Anthony A. Boiarski

Fiber Optic Particle Concentration Sensor

A particle concentration sensor would be useful in many industrial process monitoring applications where in situ measurements are required. These applications include determination of butterfat content of milk, percent insolubles in engine oil, and cell concentration in a bioreactor. A fiber optic probe was designed to measure particle concentration by monitoring the scattered light from the particle-light interaction at the end of a fiber-optic-based probe tip. Linear output was obtained from the sensor over a large range of particle loading for a suspension of 1.7 μm polystyrene microspheres in water and E. coli bacteria in a fermenter.

Integrated optic sensor with macro-flow cell

An integrated-optic channel waveguide device is configured as a biosensor. The device measures a refractive index change on the waveguide surface, so it is called a biorefractometer. With an appropriate overlay or selective coating, the device can monitor proteins in blood or pollutants and bio-warfare agents in water. We describe the design, fabrication, and testing of a sensor employing a waveguide Mach-Zehnder interferometer configuration. The device is fabricated in a glass substrate using potassium ion exchange. A patterned glass buffer layer defines the sensing and reference arms of the interferometer. A silicone-rubber macro-flow cell confines the liquid above the integrated-optical waveguide device. Salt solution data show that the biorefractometer has a sensitivity ((Delta) neff/(Delta) nLiquid) of 2 X 10-3 and can measure refractive index changes of about 0.005. Data obtained for antigen-antibody binding of the protein IgG indicate that a 10 percent signal change occurs in approximately 1 minute for a 10 (mu) g/ml concentration level.

Integrated Optic Biosensor for Environmental Monitoring

An integrated-optic biosensor monitors the concentration of liquid pollutants on the surface of a planar substrate composing single-mode channel waveguides. The concept uses a Mach- Zehnder interferometer structure to measure thickness and/or refractive index changes on the waveguide surface. These changes occur as pollutant molecules interact directly with the interferometers active arm or with a hydrophobic coating on the surface of the arm. Interferometer output data were obtained for various solutions including PPM levels of benzene and toluene in water. Theoretical analysis indicated that a hydrophobic coating on the waveguide would provide sensor specificity and detect pollutants at PPB levels.

Integrated optic sensor for measuring aflatoxin-B1 in corn

An integrated optic refractometer device was developed to perform a rapid one-step, homogeneous immunoassay. The device measures refractive index changes at the surface of a planar, singlemode, ion-exchange waveguide using difference interferometry. Anti-aflatoxin- B1 antibodies were attached to the waveguide surface to provide a bioselective coating for detecting and quantifying the aflatoxin-B1 antigen level in a sample. The detection limit of this small antigen must be determined using a competitive assay format. To determine feasibility of the competitive assay, we determined the biosensor response to a larger molecular weight competing antigen, namely HRP-labeled aflatoxin-B1. This labeled antigen will compete with unlabeled aflatoxin for binding sites on the sensor surface. Increased sample aflatoxin levels will result in a decreased time-dependent phase change of the helium-neon laser light beam. Phase change data were determined for various concentration levels of HRP-labeled aflatoxin- B1 antigen. The assay measurements were made over a 5-minute time period. Results indicated that a competitive assay is feasible. Future assay efforts should be able to demonstrate measurement of aflatoxin-B levels found in contaminated corn samples.

Integrated optic biosensor

A micro-sized biosensor is formed using integrated-optic channel waveguides in a Mach- Zehnder interferometer configuration. The device measures refractive index changes on the waveguide surface, so it is called a biorefractometer. With an appropriate overlay or selective coating, the sensor can monitor proteins in blood or pollutants and bio-warfare agents in water. The waveguides are fabricated in a glass substrate using potassium ion exchange. A patterned glass buffer layer defines the interferometers sensing and reference arms. A silicone-rubber cell arrangement brings sample analytes into contact with proteins immobilized on the integrated-optical waveguide surface. Data obtained for antigen-antibody binding of the proteins human Immunoglobulin-G and staph enterotoxin-B indicate that a 50 - 100 ng/ml concentration levels can be measured in less than ten minutes.

Integrated optic device for biochemical sensing

A novel immunosensor concept monitors antigen-antibody binding on the surface of a planar single-mode waveguide. The concept can be used as the basis for a label-free homogeneous immunoassay because only changes in the thickness and refractive index of the antigen-antibody layer are monitored by observing small changes in the effective index of the waveguide. BSA +anti- BSA binding was examined theoretically using a four-layer model and effective index measurements were obtained which agreed with the calculated values. Analysis indicated that the small effective index changes can possibly be measured with high sensitivity and at low cost using an integrated optic interferometer format.

High spatial resolution distributed fiber optic temperature sensor

A distributed fiber optic temperature sensing system was developed which consisted of a high-resolution optical time domain reflectometer (OTOR) and a special optical fiber sensor. Several 1 kilometer lengths of prototype sensing fibers were formed by coating a modified, ultraviolet light curable polymer cladding material onto a core glass during fiber production. By monitoring changes in Rayleigh backscattered light from the fiber; local temperature changes were measured along the fiber length. A demonstration system was assembled with a 20 meter sensing fiber and extensive data were collected. These measurements indicated that hot spots as small as 10 cm could be detected over a temperature range of 0 to 150°C with a measurement accuracy of ±°C

Integrated optic immunoassay for virus detection

An integrated optic refractometer device was developed to perform a rapid one-step, label-free immunoassay. The device measures refractive index changes at the surface of a planar waveguide using interferometry. Antibodies were applied to the waveguide surface to provide a bioselective coating for detecting and quantifying a specific antigen of interest. The detection limit of this biosensor was determined for adenovirus as a model for other viral analytes of military, medical, and environmental interest. As binding of the antigen occurred on the sensor surface, a time-dependent phase shift of the helium-neon laser light beam was detected and was measured over a 10-minute time period. Adenovirus was detected at levels of 250 - 2500 viral particles/ml. This detection limit was obtained for a mono-layer of antibody attached to the sensor. Use of a high-density, multi-layer antibody coating approach resulted in improved detection limits for bacteria and protein analytes of general interest.