Abstract:
A crystal mount for use in a cryogenic environment which comprises an RFID transponder capable of transmitting tracking information unique to the crystal mount or the composition of a sample mounted thereon.

Description:
FELD OF THE INVENTION  
       [0001]     The invention pertains to the field of automated identification and tracking of crystal samples via radio frequency identification (“RFID”).  
       BACKGROUND OF THE INVENTION  
       [0002]     Crystallography applications have expanded to include mass production of crystal samples of biomolecules for use in testing new biocomponents, such as experimental drug compositions, quickly and efficiently. It is often desirable to test multiple variations of the combinations being examined. Such testing applications often require multiple test cells to be used, because some samples will not crystallize, or the crystals will be of insufficient quality to permit sufficient resolution in the crystallography. Accordingly, it is often necessary to provide a sizeable number of test cells to provide a sufficient sample that some adequate crystals form with each desired combination of materials.  
         [0003]     Crystal mounts have been developed which provide a standardized platform for the growing of test crystals, and which are adapted to be used by automated sample handlers for more efficient testing. Because test crystals must be maintained at cryogenic temperatures, the crystal mounts and the handlers which manipulate them must be configured to operate when exposed to cryogenic temperatures. Further, the crystal mounts and other parts exposed to cryogenic temperatures must often be capable of withstanding repeated cycling between cryogenic temperatures and much warmer temperatures.  
         [0004]     Due to the number of crystal mounts which may be in use in any one test, and due to the increased use of automated equipment to handle the crystal mounts and record data, it is desirable to have the ability to automatically identify and catalog each crystal mount. Positional indexing of samples in sample trays may be used, but is vulnerable to any failure of the handling system to return a sample to its original position. Further, positional indexing requires some comparison between the physical position of a sample and a manual or computerized index to determine the identity of a particular sample. Such comparisons are time-consuming in an industry in which the efficiency of such operations are increasingly important.  
         [0005]     Accordingly, it is desirable to provide a sample identification system which can identify a particular crystal mount, and thus a particular crystal sample, without regard to a physically indexed location of the crystal mount. It is also desirable to provide such a system which can provide identifications quickly, and to provide the ability to place identifying detectors at convenient locations for sample tracking.  
       SUMMARY OF THE INVENTION  
       [0006]     The invention is an RFID crystal mount, comprising a radio frequency identification (“RFID”) transponder that is capable of providing a continuous identification signal attached to the crystal mount. However, use of RFID transponders requires that each mount also comprises an antenna to transmit the RFID signal to a receiver.  
         [0007]     In a typical application, a commercially available crystal mount such as the Hampton Research CrystalCap HT™ may be modified to provide an RFID crystal mount. An RFID transponder, such as a TI ISO 15693, is preferably encased in cryo epoxy to protect the transponder and its wire connections from mechanical shock. Preferred transponders provide programmable capacity, so that the transponder may be programmed with identification information related to the sample identification and, if desired, the sample composition.  
         [0008]     In a preferred embodiment, the crystal mount comprises a stem section, allowing a cylindrical section of Teflon tubing to be placed in slideable contact with the stem. Because the stem section of the crystal mount is generally a solid metal shaft, this Teflon tubing provides a thermo-mechanical buffer between the crystal mount stem and the RFID apparatus. The Teflon tubing additionally provides electrical isolation between the stem and the RFID apparatus. Preferably, the Teflon tube has an ID sized to provide close contact with the stem, so that the Teflon tube will not slide out of position once it is in place.  
         [0009]     In a preferred embodiment, a cylindrical ferritic shield, such as a Fair-Rite Products #2643000301 Shield Bead, is positioned around and in mechanical contact with the Teflon tubing. On the outside of the ferritic shield, a helically-wound antenna, comprised for example of 0.005″ enameled copper wire, is formed. This antenna is connected to an RFID transponder via an antenna lead.  
