Abstract:
Low-volume mixing includes introducing a sample into a container having at least one elastimeric section. The container is configured to leave a layer of gas between the sample and the elastomeric section. A portion of the elastomeric section is then urged into the layer of gas. The change in pressure of the gas layer thereby causes mixing of the sample. In various example embodiments, inner and outer surfaces of the elastomeric section have one or more convex portions and/or concave portions.

Description:
BACKGROUND 
       [0001]    Low-volume mixing is useful in a variety of industrial and scientific pursuits. For example, low-volume mixing is important when detecting analytes within a sample. Analytes, such as genetic material, are substances within a sample that scientists desire to detect and/or measure. 
         [0002]    An example of applications for low-volume mixing includes detection systems for diagnosing medical conditions and mapping DNA sequences. In such systems a sample containing one or more analytes is placed on a microarray, which is typically a slide that contains an array of micro-sized spots. Each spot reacts with a particular analyte, and a scientist can detect the presence or absence of an analyte by observing whether the spot reacts when exposed to the sample. Additionally, a single microarray can contain several different types of spots so that different analytes can be simultaneously detected in a single sample. 
         [0003]    When analyzing a sample, it is important to mix analytes within the sample and ensure that spots on the microarray are exposed to all of the analytes within the sample to produce as much hybridization as possible. This task is especially difficult given the very low volume of sample that is placed on the microarray. 
       SUMMARY 
       [0004]    In general terms, this patent relates to low-volume and localized mixing of a sample containing an analyte. 
         [0005]    One aspect is a method of mixing a sample. The method comprises introducing a sample into a container having an elastomeric section, wherein said sample is introduced into said container in a manner sufficient to leave a layer of gas between the sample and the elastomeric section, wherein the gas has a pressure; and urging a portion of the elastomeric section into the layer of gas, thereby changing pressure of the gas in a manner sufficient to cause mixture of the sample. 
         [0006]    Another aspect is a method of mixing a sample. The method comprises introducing a sample into a container having an elastomeric section in a manner sufficient to leave a layer of gas between the sample and the elastomeric section, wherein the gas has a pressure; urging a portion of the elastomeric section into the layer of gas without the elastomeric section touching the sample, thereby changing pressure of the gas, the changing pressure of the gas causing localized mixing of the sample adjacent to the urged portion of the elastomeric section; and repeating the act of urging a portion of the elastomeric section into the layer of gas at different locations of the elastomeric section. 
         [0007]    Another aspect is an apparatus for mixing a sample. The apparatus comprises a container defining a chamber and an opening, the chamber arranged to hold a layer of sample and a layer of gas positioned between the layer of sample and the opening. An elastomeric member is positioned over the opening. The elastomeric member has an inner surface exposed to the chamber, and the inner surface has a plurality of convex portions and concave portions, wherein urging the elastomeric member into the chamber changes the gas pressure. The changing gas pressure causes localized mixing of the sample. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a cross-sectional diagram of one example embodiment of an apparatus configured to mix a low-volume liquid; 
           [0009]      FIG. 2  is a cross-sectional diagram of the apparatus and one exemplary embodiment of a displacement member; 
           [0010]      FIG. 3  is a cross-sectional diagram of the example displacement member interacting with the apparatus; 
           [0011]      FIG. 4  is a partial perspective view of the apparatus and the example displacement member; 
           [0012]      FIGS. 5A and 5B  are cross-sectional diagrams of a magnetic actuator interacting with an apparatus configured to mix low-volume liquids; 
           [0013]      FIG. 6  is a cross-sectional diagram of the apparatus including one exemplary cover; 
           [0014]      FIG. 7  is a cross-sectional diagram of the apparatus including another exemplary cover; 
           [0015]      FIG. 8  is a cross-sectional diagram of the apparatus including yet another exemplary cover; 
           [0016]      FIG. 9  is a partial perspective schematic view of the apparatus and yet still another exemplary cover. 
       
    
    
     DETAILED DESCRIPTION 
       [0017]    Various embodiments will be described in detail with reference to the drawings, wherein like reference numerals represent like parts and assemblies throughout the several views. Reference to various embodiments does not limit the scope of the claims attached hereto. Additionally, any examples set forth in this specification are not intended to be limiting and merely set forth some of the many possible embodiments for the appended claims. 
         [0018]    Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Still, certain elements are defined below for the sake of clarity and ease of reference. 
