Producing sandwich waveguides Number:7,522,811 from the United States Patent and Trademark Office (PTO) owispatent

Title: Producing sandwich waveguides

Abstract: Complementary surface fabrication processes such as molding, casting, embossing, and so forth, are used to produce articles, structures, or components structured to operate as sandwich waveguides. Resulting complementary surface artifacts include, for example, optical quality surfaces on wall parts, other exposed artifacts that occur where a complementary solid surface contacts non-solid material during fabrication, and sub-surface artifacts such as integrally formed connections between wall parts and base parts. A body whose surface includes a waveguide's inward surfaces, outward surfaces, and light interface surfaces to receive incident light can be formed in a single step, leaving a partially bounded fluidic region that can then be covered to provide a channel that is bounded along a length yet open at its ends; other fluidic, electrical, and optical components can also be attached.

Patent Number: 7,522,811 Issued on 04/21/2009 to Schmidt,   et al.

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Inventors:	Schmidt; Oliver (Palo Alto, CA), Bassler; Michael (Menlo Park, CA), Kiesel; Peter (Palo Alto, CA)
Assignee:	Palo Alto Research Center Incorporated (Palo Alto, CA)
Appl. No.:	11/777,661
Filed:	July 13, 2007

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Current U.S. Class:	385/146 ; 385/129; 385/130
Current International Class:	G02B 6/10 (20060101)
Field of Search:	385/130,146,129

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References Cited [Referenced By]

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U.S. Patent Documents

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6483959	November 2002	Singh et al.
6490034	December 2002	Woias et al.
6558945	May 2003	Kao
6577780	June 2003	Lockhart
6580507	June 2003	Fry et al.
6800849	October 2004	Staats
6856718	February 2005	Kane et al.
6934435	August 2005	Kane
7046357	May 2006	Weinberger et al.
7064836	June 2006	Bechtel et al.
7195465	March 2007	Kane et al.
7248361	July 2007	Kiesel et al.
7268868	September 2007	Kiesel et al.
7358476	April 2008	Kiesel et al.
7386199	June 2008	Schmidt et al.
7456953	November 2008	Schmidt et al.
7479625	January 2009	Kiesel et al.
2002/0155485	October 2002	Kao
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2004/0175734	September 2004	Stahler et al.
2004/0178523	September 2004	Kim et al.
2004/0252957	December 2004	Schmidt et al.
2005/0084203	April 2005	Kane
2005/0249605	November 2005	Kane et al.
2006/0092413	May 2006	Kiesel et al.
2006/0193550	August 2006	Wawro et al.
2006/0268260	November 2006	Liu et al.
2007/0070347	March 2007	Scherer et al.
2007/0116609	May 2007	Baeurle et al.
2007/0145236	June 2007	Kiesel et al.
2007/0145249	June 2007	Kiesel et al.
2007/0146701	June 2007	Kiesel et al.
2007/0146704	June 2007	Schmidt et al.
2007/0146888	June 2007	Schmidt et al.
2007/0147189	June 2007	Schmidt et al.
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2009/0016672	January 2009	Schmidt et al.

Foreign Patent Documents

	WO 00/62050		Oct., 2000		WO
	WO 02/25269		Mar., 2002		WO
	WO 2005/108963		Nov., 2005		WO

