Abstract:
An apparatus for simultaneously aligning and interconnecting microfluidic ports is presented. Such interconnections are required to utilize microfluidic devices fabricated in Micro-Electromechanical-Systems (MEMS) technologies, that have multiple fluidic access ports (e.g. 100 micron diameter) within a small footprint, (e.g. 3 mm×6 mm). Fanout of the small ports of a microfluidic device to a larger diameter (e.g. 500 microns) facilitates packaging and interconnection of the microfluidic device to printed wiring boards, electronics packages, fluidic manifolds etc.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     The United States Government has rights in this invention pursuant to Department of Energy Contract No. DE-AC04-94AL85000 with Sandia Corporation. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates generally to the packaging of, and electrical, optical and fluidic interconnections to microfluidic, electro-microfluidic, and optical-electro-microfluidic devices. 
     Microfluidic devices may simultaneously require fluidic, optical and/or electrical interconnection. Within the context of this invention, the terms “microfluidic device”, “electro-microfluidic device”, “optical-microfluidic device”, “optical-electro-microfluidic device” and simply “device”, all refer to devices requiring microfluidic interconnects, and are used interchangeably. 
     Microfluidic devices, are generally fabricated in silicon, and control or utilize the flow of a fluid (e.g. liquid or gas). Microfluidic devices typically have very small fluidic access ports, e.g. on the order of 100 microns in diameter; have a small overall footprint e.g. 3 mm×6 mm; and are commonly made in silicon using processes developed by the Micro-Electromechanical-Systems (MEMS) and semiconductor integrated circuit (IC) industry. These devices may utilize MEMS elements, e.g. chemical sensors, biosensors, micro-valves, micro-pumps, micro-heaters, micro-pressure transducers, micro-flow sensors, micro-electrophoresis columns for DNA analysis, micro-heat exchangers, micro-chem-lab-on-a-chip, etc. Microfluidic devices have uses in biomedical, chemical analysis, power generation, drop ejection applications and in the production of ink jet printer heads. The latter of which combines electric and fluidic functions on a low-cost, integrated platform. Typically the use of microfluidics in these applications requires the integration of other technologies with the microfluidic devices. For example: optical means may be used to sense genetic content, electronics may be used for chemical sensing, electro-magnetics may be required for electrical power generation, or electrical power may be required for thermal drop ejection. 
     MEMS microfluidic devices may be fabricated by either bulk micromachining methods, or by surface micromachining technologies. Surface micromachining produces fluidic channel dimensions that are smaller than for bulk micromachining. For example, a typical bulk micromachined channel may have a channel depth of 50 to 100 microns (0.002 to 0.004 inches), whereas a typical surface micromachined channel depth may be on the order of 1 to 5 microns (0.00008 to 0.0002 inches). Making a reliable fluidic connection between two channels having microscale dimensions (e.g. 100 microns or less) is a critical problem. The application of a microfluidic device may require fluidic connection and transitioning from the microscale, e.g. dimensions on the order of 100 microns or less, to the mesoscale, e.g. dimensions on the order of 500 microns, to the macroscale, e.g. dimensions on the order of 1 mm ( 1/16 inch). Where at the macroscale, fluidic interconnections may be made by conventional tubing or SWAGELOK™ (Swagelok, Inc., Solon, Ohio) connectors. 
     Another difficulty encountered in packaging microfluidic devices is that multiple fluidic interconnections often need to be made in a very small area. For example: Tens of very small (e.g. 10 to 200 micron diameter inlet and outlet ports) fluidic connections may be required within the area of a typical microfluidic device (e.g. on the order of 3 mm×6 mm). These fluidic connections may be closely spaced (e.g. 300 to 500 microns between fluidic connecting ports) and may require precise alignment (on the order of 1 to 10 microns). Attempts to manually assemble multiple micro-fluidic connections, within the required alignment tolerances, can prove difficult, labor-intensive and costly. See for example: Galambos, et. al, “Packaging Dissimilar Materials for Microfluidic Applications”, Proceedings of IMECE&#39;02, 2002 ASME International Mechanical Engineering Congress and Exposition, New Orleans, La., Nov. 17–22, 2002. 
