Jennifer L. Elster

Optical fiber extrinsic Fabry-Perot interferometric (EFPI)-based biosensors

A novel system incorporating optical fiber extrinsic Fabry- Perot interferometric (EFPI)-based sensors for rapid detection of biological targets is presented. With the appropriate configuration, the EFPI senor is able to measure key environmental parameters by monitoring the interferometric fringes resulting from an optical path differences of reflected signals. The optical fiber EFPI sensor has been demonstrated for strain, pressure, and temperature measurements and can be readily modified for refractive index measurements by allowing solutions to flow into an open cavity. The sensor allows for highly sensitive, real-time, refractive index measurements and by applying affinity coatings containing ligands within this cavity, specific binding of target molecules can be accomplished. As target molecules bind to the coating, there is an increased density within the film, causing a measurable refractive index change that correlates to the concentration of detected target molecules. This sensor platform offers enhanced sensing capabilities for clinical diagnostics, pharmaceutical screening, environmental monitoring, food pathogen detection, biological warfare agent detection, and industrial bioprocessing. Promising applications also exist for process monitoring within the food/beverage, petroleum, and chemical industry.

Optical-fiber-based chemical sensors for detection of corrosion precursors and by-products

Optical fiber sensors are a novel and ideal approach for making chemical and physical measurements in a variety of harsh environments. They do not corrode, are resistant to most chemicals, immune to electromagnetic interference, light weight, inherently small and have a flexible geometry. This paper presents recent test results using optical fiber long-period grating (LPG) sensors to monitor corrosion precursors and by-products. With the appropriate coating, the LPG sensor can be designed to identify a variety of environmental target molecules, such as moisture, pH, sulfates, chlorates, nitrates and metal-ions in otherwise inaccessible regions of metallic structures. Detection of these chemicals can be used to determine if the environment within a particular area of an airplane or infrastructure is becoming conducive to corrosion or whether the corrosion process is active. The LPG sensors offer a clear advantage over similar electrochemical sensors since they can be rendered immune to temperature cross-sensitivity, multiplexed along a single fiber, and can be demodulated using a simple, low-cost spectrum analyzer. By coating the LPG sensor with specially designed affinity coatings that selectively absorb target molecules, selective, real-time monitoring of environmental conditions is possible. This sensing platform shows great promise for corrosion by- product detection in pipe networks, civil infrastructure, process control, and petroleum production operations and can be applied as biological sensors for in-vitro detection of pathogens, and chemical sensors for environmental and industrial process monitoring.

Assessment of Strike of Adult Killer Whales by an OpenHydro Tidal Turbine Blade

Report to DOE on an analysis to determine the effects of a potential impact to an endangered whale from tidal turbines proposed for deployment in Puget Sound.

Kinetic behavior of polymer-coated long-period-grating fiber-optic sensors.

A new method of analysis employing the time-dependent response of long-period-grating (LPG) fiber-optic sensors is introduced. The current kinetic approach allows analysis of the time-dependent wavelength shift of the sensor, in contrast to previous studies, in which the LPG sensing element has been operated in an equilibrium mode and modeled with Langmuir adsorption behavior. A detailed kinetic model presented is based on diffusion of the analyte through the outer protective membrane coating into the affinity coating, which is bound to the fiber cladding. A simpler phenomenological approach presented is based on measurement of the slope of the time-dependent response of the LPG sensor. We demonstrate the principles of the kinetic methods by employing a commercial Cu+2 sensor with a carboxymethylcellulose sensing element. The detailed mathematical model fits the time-dependent behavior well and provides a means of calibrating the concentration-dependent time response. In the current approach, copper concentrations below parts per 10(6) are reliably analyzed. The kinetic model allows early-time measurement for low concentrations of the analyte, where equilibration times are long. This kinetic model should be generally applicable to other affinity-coated LPG fiber-optic sensors.

Flight Demonstration of Fiber Optic Sensors

Luna Innovations has developed a prototype 8-channel fiber optic sensor system to demonstrate fiber optic sensor operation in flight environments. As an intial flight demonstration, long period grating (LPG) relative humidity sensors along with extrinsic Fabry-Perot interferometric (EFPI) pressure and temperature sensors were installed in an aging Delta 767-300ER jet. The fiber optic signal-conditioning system is a multi-purpose platform that can also be used to operate other types of fiber optic LPG and EFPI sensors, including strain gages, metal-ion corrosion sensors, and fiber Bragg grating (FBG) sensors. The system configuration and operation is described.

High-temperature fiber optic strain sensors in fatigue-loading conditions

Optical fiber sensors are used to monitor strain at elevated temperatures on modern high- temperature alloys during cyclic loading. Presented are the application and operation of metal coated silica-based fibers and extrinsic Fabry-Perot strain sensors monitoring fatigue tests at high-temperatures. The resultant strains from varying fatigue cycles and temperatures, from ambient to 2070 degrees F (1132 degrees Celsius), were monitored with surface-attached, short gage length, low finesse Fabry-Perot interferometric optical fiber sensor elements. The results demonstrate that the fiber optic strain sensors are able to withstand extreme temperatures, while maintaining a high level of performance. The capabilities of the fiber optic strain sensors make it possible to monitor material property changes during high- temperature fatigue loading.

Fiber optic affinity ligand sensor for quantification of petroleum and bioremediation

A novel system incorporating optical fiber long-period grating (LPG)-based sensors for rapid detection of biological targets is presented to address the current need for highly responsive, inexpensive, instrumentation for in-situ subsurface bioremediation technologies. With the appropriate configuration, the LPG sensor is able to measure key environmental parameters. The sensor allows for highly sensitive, real-time, refractive index measurements and by applying affinity coatings to the fiber surface, specific binding of molecules can be accomplished using swellable polymers or ligand-based affinity coatings. Advantages of the sensors have are that they are highly responsive, low profile, and can be serially multiplexed within a single-ended probe-like arrangement. This arrangement can be utilized either locally for site characterization or as a distributed sensor to map contaminant levels at multiple depths over a large area. The performance advantages make optical fiber sensors ideal for detection of environmental targets in drinking water, groundwater, soil, and other complex samples. This paper presents recent long-period grating-based sensor results that demonstrate the potential for bioremediation as well as a variety of other chemical and biological sensing applications.