Other References

Weismann, R., Kalveram, S., Rudolph, S., Johnck, M., and Neyer, A., "Singlemode polymer waveguides for optical backplanes," Electronics Letters, vol. 32, No. 25, Dec. 5, 1996, pp. 2329-2330. cited by other . Kalvaram, S., and Neyer, A., "Precision moulding techniques for optical waveguide devices," SPIE, vol. 3135, 1997, pp. 2-11. cited by other . Becker, H., and Gartner, C., "Polymer microfabrication methods for microfluidic analytical applications," Electrophoresis, vol. 21, 2000, pp. 12-26. cited by other . Bernini, R., Campopiano, S., and Zeni, L., "Silicon Micromachined Hollow Optical Waveguides for Sensing Applications," IEEE Journal on Selected Topics in Quantum Electronics, vol. 8, No. 1, Jan./Feb. 2002, pp. 106-110. cited by other . Adams, M.L., Enzelberger, M., Quake, S., and Scherer, A., "Microfluidic integration on detector arrays for absorption and fluorescence micro-spectrometers," Sensors and Actuators A, vol. 104, 2003, pp. 25-31. cited by other . Singh, K., Liu, C., Capjack, C., Rozmus, W., and Backhouse, C.J., "Analysis of cellular structure by light scattering measurements in a new cytometer design based on a liquid-core waveguide," IEE Proc.-Nanobiotechnol., vol. 151, No. 1, Feb. 2004, pp. 10-16. cited by other . Kim, J.T., Choi, C.-G., Sung, H.-K., "Polymer-Planar-Lightwave-Circuit-Type Variable Optical Attenuator Fabricated by Hot Embossing Process," ETRI Journal, vol. 27, No. 1, Feb. 2005, pp. 122-125. cited by other . Schmidt, O., Bassler, M., Kiesel, P., Johnson, N.M., and Dohler, G.H., "Guiding light in fluids," Applied Physics Letters, vol. 88, 2006, 151109-1-151109-3. cited by other . Schmidt, O., Bassler, M., Kiesel, P., Johnson, N.M., and Dohler, G.H., "Enhanced light-target interaction using a novel anti-resonant waveguide concept," SPIE Proc. 6094, p. 80, 2006, 9 pages. cited by other . "4-Channel Optical Transceiver Applying 3-Dimensional Polymeric Waveguide," FIND, vol. 24, No. 4, 2006, pp. 1-5. cited by other . Univ. of Dortmund, "Polymeric integrated optic single-mode components-Industrial scale production technologies," printed from www-mst.e-technik.uni-dortmund.de--Mar. 21, 2007, 2 pg. cited by other . Schmidt, O., Bassler, M., Kiesel, P., Knollenberg, C., and Johnson, N., "Fluorescence Spectrometer-on-a-fluidic-chip," Lab Chip, 2007, DOI:10.1039/b618879f, 4 pages. cited by other . Goddard, N.J., Singh, K., Bounaira, F., Holmes, R.J., Baldock, S.J., Pickering, L.W., Fielden, P.R., and Snook, R.D., "Anti-Resonant Reflecting Optical Waveguides (Arrows), as Optimal Optical Detectors for MicroTAS Applications," printed from dias.umist.ac.uk on Aug. 1, 2005, pp. 1-5. cited by other . U.S. Appl. No. 11/777,712, submitted Jul. 13, 2007, 58 pages. cited by other . Notice of Allowance and Fee(s) Due in U.S. Appl. No. 12/098,584, mailed Oct. 6, 2008, 16 pages, published in PAIR. cited by other.

Primary Examiner: Doan; Jennifer
Attorney, Agent or Firm: Leading-Edge Law Group, PLC Beran; James T.

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Government Interests

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This invention was made with Government support under contract N0001405-C-0430 awarded by the Office of Naval Research. The Government has certain rights in the invention.

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Claims

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What is claimed is:

1. A method comprising: producing an article that includes: a body with light-transmissive first and second wall parts; first and second inward surfaces on the first and second wall parts, respectively; the inward surfaces facing each other and being separated by a fluidic region that can contain fluid; first and second outward surfaces on the first and second wall parts, respectively; each outward surface facing away from the fluidic region; the inward and outward surfaces all being approximately parallel; and one or more light interface surfaces, each light interface surface being on one of the first and second wall parts and not being parallel to any of the inward and outward surfaces; the act of producing the article including: performing a complementary surface fabrication process to produce each of the inward and outward surfaces and a set of at least one of the light interface surfaces with a respective portion that has optical quality; the article being structured to operate as a sandwich waveguide with fluid in the fluidic region between the inward surfaces and with light entering the fluidic region through at least one of the set of light interface surfaces.

2. The method of claim 1 in which the act of performing a complementary surface fabrication process produces the first and second inward surfaces, the first and second outward surfaces, and the set of light interface surfaces concurrently.

3. The method of claim 2 in which the act of performing a complementary surface fabrication process produces the first and second inward surfaces, the first and second outward surfaces, and the set of light interface surfaces in a single step.

4. The method of claim 1 in which the act of performing a complementary surface fabrication process includes at least one of molding, casting, and embossing.

5. The method of claim 1 in which the act of performing a complementary surface fabrication process includes one of injection molding and hot embossing.

6. The method of claim 1 in which the act of performing a complementary surface fabrication process includes injection molding a non-solid material, the non-solid material including at least one of acetal, nylon, polypropylene, polycarbonate, acrylonitrile butadiene styrene, polybutylene, polystyrene, and acrylic.

7. The method of claim 1 in which the act of performing a complementary surface fabrication process includes hot embossing a non-solid material, the non-solid material including at least one of polymethyl methacrylate, polycarbonate, polyether imide, polytetrafluoroethylene, and polyetheretherketone.

8. An article of manufacture comprising: a body with light-transmissive first and second wall parts; first and second inward surfaces on the first and second wall parts, respectively; the inward surfaces facing each other and being separated by a fluidic region that can contain fluid; at least a portion of each of the inward surfaces having optical quality; first and second outward surfaces on the first and second wall parts, respectively; each outward surface facing away from the fluidic region; at least a portion of each outward surface having optical quality; the inward and outward surfaces all being approximately parallel; and one or more light interface surfaces, each light interface surface being on one of the first and second wall parts and not being parallel to any of the inward and outward surfaces; each of a set of the light interface surfaces having at least a portion with optical quality; the article being structured to operate as a sandwich waveguide with fluid in the fluidic region between the inward surfaces and with light entering the fluidic region through at least one of the set of light interface surfaces; the article including a set of one or more complementary surface artifacts.