     What is needed is a system for interconnection to microfluidic devices that can provide; multiple interconnections in a small area, alignment precision on the order of 1 to 10 microns, be leak tight, easy to assemble, chemically resistant, possess a low dead volume, have smooth fluidic transitions, and be low cost to assemble, and be amenable to automated assembly. Additionally what is needed is a packaging approach that can provide microfluidic, electrical and optical interconnections, for integrating fluidic, electrical, optical, and hybrid devices that can contain a combination of functionality. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are incorporated in and form part of the specification, illustrate several embodiments of the present invention and, together with the description, serve to explain the principles of the invention. The drawings provided herein are not drawn to scale. 
         FIG. 1A  illustrates the upper surface of an electro-microfluidic device. 
         FIG. 1B  illustrates the lower surface of an electro-microfluidic device. 
         FIG. 1C  is a cross-section of an electro-microfluidic device. 
         FIG. 2A  is a perspective view of an embodiment of the invention. 
         FIG. 2B  is a cross-section of the embodiment in  FIG. 2A . 
         FIG. 3  is a cross-section of another embodiment of the invention. 
         FIG. 4A  is a perspective view of another embodiment of the invention. 
         FIG. 4B  is a cross-section of the embodiment in  FIG. 4A . 
         FIG. 5  is a cross-section of another embodiment of the invention. 
         FIG. 6A  is a cross-section of another embodiment of the invention. 
         FIG. 6B  is a top view of the embodiment in  FIG. 6A . 
         FIG. 7  is a cross-section of another embodiment of the invention. 
         FIG. 8  is a cross-section of another embodiment of the invention. 
         FIG. 9  is a cross-section of another embodiment of the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1A through 1C  illustrate a typical microfluidic device  30  having a top surface  34  and opposed lower surface  36 .  FIG. 1A  is a view of the top surface of microfluidic device  30 ,  FIG. 1B  is a view of the opposed lower surface of the device and  FIG. 1C  is a cross sectional view of the device. The microfluidic device  30  may be formed using bulk micromachining methods, or by surface micro-machining methods as described in U.S. Pat. No. 6,537,437 to Galambos et. al., herein incorporated by reference, and referred to in the following as the &#39;437 patent. As used in the context of this specification, the term “microfluidic device” or simply a “device” refers to any device requiring microfluidic connections and includes devices additionally requiring electrical and/or optical interconnections, e.g. “electro-microfluidic” and “opto-electro-microfluidic” devices. Microfluidic devices typically have very small fluidic access ports, e.g. 100 micron diameter; have a small overall footprint e.g. 3 mm×6 mm; and are commonly made in silicon using processes developed by the MEMS and semiconductor IC industries. 
     Referring to  FIG. 1A , microfluidic device  30  may con contain multiple functional elements  42  including: chemical sensors, biosensors, valves, pumps, heaters, pressure transducers, flow sensors, electrophoresis columns for DNA analysis, heat exchangers, chem-lab on a chip, etc. Microfluidic functional elements  42  may be disposed along a fluidic pathway  32 , fabricated in microfluidic device  30 . Microfluidic pathways  32  can be terminated at a fluidic access port. A fluidic access port may comprise a fluidic opening  40 , in fluid communication with fluidic pathway  32 , wherein fluidic opening  40  is disposed on the bounding surface of cavity  38 . Functional elements  42  may require fluidic, electrical and optical interconnection to other functional elements within the same device  30 , to other microfluidic devices, or interconnection to electro-microfluidic packaging, fluidic printed wiring boards, power supplies, fluid sources, fluid delivery tubing and piping, support electronics, data collection and processing systems, etc. Electrical connections as required, can be accomplished through conductive bond pads  44 , disposed on a surface of device  30 , where the conductive bond pads are electrically connected to circuitry as may be fabricated in device  30 . 
     Referring to  FIG. 1B , there can be a multiple of cavities  38  within the footprint (e.g. on the order of 3 mm×6 mm) of device  30 . 
     Referring to  FIG. 1C , fluidic pathway  32  may be formed on the top surface  34  of device  30 , and be fluidically connected to fluidic opening  0 . 40  disposed on the bounding surface  39  of cavity  38 . Fluidic pathway  32  may be on the order of 1 to 5 microns in cross-sectional dimension, fluidic opening  40  may be on the order of 20 to 100 microns in diameter, and cavity  38  may be on the order of 100 to 500 microns in diameter. For illustrative purposes cavities  38  are shown as cylindrical features extending into the bulk of device  30  from the lower surface  36 . For the purposes of the present invention, the cavity can comprise any geometric or irregular shape, defined by a bounding surface  39 , whereupon fluidic opening  40  is disposed. 
