Patent Publication Number: US-2012045787-A1

Title: Flexible micro-carrier system

Description:
This application claims the benefit of provisional patent application No. 61/439,266, filed Feb. 3, 2011, and provisional patent No. 61/375,227, filed Aug. 19, 2010, which are hereby incorporated by reference herein in their entireties. 
    
    
     BACKGROUND 
     This relates generally to analysis systems such as optofluidic microscope systems, and, more particularly, to micro-carriers for carrying specimens through such analysis systems. 
     Optofluidic microscopes have been developed that can be used to generate images of cells and other biological specimens. The cells are suspended in a fluid. The fluid flows over a set of image sensor pixels in a channel. The image sensor pixels may be associated with an image sensor pixel array that is masked using a metal layer with a pattern of small holes. In a typical arrangement, the holes and corresponding image sensor pixels are arranged in a diagonal line that crosses the channel. As cells flow through the channel, image data from the pixels may be acquired and processed to form high-resolution images of the cells. 
     In a conventional optofluidic microscope, cells or other samples are identified based on images of the samples themselves. The identification process may require intensive processing or post-processing of image data. 
     It would be desirable to be able to provide optofluidic microscopes or other analysis systems with systems for simultaneously identifying, carrying and manipulating samples. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagram of an illustrative diagram of micro-carrier systems in an analysis and testing environment in accordance with an embodiment of the present invention. 
         FIG. 2  is a diagram of an illustrative diagram of micro-carrier systems in a system for imaging and processing cells and other biological specimens in accordance with an embodiment of the present invention. 
         FIG. 3  is a top view of an illustrative micro-carrier system having multiple functional regions in accordance with an embodiment of the present invention. 
         FIG. 4  is a top view of an illustrative rectilinear identifier region of a micro-carrier system in accordance with an embodiment of the present invention. 
         FIG. 5  is a cross-sectional side view of an illustrative portion of a micro-carrier system in the vicinity of an identifier region of the micro-carrier system in accordance with an embodiment of the present invention. 
         FIG. 6  is a top view of an illustrative round identifier region of a micro-carrier system in accordance with an embodiment of the present invention. 
         FIG. 7  is a cross-sectional side-view of an illustrative micro-carrier system in the vicinity of an active region of the micro-carrier system in accordance with an embodiment of the present invention. 
         FIG. 8  is a cross-sectional side-view of an illustrative micro-carrier system in the vicinity of an active region of the micro-carrier system in accordance with an embodiment of the present invention. 
         FIG. 9  is a cross-sectional side-view of an illustrative micro-carrier system in the vicinity of magnetic control structures in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     An analysis system of the type that may include cells and other samples such as biological specimens carried on micro-carriers is shown in  FIG. 1 . As shown in  FIG. 1 , system  10  may include fluid  20  in fluid channel  16 . Fluid channel  16  may be any channel through which fluid  20  may flow (e.g., a blood vessel, digestive tract, plastic, glass or metal tubing as part of a larger system, a channel in an optofluidic microscope, etc.) Channels  16  may have lateral dimensions (dimensions parallel to dimensions x and z in the example of  FIG. 1 ) of a millimeter or less (as an example). The length of each channel (the dimension of channel  16  along dimension y in the example of  FIG. 1 ) may be 1-10 mm, less than 10 mm, more than 10 mm, or other suitable length. 
     During operation, fluid  20  may flow through channel  16  as illustrated by arrows  21 . A fluid source such as source  14  may be used to introduce fluid into channel  16  through entrance port  24 . Fluid may, for example, be dispensed from a pipette, from a drop on top of port  24 , from a fluid-filled reservoir, from tubing that is coupled to an external pump, from a biological source as pumping from a heart or ingestion through a mouth, etc. Fluid may exit channel  16  through exit port  26  and may, if desired, be collected in reservoir  18 . Reservoirs (sometimes referred to as chambers) may also be formed within portions of channel  16 . 