9. The article of claim 8 in which each of the complementary surface artifacts is in at least one of the body, the first and second inward surfaces, the first and second outward surfaces, and the set of light interface surfaces.

10. The article of claim 9 in which the set of complementary surface artifacts includes the portions of the first and second inward surfaces, of the first and second outward portions, and of the set of light interface surfaces that have optical quality.

11. The article of claim 8 in which the set of complementary surface artifacts includes at least one of an exposed artifact and a sub-surface artifact.

12. The article of claim 8 in which the first and second wall parts are approximately equal in height.

13. A device that includes the article of claim 8, the device further including: a cover part connected over the first and second wall parts.

14. The device of claim 13 in which the fluidic region extends in a longitudinal direction between first and second open ends; the device further including: first and second ducting components connected to the article and cover part at the first and second open ends, respectively.

15. The device of claim 13 in which the first and second outward surfaces are structured to provide approximately total internal reflection when the article is operating as a sandwich waveguide; the device further including: a photosensing component that senses light emanating from at least one of the first and second outward surfaces.

16. The device of claim 13, further including: a light source component that provides light that is incident on at least one of the set of light interface surfaces.

17. A method of using the article of claim 8, the method comprising: positioning fluid in the fluidic region; and causing the article to operate as a sandwich waveguide in which light propagates through the fluid in the fluidic region.

18. The method of claim 17 in which the act of causing the article to operate as a sandwich waveguide includes providing incident light on at least one of the light interface surfaces.

19. The method of claim 17, further comprising: while the article operates as a sandwich waveguide, photosensing light emanating from at least one of the first and second outward surfaces.

20. The method of claim 17 in which the act of positioning fluid includes positioning analyte carried by the fluid in the fluidic region, the analyte interacting with the propagating light and, in response, causing light to emanate from the fluidic region.

21. An article of manufacture comprising: an integrally formed body; and on the body, a surface that includes: a base area extending between first and second lateral borders; and first and second inward areas that meet the base area at the first and second lateral borders, respectively, each of the first and second inward areas extending from the base area to a respective open edge; at least a portion of each of the inward areas having optical quality; the first and second inward areas being approximately parallel, facing each other and being separated by a fluidic region that can contain fluid; along a length of the fluidic region, the base area and the first and second inward areas bounding the fluidic region except between the open edges of the first and second inward areas; the body and surface being structured to operate as a sandwich waveguide with fluid in the fluidic region between portions of the inward areas that have optical quality; the article including a set of one or more complementary surface artifacts, each of the artifacts being in at least one of the body and the surface.

22. A method comprising: producing an article that includes: an integrally formed body; and on the body, a surface that includes: a base area extending between first and second lateral borders; and first and second inward areas that meet the base area at the first and second lateral borders, respectively, each of the first and second inward areas extending from the base area to a respective open edge; the first and second inward areas being approximately parallel, facing each other and being separated by a fluidic region that can contain fluid; along a length of the fluidic region, the base area and the first and second inward areas bounding the fluidic region except between the open edges of the first and second inward areas; the act of producing the article including: performing a complementary surface fabrication process to produce the body and the surface with each of the inward areas having a respective portion that has optical quality; the body and surface being structured to operate as a sandwich waveguide with fluid in the fluidic region between portions of the inward areas that have optical quality.

23. An article of manufacture comprising: an integrally formed body; and on the body, a surface that includes: a base area extending between first and second lateral borders; and first and second inward areas that meet the base area at the first and second lateral borders, respectively, each of the first and second inward areas extending from the base area to a respective open edge; at least a portion of each of the inward areas having optical quality; the first and second inward areas being approximately parallel, facing each other and being separated by a fluidic region that can contain fluid; along a length of the fluidic region, the base area and the first and second inward areas bounding the fluidic region except between the open edges of the first and second inward areas; the body including light-transmissive first and second parts, the first and second inward areas being on the first and second parts, respectively; the body and surface being structured to operate as a waveguide with fluid in the fluidic region between portions of the inward areas that have optical quality, the fluid having lower refractive index than the first and second parts; the article including a set of one or more complementary surface artifacts, each of the artifacts being in at least one of the body and the surface.

24. The article of claim 23 in which each of the base area and the first and second inward areas is approximately planar, each of the first and second inward areas being approximately perpendicular to the base area.

25. The article of claim 23 in which the first and second parts are wall parts; the surface further including: first and second outward areas on the first and second parts, respectively; each outward area facing away from the fluidic region; at least a portion of each outward area having optical quality, each outward area portion with optical quality being a complementary surface artifact; the inward and outward areas all being approximately parallel.

26. The article of claim 25 in which the surface further includes: one or more light interface areas, each light interface area being on one of the first and second parts and not being parallel to any of the inward and outward areas; each of a set of the light interface areas having at least a portion with optical quality, each light interface area portion with optical quality being a complementary surface artifact; the body and surface being structured to operate as an anti-resonant waveguide with fluid in the fluidic region and with light entering the fluidic region through at least one of the set of light interface areas.