       FIG. 2A  shows an embodiment of the present invention, wherein a substrate  46  has an upper surface  48  and an opposed lower surface  50 . Substrate  46  is generally planar and may be fabricated from silicon, glass, ceramic, polymeric or metallic materials. Disposed on upper surface  48  are one or more raised extensions  52 . A fluidic opening  54  may be disposed on the bounding surface  56  of extension  52 . Fluidic opening  54  can be connected to fluidic pathway  58  within substrate  46 . A plurality of fluidic pathways  58  may extend through the thickness of substrate  46 , or may traverse laterally through the bulk of the substrate, interconnecting with other fluidic pathways, and may interconnect one or more fluidic openings  54 . Fluidic opening  54  may be on the order of 20 to 100 microns in diameter. Extension  52 , may be on the order of 100 to 500 microns in diameter. The bounding surface  56  of an extension may be spaced from upper surface  48  by a distance on the order of 100 to 500 microns. For illustrative purposes extensions  52  are shown as cylindrical features extending outward from upper surface  48 . For the purposes of the present invention, the extensions can comprise any geometric or irregular shape, defined by a bounding surface  56 , whereon fluidic opening  54  is disposed. One or more extensions  52 , may extend from upper surface  48  of substrate  46 , and may be spaced and dimensioned so as to interfit with corresponding cavities  38  on microfluidic device  30 . 
     As shown in  FIG. 2B , placing microfluidic device  30  onto substrate  46  so that extensions  52  interfit with cavities  38 , connects fluidic opening  54  with fluidic opening  40 , thereby providing fluidic interconnection of microfluidic channel  32  in device  30 , with fluidic pathway  58  within substrate  46 . For embodiments where device  30  and substrate  46  comprise silicon, cavities  38  and extensions  52  may be formed by a deep reactive ion etching (RIE) process. Such a process is disclosed in U.S. Pat. No. 5,501,893 to Laermer et. al. which is herein incorporated by reference. 
     Using precision machining processes (e.g. micro-machining, RIE, electrical discharge machining (EDM), embossing, micro-molding, micro-milling, micro-drilling etc.) to fabricate access ports  38  in device  30 , and interfitting extensions  52  (and  53 ) on substrate  46 , precise alignment (e.g. on the order of 1 to 10 microns) of fluidic opening  40  in device  30  with fluidic opening  54  in substrate  46  can be maintained. By these means, a plurality of fluidic interconnections may easily and simultaneously be made, fluidically coupling a plurality of micro-channels  32  in device  30  with multiple fluidic pathways  58  in substrate  46 . 
     Extensions  53  may exist that do not contain a fluidic opening and as such may be used for alignment of device  30  to substrate  46 . Fluidic opening  54  and extension  52  are illustrated as circular in cross-section to interfit with cavity  38 . Other cross-sections are anticipated and may include; square, rectangular, polygonal, elliptical etc. For simplicity, only one microfluidic device  30  is shown to be interconnected with substrate  46 , while interconnection of multiple devices  30  or additional substrates, to substrate  46  are anticipated by the present invention. 
     Referring again to  FIG. 2B , the lower surface of microfluidic device  30  may be joined to the upper surface  48  of substrate  46  by a bonding means to effect mechanical attachment of the device to the substrate, and may additionally provide for sealing the fluidic interconnections. Where device  30  and substrate  46  comprise silicon, oxidized silicon, or glass, suitable bonding means can include anodic bonding and direct bonding methods. In such bonding processes, interdiffusion occurs between the two surfaces being joined, typically under the stimuli of one or more of heat, electrical potential and pressure. A distinct bonding layer may not be visible to the unaided eye but, rather the bonding layer may consist of an atomically diffused layer. 