     System  10  may include other components such as image sensor integrated circuit  34 , fluid and particle flow control structures  38 , external illuminating light sources  32 , or other components. Image sensor integrated circuit  34  may be formed from a semiconductor substrate material such as silicon and may contain numerous image sensor pixels. Complementary metal-oxide-semiconductor (CMOS) technology or other image sensor integrated circuit technologies may be used in forming image sensor pixels in integrated circuit  34 . Image sensor integrated circuit  34  may include color filters, transparent cover layers or other covering layers. Image sensor integrated circuit  34  may be formed outside of, wholly within, or partially inside and partially outside of channel  16 . External illuminating light source  32  may include multiple independent light generating components  32 - 1 ,  32 - 2 ,  32 - 3  . . .  32 -N for generating light of different colors and frequencies (e.g., laser light, x-rays, etc.) for illuminating micro-carriers  17  inside channel  16 . 
     The rate at which fluid flows through channel  16  may be controlled using fluid flow rate control structures  38 . Fluid  20  may contain micro-carriers  17  having a round exterior shape, having an oval exterior shape, having a rectilinear exterior shape or other suitable shape. Micro-carriers  17  may carry materials to be analyzed such as cells, reagents, reactants or other biological elements or particles. Micro-carriers  17  may include portions containing identifying information of the carried materials. Materials carried by micro-carriers  17  may be identified and analyzed while in channel  16  (e.g., as micro-carriers  17  pass by image sensor  34 ). Control circuitry  42  (which may be implemented as external circuitry or as circuitry that is embedded within image sensor integrated circuit  34 ) may be used to process the image data that is acquired using integrated circuit image sensor  34 . 
     Micro-carriers  17  may, if desired, be collected using reservoir  18  for later analysis or may be configured to dissolve in fluid  20  after a given amount of time. Collecting micro-carriers in reservoir  18  may include magnetically or electrically capturing micro-carriers  17  in docking stations within channel  16 , extracting micro-carriers  17  from exit port  26  with a syringe or other extraction device, collection of bodily fluids such as blood, urine, etc. or other collection methods. 
     A particular system (discussed as an example herein) of the type that may be used to image and otherwise evaluate cells and other samples such as biological specimens carried on micro-carriers  17  is shown in  FIG. 2 . As shown in  FIG. 2 , system  10  may include optofluidic microscope  12 . Microscope  12  may include an image sensor integrated circuit such as image sensor integrated circuit  34 . Image sensor integrated circuit  34  may be formed from a semiconductor substrate material such as silicon and may contain numerous image sensor pixels  36 . Complementary metal-oxide-semiconductor (CMOS) technology or other image sensor integrated circuit technologies may be used in forming image sensor pixels  36  and integrated circuit  34 . 
     Image sensor pixels  36  may form part of an array of image sensor pixels on image sensor integrated circuit  34  (e.g., a rectangular array). Some of the pixels may be actively used for gathering light. Other pixels may be inactive or may be omitted from the array during fabrication. In arrays in which fabricated pixels are to remain inactive, the inactive pixels may be covered with metal or other opaque materials, may be depowered, or may otherwise be inactivated. There may be any suitable number of pixels fabricated in integrated circuit  34  (e.g., tens, hundreds, thousands, millions, etc.). The number of active pixels in integrated circuit  34  may be tens, hundreds, thousands, or more). 
     Image sensor integrated circuit  34  may be covered with a transparent layer of material such as glass layer  28  or other covering layers. Layer  28  may, if desired, be colored or covered with filter coatings (e.g., coatings of one or more different colors to filter light). Image sensor pixels  36  may be covered with color filter layer  37 . Color filter layer  37  may be color filtering material formed individually on image sensor pixels  36  or applied as a flat planar coating covering the lower surface of fluid channel  16 . Color filter layer  37  may include portions with red color filters, portions with blue color filters, portions having green color filers, portions having tiled color filters (e.g., tiled Bayer pattern filters, etc.). If desired, color filter layer  37  may include infrared-blocking filters, ultraviolet light blocking filters, visible-light-blocking-and-infrared-passing filters, etc. Structures such as standoffs  40  (e.g., polymer standoffs) may be used to elevate the lower surface of glass layer  28  from the upper surface of image sensor integrated circuit  34 . This forms one or more channels such as channels  16 . Channels  16  may have lateral dimensions (dimensions parallel to dimensions x and z in the example of  FIG. 2 ) of a millimeter or less (as an example). The length of each channel (the dimension of fluid channel  16  along dimension y in the example of  FIG. 2 ) may be 1-10 mm, less than 10 mm, more than 10 mm, or other suitable length. Standoff structures  40  may be patterned to form sidewalls  23  for channels such as channel  16 . Sidewalls  23  and other surfaces of channel  16  may be treated to facilitate or control the flow of fluid  20  through channel  16  (e.g., sidewalls may be plasma treated, coated with hydrophobic material, coated with hydrophilic material, coated with oleophobic material, coated with oleophilic material, etc.). 