27. A method of producing the article of claim 23, the method comprising: performing a complementary surface fabrication process to produce the body and the surface with each of the inward areas having a respective portion that has optical quality.

28. The method of claim 27 in which the first and second parts are wall parts; the surface further including: first and second outward areas on the first and second parts, respectively; each outward area facing away from the fluidic region; and one or more light interface areas, each light interface area being on one of the first and second parts and not being parallel to any of the inward and outward areas; the act of performing a complementary surface fabrication process producing the first and second inward areas, the first and second outward areas, and the set of light interface areas concurrently.

29. The method of claim 28 in which the act of performing a complementary surface fabrication process produces the first and second inward areas, the first and second outward areas, and the set of light interface areas in a single step.

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Description

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This application is related to the following applications, each of which is hereby incorporated by reference in its entirety: "Anti-Resonant Waveguide Sensors", U.S. patent application No. 10/976,434, published as U.S. Patent Application Pub. No. 2006/0092413; "Fluorescence Reader Based on Anti-Resonant Waveguide Excitation", U.S. patent application Ser. No. 11/315,797; "Providing Light to Channels or Portions", U.S. patent application Ser. No. 11/316,660; "Producing Fluidic Waveguides", U.S. patent application Ser. No. 11/777,712; and "A Method and Apparatus for Improved Light Distribution in an Anti-Resonant Waveguide Sensor", U.S. patent application Ser. No. 11/777,976.

BACKGROUND OF THE INVENTION

The present invention relates generally to waveguide techniques, such as with waveguides in which facing surfaces are approximately parallel and separated by a region that can contain fluid.

U.S. Patent Application Publication No. 2006/0092413 describes anti-resonant waveguide sensors in which light is guided within a medium between a substrate and a covering layer both made from a transparent material such as glass; the transparent material has an index of refraction slightly higher than the medium, which can be a sample such as a thin film of liquid, gas, or aerosol carrying a target analyte. As a result, an anti-resonant wave can be generated in the medium in accordance with eigensolutions of a Helmholtz equation. Each eigensolution can be called an optical mode, and can be excited by directing a beam of light at the waveguide at a specific angle of incidence. The waveguide can have a tilted entrance facet to minimize reflection of an incident beam; other possible geometries include curved end facets and cylindrical sample shapes. A laser, a source of white light, or a light-emitting diode can provide the incident beam, while detectors can detect light propagating through the sample or scattered, refracted, or fluoresced by the sample, such as with wavelength sensitive elements.

Singh, K., Liu, C., Capjack, C., Rosmus, W., and Backhouse, J., "Analysis of cellular structure by light scattering measurements in a new cytometer design based on a liquid-core waveguide", IEEE Proc.-Nanobiotechnol., Vol. 151, No. 1, February 2004, pp. 10-16, describes a microfluidic optical cytometer used to generate and observe light scattered from biological cells. The cytometer includes a leaky waveguide, and an incoming laser beam can be coupled into the waveguide through a prism at an angle of incidence for a waveguide mode. A waveguide can include a microfluidic channel fabricated on a glass substrate with a glass superstrate, where the liquid microchannel can be a low index waveguide core 10-30 .mu.m deep. One method to form a microchannel structure is to deposit a spin-coated or dip-coated polymer layer on the substrate, about 30 .mu.m thick, and then pattern the layer with desired microchannels, about 1 mm in width. The superstrate is then bonded onto the patterned polymer layer, forming the microchannel waveguide structure. The polymer layer serves to separate the two glass slides, and is not illuminated; photoresist is particularly useful as the polymer layer. Images of scattered light can be taken using an optical microscope and a CCD camera, either to view an image of a cell or to obtain its characteristic scattering pattern.

It would be advantageous to have improved waveguide techniques.

SUMMARY OF THE INVENTION

The invention provides various exemplary embodiments, including products, methods, articles, and devices. In general, the embodiments involve articles, structures, parts, or components that can operate as waveguides.

These and other features and advantages of exemplary embodiments of the invention are described below with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view of an article that can be operated as a sandwich waveguide.

FIG. 2 is cross-sectional view taken along the line 2-2 in FIG. 1.

FIG. 3 is another cross-sectional view taken along the line 3-3 in FIG. 1.

FIG. 4 is a schematic diagram showing how light can propagate through a sandwich waveguide.

FIG. 5 is a cross-sectional view of an article that can be operated as a sandwich waveguide, illustratively along the line 5-5 in FIG. 4.

FIG. 6 is a flowchart showing stages in producing a fluidic structure using components such as the article of FIG. 5.

FIG. 7 is a top view of an article that can be implemented with techniques illustrated in FIGS. 4-6.

FIG. 8 is a cross-sectional view taken along the line 8-8 in FIG. 7.

FIG. 9 is a top view of another article that can be produced with techniques as in FIGS. 4-6.

FIG. 10 is a cross section taken along the line 10-10 in FIG. 9.