     In  FIG. 3 , another embodiment of the present invention comprises an adhesive layer  60 , disposed between the lower surface of device  30  and the upper surface  48  of substrate  46 . As used in this specification, the term “adhesive layer” refers to liquid adhesive, sheet adhesive, double sided adhesive, conductive adhesive, non-conductive adhesive, thermoplastic polymer, thermoset polymer, transfer tape, epoxy, cyanate ester, cyanoacrylates, polyester, polyamide and polyimide. For the purposes of this specification, the term “adhesive layer” also refers to materials used in processes including soldering, brazing and fusible glass sealing. The length of extension  52  and depth of cavity  38  can be adjusted to accommodate the thickness of a bonding layer or an adhesive layer  60 , and there only needs to be minimal interfitting of the extension into the cavity (e.g. on the order of 10 microns or greater) to provide an interconnection. 
       FIG. 4A  is a perspective view of another embodiment according to the present invention. A plurality of extensions  52  are disposed on the upper surface  48  of substrate  46  and are dimensioned and spaced to interfit into cavities  38  on the lower surface  36  of microfluidic device  30 . A first adhesive layer  60  is disposed between the lower surface  36  of device  30  and the upper surface  48  of substrate  46 . Adhesive layer  60  may comprise through holes  62  that are substantially aligned with and dimensioned to allow extensions  52 , clearance to pass through the adhesive layer, and interfit with cavities  38 . Through holes  62  may have a diameter greater than the diameter of the extensions  52  and may be on the order of 100 to 500 microns. Adhesive layer  60  may provide mechanical bonding of microfluidic device  30  to substrate  46 , and may additionally provide sealing of the fluidic connection between extension  52  and cavity  38 . 
     A second adhesive layer  64  is disposed between the lower surface  50  of substrate  46  and the upper surface  74  of a second substrate  70 . Second substrate  70  may comprise a plurality of fluidic openings  72 . Fluidic openings  72  may be on the order of 500 microns in diameter or greater. Adhesive layer  64  may comprise a plurality of channels  65 , disposed through the thickness of the adhesive layer. Channels  65  interconnect fluidic opening  54  (through fluidic pathway  58 ) with fluidic opening  72 . Channels  65  may have a small diameter end  66  (e.g. 100–500 microns in diameter) and a larger diameter end  68  (e.g. on the order of 500 microns or greater). Large diameter end  68  may be spaced radially outward from small diameter end  66  so as to provide a fanout of the fluidic interconnection. The center of small diameter end  66  is substantially aligned with the center of fluidic opening  54 , and the center of large diameter end  68  is substantially aligned with the center of fluidic opening  72 . A fanout as may be incorporated in channel  65  and provides for a greater spacing between the centers of adjacent larger diameter fluidic openings (e.g. 72) than the spacing between the centers of adjacent smaller diameter holes (e.g. 54). Channels  65  may also interconnect one or more fluidic openings  54  to one or more fluidic openings  72 . 
     Referring to  FIG. 4B , assembly of the microfluidic device  30 , substrate  46  and second substrate  70  by means of adhesive layers  60  and  64 , completes one or more fluidic interconnections, where large diameter fluidic opening  72  (e.g. on the order of 500 microns or greater) is fluidically connected to microfluidic channel  32  (e.g. on the order of 1 to 5 microns) by means of fanout channel  65 , fluidic pathway  58  and fluidic opening  40 . Alignment (e.g. on the order of 1 to 10 microns) of the smaller diameter (e.g. on the order of 20 to 100 micron) fluidic opening  40 , in device  30 , to fluidic opening  54  (e.g. on the order of 20 to 100 micron) in substrate  46  is provided for by the interfitting of extension  52  with cavity  38 . The outer diameter of extension  52  may be nearly equal to the diameter of cavity  38  to provide a tight “interference fit”, or the diameter of extension  52  may be slightly less (e.g. on the order of 1 to 20 microns less) than the diameter of fluidic opening  38  to facilitate assembly as an application warrants. 
     Substrate  70  may comprise an electrically insulating material (e.g. a ceramic, a polymer, a plastic, a glass, a glass-ceramic composite, a glass-polymer composite, a resin material, a fiber-reinforced composite, a glass-coated metal, or a printed wiring board composition, FR-4, epoxy-glass composite, epoxy-polyimide composite, polyamide, fluoropolymer, polyether ether ketone or polydimethylsiloxane). The ceramic material can comprise alumina, beryllium oxide, silicon nitride, aluminum nitride, titanium nitride, titanium carbide, silicon carbide, diamond and diamond like substrates, glass-ceramic composite, glass-coated metal, low temperature co-fired ceramic multilayered material or high-temperature co-fired ceramic multilayered material. Fabrication of ceramic substrates can be performed by processes such as slip casting, machining in the green state, cold isostatic pressing (CIP), hot isostatic pressing (HIP) or sintering. Fabrication of plastic and polymer substrates may be performed by processes such as transfer molding, injection molding, embossing, lamination and machining. Substrate  70  may comprise a test fixture, test head, printed wiring board, electronics package, flexible interconnect (flexible printed wiring board) or fluidic manifold. 