     During operation, fluid  20  flows through channel  16  as illustrated by arrows  21 . A fluid source such as source  14  may be used to introduce fluid into channel  16  through entrance port  24 . Fluid may, for example, be dispensed from a pipette, from a drop on top of port  24 , from a fluid-filled reservoir, from tubing that is coupled to an external pump, etc. Fluid may exit channel  16  through exit port  26  and may, if desired, be collected in reservoir  18 . Reservoirs (sometimes referred to as chambers) may also be formed within portions of channel  16 . 
     The rate at which fluid flows through channel  16  may be controlled using fluid flow rate control structures. Examples of fluid flow rate control structures that may be used in system  10  include pumps, electrodes, microelectromechanical systems (MEMS) devices, magnets, etc. If desired, structures such as these (e.g., MEMs structures or patterns of electrodes) may be used to form fluid flow control gates (i.e., structures that selectively block fluid flow or allow fluid to pass and/or that route fluid flow in particular directions). In the example of  FIG. 2 , channel  16  has been provided with electrodes such as electrodes  38 . By controlling the voltage applied across electrodes such as electrodes  38 , the flow rate of fluids in channel  16  such as ionic fluids may be controlled by control circuitry  42 . Electrodes  38  may also be configured to interact with magnetic control structures attached to micro-carriers  17 . Micro-carriers may be guided, directed, held, or otherwise manipulated in three dimensions using magnetic control structures and electrodes  38  through channel  16  or into docks of corresponding shape for mating with micro-carriers  17  within fluid channel  16 . 
     Fluid  20  may contain micro-carriers such as micro-carriers  17 . Micro-carriers  17  may include active regions (sometimes referred to herein as sample regions) containing cells or other biological elements, particles or other materials. As micro-carriers such as micro-carriers  17  pass by sensor pixels  36 , image data may be acquired. In effect, the micro-carrier may be “scanned” across the pattern of sensor pixels  36  in channel  16  in much the same way that a printed image is scanned in a fax machine. Alternatively, image sensor pixels  36  may be used together to capture static images of micro-carrier  17 . As an example, fluid flow rate control structures  38  may be used to hold micro-carrier  17  in a fixed position during capture of light from micro-carrier  17  (e.g., light reflected from active or identifier regions of micro-carrier  17 , light emitted by active or identifier regions of micro-carrier  17 , etc.). Control circuitry  42  (which may be implemented as external circuitry or as circuitry that is embedded within image sensor integrated circuit  34 ) may be used to process the image data that is acquired using sensor pixels  36 . Because the size of each image sensor pixel  36  is typically small (e.g., on the order of 0.5-5.6 microns or less in width), precise image data may be acquired. This allows high-resolution images of cells such as micro-carriers  17  to be produced. A typical micro-carrier may have dimensions on the order of 10-50 microns (as an example). Portions of micro-carriers  17  carrying cells or other biological material may have dimensions on the order of 0.5-20 microns (as an example). 
     Portions of micro-carriers  17  may include coded identifying information of the types, quantities, locations, etc. (e.g., using color coded bit patterns on the surface of micro-carriers  17 ) of materials carried in active regions of micro-carriers  17 , identifying information of the processing and analysis history of micro-carriers  17 , etc. Coded information may be imaged using image sensor pixels  36  of image sensor integrated circuit  34 . Images of coded information on micro-carriers  17  may be used by control circuitry or other external circuitry to identify multiple types of biological samples on a single micro-carrier while micro-carrier is in channel  16  of microscope  12 , to identify the analysis and processing history of micro-carriers  17 , to identify the spatial orientation of micro-carriers  17 , etc. Arrangements in which micro-carriers are imaged are sometimes described herein as an example. 