         [0019]    An “array”, unless a contrary intention appears, includes any one-, two- or three-dimensional arrangement of addressable regions bearing a particular chemical moiety or moieties (for example, biopolymers such as polynucleotide sequences) associated with those regions. An array is “addressable” in that it has multiple regions of different moieties (for example, different polynucleotide sequences) such that a region (also referenced as a “feature” or “spot” of the array) at a particular predetermined location (an “address”) on the array will detect a particular target or class of targets (although a feature may incidentally detect non-targets of that feature). Note that the finite small areas on the array which can be illuminated and from which any resulting emitted light can be simultaneously (or shortly thereafter) detected, define pixels which are typically substantially smaller than a feature (typically having an area about 1/10 to 1/100 the area of a feature). Array features may be separated by intervening spaces. In the case of an array, the “target” is a moiety in a mobile phase (typically fluid), to be detected by probes (“target probes”) which are bound to the substrate at the various features. However, either of the “target” or “target probes” may be the one which is to be evaluated by the other (thus, either one could be an unknown mixture of polynucleotides to be evaluated by binding with the other). An “array layout” refers to one or more characteristics of the features, such as feature positioning on the substrate, one or more feature dimensions, and an indication of a moiety at a given location. The array “substrate” includes everything of the array unit behind the substrate front surface. “Hybridizing” and “binding”, with respect to polynucleotides, are used interchangeably. 
         [0020]    A “biopolymer” is a polymer of one or more types of repeating units. Biopolymers are typically found in biological systems and particularly include polysaccharides (such as carbohydrates), and peptides (which term is used to include polypeptides and proteins) and polynucleotides as well as their analogs such as those compounds composed of or containing amino acid analogs or non-amino acid groups, or nucleotide analogs or non-nucleotide groups. This includes polynucleotides in which the conventional backbone has been replaced with a non-naturally occurring or synthetic backbone and nucleic acids (or synthetic or naturally occurring analogs) in which one or more of the conventional bases has been replaced with a group (natural or synthetic) capable of participating in Watson-Crick type hydrogen bonding interactions. Polynucleotides include single or multiple stranded configurations, where one or more of the strands may or may not be completely aligned with another. A “nucleotide” refers to a sub-unit of a nucleic acid and has a phosphate group, a 5 carbon sugar and a nitrogen containing base, as well as functional analogs (whether synthetic or naturally occurring) of such sub-units which in the polymer form (as a polynucleotide) can hybridize with naturally occurring polynucleotides in a sequence specific manner analogous to that of two naturally occurring polynucleotides. For example, a “biopolymer” includes DNA (including cDNA), RNA, oligonucleotides, and PNA and other polynucleotides as described in U.S. Pat. No. 5,948,902 and references cited therein (all of which are incorporated herein by reference), regardless of the source. An “oligonucleotide” generally refers to a nucleotide multimer of about 10 to 100 nucleotides in length, while a “polynucleotide” includes a nucleotide multimer having any number of nucleotides. A “biomonomer” references a single unit, which can be linked with the same or other biomonomers to form a biopolymer (for example, a single amino acid or nucleotide with two linking groups one or both of which may have removable protecting groups). A biomonomer fluid or biopolymer fluid reference a liquid containing either a biomonomer or biopolymer, respectively (typically in solution). 
         [0021]    Referring now to  FIG. 1 , the exemplary embodiment of an apparatus  100  for localized mixing of a low-volume liquid  110  includes a container  102  and a cover member  104 . The container  102  generally defines a chamber  106  and an opening. The chamber  106  is configured to retain a liquid  110 , such as a liquid sample containing an analyte, leaving a layer of gas  120  positioned between the liquid  110  and the opening. 
         [0022]    The container  102  further includes an inlet  101  for injecting liquids, such as the liquid  110 , into the container  102 . The container  102  further includes an outlet  103  for emptying the liquid  110  from the container  102 . 
         [0023]    In general, the chamber  106  has a length L and a depth D. In some embodiments, the length L of the chamber  106  is substantially greater than the depth D of the chamber  106 . The length L of a chamber  106  generally ranges from about 0.1 mm to about 500 mm, although other ranges are possible. In one possible embodiment, the length L of the chamber  106  is about 100 mm. The depth D of the chamber  106  generally ranges from about 0.01 mm to about 50 mm, although other ranges are possible. In one possible embodiment, the depth D of the chamber  106  is about 1 mm. These embodiments are provided as an example, and other embodiments can include dimensions outside of these ranges. 