     In the present invention, adhesive layers  60  and  64  can be any type of adhesive material. Layers  60  and  64  may be a thin double-sided adhesive film. The terms “adhesive tape” and “adhesive film” have the same meaning within this specification. The film can have a thickness on the order of from 0.05 mm to 0.25 mm. The film may be VHB™ acrylic adhesive transfer tape, e.g. F-9460PC (50 microns thick), F-9469PC (130 microns thick), or F-9473PC (250 microns thick), manufactured by the 3M Corporation, St. Paul, Minn. An adhesive transfer tape generally comprises a film of adhesive disposed in-between one or two sheets of a releasable, non-stick paper protective liner. Alternatively, the adhesive film can be applied to both sides of a polymeric carrier film (e.g. core, or backing) such as “double-sticky” or “double-sided” adhesive tape. The carrier film can included a foam layer to provide increased compliance for bonding rough surfaces. If required, electrically conductive particles (e.g. silver or copper) can be embedded within the adhesive material to increase thermal and electrical conductivity. 
     Alternatively, adhesive layers  60  and  64  may comprise a liquid of either thermoplastic or thermoset adhesives. Electrically conductive epoxy die-attach adhesives may be used to attach (e.g. adhere) the microfluidic device  30  to substrate  46  while providing electrical interconnection as well. Alternatively, adhesive layers  60  and  64  may comprise a film of adhesive sprayed, evaporated or vapor deposited onto a surface (e.g. first substrate upper surface  48 ). Typical materials that may comprise adhesive layer  60  include epoxies, cyanate esters, cyanoacrylates, polyesters, polyamides, polyimides and combinations thereof. As yet another alternative, adhesive layers  60  and  64  may comprise materials as used in processes including soldering, brazing and fusible glass sealing. 
       FIG. 4B  illustrates an embodiment where device  30  is adhesively bonded to substrate  46  by adhesive layer  60 . As described above, other embodiments are envisioned wherein adhesive layer  60  in  FIG. 4B  may be replaced with a bonding means such as direct bonding or anodic bonding. 
       FIG. 5  illustrates an embodiment of the invention where an adhesive layer  60  is in contact with the lower surface of device  30  and the upper surface of substrate  46 . A sealing means  92  contacts the lower surface of substrate  46  and the upper surface of second substrate  70 . Sealing means  92  can be a compliant material (e.g. a gasket) for substantially sealing the fluidic interconnect and may comprise paper or other fibrous materials, rubber, neoprene, Buna-n rubber, gum rubber, fluoro-elastomers, viton, silicone, silicone rubber, Teflon, grafoil, hypalon and vinyl. Through holes  65  can exist in sealing means  92 , providing fluidic interconnection of fluidic opening  72  in second substrate  70  with fluidic opening  54  in substrate  46  via fluidic pathway  58 . Clamping means  90  is provided for applying pressure to sealing means  92 , between the upper surface of second substrate  70  and the lower surface of substrate  46 . Clamping means  90  can include; spring clamps, threaded fasteners, dead weights, clips, cam locking devices, vacuum clamping, pressurized gas activated clamps or pawls. 
       FIG. 5  illustrates an embodiment where device  30  is adhesively bonded to substrate  46  by adhesive layer  60 . As described above, other embodiments are envisioned wherein adhesive layer  60  in  FIG. 4B  may be replaced with a bonding means such as direct bonding or anodic bonding. 
       FIG. 6A  illustrates another embodiment of the present invention where microfluidic device  30  is bonded to substrate  46  by adhesive layer  60 , and substrate  46  is bonded to base  76  by adhesive layer  64 . Base  76  may comprise an electronics package, e.g. as described in U.S. Pat. No. 6,443,179 issued to Benavides et. al. herein incorporated by reference. Base  76  may comprise a polymer, ceramic, glass or metal package, for e.g.: a DIP (dual in-line package), TO style can package, quad flatpack (QFP), pin grid array (PGA), ball grid array (BGA), small outline (SO), chip carrier (CC), or plastic leaded chip carrier (PLCC). 