     During imaging operations, control circuit  42  (e.g., on-chip and/or off-chip control circuitry) may be used to control the operation of light source  32 . Light source  32  may be based on one or more lamps, light-emitting diodes, lasers, or other sources of light. Light source  32  may be a white light source or may contain one or more light-generating elements  32 - 1 ,  32 - 2 ,  32 - 3  . . .  32 -N that emit different colors of light. For example, light-source  32  may contain multiple light-emitting diodes of different colors or may contain white-light light-emitting diodes or other white light sources that are provided with different respective colored filters. Light source  32  may be configured to emit laser light of a desired frequency or combination of frequencies. If desired, layer  28  and layer  37  may be implemented using colored transparent material in one or more regions that serve as one or more color filters. In response to control signals from control circuitry  42 , light source  32  may produce light  30  of a desired color, intensity, polarization or illumination direction. As an example, in response to control signals from control circuitry  42 , elements  32 - 1 ,  32 - 2 ,  32 - 3  . . .  32 -N may be lit sequentially while fluid rate control structures  38  hold micro-carriers  17  in a single position (e.g., so that micro-carriers  17  may be lit from differing angles and in differing colors). Light  30  may pass through glass layer  28  to illuminate the micro-carriers  17  in channel  16 . A detailed view of an exemplary micro-carrier such as micro-carriers  17  that may be implemented in test and analysis systems such as system  10  is shown in  FIG. 3 . 
       FIG. 3  is a top view of an illustrative micro-carrier system for identifying and transporting chemical, biological or other materials. As shown in  FIG. 3 , micro-carrier  17  may be formed from carrier structures  63 . Carrier structure  63  may have relatively small dimensions. For example, carrier structure  63  may have dimensions of less than 1 mm, less than 1000 microns, less than 250 microns, less than 100 microns, less than 50 microns, etc. Use of relatively small dimensions for carrier structure  63  may allow micro-carrier system  17  to be used in applications where large sizes might become stuck or might otherwise not be acceptable. For example, the small dimensions of carrier structure  63  may allow carrier structure  63  to be deployed in the blood stream of a patient. 
     Carrier structure  63  of carrier  17  may include functional regions such as identifier region  60  and active region  62 . Identifier region  60  may include coded information (e.g., identifying information in the form of color filters or other light absorbing, reflecting or polarizing structures formed on the surface of micro-carrier  17 ). Identifier region  60  may be formed in one region of micro-carrier  17  or may have portions in multiple regions of micro-carrier  17  (e.g., two or more identifier regions spatially separated on carrier structure  63  to aid in determining the spatial orientation of micro-carrier  17 ). Coded information in identifier region  60  may be used to identify materials carried in active region  62 , may be used to record the history of micro-carrier  17  (e.g., previous tests, identifying information of a patient from which material carried in active region  62  was taken, etc.) may be used to identify sub-regions of active region  62  carrying different samples, may be used to determine the spatial orientation of micro-carrier  17 , or may encode other information. 
     Active regions such as active region  62  of sample carrier  17  of  FIG. 3  (sometimes referred to herein as sample gathering regions, sample chambers, fluid sample chambers, sampling regions, reactant regions, sample analysis regions, etc.) may be used to gather samples through openings such as channel  66 . For example, if carrier  17  is placed or immersed in a fluid, a sample of the fluid may be gathered by sample gathering region  62  through channel  66 . Reactants (e.g., one or more reactant coatings) may be provided in region  62  to react with fluid samples and therefore assist in the analysis of the fluid samples. 
