Abstract:
A magnetically recordable label embedded within a plastic object such as a microtiter plate. The label comprises a magnetic recording medium such as a recording wire, and is concealed within the object or within a sealed enclosure attached to the object. The label can be written to or read from by a recording head passing adjacent to the label. Because the label is completely enclosed, it is shielded from degrading effects that may be present in the environment.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to improved techniques for labeling microtiter plates and the like. More particularly, the invention relates to a high information capacity machine-readable magnetic label formed from magnetic recording wire and embedded in a microtiter plate or the like. Among several aspects, increased resistance to environmental degradation is provided. 
     BACKGROUND OF THE INVENTION 
     Labels are used under many conditions, in many different environments. In particular, chemical laboratories and operations include many objects in which labeling is critical, such as microtiter plates and the like. In many environments in which such plates are employed, chemicals, reagents, solvents and the like may degrade a typical label over time. One example of an object for which labeling is important, and which is commonly used in an environment likely to degrade a typical label, is a microtiter plate used in growing cell cultures for synthesizing and/or screening chemical compounds. A microtiter plate typically contains a number of wells, each well holding a separate sample or culture. The number of wells in a plate may be very large, on the order of tens or hundreds of wells in a single plate. For example, 1536-well plates are increasing in popularity in a number of applications. Each plate therefore holds numerous cultures or samples in its wells, with each culture or sample having a significant amount of work invested. Each plate must be properly identified during each handling step, and a misidentification can cause a plate to be subjected to an incorrect process or environment, or can result in the loss of valuable information about the structures or activities of compounds. It is important, therefore, that a microtiter plate be accurately labeled, since the cost of an inaccurate or misread label can be very high. Moreover, each label must contain sufficient information to uniquely distinguish the plate with which it may be associated. Additionally, as microtiter plates continue to be developed it is possible to add more and more wells to smaller and smaller plates. This potentially increases the information content needed in a label, while simultaneously decreasing the space available for the label. An example of a plate having a large number of wells combined with a relatively small dimension is a 1536-well plate, which is gaining in popularity. These plates have dimensions of approximately 3 inches by 5 inches. 
     Barcode labels can provide sufficient information density to serve as labels for microtiter plates, but the use of barcode labels encounters certain inherent problems. The simplest way of using a barcode label is to print a paper label and affix it to an object, such as a microtiter plate, through adhesion. However, this is difficult in the case of microtiter plates, as the plates are typically made of the most chemically inert materials available, such as, polypropylene or polystyrene, and these materials typically do not accept adhesives easily. Moreover, in the environment of a chemical laboratory a barcode label suffers from exposure to various reagents and solvents in the environment and is subject to degradation. This is a problem with any label that must be read by visual optical means, as each such label will typically be placed on an outer surface of the labeled object. Such placement allows the label to be contacted by, and degraded by, chemicals in the environment. 
     Various approaches have been taken to solve the problem of adhesion of a barcode label and of label degradation. These include laser etching of a label onto a plate, embedding of a radio frequency transmitter into the plate, color coding, embedding various fluorescent materials having differing emitting spectral frequencies, and other methods. Methods used to date have been expensive in production of the labeled plates or of the reading equipment, have not yielded sufficient information density in the label, or are insufficiently reliable. 
     There exists, therefore, a need in the art for a label having a high information capacity, which can be used in a chemical environment without the risk of an unacceptably high level of degradation due to environmental exposure to harsh chemicals and the like, which is reliable, and which is inexpensive to produce and read. 
     SUMMARY OF THE INVENTION 
     A label according to one aspect of the present invention includes a piece of magnetic recording medium, such as recording wire, embedded within a hollow in a microtiter plate. The recording wire is capable of storing information along its length by maintaining a pattern of sequentially magnetized segments. Information is encoded onto the wire by moving the wire adjacent a fixed recording head or, alternatively, by moving a recording head along the wire. The recording head emits a reversible-polarity field which magnetizes each segment of the wire to a desired polarity, thereby encoding information onto the wire by magnetizing sequential segments of the wire to either a north-south or a south-north polarity. Each magnetized segment has a width not less than the distance between the recording head and the wire. Similarly, the wire is read by moving the wire adjacent a read head or, alternatively, moving a read head along the wire. The sequentially magnetized segments of the wire induce field changes in a field emitted by the read head. The field changes are decoded to extract the information. The label data can be displayed to an operator or an automatic system in order to identify the plate. Alternatively, the label data can be used as an index to information about the plate, in order to allow retrieval of information. 