     Assembly of the microfluidic device  30 , substrate  46  and base  76  by means of adhesive layers  60  and  64 , completes one or more fluidic interconnections, where large diameter fluidic opening  78  (e.g. on the order of 500 microns or greater) in base  76 , is aligned and fluidically connected to microfluidic channel  32  (e.g. on the order of 1 to 5 microns) by means of fanout channel  65 , fluidic pathway  58  and fluidic opening  40 . Alignment (e.g. on the order of 1 to 10 microns) of the smaller diameter (e.g. on the order of 20 to 100 micron) fluidic opening  40 , to fluidic opening  54  (e.g. on the order of 20 to 100 micron) in substrate  46  is provided for by the interfitting of extension  52  with cavity  38 . The diameter of extension  52  may be nearly equal to the diameter of cavity  38  to provide a tight “interference fit”, or the diameter of extension  52  may be slightly smaller (e.g. on the order of 1 to 20 microns smaller) than the diameter of cavity  38  to facilitate assembly as an application warrants. Alignment (e.g. on the order of 25 microns or greater) of the larger diameter end  68  of fanout channel  65  to fluidic opening  78  may be accomplished manually or through the use of automated assembly equipment (e.g. a “pick and place” system). 
     Adhesive layer  64  may be aligned and “pre-assembled” to base  76  prior to placing substrate  46  onto base  76 . Base  76  may comprise a recessed cavity having an inner edge  86  into which substrate  46  is placed. Alignment of substrate  46  to base  76 , and therefore to fanout channels  65  in adhesive layer  64 , may be provided by minimizing the spacing between the cavity inner edge  86  and the outer edge  84  of substrate  46 . For example, the spacing may be on the order of 50 microns or greater, depending on an applications requirements. 
     Referring to  FIG. 6B , base  76  may comprise conductive leads  80  that may be electrically interconnected to conductive pads  44  on device  30 . Electrical interconnection of pads  44  to leads  80  may be by means of wire bonds  82  as illustrated, or alternatively may be made by other methods including solder bumps, tape automated bonding (TAB), conductive adhesives, flip chip or beam lead bonding. Base  76  may be further interconnected to (not shown) a test fixture, test head, printed wiring board, flexible interconnect (flexible printed wiring board) or fluidic manifold. 
     Referring to  FIG. 7 , in another embodiment of the invention, fanout channels  65  may be fabricated in the back surface  50  of substrate  46 . 
     Referring to  FIG. 8 , in another embodiment of the invention, fanout channels  65  may alternatively be fabricated in the upper surface  77  of the base  76 . Example processes used to fabricate fanout channels  65  according to the embodiments shown in  FIGS. 7 and 8  may include: precision machining, chemical or plasma etching, RIE, micromachining, EDM, embossing, molding, micro-molding, micro-milling, micro-drilling etc. For the purposes of the present invention, providing a fanout in the fluidic connection of a substrate  46  to a base  76  (or another substrate) comprises those embodiments where a fanout channel is provided in substrate  46 , or base  76 , or within the adhesive layer  64 . 
       FIG. 9  illustrates another embodiment of the present invention, where microfluidic device  30  comprising a microfluidic channel  32 , fluidically connected to cavity  38  by fluidic opening  40 , additionally comprises means for optically accessing the microfluidic channel  32 , in device  30 . The means for optically accessing device  30  comprises an optical access  41  to the microfluidic channel  32 , connected to an optical cavity  39  on the lower surface of device  30 , connected to an optical pathway  59  in substrate  46 , connected to an optical pathway  71  in base  76 . Optical access cavity  39  has substantially the same dimensions as described above for fluidic access cavity  38 . Optical access means may provide, for example, an optical path from the exterior of device  30 , through optical access port  39  and optical pathway  41 , to microfluidic channel  32 , for e.g. allowing spectroscopic or chemical analysis (e.g. 43) of a fluid contained within microfluidic channel  32 . As described in Patent &#39;437 to Galambos et. al., fluidic channel  32  may comprise optically transparent materials, e.g. such as silicon nitride. Fluidic  40  and optical  41  pathways may be on the order of 20 to 100 microns in diameter. Fluidic  38  and optical access cavities may be on the order of 100 to 500 microns in diameter. 