FIG. 11 is a top view of a stack of articles that can be produced with techniques as in FIGS. 4-6.

FIG. 12 is a cross-sectional view of the stack of FIG. 11, taken along the line 12-12.

DETAILED DESCRIPTION

In the following detailed description, numeric values and ranges are provided for various aspects of the implementations described. These values and ranges are to be treated as examples only, and are not intended to limit the scope of the claims. In addition, a number of materials are identified as suitable for various facets of the implementations. These materials are to be treated as exemplary, and are not intended to limit the scope of the claims.

"Light" refers herein to electromagnetic radiation of any wavelength or frequency; unless otherwise indicated, a specific value for light wavelength or frequency is that of light propagating through vacuum.

Light can also be described as provided by a "light source," which, unless otherwise specified, refers herein to any device, component, or structure that can provide light of the type described; examples of light sources relevant to the below-described implementations include various kinds of pulsed and unpulsed lasers and laser structures, light emitting diodes (LEDs), superluminescent LEDs (SLEDs), resonant cavity LEDs, sources of broadband light that is spectrally filtered such as with a monochromator, and so forth.

To "propagate" light through a region or structure is to transmit or otherwise cause the light to propagate through the region or structure. The light may be referred to as "propagated light" or "propagating light".

Propagating light can often be usefully characterized by direction of propagation, with direction typically illustrated by one or more rays. Where light changes direction in a way that can be illustrated as a vertex between an incoming ray and one outgoing ray, the change may be referred to as a "reflection"; similarly, to "reflect" light is to cause the light to change its direction of propagation approximately at a surface, referred to herein as a "reflection surface". Where light changes direction at a surface in a way that can be illustrated as a vertex between an incoming ray and two outgoing rays, one on each side of the surface, the change may be referred to as a "refraction", the surface may be referred to as a "refractive surface", and the two outgoing rays may be referred to as "transmitted" and "reflected", consistent with the above definition of reflection. The direction of a transmitted ray depends on the indices of refraction on the two sides of a refractive surface in accordance with well known relationships.

The term "waveguide", as used herein, refers to any combination of one or more components that operate to enable light of at least some energy range to propagate in some range of directions. Propagation of light enabled by a waveguide is sometimes referred to herein as "waveguiding". The term "propagation mode" is used herein to describe waveguiding in which light intensity is sufficiently stable or regular in its variation as a function of time that resulting light intensities can be described as a function of position within a waveguide; each propagation mode can therefore be specified by a respective intensity/position function.

One specific type of waveguide is a "sandwich waveguide", explained in greater detail below. The exemplary implementations described below address problems that arise in producing sandwich waveguides. Most currently known techniques to do so involve operations that are labor intensive and not suitable for mass production. Specifically, mechanical operations such as machining, milling, drilling, and polishing are typically required for each article that operates as a sandwich waveguide. For example, if the article includes glass parts, one of the parts is typically polished to produce a facet through which incident light is received. In addition, where a sandwich waveguide includes fluid, fabrication of fluidic components may also be required.

Articles that operate as sandwich waveguides can include various types of parts and components. As used herein, the term "body" is used with a meaning that relates to the related term "surface": As noted above, propagation of light can change at a surface, such as at a reflection surface or a refractive surface. A "body" is a part or component of material on which such surfaces can exist. The term "surface" can thereby refer to a simple surface such as an "approximately planar surface", meaning a surface area that approximates a plane; the term "surface", however, can also refer to a composite surface that includes a number of surface areas or portions of such areas, any of which can, in an appropriate context, be referred to as a "surface". In addition to being described by shape, surfaces, surface areas, or portions of such areas can be described by position or orientation. Also, surfaces, surface areas, or portions can be described by operation; for example, a "light interface" surface, area, or portion would operate as an interface between light on its two sides, such as a surface, area, or portion at which incident light is received or exiting light is coupled out.

A "light-transmissive" body, component, or part is made of material that allows light transmission through it; where an application requires light within a certain range of photon energies, the term "light-transmissive" refers to light transmission substantially throughout the application's range. A light-transmissive body or its parts may, for example, be "integrally formed" of light-transmissive material, meaning that the body or a larger body from which the body has been produced is a single piece of the light-transmissive material and does not include internal connections formed in some other way after the single piece was formed.

Unless the context indicates otherwise, the terms "circuitry" and "circuit" are used herein to refer to structures in which one or more electronic components have sufficient electrical connections to operate together or in a related manner. In some instances, an item of circuitry can include more than one circuit.

To "photosense" is to sense photons, and to "photosense quantity" of photons is to obtain information indicating a quantity of the photons. The terms "photosensor" and "photosensing component" are used herein to refer generally to any element or combination of elements that senses photons, whether by photosensing quantity or any other information about the photons. A photosensor could, for example, provide an electrical signal or other signal that indicates results of sensing, such as a signal indicating quantity of incident photons.

