Hydrocarbon Sensing Methods and Apparatus

Patent metadata

Field	Value
Publication number	US-2016116403-A1
Application number	US-201414889839-A
Country	US
Kind code	A1
Filing date	May 8, 2014
Priority date	May 8, 2013
Publication date	Apr 28, 2016
Grant date	—

Abstract

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.

First claim

1 . An apparatus for sensing a hydrocarbon, the apparatus comprising:
a waveguide comprising:
a core;
a first cladding layer disposed on a first side of the core; and
a second cladding layer disposed on a second side of the core, the second cladding layer comprising a continuous film of at least one hydrophobic polymer, the continuous film defining (i) a first measurement region having a first surface with a first hydrophobicity and (ii) a second sensing region having a second surface with a second hydrophobicity greater than the first hydrophobicity;
at least one first photodetector, disposed opposite the core from the first measurement region, to sense an intensity of light evanescently coupled out of the waveguide in the first measurement region; and at least one second photodetector, disposed opposite the core from the second sensing region, to sense a change in intensity of light evanescently coupled out of the waveguide in the second sensing region due to a change in refractive index in the at least one hydrophobic polymer caused by diffusion of the hydrocarbon into the at least one hydrophobic polymer via the second surface.

2 . The apparatus of claim 1 , wherein the hydrocarbon comprises at least one of an aromatic hydrocarbon, a polyaromatic hydrocarbon, benzene, toluene, ethylbenzene, or xylene.

3 . The apparatus of claim 1 , wherein the waveguide is a single-mode waveguide.

4 . The apparatus of claim 1 , wherein the first measurement region comprises:
a hydrophilic material, disposed on the continuous film of at least one hydrophobic polymer, to inhibit diffusion of the hydrocarbon into the at least one hydrophobic polymer, the hydrophilic material defining the first surface.

5 . The apparatus of claim 4 , wherein the second surface is etched to provide the second hydrophobicity.

6 . The apparatus of claim 5 , wherein the second surface is oxygen plasma etched to provide the second hydrophobicity.

7 . The apparatus of claim 1 , wherein the second surface is textured to provide the second hydrophobicity.

8 . The apparatus of claim 1 , wherein:
the first measurement region comprises the at least one hydrophobic polymer disposed at a first thickness on the core, and the second measurement region comprises the at least one hydrophobic polymer disposed at a second thickness on the core, the second thickness being smaller than the first thickness.

9 . The apparatus of claim 1 , wherein the continuous film comprises a plurality of layers of the at least one hydrophobic polymer.

10 . The apparatus of claim 9 , wherein a surface of at least one layer in the plurality of layers is oxygen plasma etched.

11 . The apparatus of claim 1 , wherein the at least one hydrophobic polymer comprises:
a first hydrophobic polymer to detect a first type of hydrocarbon; and a second hydrophobic polymer to detect a second type of hydrocarbon.

12 . The apparatus of claim 1 , further comprising:
a processor, operably coupled to the at least one first detector and the at least one second detector, to determine the presence of the hydrocarbon based on (i) the intensity of light sensed by the at least one first photodetector and (ii) the change in intensity of light sensed by the at least one second photodetector.

13 . A method of sensing a hydrocarbon, the method comprising:
(A) coupling light into a waveguide comprising a core, a first cladding layer disposed on a first side of the core, and a second cladding layer disposed on a second side of the core, the second cladding layer comprising a continuous film of at least one hydrophobic polymer that defines (i) a first measurement region having a first surface with a first hydrophobicity and (ii) a second measurement region having a second surface with a second hydrophobicity greater than the first hydrophobicity; (B) exposing the second surface to a solution containing the hydrocarbon so as to cause a change in refractive index of the at least one hydrophobic polymer in the first measurement region via diffusion of the hydrocarbon into the at least one hydrophobic polymer; and (C) sensing a change in intensity of light evanescently coupled out of the waveguide in the second measurement region due to the change in refractive index in (B).

14 . The method of claim 13 , wherein the hydrocarbon comprises at least one of an aromatic hydrocarbon, a polyaromatic hydrocarbon, benzene, toluene, ethylbenzene, or xylene.

15 . The method of claim 13 , wherein (B) further comprises:
allowing the solution containing the hydrocarbon to diffuse through an etched portion of the second surface.

16 . The method of claim 13 , wherein (B) further comprises:
allowing the hydrocarbon to diffuse through a plurality of layers of the at least one hydrophobic polymer.

17 . The method of claim 13 , wherein (B) further comprises:
exposing the first measurement region to the solution containing the hydrocarbon.

18 . The method of claim 17 , wherein (B) further comprises:
inhibiting diffusion of the hydrocarbon into the first measurement region.

19 . The method of claim 13 , wherein (C) comprises sensing the change in intensity in less than about 10 minutes.

20 . The method of claim 13 , further comprising:
(D) sensing an intensity of light evanescently coupled out of the waveguide in the first measurement region; and

21 . The method of claim 20 , further comprising:
(E) determining the presence of the hydrocarbon based on (i) the intensity of light sensed in (C) and (ii) the change in intensity of light sensed in (D).

22 . An apparatus for sensing a hydrocarbon, the apparatus comprising:
a single-mode waveguide comprising a first cladding layer, a second cladding layer defining a measurement region comprising a hydrophobic material, and a core disposed between the first cladding layer and the second cladding layer; and at least one photodetector, in optical communication with the single-mode waveguide, to sense a change in intensity of light guided by the waveguide due to a change in refractive index of the measurement region of the second cladding layer caused by diffusion of the hydrocarbon into the hydrophobic material.

23 . A method of sensing a presence of a hydrocarbon with a waveguide that comprises a first cladding layer, a second cladding layer defining a measurement region comprising a hydrophobic material, and a core disposed between the first cladding layer and the second cladding layer, the method comprising:
(A) coupling light in the waveguide; (B) exposing the measurement region to the hydrocarbon so as to cause the hydrocarbon to diffuse into the hydrophobic material, thereby causing a change in a refractive index of the hydrophobic material; (C) measuring a change in intensity distribution of light evanescently coupled into the first cladding layer caused by diffusion of the hydrocarbon into the hydrophobic polymer in (B); (D) determining the presence of the hydrocarbon based at least in part on the change in intensity distribution measured in (C).

24 . A method of measuring a change in a hydrocarbon concentration of a solution, the method comprising:
(A) coupling light into a single-mode waveguide that comprises a hydrophobic cladding; (B) exposing the hydrophobic cladding to the solution so as to cause a hydrocarbon to diffuse from the solution into the hydrophobic cladding; (C) measuring a change in intensity of light evanescently coupled

Assignees

• Univ Colorado State Res Found

Inventors

• Lear Kevin
• Erickson Timothy

Classifications

• G02B2006/12123

  Diode · CPC title

• G02B6/4291

  by accessing the evanescent field of the light guide · CPC title

• G02B6/12004

  Combinations of two or more optical elements · CPC title

• G01N21/4133 Primary

  Refractometers, e.g. differential · CPC title

• G02B6/1221 Primary

  made from organic materials · CPC title