     Substrate  46  provides for alignment and interconnection of the optical and fluidic access cavities of device  30 , and may additionally provide for electrical interconnection of device  30 , to a base, for example, electronics package  76 . A base may alternatively comprise a test fixture, test head, printed wiring board, flexible interconnect (flexible printed wiring board) or fluidic manifold. An extension  51  of upper surface  48  of substrate  46  may be dimensioned and spaced to interfit with optical access cavity  39  of device  30  and may provide for alignment and interconnection of optical pathway  41  with an optical pathway  59  within substrate  46 . Extension  52  of the upper surface  48  of substrate  46  may be dimensioned and spaced to interfit with fluidic access port  38  to provide for alignment and interconnection of fluidic pathway  40  within device  30 , to fluidic pathway  58  within substrate  46 . By means of the raised extensions  51  and  52 , dimensioned and spaced to interfit with optical and fluidic access cavities  39  and  38  respectively, multiple optical and fluidic interconnects can be made simultaneously between device  30  and substrate  46 . An adhesive layer  60  may be disposed between device  30  and substrate  46  to provide mechanical attachment of the device to the substrate and may provide for sealing of the optical and fluidic interconnects. Through holes may be provided in adhesive layer  60  to provide clearance for, and allow raised extensions  51  and  52  to mate into cavities  39  and  38  respectively. 
     An adhesive layer  64  comprising through holes  65 , may be disposed between substrate  46  and base  76  to provide mechanical attachment of substrate  46  to base  76 , and may provide for sealing of optical  59  and fluidic  58  pathways in substrate  46  to optical  71  and fluidic  73  pathways in base  76 . 
     Assembly of the microfluidic device  30 , substrate  46  and base  76  by means of adhesive layers  60  and  64 , can provide multiple optical and fluidic interconnections, where large diameter fluidic opening  72  (e.g. on the order of 500 microns or greater) is fluidically connected to microfluidic channel  32  (e.g. on the order of 1 to 5 microns) by means of fluidic pathway  73  in base  76 , fluidic pathway  58  in substrate  46 , and fluidic pathway  40 , in device  30 . Similarly, means for optically accessing fluidic channel  32  is provided by optical pathway  71  disposed through substrate  76 , connected to optical pathway  59  through substrate  46 , and further aligned and connected to optical pathway  41  in device  30 . Alignment (e.g. on the order of 1 to 10 microns) of the smaller diameter (e.g. on the order of 20 to 100 micron) fluidic and optical pathways  40 , and  41  respectively, in device  30 , to fluidic and optical pathways  58  and  59  respectively (e.g. on the order of 20 to 100 micron) in substrate  46  are provided for by the interfitting of extensions  52  and  51 , to the fluidic and optical openings  38  and  39  respectively. 
     Electrical interconnection of device  30  to base  76  may be by means of wire bonds  82  as illustrated, or alternatively may be made by other methods including solder bumps, tape automated bonding (TAB), conductive adhesives, flip chip or beam lead bonding. Base  76  may be further interconnected to (not shown) a test fixture, test head, printed wiring board, flexible interconnect (flexible printed wiring board) or fluidic manifold. 
     Means for optically accessing device  30  can include optical pathways as through holes (e.g.  41 ,  59  and  71 ) in the device  30 , substrate  46  and base  76 . Means for optically accessing device  30  can also include filling of the optical pathways with an optically transparent material such as glass, polymers, silicon nitride, polydimethylsiloxane, photo-definable glass (Foturan™), silicon, silicon dioxide. Optical pathways  59  and  71  may extend through the thickness of the substrate  46  and base  76  respectively, or may extend laterally through their bulk as well. 
     Base  76  may be further mounted on a test fixture, test head, printed wiring board, flexible interconnect (flexible printed wiring board) or fluidic manifold (not shown) as needed for a particular application. 
     As illustrated in  FIG. 9 , fanout of small diameter fluidic openings  54  to large diameter fluidic openings  72  may be accomplished by channels  65  fabricated within substrate  46 . The present invention anticipates alternatively fabricating fanout channels within base  76  or by means of cutouts through adhesive layer  64 .