     A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following Detailed Description and the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a microtiter plate containing a wire label according to the present invention and a write head for recording information onto the label according to the present invention; 
     FIG. 2 illustrates additional details of an area of a microtiter plate containing a wire label according to the present invention; 
     FIG. 3 illustrates a wire label according to the present invention, showing additional details of encodation of the information; 
     FIG. 4 illustrates a conveyor equipped with a label reader according to the present invention; 
     FIG. 5 illustrates a benchtop label reader according to the present invention; and 
     FIG. 6 illustrates a method of labeling using an embedded magnetically recorded label according to the present invention. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 illustrates a microtiter plate  100  having an illustrated section  102  in which is placed a recordable wire  104  according to the present invention. The recordable wire  104  is located near an outer surface of the plate  100 , but is preferably not visible, preferably being completely concealed within the plate  100 . The recordable wire is adapted to accept magnetization of segments with differing polarities. When these segments are created, they are capable of inducing changes in a magnetic field extending from outside the plate  100  to inside the plate  100 . These changes can therefore be decoded to recover information recorded on the wire  104 . The information recorded on the wire  104  is information serving to uniquely identify the plate  100 . The wire  104  may be written to by passing a write head  106  along the wire  104 . The write head  106  preferably includes an electromagnet  108  which when magnetized has adjacent north and south poles. A wire coil  110  is wrapped around the electromagnet  108 . The wire coil  110  is connected to a current source  112 , which is capable of passing a current through the wire coil  110 , the current source  112  being able to pass current in either direction to induce a desired polarity in the electromagnet  108  as directed by a label encoder  114 . As the write head  106  is passed along the wire  104 , current is passed through the wire coil  110 , according to the information desired to be written to the wire  104 , to induce polarized segments along the wire  104 . During the writing process, the write head  106  must be placed at a distance from the wire  104  less than or equal to the desired width of each segment to be created. 
     FIG. 2 is a more detailed illustration of the illustrated section  102  of the microtiter plate  100 . The recorded wire label  104  is located within a prefabricated pocket  202  of the plate  100 . The recording wire  104  is chosen to emit a field extending a desired distance beyond the plate  100 , and is preferably chosen of a corrosion resistant material such as stainless steel. The pocket  202  may conveniently be formed during a molding process and the recording wire  104  inserted at the time of molding, but the wire  104  may also be inserted after molding through cold or hot pressing, melting in, inserting in the groove, wrapping, gluing or any other chosen process. The pocket  202  is shown in a cutaway view so that the wire  104  can be seen, but the wire is preferably entirely embedded within the plate  100 . This protects the wire from environmental degradation, but does not affect its usefulness as a label, because the wire  104  can be read from and written to by a field originating outside the plate  100 , and can thus be read from and written to while protected within the plate  100 . 
     FIG. 3 illustrates a piece of recording wire  300  encoded according to the teachings of the present invention. Sections  302 A- 302 D have been magnetized to form a label, with each of the sections  302 A- 302 D representing a single bit. In the present illustration, a north-south orientation represents a binary one and a south-north orientation represents a binary zero, but any desired scheme for representation of bits may be suitably used. Commonly available recording wires allow storage of approximately 12 bits per inch. 
     FIG. 4 illustrates a conveyor system  400  adapted to accommodate a microtiter plate such as the microtiter plate  402 , which includes a plate label  404  according to the present invention, the plate label being a magnetic recording label containing information identifying the plate  402 . The conveyor system  400  includes a conveyor belt  406  on which the microtiter plate  402  is placed. The microtiter plate  402  is passed through various stages. At each stage, one or more processes is carried out on each of one or more of the wells of the plate  402 . As the plate  402  is placed on the conveyor system  402 , the plate  402  passes a reading head  408  which is part of the conveyor system  400 . The reading head is suitably connected to a decoder  410 , which is in turn suitably connected to a computer system  412 . The decoder  410  decodes the label information and provides it to the computer system  412 . The computer system  412  uses the label information to identify the plate  402  and to control the operations performed on the plate  402 . The computer system  412  preferably provides access to a lookup table  414  in which is stored information relating to the plate  402 . Pertinent information is retrieved from the lookup table  414  during operations on the plate  402 , and updated information is stored in the lookup table  414  as appropriate during operations on the plate  402 . 
     The conveyor system  400  may also write information concerning processing to which the plate has been subjected. The plate  402  may suitably include a process label  416  on which can be stored information concerning operations performed on the plate  402 . This information can be used by the computer system  412  for further authentication of a plate  402  and identification of the stage of processing of the plate  402 . As the process label  416  passes the read head  408 , the computer system  412  reads the process label  416  to determine the process information written on the label  416 . If the process information on the label  416  matches the information stored in the lookup table  412 , processing proceeds. If not, processing is halted and an operator is notified. After the label  404  and the process label  416  have been read, if processing is to proceed, the process label next passes by a write head  418 , which is connected to an encoder  420 . The computer system  412  supplies process information to the encoder  420 , which writes the process information onto the process label  416 . This is preferably done at the same time as the updating of the process information in the lookup table  414 . 