     Micro-carrier  17  may include one or more magnetic control structures  64  (e.g., magnets that may be used as “handles” for magnetically three-dimensionally positioning, orienting and directing micro-carriers  17 ). Active region  62  may be formed on an exterior surface of micro-carrier  17  or may be formed as a cavity (sometimes referred to herein as a chamber or sample gathering chamber) inside micro-carrier  17 . Active regions  62  of that are formed as cavities inside micro-carrier  17  may have an associated access ports such as access port  66  of  FIG. 3 . Access port  66  may have properties designed to allow desired materials to enter active region  62  (e.g., the size, shape, surface features, surface coatings, etc of access port  66  may inhibit or encourage entrance of certain fluids or other materials). Identifier region  60 , active region  62  and magnetic control structures  64  of micro-carrier  17  may facilitate simultaneous, real time, in-situ identification, controlled manipulation and targeted, controlled analysis of multiple samples carried in active region  62  in analysis and test systems such as optofluidic microscope  12  of  FIG. 2 . Micro-carriers  17  may be made small enough for ingestion (and later collection and analysis), small enough for injection into bodily tissues or blood vessels, or for insertion into other environments for later extraction and analysis, as described in connection with system  10  of  FIG. 1 . 
     Micro-carrier  17  may be formed from glass, silicon, plastic, or other suitable materials or combinations of materials. The materials that are used in forming the carrier structure for micro-carrier  17  may be transparent to facilitate imaging of fluid samples that are captured within micro-carrier  17 . Bio-compatible materials may be used in forming the carrier structure for micro-carrier  17  to allow micro-carrier  17  to be introduced into blood vessels or other biologically sensitive environments. If desired, the carrier structure may be formed from materials that are suitable for patterning using mass production techniques such as semiconductor fabrication techniques, advanced printing techniques (e.g., ink-jetting) or other patterning techniques. 
     Micro-carrier  17  may be formed a single structure or may be a formed by attaching two or more layers allowing the formation of cavities between portions of the layers. In one preferred embodiment, micro-carrier  17  may preferably be formed using wafer based silicon processing techniques and advanced packaging technology. Many micro-carriers  17  may be formed on a single silicon wafer and singulated into individual carriers using wafer thinning, lithography, dry or wet etching. Forming micro-carriers  17  from a single silicon wafer may help avoid the need for mechanical dicing steps during formation of micro-carriers. During formation of micro-carriers  17 , an intermediate carrier (e.g., a film or other wafer) may be used. Micro-carrier  17  may be made to be wholly or partially transparent by including light absorbing or color filtering layers on the surface of micro-carrier  17 . As an alternative to permanent material such as glass or silicon, micro-carrier  17  may be formed from a cellulose material or other fluid-soluble material designed to dissolve in a fluid (e.g., material that is configured to dissolve after a certain amount of time inside a patient&#39;s digestive track if not extracted for analysis). 
     Micro-carriers  17  may have dimensions on the order of 10-50 microns (as an example) with a thickness on the order of 10 microns or less (as an example). Other dimensions may be used for forming carrier structure that makes up micro-carriers  17  if desired. For example, a micro-carrier  17  may be formed from a carrier structure with a maximum dimension that is less than 1000 microns, less than 500 microns, less than 100 microns, in the range of 10-100 microns, etc. Multiple micro-carriers  17  each having different size and exterior shape may be used in a single analysis and test system such as system  19 . Micro-carriers  17  may, for example, have a substantially rectilinear shape (as in the example of  FIG. 3 ), may have a substantially rounds exterior shape, may have a substantially oval exterior shape or may have any other suitable exterior shape. The overall exterior shape of micro-carriers such as micro-carrier  17  may be used to convey information (i.e., certain shapes may carry corresponding types of materials), or may be used for mechanical orientation or selective docking of micro-carriers  17  (i.e. in docks of corresponding shape inside a channel such as channel  16  of  FIG. 1 ). 