         [0024]    The cover member  104  is configured to couple to the chamber  106  proximate the opening. The cover member  104  has an inner surface  105  exposed to the chamber  106  and an opposite, outer surface  107 . The inner surface  105  of the cover member  104  is arranged to avoid contacting the liquid sample  110 , when the sample  110  is injected into the chamber  106 . Although particular structure and configuration for the cover member  104  are illustrated in the exemplary embodiment, other embodiments might use different structures and configurations. 
         [0025]    At least a portion  130  of the cover member  104  is generally formed of an elastimeric material having a thickness T. One possible example of material that can be used to form the elastimeric portion  130  of the cover member  104  is silicone rubber. In other possible embodiments, the elastimeric portion  130  of the cover member  104  can be made from other types of material, including polyethylene, Polypropylene, Buna N, Viton, Hypalon, Teflon, PCTFE, Neoprene, Santoprene, Tygon, and others. In some embodiments, the entire cover member  104  is formed from the elastimeric material. In other embodiments, the elastimeric material forms only a portion  130  of the cover member  104 . These embodiments are exemplary only, and any suitable material may be used. 
         [0026]    In one example embodiment, a seal member  109  is seated on the container  102  proximate the opening and configured to couple the elastimeric member  104  to the container  102 . The shape and dimensions of the seal member  109  can vary depending on the shape and dimensions of the container  102 . The elastimeric member  104  and seal member  109  cooperate with the container  102  to retain the liquid within the chamber  106 . 
         [0027]    In use, a liquid  110 , for example a sample containing an analyte, is injected into the chamber  106  of the container  102  through the inlet  101 . The liquid  110  is positioned within the chamber  106  so that a gas layer  120  exists between the liquid  110  and a cover member  104 . 
         [0028]    Generally, a low volume of the liquid  110  is injected into the chamber  106 . For example, in some embodiments, the liquid  110  has a length L′ ranging from about 10 mm to about 100 mm and a depth D′ ranging from about 0.1 mm to about 10 mm, although other ranges may be possible. In one example embodiment, the liquid  110  includes about 1 ml of liquid, with a depth of about 1 mm. These embodiments are provided as an example, however, and other embodiments including liquids  110  of sufficiently low volume that mixing presents a challenge can include dimensions outside of the specified range. 
         [0029]    In some embodiments, a holder or substrate  108  is housed within the chamber  106  at an opposite side of the chamber  106  from the cover member  104 . The substrate  108  is generally dimensioned to fit within the chamber  106  without contacting the elastimeric member  104 . In one embodiment, the substrate  108  includes a microarray. 
         [0030]    In use, referring now to  FIGS. 2-4 , the liquid  110  is locally mixed by urging one or more elastimeric portions  130  of the cover  104  into the gas layer  120  of the chamber  106  using a displacement member  150 .  FIG. 2  depicts a deformation member  150  moving in a direction Z 1  along a first axis Z towards the outer surface  107  of the elastimeric member  104 . One example embodiment of a displacement member  150  includes the finger of a user. In other possible embodiments, the deformation member  150  includes other suitable mechanical actuators. 
         [0031]      FIG. 3  depicts the deformation member  150  urging an elastimeric portion  130  of the cover member  104  into the chamber  106  of the container  102 . Urging the elastimeric portion  130  of the cover  104  at a location P 1  into the gas layer  120  causes the gas layer  120  at the location of the portion P 1  to exert a force, such as a shear force, against the adjacent portion P 1 ′ of the liquid  110 . Driving the gas  120  into liquid  110  displaces the liquid  110  at the corresponding location P 1 ′ and creates turbulence. 
         [0032]    Mixing of the liquid  110  results from repeatedly urging one or more elastimeric portions  130  of the cover member  104  into the gas layer  120 , thereby creating turbulence within the contained liquid  110 . In the exemplary embodiment, the elastimeric portion  130  is urged into only the gas layer  120 , and not into contact with the contained liquid  110 . In some embodiments, the deformation member  150  is moved at a particular constant frequency. In other embodiments, the frequency of movement of the displacement member  150  changes over time. 
         [0033]    Referring to  FIG. 4 , the deformation member  150  is displaceable along at least the first axis Z. In some embodiments, the deformation member  150  is also displaceable along a second axis X. In these embodiments, the deformation member  150 , consequently, can urge multiple locations on the cover  104  into the gas layer  120  of the chamber  106 . In other embodiments, the deformation member  150  is displaceable along the first axis Z, the second axis X, and a third axis Y. In one possible embodiment, axes Z, X, and Y are orthogonal to one another. 