     It should be noted that it is not necessary that process label information be written onto a special process label different from the plate label. If desired, process label information and plate label information can be written onto the same label, which can be read and interpreted to yield information about the identity of the plate, as well as the processes to which the plate has been subjected. 
     FIG. 5 illustrates a label reading device  500  used to read a plate label  502 , according to the present invention, embedded in a microtiter plate  504 . The plate  504  is inserted into a suitable slot  506  in the read/write device  500 . The reading device  500  includes a read head  508  which is adapted to move along a track  510  adjacent to a position of the label  502  when the plate  504  is properly inserted into the slot  506 . The read/write device  500  may suitably include a keypad  512  for entering selections, a display  514  for displaying information to a user, and programming and decoding circuitry  516  suitable for translating signals from the read head  508  into values to be displayed. When it is desired to read the plate label  502  on the plate  504 , the plate  504  is inserted into the slot  506  and an appropriate selection is made on the keypad  512 . The read head  508  moves alongside the label  502 , and the varying polarity sections on the label  502  induce corresponding polarities in the read/write head  508 . These polarities are transmitted to the control circuitry  516 , translated into bits, and decoded. The control circuitry  516  may simply send the label information to the display  514  for reading by the operator, or may alternatively provide access to a lookup table  518  containing information about the plate  504 . In that case, the plate label information would provide an index to the lookup table  518  so that the operator may choose to access information relating to the plate, such as the contents of each well or the stage in processing which the plate has reached. As the operator works on the plate  504 , he may also enter updated information into the lookup table using the keypad  512 . The updated information would thus be accessible at further stages in the processing of the plate  504 . 
     The label reading device  500  may also read a second label, or process label  520  in the plate  504 . The second label  520  would contain information about processes to which the plate  504  has been subjected. In the case of a process label  520 , the lookup table  518  would contain process information indexed to the information on the process label  520 , relating to processes to which the plate  504  has been subjected. The process information would be sent to the display  514  by the control circuitry  516 . 
     A label reading device such as the device  500  provides convenience for an operator, giving the operator the ability to identify a plate and obtain information about the plate. A label reading device need not be of the particular configuration illustrated by the device  500 , and may be designed in any of a number of different configurations, for example, with the read head being contained in a wand which the operator may pass along the plate  504  in the vicinity of the label  502 . 
     FIG. 6 is a flowchart illustrating the steps of a method  600  of embedded labeling according to the present invention. At step  602 , a first magnetic recording wire of a desired length is selected, with at least one inch of wire being provided for every 12 bits of label information desired, the first wire being adapted to serve as a label wire. At step  604 , a second recording wire is selected, to serve as a process label wire. At step  606 , the first wire and the second wire are embedded in a plastic object that is desired to be labeled. The first and second wire are preferably embedded during the molding process into a pocket or pockets formed prior to insertion of the wires, but embedding may be accomplished in any number of ways. At step  608 , plate identification information is recorded on the first wire by appropriate polarization of sequential sections of the wire, preferably performed by either moving a write head or read/write head along the wire or, alternatively, by moving the wire alongside the write head or read/write head. At step  610 , process information is recorded on the second wire to identify processes to which the plate has been subjected. At step  612 , plate label information is read from the wire by decoding polarized sections along the wire, by moving a read or read/write head along the wire or by moving the wire along a read or read/write head. At step  614 , process label information is read from the second wire, by decoding polarized sections along the wire, by moving a read or read/write head along the wire or by moving the wire along a read or read/write head. At step  616 , the plate label information is used as an index to identify the plate or as an index to information about the plate, either as an index for storing information about the plate for later retrieval, or as an index for retrieval of information about the plate. The information associated with the label may advantageously be used to identify and control operations already performed or to be performed on the plate. At step  618 , the process label information is used as an index to identify processes to which the plate has been, or will be, subjected thereby allowing interpreting the label information to identify the plate and/or the processes to which the plate has been or will be subjected. Steps  606  and  608 - 610  need not be performed in sequence, but instead any step may be performed when appropriate. Typically, step  608  is performed when a plate is fabricated, or alternatively when a plate is placed into operation or placed into reuse, and steps  610 - 618  are performed as required during operation on the plate. 
     While the present invention is disclosed in the context of a presently preferred embodiment, it will be recognized that a wide variety of implementations may be employed by persons of ordinary skill in the art consistent with the above discussion and the claims which follow below.