       FIG. 4  is a top view of an identifier region such as identifier region  60  of  FIG. 3 . As shown in  FIG. 4 , identifier region may include information coding structures  70  (sometimes referred to herein as coded information  70 ). Information coding structures  70  may be formed from materials selected from the group consisting of: color coded materials, patterned opaque structures, optical filters, polarizers, color filter array structures, structures covered with microlenses, and photonic nano-structures. Coded information  70  in identifier region  60  may represent simple binary coding (i.e., black and white materials such as absorbing and reflecting materials  74  and  72  respectively), may use color coding or may use polarization coding (i.e., coding information by forming portions of identifier region  60  covered with different light polarizing materials). Information coding structures  70  may include regions such as reflective regions  72  and light absorbing regions  74 . Reflective regions  72  and absorbing regions  74  may be configured to encode information more complex than a simple binary string (e.g., absorbing and reflecting portions may have differing sizes as in a bar code). Reflective regions  72  may be formed on the surface of micro-carrier  17  using metal film patterning, photo-lithography and etching, screen printing or ink-jetting of reflective material or other methods. Absorbing regions  74  may be formed by screen printing light absorbing material (or depositing material using other deposition methods such as ink-jetting) onto the surface of micro-carrier  17 . Identifier region  60  may include substantially transparent portions such as transparent portion  76 , portions coated with light polarizing materials such as polarizing portion  77  and portions configured to absorb light of different color such as color filter regions  78 . 
     As shown in the cross-sectional side view of  FIG. 5  (taken along line C of carrier structure  63  of micro-carrier  17  of  FIG. 3 ) information coding structures  70  of identifier region  60  may optionally include microlenses  80  covering color filter regions  78 . Information coding structures  70  may be formed from materials selected from the group consisting of: color coded materials, patterned opaque structures, optical filters, polarizers, color filter array structures, and structures covered with microlenses. Color filter regions  78  and microlenses  80  may be formed as separate structures added to the surface of micro-carrier  17  or may be formed as an integrated portion of micro-carrier  17 . In one preferred embodiment, color filter regions  78 , polarizing portions  76 , absorbing regions  74 , reflecting regions  71 , microlenses  80  and transparent portions  77  may be formed during a wafer level processing that includes formation of active region  72  of micro-carrier  17  (i.e., all portions of micro-carrier  17  may be formed as integrated portions of a single silicon die). Color filter regions  78  of  FIGS. 4 and 5  may be patterned to form red-green-blue (RBG), cyan-magenta-yellow-key (CMYK), infrared or other filter patterns. In the example of  FIG. 5 , color filter regions  78  may be formed with or without microlenses  80 . Identifier region  60  may include any combination of color filter regions  78 , polarizing portions  76 , absorbing regions  74 , reflecting regions  72 , microlenses  80  and transparent portions  77 . 
     The size, complexity, orientation, shape, etc. of identifier region  60  may be optimized differently for different applications (e.g., using micro-carriers in different fluids, in different analysis systems, for carrying different biological materials, etc.). Identifier region  60  containing coded information  70  may (as shown in  FIG. 5 ) be substantially rectilinear in shape or may substantially round in shape as shown in  FIG. 6 . Information coding structures  70  of identifier region  60  of  FIG. 6  may include one or more circular regions  90 . Circular regions  90  may include color filter regions, metal light blocking regions, regions coated with light absorbing material, transparent regions, light polarizing regions or other regions. Coded information  70  of identifier region  60  may be arbitrarily complex and may correspond to the complexity of materials carried in active region  62 . For example, coded information  70  in identifier region  60  may be used to identify materials carried in active region  62 , may be used to record the history of micro-carrier  17  (e.g., previous tests, identifying information of a patient from which material carried in active region  62  was taken, etc.) may be used to identify sub-regions of active region  62  carrying different samples, or may encode other information. Circular regions  90  may include one or more sub-regions such as sub-regions  91  that encode different information from other sub-regions  91 . In the example of  FIG. 6 , identifier region  60  having four circular code regions is merely exemplary and identifier regions  60  may have more or less than four circular regions and regions having other shapes. 
       FIG. 7  is a cross-sectional side view of a portion of carrier structure  63  of micro-carrier  17  of  FIG. 3  (along line A) in the vicinity of active region  62 . As shown in  FIG. 7 , active region  62  may have multiple portions  100  (e.g., regions that are separated from each other with walls or other separating structures  101 ). Active region  62  may have any number of portions  100  (e.g., two portions, two or more portions, three portions, three or more portions, four portions, four or more portions, ten or more portions, twenty or more portions, fifty or more portions, 10-100 portions, 96 portions, hundreds of portions, more than 100 portions, etc.) Portions  100  of active region  62  may be used to attach different materials (e.g., reagents, reactants, cells, pharmaceuticals, viruses, bacteria, antigens or other materials). Portions  100  of active region  62  may be used to attach different concentrations of a single material. As an example, portions  100  may be used as a microscopic version of macroscopic pharmaceutical trays in which multiple drugs are exposed to a virus, cancer cells, etc. to test drug viability. 