In the implementations described herein, structures, systems, or parts or components of structures or articles may sometimes be referred to as "attached" to each other or to other structures, articles, parts, or components or visa versa, and operations are performed that "attach" structures, articles, or parts or components of structures or articles to each other or to other things or visa versa; the terms "attached", "attach", and related terms refer to any type of connecting that could be performed in the context. One type of attaching is "mounting", which occurs when a first part or component is attached to a second part or component that functions as a support for the first. In contrast, the more generic term "connecting" includes not only "attaching" and "mounting", but also integrally forming a body or a body's components or parts as described above and making other types of connections such as electrical connections between or among devices or components of circuitry. A combination of one or more parts connected in any way is sometimes referred to herein as a "structure".

A structure may be described by its operation, such as a "support structure" that can operate as a support; similarly, a "waveguide structure" includes parts or components that can operate as a waveguide. In addition, a structure may be characterized by the nature of its parts or the way in which they are connected; for example, a "layered structure" is a structure that includes one or more layers.

Within a structure or other article, components and parts may be referred to in a similar manner. One component of an article that includes a waveguide structure, for example, can be a "photosensing component" or simply "photosensor", as defined above; similarly, a "light source component" includes one or more light sources, which could provide light to a waveguide structure; an "optical component" performs an optical operation; an "electrical component" performs an electrical operation; a "fluidic component" performs a fluidic operation; a "light-transmissive component" transmits light; a "ducting component" performs ducting or operates as a duct; a "covering component" covers something, such as a part, component, or region; a "mounting surface" or "mounting area" is a surface or area on which something can be mounted; and other examples are defined further below. Other parts or components can be characterized by their structure.

Some of the components described herein employ structures with one or more dimensions smaller than 1 mm, and various techniques have been proposed for producing such structures. In particular, some techniques for producing such structures are referred to as "microfabrication." Examples of microfabrication include various techniques for depositing materials such as growth of epitaxial material, sputter deposition, evaporation techniques, plating techniques, spin coating, printing, and other such techniques; techniques for patterning materials, such as etching or otherwise removing exposed regions of thin films through a photolithographically patterned resist layer or other patterned layer; techniques for polishing, planarizing, or otherwise modifying exposed surfaces of materials; and so forth.

An "integrated circuit" or "IC" is a structure with electrical components and connections produced by microfabrication or similar processes. Implementations of ICs described herein include features characterized as "cells" (or "elements") and "arrays", terms that are used with related meanings: An "array" is an arrangement of "cells" or "elements"; unless otherwise indicated by the context, such as for a biological cell, the words "cell" and "element" are used interchangeably herein to mean a cell or an element of an array. An IC includes a "photosensor array" if the IC includes an array of cells, and at least some of the cells include respective photosensors.

In general, some of the structures, elements, and components described herein are supported on a "support structure" or "support surface", which terms are used herein to mean a structure or a structure's surface that can support other structures. More specifically, a support structure could be a "substrate", used herein to mean a support structure on a surface of which other structures can be formed or attached by microfabrication or similar process.

The surface of a substrate or other support surface is treated herein as providing a directional orientation as follows: A direction away from the surface is "up", "over", or "above", while a direction toward the surface is "down", "under", or "below". The terms "upper" and "top" are typically applied to structures, components, or surfaces disposed away from the surface, while "lower" or "underlying" are applied to structures, components, or surfaces disposed toward the surface. In general, it should be understood that the above directional orientation is arbitrary and only for ease of description, and that a support structure or substrate may have any appropriate orientation.

FIGS. 1-3 illustrate an example of article 10 with components that can be operated as a "sandwich waveguide", meaning a waveguide in which two light-transmissive parts or components have facing surfaces that are approximately parallel and separated by a region with a lower refractive index than the light-transmissive components; the light-transmissive components could, for example, include glass or polymer material, and, for operation as a sandwich waveguide, the region between them could, for example, contain a liquid, gas, aerosol, or other fluid with a lower index of refraction; the term "fluid" is used herein to encompass liquids, gasses, and aerosols.

In principle, components could be operated as a sandwich waveguide without being connected, but components of article 10 are connected in such a way that article 10 includes a "sandwich waveguide structure", meaning a structure that can be operated as a sandwich waveguide. In addition, article 10 includes a "fluidic structure", used herein to refer to a structure that depends for its operation on fluid positioning or fluid flow, such as, for liquids or gases, in response to pressure or, for liquids, as a result of surface tension effects. The related term "channel" refers herein to any tube or other enclosed passage within a fluidic structure through which fluid flows during operation. A channel is therefore an example of a "fluidic region", used herein to refer to a region that can contain fluid. An operation "positions" fluid in a channel if it changes the fluid's position in any way that leaves the fluid in the channel.

An object "travels" within a channel or a portion of a channel or is caused "to travel" within a channel or a portion if the object moves through a succession of positions in the channel or portion. Similarly, light "emanates" from a channel or a portion of a channel if the light emanates from one or more objects within the channel or portion, where the term "object" is broadly understood to include even single molecules and small volumes of fluid from which light can emanate.

