric Field to the test sample and a way to measure the change in the dielectric permittivity. The metal is highly lossy, so the laterally propagating Electromagnetic field loses its intensity rapidly as it runs parallel to the surface. For a fixed wavelength, though, SP modes are only excited for a particular angle of incidence.
My research group is focused on the application of sub-wavelength optical phenomena and fabrication methods to the development of novel devices and instrumentation for the life sciences. The group is highly interdisciplinary, with expertise in the areas of microfabrication, nanotechnology, computer simulation, instrumentation, molecular biology, and cell biology. In particular, we are working on biosensors based upon photonic crystal concepts that can either be built from low-cost flexible plastic materials, or integrated with semiconductor-based active devices, such as light sources and photodetectors, for high performance integrated detection systems.
Using a combination of micrometer-scale and nanometer-scale fabrication tools, we are devising novel methods and materials for producing electro-optic devices with nanometer-scale features that can be scaled for low-cost manufacturing. Many of our techniques are geared for compatibility with flexible plastic materials, leading to applications such as low cost disposable sensors, wearable sensors, flexible electronics, and flexible displays. Because our structures manipulate light at a scale that is smaller than an optical wavelength, we rely on computer simulation tools such as Rigorous Coupled Wave Analysis (RCWA) and Finite Difference Time Doman (FDTD) to model, design, and understand optical phenomena within photonic crystals and related devices.
In addition to fabricating devices, our group is also focused on the design, prototyping, and testing of biosensor instrumentation for high sensitivity, portability, and resolution. Advanced instruments enable high resolution imaging of biochemical and cellular interactions with the ability to monitor images of biochemical interactions as a function of time. Using the sensors and instrumentation, we are exploring new applications for optical biosensor technology including protein microarrays, biosensor/mass spectrometry systems, and microfluidics-based assays using nanoliter quantities of reagents. The methods and systems developed in the laboratory are applied in the fields of life science research, drug discovery, diagnostic testing, and environmental monitoring. -From Professor Cunningham's Faculty Profile
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University of Illinois at Urbana-Champaign, Urbana, IL