     Micro-carrier  17  having a microscopic tray of pharmaceuticals that may be submerged in fluid  20  of  FIG. 2  may facilitate rapid parallel testing of multiple drugs. Some portions  100  of active area  62  may (as shown in  FIG. 7 ) have a time-released coating such as time-released coating  102 . Time-released coating  102  may be formed from a cellulose material or other fluid-soluble material designed to dissolve over time while submerged in a fluid such as fluid  20  of  FIGS. 1 and 2  thereby exposing some portions of active region  62  to fluid  20  at a time later than the time of immersion of micro-carrier  17  in fluid  20 . Multiple time-released coatings such as time-released coating  102  may dissolve at different rates thereby exposing different portions  100  to fluid  20  at different times. In the example of  FIG. 7 , active region  62  is formed on the surface of micro-carrier  17 . Time released coating  102  may, if desired, be formed from heat activated material, light activated material or other material designed to be activated or deactivated in an analysis environment for exposing some portions of active region  62  to fluid  20  at a time later than the time of immersion of micro-carrier  17  in fluid  20 . An active region may be formed on the surface of micro-carrier  17  by screen printing, etching, ink-jetting, or other suitable methods. Identifier regions such as identifier region  60  of  FIG. 3  may be have coded information  70  corresponding to the quantities, concentrations, deposition history, etc. of materials in portions  100  of active region  62 . 
     As described in connection with  FIG. 3 , carrier structure  63  of micro-carrier  17  may be formed from multiple layers such as layers  112  of  FIG. 8 . As shown in  FIG. 8 , (a cross-sectional side view of micro-carrier  17  of  FIG. 2  taken along line B of  FIG. 2 ) active region  62  may, if desired, be formed using one or more cavities such as cavities  110  (sometimes referred to herein as a chambers, sample gathering chambers, or fluid sample chambers). Cavities  110  may have corresponding access ports such as access port  66 . Access ports  66  may have a time-released coating such as time-released coating  102  that prevents fluid  20  from entering sample gathering region  110  before time-released coating  102  dissolves in fluid  20 . Time-released coating  102  may be formed from a cellulose material or other fluid-soluble material designed to dissolve over time while submerged in a fluid such as fluid  20  of  FIGS. 1 and 2  thereby exposing some portions of active region  62  to fluid  20  at a time later than the time of immersion of micro-carrier  17  in fluid  20 . Alternatively, time released coating  102  may, if desired, be formed from heat activated material, light activated material or other material designed to be activated or deactivated in an analysis environment for exposing some portions of active region  62  to fluid  20  at a time later than the time of immersion of micro-carrier  17  in fluid  20  or for exposing some portions of active region  62  to fluid  20  for a shorter duration than other portions of active region  62 . Layers  112  of micro-carrier  17  may be assembled using wafer level processing techniques, ink-jetting, row-to-row printing or other processing techniques to enable the creation of cavities (reservoirs)  110 . Cavities  110  may be used to pre-deposit materials (e.g., reagents, cell samples, etc.) prior to immersion of micro-carrier  17  in a fluid such as fluid  20  of  FIGS. 1 and 2 . Targeted reactions of particles or cells in active region  62  with fluid  20  gathered by fluid sample chambers  110  following immersion of micro-carrier  17  in fluid  20  may be observed real-time as in the case of an optofluidic microscope (see  FIG. 2 ) or may be later observed following collection of micro-carriers  17  (as in the case of ingestion of micro-carriers  17 ). Identifier regions such as identifier region  60  of  FIG. 3  may include coded information  70  corresponding to the types, quantities, concentrations, deposition history, etc. of materials pre-deposited in cavities  110  of active region  62 . 