A channel or portion of a channel is treated herein as providing a directional orientation as follows: A "cross section" lies in a plane perpendicular to a direction in which a local net flow of fluid through the channel or portion can occur; a direction in which a cross section extends can be referred to as a "transverse direction" or a "lateral direction". "Longitudinal direction" is direction perpendicular to a cross section of a channel or portion; since longitudinal direction can differ for different cross sections, longitudinal direction may not be linear, but could include one or more curves or bends. Similarly, "length" of a channel or portion is measured in its longitudinal direction, and the term "lengthwise" similarly refers to motion or extent in a longitudinal direction of a channel or portion. Relative to a longitudinal direction, an "oblique direction" is a direction that is neither parallel to nor perpendicular to the longitudinal direction. A channel or portion with approximately uniform cross section and substantially linear longitudinal direction can be referred to as "straight", and the channels and portions described herein are generally straight unless otherwise indicated.

In order to contain fluid, a channel or other fluidic region is typically "bounded", meaning that surfaces or surface areas bound it on at least some sides. A "boundary" of a channel or portion is the surface or combination of surfaces within which fluid contained in the channel is confined. A "port" is an opening that extends through the boundary of a channel or portion such that fluid can enter or exit through the port; in general, a port is relatively small compared to the length of the channel or portion, and the boundary is treated as extending across the port as if the port did not exist. In a given cross section of a channel or portion it may therefore be "surrounded" along most of its boundary by material, meaning that more than half of its boundary in the cross section is bounded by material rather than being a port or ports.

FIG. 1 shows article 10 in a top view through one of the two light-transmissive components. In this view, the inner region between the light-transmissive components includes two main portions, channel portion 12 that can contain fluid and non-channel portion 14 that surrounds channel portion 12; channel portion is illustratively shaped like a "T", but could instead have an L-shape or any other suitable shape. Between portions 12 and 14 is groove 16, which can be more fully understood from FIGS. 2 and 3. Ports 18 are openings through one of the light-transmissive components, allowing entry and exit of fluid into and out of channel portion 12.

The cross section in FIG. 2 shows how light-transmissive components 20 and 22 are separated by spacers 24. As explained in greater detail below, components 20 and 22 can include acrylic, and non-channel portion 14 can be filled with epoxy material that seals a boundary around channel portion 12 and that also contains spacers 24, such as glass microspheres in suspension. In one implementation, channel portion 12 was 5 mm wide, but could have any suitable width.

The cross section in FIG. 3 further illustrates how light-transmissive component 20 has oblique surface 30, a light interface surface that is illustratively at an angle of approximately 45.degree. to the inward-facing surfaces of components 20 and 22. As a result, incident excitation light at a direction approximately perpendicular to surface 30, as illustrated by arrow 32, can cause and couple with light propagating through channel portion 12, as illustrated by arrow 34 (FIG. 4, described below, illustrates more accurately how light would propagate through channel portion 12). Article 10 therefore includes a sandwich waveguide structure as defined above. Alternatively, light propagating in such a waveguide can also couple out of the waveguide through an interface surface such as surface 30.

In the illustrated implementation, the end of channel portion 12 at right in FIG. 3 is open, providing an additional port 36 through which fluid can enter into or exit out of channel portion 12. Alternatively, article 10, instead of ending at transverse end surface 38, could extend to another area with ports similar to ports 18, such as with a part symmetrical about the position of surface 38; in this case, fluid could flow through channel portion 12 between ports 18 and similar ports at the opposite end of channel portion 12.

Articles similar to article 10 in FIGS. 1-3 have been successfully fabricated with a process described below, using light-transmissive components 20 and 22 made from acrylic and ultraviolet (UV) curable epoxy injected into non-channel portion 14. Schmidt, O., Bassler, M., Kiesel, P., Knollenberg, C., and Johnson, N., "Fluorescence Spectrometer-on-a-fluidic-chip", Lab on a Chip, 2007, DOI: 10.1039/b618879f, incorporated herein by reference, describes results obtained with such an implementation. The process is not, however, well-suited for mass production, in part because it is labor-intensive.

The process can begin by cutting equal area pieces of a large acrylic sheet with a laser cutter, with one piece being for light-transmissive component 20 and another being for light-transmissive component 22. In one implementation, a 1.5 mm thick acrylic sheet was used, and each light-transmissive component was a rectangle measuring 25 mm.times.75 mm. Treating light-transmissive component 22 as a substrate, a mirror can then be evaporated onto its lower or upper surface, the surface that will be disposed away from or towards component 20. Light-transmissive component 20 can be polished to produce oblique surface 30 of optical quality and with an appropriate angle for incident light, i.e. an angle at which incident light can couple with light propagating within channel portion 12. As with component 22, mirrors can be evaporated, such as on end surfaces 38 and 40, to provide a form of light recycling within channel portion 12. Techniques that employ mirrors are described in greater detail in co-pending U.S. patent application Ser. No. 11/777,976, entitled "A Method and Apparatus for Improved Light Distribution in an Anti-Resonant Waveguide Sensor" and incorporated herein in its entirety. Also, 50 .mu.m deep groove 16 can be formed in the lower surface of component 20 or upper surface of component 22, and ports 18 can also be formed, all using a laser cutter or drill.

