Colorado State University Research Foundation

Timothy A Erickson

Kevin L Lear

A sensor for hydrocarbons uses a waveguide with a first cladding layer, a second cladding layer with a measurement region with hydrophobic measurement material, and a core between the first and second cladding layers. Light is coupled into the waveguide. The measurement material is exposed to the hydrocarbon allowing the hydrocarbon to diffuse into it and change refractive index of the material, which changes intensity of light evanescently coupled through the first cladding layer. Light coupled through the first cladding layer is measured to determine exposure of the sensor to the hydrocarbons.

Hydrocarbon sensing methods and apparatus

A chip-scale, reusable sensor can detect aromatic hydrocarbons, such as benzene, toluene, ethylbenzene, and xylenes (BTEX), rapidly in water without sample preparation. The device is capable of real-time, continuous monitoring for BTEX solutes, which diffuse into a film, such as a polymer, on the sensors surface. In operation, BTEX analytes concentrate in the film, causing an increase in refractive index, which modulates evanescent coupling into the chips integrated photodetector array. Integration of the photodetector array simplifies system instrumentation and permits incorporation of an on-chip photocurrent reference region in the immediate vicinity of the sensing region, reducing drift due to temperature fluctuations. In some examples, the chip responds linearly for BTEX concentrations between 1 ppm and 30 ppm, with a limit of detection of 359 ppb, 249 ppb, and 103 ppb for benzene, toluene, and xylene in water, respectively.

An analyte-detection system has an optical waveguide with first and second cladding layers adjacent a core; a light source coupled to provide light to the waveguide; a photodetector such as a metal-semiconductor-metal, vertical PIN, or horizontal PIN photodetectors, the photodetector having an absorber configured to detect light escaping from the waveguide through the first cladding layer; multiple, separate, photocurrent collectors, where each photocurrent collector collects current from a separate portion of the photodetector absorber; and at least one current-sensing amplifier for receiving photocurrent. The photodetector absorber is an undivided absorber region for multiple photocurrent collectors. Either separate amplifiers are provided for each of the multiple photocurrent collection lines, or multiplexing logic couples selected photocurrent collectors to amplifiers, while coupling unselected photocurrent collectors to a bias generator.

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Beaverton, OR, United States of America

Timothy A Erickson