         [0034]    In some embodiments, referring to  FIGS. 5A and 5B , a magnetic or electrical actuator  150 ′ can be used to urge the cover member  104  into and out of the chamber  106  in place of the displacement member  150 . In some embodiments, portions of the elastimeric cover  104  are coated in a material  155  having a magnetic polarity or configured to acquire a magnetic polarity. In these embodiments, a magnet  150 ′ having the same polarity is then positioned near a portion P 3  of the cover  104 , thereby urging the portion P 3  into the gas layer  120  of the chamber  106 . In another embodiment, a magnet (not shown) having a polarity opposite the polarity of the material  155  is positioned near the portion P 3  of the cover  104 . In this embodiment, the magnet attracts the material  155 , thereby “pulling” the elastimeric portion  130  of the cover  104  towards the magnet  150 ′. In still other embodiments, however, any suitable electrical and/or magnetic actuator can be used. 
         [0035]    Referring now to  FIGS. 6-8 , embodiments of the elastimeric cover can include protrusions and depressions to aid in mixing the fluid within the container.  FIG. 6  illustrates a schematic cross-sectional diagram of one example embodiment of a cover member  104 ′ mounted on the container  102 . In some embodiments, the outer surface  107 ′ of the cover  104 ′ includes one or more protrusions  212 . In other embodiments, the inner surface  105 ′ includes one or more protrusions  212 ′. In still other embodiments, both the inner surface  105 ′ and the outer surface  107 ′ include at least one protrusion  212 ,  212 ′, respectively. 
         [0036]    In some possible embodiments, the protrusions  212 ,  212 ′ of the cover member  104 ′″ can be formed by enlarging a thickness T of the cover member  104 ′″ to a thickness T′ in particular locations. In one possible embodiment, adding further elastimeric material to some of the elastimeric portions  130 ′″ of the cover member  104 ′″ to form the protrusions  212 ,  212 ′. In another possible embodiment, a non-elastimeric material is added to the cover  104 ′″ to form the protrusions  212 ,  212 ′. 
         [0037]      FIG. 7  illustrates a schematic cross-sectional diagram of another example embodiment of a cover member  104 ″ mounted on the container  102 . In some embodiments, the outer surface  107 ″ of the cover  104 ″ includes at least one depression  214 . In other embodiments, the inner surface  105 ″ includes at least one depression  214 ′. In still other embodiments, both the inner surface  105 ″ and the outer surface  107 ″ include at least one depression  214 ,  214 ′, respectively. 
         [0038]    In some possible embodiments, the depressions  214 ,  214 ′ of the cover member  104 ′″ can be formed by decreasing the thickness T of the cover member  104 ′″ to a thickness T″ in particular locations. In one possible embodiment, the depressions  214 ,  214 ′ are formed by removing elastimeric material from some of the elastimeric portions  130 ′″ of the cover member  104 ′″. 
         [0039]    In another possible embodiment, the cover member  104  is formed with three layers of material, with two outer layers and a middle layer. The middle layer defines a plurality of holes. The two outer layers are adhered to each other through the holes in the middle layer forming a depression. The two outer layers seal the holes in the middle layer so that no fluid leaks through the cover member  104 . 
         [0040]      FIG. 8  illustrates a schematic cross-sectional diagram of yet another example embodiment of a cover member  104 ′″ mounted on the container  102 . In some possible embodiments, protrusions  212 ,  212 ′ and depressions  214 ,  214 ′ are arranged in one or more locations on only the inner surface  105 ′″ or on only the outer surface  107 ′″ of the cover  104 ′″. In other possible embodiments, both the inner and outer surfaces  105 ′″,  107 ′″, respectively, include protrusions  212 ,  212 ′ and depressions  214 ,  214 ′ arranged in one or more locations along the surfaces  105 ′″,  107 ′″ of the cover  104 ′″. 
         [0041]    In one of these embodiments, a protrusion  212  on the outer surface  107 ′″ is aligned with a protrusion  212 ′ on the inner surface  105 ′″ of the cover member  104 ′″, or vice versa. In another embodiment, the protrusion  212  in the outer surface  107 ″ is aligned with a depression  214 ′ in the inner surface  105 ′″. Of course, in still another embodiment, a depression  214  on the outer surface  107 ′″ could align with a protrusion  212 ′ on the inner surface  105 ′″. In other embodiments, however, the protrusions  212 ,  212 ′ and depressions  214 ,  214 ′ do not align with one another. 