When components 20 and 22 are fully prepared, spacers 24 can be positioned on the upper surface of component 22, i.e. the surface that will be disposed toward the lower surface of component 20. In one successful implementation, each spacer 24 was a glass microsphere with a diameter of 100 .mu.m and spacers were positioned by depositing drops of UV curable epoxy that included spacers. Then, component 20 was positioned in alignment with component 22 and mounted on it to form a sandwich structure in which spacers 24 defined a distance between components 20 and 22, the distance that also serves as the height of channel portion 12. UV light was then applied to cure the epoxy in which spacers 24 were deposited.

Non-channel portion 14 can then be filled with UV curable epoxy to seal channel portion 12 so that fluid is held within it. This has been successfully accomplished by using capillary force suction to inject pure, low viscosity UV curable epoxy into non-channel portion 14 from the side of the sandwich structure with spacers. Epoxy injected in this manner stops flowing when it reaches groove 16. Then, UV light can be applied to cure the epoxy in non-channel portion 14.

Rather than using spacers and injected epoxy, an appropriate polymer material such as SU-8 could be deposited on the upper surface of component 22 and photolithographically removed from channel portion 12. In this alternative implementation, the polymer layer portion remaining after photolithography would seal channel portion 12 and would also determine distance between components 20 and 22. Similarly, a double-sided tape can be used such as 501FL or 9461P tape from 3M Company. Channel portion 12 can be cut out of the tape with a laser cutter before the tape is applied to surfaces of components 20 and 22.

After producing a structure as described above, additional operations can be performed to attach fluidic components such as tubing 42 and 44 (FIGS. 2 and 3) and also optical and electrical components. For example, such operations could attach one or more light sources and one or more photosensing components that, for example, include optical fibers and spectrometers or include one or more ICs positioned along channel portion 12, such as with techniques described in U.S. patent application Ser. No. 11/316,660, entitled "Providing Light to Channels or Portions", and incorporated herein by reference, or receiving emanating light through an imaging component such as a lens.

In exemplary implementations, a cross section of channel portion 12 can be 3 mm wide and as high as the distance between components 20 and 22, which can be determined by the diameter of spacers 24. Rather than 100 .mu.m spacers as mentioned above, spacers of other diameters could be used, such as 25 .mu.m. Various other thicknesses of acrylic could be used for components 20 and 22, such as 1.0 mm.

Article 10 in FIGS. 1-3 provides an initial example of an article, structure, or component that is "structured to operate as a sandwich waveguide", an expression that is used herein to refer to a combination of structural features that allow sandwich waveguide operation. Such an article, structure, component, or part is sometimes treated herein as providing a directional orientation as follows: Facing surfaces that are approximately parallel are referred to as "inward surfaces", while surfaces that face away from the region between the inward surfaces are referred to as "outward surfaces".

FIG. 4 illustrates schematically one example of how light can propagate through a sandwich waveguide such as that provided by article 10 in response to incident light similar to that represented by arrow 32 in FIG. 3. In FIG. 4, waveguide 100 illustratively includes four surfaces between regions of different refractive indices. Inner surfaces 102 and 104 are on either side of a channel that can contain fluid, with a refractive index of n.sub.f; the fluid can carry analytes or objects through the channel as described in U.S. patent application Ser. No. 11/316,660, entitled "Providing Light to Channels or Portions" and incorporated herein by reference. Outer surface 106 is at the opposite side of light-transmissive component 108 with a refractive index n.sub.h1>n.sub.f. Incident surface 109 is illustratively a light interface surface that receives incident light from illumination component 110, such as in one of the ways illustrated by arrows 112 and 114. Outer surface 116 is on the opposite side of light-transmissive component 118 with refractive index n.sub.h2>n.sub.f.

Regions outside surfaces 106 and 116 can be filled, for example, with air or another substance with a refractive index n.sub.0<n.sub.f. As a result, virtually all incident light from component 110 is confined between outer surfaces 106 and 116 due to total internal reflection (TIR), and one of a number of possible propagation modes can be excited in which the majority of light intensity is in the channel between surfaces 102 and 104. This is suggested schematically by rays 120, 122, and 124 which propagate within channel portion 12.

Various examples of propagation modes referred to as "anti-resonant waveguide modes" are described in Kiesel, et al., U.S. Patent Application Publication No. 2006/0092413; U.S. patent application Ser. No. 11/316,660, entitled "Providing Light to Channels or Portions"; and U.S. patent application Ser. No. 11/315,797, entitled "Fluorescent Reader Based on Anti-Resonant Waveguide Excitation", all of which are incorporated herein by re