     Active regions  62  may have portions  100  on the surface of micro-carrier  17  (see  FIG. 7 ) or may have portions  100  internal to cavities  110  of micro-carrier  17  as shown in  FIG. 8 . Portions  100  of fluid sample chambers  110  may have corresponding optical filters such as color filter regions  78 , microlenses  80  or transparent regions  76  to facilitate imaging of materials by filtering, focusing or otherwise manipulating light entering chambers  110  of active region  62  using (for example) image pixels  36  of image sensor integrated circuit  34  of  FIG. 2 . 
       FIG. 9  is a cross-sectional side view of a portion of carrier structure  63  of micro-carrier  17  of  FIG. 3  in the vicinity of magnetic control structures  64 . As shown in  FIG. 9 , magnetic control structures may be partially embedded in a surface of carrier structure  63  or may be formed entirely within carrier structure  63 . Multiple magnetic control structures may be formed in several positions within carrier structure  63  (e.g., one magnet each near opposing top and bottom surfaces of carrier structure  63 , one magnet each near opposing side walls of micro-carrier  17 , etc.). Magnetic control structures  64  may be implanted in carrier structure  63  or may be formed as an integral portion of carrier structure  63 . Magnetic control structures  64  may interact with magnetic fields generated using, for example, electrodes  38  of  FIGS. 1 and 2 . Magnetic control structures  64  may be used to three-dimensionally move, guide, direct, hold, or otherwise manipulate micro-carriers such as micro-carrier  17  within a fluid such as fluid  20  of  FIGS. 1 and 2  (e.g. to move micro-carrier  17  through channel  16 , to direct micro-carriers to docking stations within channel  16 , to stir or otherwise rotate micro-carriers within fluid  20 , to move micro-carrier  17  into a position of best focus with respect to image sensors for capturing light from micro-carrier  17 , etc.). 
     Various embodiments have been described illustrating a micro-carrier system for use in carrying and identifying materials to be analyzed (e.g., imaged, exposed to other materials, etc.) through an analysis system such as an optofluidic microscope. The micro-carrier system may include an active region for carrying the material to be analyzed and an identifier region having coded information for identifying the material itself (e.g., types, compositions, quantities, concentrations, deposition history, etc. of materials) or for identifying previous analyses performed on the materials, etc. The active region of the micro-carrier system may be formed on a surface of the micro-carrier system or in a cavity of chamber within the micro-carrier system. The active region may have multiple separate portions for carrying different materials, material samples from different sources, materials in different concentrations, etc. The active region (sample gathering region) may have optically functional elements such as microlenses, color filters, polarizers, etc. that control light entering the active region. The micro-carrier system may be formed from a single structure such as glass or a single silicon die. The micro-carrier system may have an overall exterior shape configured to match the shape of a docking station in the analysis system. 
     The coded information in the identifier region of the micro-carrier system may be formed using information coding structures such as color filter elements, microlenses or other light absorbing or light reflecting materials formed on the carrier (e.g., on the silicon die) and may be readable using an image sensor in an optofluidic microscope or other imaging device. Analysis systems (e.g., optofluidic microscopes) may gather light that comes from the material in the active region. Gathering light that comes from the material in the active region may include gather images of materials in active regions of micro-carriers during analysis, gathering light emitted by materials in active regions, etc. For example, an image of a fluid sample (gathered by a fluid sample chamber in the carrier structure of a micro-carrier when the micro-carrier is immersed in a fluid) may be obtained using an optofluidic microscope. Images of active regions gathered by analysis systems may also include images of a reactant that has reacted with a fluid sample in a fluid sample chamber of a micro-carrier. 
     The micro-carrier system may have carrier structures (substrates) with maximum lateral dimensions of less than 1000 microns, less than 500 microns, less than 100 microns, less than 50 microns, in the range of 1-100 microns, in the range of 10-50 microns, more than 100 microns or any other suitable size. Micro-carrier systems may include magnetic control structure for use in guiding or three-dimensionally positioning the micro-carrier system within an analysis system or holding the micro-carrier in a docking station in fluid channels in the analysis system. 
     The foregoing is merely illustrative of the principles of this invention which can be practiced in other embodiments.