         [0042]    In some possible embodiments, the protrusions  212  located on the outer surface  107 ′″ have similar dimensions to the protrusions  212 ′ located on the inner surface  105 ′″. In other possible embodiments, the protrusions  212  located on the outer surface  107 ′″ protrude to a greater or lesser extent than the protrusions  212 ′ located on the inner surface  105 ′″. Generally, the protrusions  212 ′ located on the inner surface  105 ′″ are dimensioned to protrude into the chamber only far enough to extend into the gas layer  120 , but not contact the liquid  110  retained within the container  102 . In one embodiment, the protrusions  212 ′ extend from about 0.1 mm to about 10 mm away from the cover member  104 ′″. Of course, this range is exemplary only and other ranges may be possible. 
         [0043]    The protrusions  212 ,  212 ′ and depressions  214 ,  214 ′ aid in mixing a liquid contained within the chamber  106 . In particular, the presence of protrusions  212 ,  212 ′ and depressions  214 ,  214 ′ can affect the amount of gas  120  being forced into the liquid  110  and the force with which the gas  120  is driven into the liquid  110 . In one embodiment, for example, the volume of gas changes as much as 50% when cover member  104 ″,  104 ′″ is urged into the gas layer  120 , although other ranges are possible. 
         [0044]    In some embodiments, referring to  FIG. 9 , the elastimeric portions  130 ′″ of the cover member  104 ′″ includes rows formed of alternating protrusions  212  and depressions  214 . In another possible embodiment (not shown), the cover member can include alternating rows in which each row is formed from only protrusions  212  or only depressions  214 . Of course, any suitable arrangement of the protrusions  212  and depressions  214  can be used. 
         [0045]    The container  102  shown in the exemplary embodiment of  FIG. 9  is generally rectangular. However, in other possible embodiments, the container can be a variety of shapes. For example, one possible embodiment (not shown) of the container can have a generally oval shape when viewed from above the cover member. Another possible embodiment (not shown) of the container  102  can have a generally circular shape. 
         [0046]    Arrays processed using the methods and structures disclosed herein find use in a variety of different applications, where such applications are generally analyte detection applications in which the presence of a particular analyte (i.e., target) in a given sample is detected at least qualitatively, if not quantitatively. Protocols for carrying out such assays are well known to those of skill in the art and need not be described in great detail here. Generally, the sample suspected of containing the analyte of interest is contacted with an array according to the subject methods and structures under conditions sufficient for the analyte to bind to its respective binding pair member (i.e., probe) that is present on the array. Thus, if the analyte of interest is present in the sample, it binds to the array at the site of its complementary binding member and a complex is formed on the array surface. The presence of this binding complex on the array surface is then detected, e.g. through use of a signal production system, e.g. an isotopic or fluorescent label present on the analyte, etc. The presence of the analyte in the sample is then deduced from the detection of binding complexes on the substrate surface. Specific analyte detection applications of interest include, but are not limited to, hybridization assays in which nucleic acid arrays are employed. 
         [0047]    In these assays, a sample to be contacted with an array may first be prepared, where preparation may include labeling of the targets with a detectable label, e.g. a member of signal producing system. Generally, such detectable labels include, but are not limited to, radioactive isotopes, fluorescers, chemiluminescers, enzymes, enzyme substrates, enzyme cofactors, enzyme inhibitors, dyes, metal ions, metal sols, ligands (e.g., biotin or haptens) and the like. Thus, at some time prior to the detection step, described below, any target analyte present in the initial sample contacted with the array may be labeled with a detectable label. Labeling can occur either prior to or following contact with the array. In other words, the analyte, e.g., nucleic acids, present in the fluid sample contacted with the array according to the subject methods and structures may be labeled prior to or after contact, e.g., hybridization, with the array. In some embodiments of the subject methods, the sample analytes e.g., nucleic acids, are directly labeled with a detectable label, wherein the label may be covalently or non-covalently attached to the nucleic acids of the sample. For example, in the case of nucleic acids, the nucleic acids, including the target nucleotide sequence, may be labeled with biotin, exposed to hybridization conditions, wherein the labeled target nucleotide sequence binds to an avidin-label or an avidin-generating species. In an alternative embodiment, the target analyte such as the target nucleotide sequence is indirectly labeled with a detectable label, wherein the label may be covalently or non-covalently attached to the target nucleotide sequence. For example, the label may be non-covalently attached to a linker group, which in turn is (i) covalently attached to the target nucleotide sequence, or (ii) comprises a sequence which is complementary to the target nucleotide sequence. In another example, the probes may be extended, after hybridization, using chain-extension technology or sandwich-assay technology to generate a detectable signal (see, e.g., U.S. Pat. No. 5,200,314). 