         [0010]     As those of skill in the art will recognize, if a Teflon tube is used to provide mechanical attachment between the stem section and the ferritic shield, the tube can be sized to and OD which provides a close-tolerance fit with the ID of the ferritic shield, providing a convenient and secure means of mounting the ferritic shield.  
         [0011]     Either before or after the RFID crystal mount is assembled, the RFID transponder may be programmed with information identifying the particular RFID crystal mount, or identifying the composition of the crystal mounted to it.  
         [0012]     In an alternative embodiment, the ferritic shield may be secured directly to the crystal mount with cryo epoxy or another adhesive which can tolerate cryogenic temperatures. However, the brittleness of the ferritic shield must be considered when providing such an attachment.  
         [0013]     In another alternative embodiment, the antenna may be secured directly to the crystal mount, without the use of a ferritic shield. The ferritic shield provides a benefit in reducing potential interference between the antenna and the metal in the crystal mount. Those of skill in the art will recognize, however, that such potential interference may be tolerated in some applications without departing from the spirit of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  is a cross-sectional view of one embodiment of the invention.  
         [0015]      FIG. 2  is a cross-sectional view of another embodiment of the invention.  
         [0016]      FIG. 3  is a schematic diagram of a method of operation of the invention.  
     
    
     DETAILED DESCRIPTION  
       [0017]     Referring to  FIG. 1 , an embodiment of the present invention is shown in cross-section. An RFID crystal mount  10  comprises a base  12 , which in turn comprises a stem  16 , and crystal holder  18 . A base well  14  provides a connector bore for retaining magnets to hold the RFID crystal mount  10 , for example, when it is in a magazine (not shown) or on a goniometer (not shown). Relief area  13  provides a gripping point for a manipulator arm (not shown) to grasp the RFID crystal mount  10  to move it.  
         [0018]     A Teflon tube  20  is closely fitted around the stem  16 , and provides thermo-mechani-cal and electrical isolation between the stem  16  and a ferritic shield  22 . Preferably, the Teflon tube  20  is fitted in close tolerance to the ferritic shield  22  to provide a secure mounting for the ferritic shield  22 . In an alternative embodiment, the Teflon tube  20  may be omitted, or replace by cryo epoxy (not shown) or an alternative adhesive which can tolerate cryogenic temperatures.  
         [0019]     An antenna  24  is wound around the outside of the ferritic shield  22 , and is in signal communication with an RFID transponder  26  via antenna lead  28 . Antenna  24  may be helically-wound, or wound in another fashion to provide adequate reception of the signal from the RFID transponder  26 . Preferably, the RFID transponder  26  is encased in cryo epoxy  30  to protect the RFID transponder  26  and its connections from mechanical shock.  
         [0020]     Referring to  FIG. 2 , in an alternative embodiment, an antenna  224  may be directly attached to the RFID crystal mount  210  by cryo epoxy  232  or some other non-conductive adhesive which can tolerate cryogenic temperatures. As in the previous embodiment, antenna  224  is in signal communication with RFID transponder  226  via antenna lead  228 .  
         [0021]     Referring to  FIG. 3 , a method of operation of the invention is shown schematically. When interrogated by a sampling RFID transponder  312 , the RFID crystal mount  310  transmits signals  318  to the sampling RFID transponder  312 . A processor  314 , such as a computer, tracks RFID crystal mount  310  by receiving signals  322  from sampling RFID transponder  312 . Processor  314  may also send instructions  320  to sampling RFID transponder  312  to transmit information  316  to RFID crystal mount  310 . In this way, the content of signals  318  from the RFID crystal mount  310  may be programmed to include information unique to the RFID crystal mount  310 , such as a unique identifying code or information regarding the content of the sample currently mounted on the RFID crystal mount  310 . Such programming may optionally be performed either before or after a crystal is mounted to RFID crystal mount  310 .  
         [0022]     The above examples are included for demonstration purposes only and not as limitations on the scope of the invention. Other variations in the construction of the invention may be made without departing from the spirit of the invention, and those of skill in the art will recognize that these descriptions are provide by way of example only.