         [0048]    In certain embodiments, the label is a fluorescent compound, i.e., capable of emitting radiation (visible or invisible) upon stimulation by radiation of a wavelength different from that of the emitted radiation, or through other manners of excitation, e.g. chemical or non-radiative energy transfer. The label may be a fluorescent dye. Usually, a target with a fluorescent label includes a fluorescent group covalently attached to a nucleic acid molecule capable of binding specifically to the complementary probe nucleotide sequence. 
         [0049]    Following sample preparation (labeling, pre-amplification, etc.), the sample may be introduced to the array. The sample is contacted with the array under appropriate conditions using the subject methods and structures to form binding complexes on the surface of the substrate by the interaction of the surface-bound probe molecule and the complementary target molecule in the sample. The presence of target/probe complexes, e.g., hybridized complexes, may then be detected. In the case of hybridization assays, the sample is typically contacted with an array under stringent hybridization conditions, whereby complexes are formed between target nucleic acids that agent are complementary to probe sequences attached to the array surface, i.e., duplex nucleic acids are formed on the surface of the substrate by the interaction of the probe nucleic acid and its complement target nucleic acid present in the sample. A “stringent hybridization” and “stringent hybridization wash conditions” in the context of nucleic acid hybridization (e.g., as in array, Southern or Northern hybridizations) are sequence dependent, and are different under different experimental parameters. 
         [0050]    The array is then incubated with the sample under appropriate array assay conditions, e.g., hybridization conditions, as mentioned above, where conditions may vary depending on the particular biopolymeric array and binding pair. Once incubation is complete, the array is typically washed at least one time to remove any unbound and non-specifically bound sample from the substrate; generally at least two wash cycles are used. Washing agents used in array assays are known in the art and, of course, may vary depending on the particular binding pair used in the particular assay. For example, in those embodiments employing nucleic acid hybridization, washing agents of interest include, but are not limited to, salt solutions such as sodium, sodium phosphate (SSP) and sodium, sodium chloride (SSC) and the like as is known in the art, at different concentrations and which may include some surfactant as well. 
         [0051]    Following the washing procedure, the array may then be interrogated or read to detect any resultant surface bound binding pair or target/probe complexes, e.g., duplex nucleic acids, to obtain signal data related to the presence of the surface bound binding complexes, i.e., the label is detected using colorimetric, fluorimetric, chemiluminescent, bioluminescent means or other appropriate means. The obtained signal data from the reading may be in any convenient form, i.e., may be in raw form or may be in a processed form. 
         [0052]    In using an array processed using the subject methods and structures set forth herein, the array typically is exposed to a sample (for example, a fluorescently labeled analyte, e.g., protein containing sample) and the array then read. Reading of the array to obtain signal data may be accomplished by illuminating the array and reading the location and intensity of resulting fluorescence (if such methodology was employed) at each feature of the array to obtain a result. For example, an array scanner may be used for this purpose that is similar to the Agilent MICROARRAY SCANNER available from Agilent Technologies, Palo Alto, Calif. Other suitable apparatus and methods for reading an array to obtain signal data are described in U.S. Pat. Nos. 6,756,202 and 6,406,849, the disclosures of which are herein incorporated by reference. However, arrays may be read by any other method or apparatus than the foregoing, with other reading methods including other optical techniques (for example, detecting chemiluminescent or electroluminescent labels) or electrical techniques (where each feature is provided with an electrode to detect hybridization at that feature in a manner disclosed in U.S. Pat. No. 6,221,583, the disclosure of which is herein incorporated by reference, and elsewhere). 
         [0053]    The various embodiments described above are provided by way of illustration only and should not be construed to limit the claims attached hereto. Those skilled in the art will readily recognize various modifications and changes that may be made without following the example embodiments and applications illustrated and described herein, and without departing from the true spirit and scope of the following claims.