Abstract:
A system and method for utilizing RFID tags in environments where radiation is used is disclosed. RFID tags are secured to various components of a pharmaceutical system, thereby enabling the customer to download pertinent information about the component, such as lot number, date of manufacturer, test parameters, etc. The tags can be applied to the component during or immediately after manufacture and can be subjected to the sterilization process without risk of data loss or corruption. The memory device within the tag utilizes a technology that does not rely upon charge storage as its mechanism to store information.

Description:
BACKGROUND OF THE INVENTION 
     The use of RFID tags has become prevalent, especially in the management of assets, particularly those applications associated with inventory management. For example, the use of RFID tags permits the monitoring of the production line and the movement of assets or components through the supply chain. 
     To further illustrate this concept, a manufacturing entity may adhere RFID tags to components as they enter the production facility. These components are then inserted into the production flow, forming sub-assemblies in combination with other components, and finally resulting in a finished product. The use of RFID tags allows the personnel within the manufacturing entity to track the movement of the specific component throughout the manufacturing process. It also allows the entity to be able to identify the specific components that comprise any particular assembly or finished product. 
     In addition, the use of RFID tags has also been advocated within the drug and pharmaceutical industries. In February 2004, the United States Food and Drug Administration issued a report advocating the use of RFID tags to label and monitor drugs. This is an attempt to provide pedigree and to limit the infiltration of counterfeit prescription drugs into the market and to consumers. 
     Since their introduction, RFID tags have been used in many applications, such as to identify and provide information for process control in filter products. U.S. Pat. No. 5,674,381, issued to Den Dekker in 1997, discloses the use of “electronic labels” in conjunction with filtering apparatus and replaceable filter assemblies. Specifically, the patent discloses a filter having an electronic label that has a read/write memory and an associated filtering apparatus that has readout means responsive to the label. The electronic label is adapted to count and store the actual operating hours of the replaceable filter. The filtering apparatus is adapted to allow use or refusal of the filter, based on this real-time number. The patent also discloses that the electronic label can be used to store identification information about the replaceable filter. 
     A patent application by Baker et al, published in 2005 as U.S. Patent Application Publication No. US2005/0205658, discloses a process equipment tracking system. This system includes the use of RFID tags in conjunction with process equipment. The RFID tag is described as capable of storing “at least one trackable event”. These trackable events are enumerated as cleaning dates, and batch process dates. The publication also discloses an RFID reader that is connectable to a PC or an internet, where a process equipment database exists. This database contains multiple trackable events and can supply information useful in determining “a service life of the process equipment based on the accumulated data”. The application includes the use of this type of system with a variety of process equipment, such as valves, pumps, filters, and ultraviolet lamps. 
     Another patent application, filed by Jornitz et al and published in 2004 as U.S. Patent Application Publication No. 2004/0256328, discloses a device and method for monitoring the integrity of filtering installations. This publication describes the use of filters containing an onboard memory chip and communications device, in conjunction with a filter housing. The filter housing acts as a monitoring and integrity tester. That application also discloses a set of steps to be used to insure the integrity of the filtering elements used in multi-round housings. These steps include querying the memory element to verify the type of filter that is being used, its limit data, and its production release data. 
     Despite the improvements that have occurred through the use of RFID tags, there are additional areas that have not been satisfactorily addressed. For example, to date, RFID tags cannot be employed in environments that require or utilize sterilization utilizing radiation. This is due to the fact that the memory storage devices within the RFID tag cannot withstand those types of radiation. When subjected to sterilization utilizing radiation, specifically gamma radiation, the contents of these memory elements are corrupted, thereby rendering them useless in this environment. However, there are a number of applications, such as, but not limited to, the drug and pharmaceutical industries, where sterilization utilizing radiation of the system is a requirement. Therefore, it would be extremely beneficial to these industries and others, to have an RFID tag which could withstand this type of radiation without data loss or corruption. 
     SUMMARY OF THE INVENTION 
     The shortcomings of the prior art are overcome by the present invention, which describes a system and method for utilizing RFID tags in environments where radiation is used. RFID tags are secured to various components of a pharmaceutical system, thereby enabling the customer to download pertinent information about the component, such as lot number, date of manufacturer, test parameters, etc. The tags can be applied to the component during manufacturing or immediately after the final assembly and can be subjected to the sterilization process without risk of data loss or corruption. The memory device within the tag utilizes a technology that does not rely upon charge storage as its mechanism to store information. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows several RFID tags with a ferroelectric memory, in accordance with one embodiment of the disclosed invention, and several conventional RFID tags, each being subjected to gamma radiation. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The use of RFID tags has become more and more prevalent. However, in certain applications, their use is limited, or not possible. For example, any environment in which the tag must be subjected to radiation will corrupt or destroy the contents of the memory device within the tag. Therefore, devices that are gamma irradiated, such as pharmaceutical components, or subject to x-rays, such as devices that pass through airport security systems, currently cannot utilize RFID tags. Thus, products used in these environments must find alternative solutions. For example, in some cases, a simple barcode is affixed to the device, and a database is used to store and retrieve the pertinent information associated with that barcode. In other words, the memory element of the tag is literally removed and kept elsewhere. While this allows the data associated with the device to be saved and retrieved, it requires computer access and a remote database for storage. This solution is further complicated when the device manufacturer and the device user both want to access and update the associated information. Such an arrangement requires joint access to the database, which may be difficult or impossible due to the need for confidentiality and data protection. 
     A second solution involves affixing the RFID tag at a point in the process after the irradiation of the device. For example, pharmaceutical components are often subjected to gamma radiation. Application of the RFID tag after this step can bypass the memory corruption issue. However, data associated with that component which was created before the radiation step must be somehow saved and associated with the appropriate component, so that the later affixed tag contains all of the required information. 
     A third solution is to prohibit the use of radiation with the device. Thus, users must find an alternate approach to achieve the results sought by irradiating the device (such as heat sterilization). Obviously, none of these solutions is optimal. 
     It should be noted that although the present application describes the use of RFID tags, the invention is not so limited. The fundamental issue to be solved is a limitation of the memory device used, and is not related to the particular communication protocol. Thus, while the memory devices within RFID tags clearly are affected by radiation, so too are devices which use memory devices with other communication protocols, such as Zigbee (IEEE 802.15.4), Bluetooth (IEEE 802.15.1), WiFi (IEEE 802.11), IrDA, and others. 
     At the root of the problem is the inability for a traditional memory device to withstand radiation. This is a very well known problem, and affects all types of memory, including FLASH, EEPROM, DRAM and SRAM. Since each of the aforementioned memory device utilizes stored charge to represent the value of each binary bit, each is susceptible to corruption caused by radiation. In this case, the charge stored in the capacitor is either depleted or enhanced by the radiation, thereby affecting its value. 
     There are other memory technologies that use mechanisms other than charge storage to retain the value of a bit. For example, FRAMs, or ferro-electric RAMs, utilize molecules having a bi-stable structure to store state, wherein one of the stable molecular configurations represents a ‘1’, and the other stable configuration represents a ‘0’. Several common molecules used in FRAMs are PZT (lead-zirconate-titanate), SBT (strontium-bismuth-tantalate) and BLT (lanthanum substituted bismuth-tantalate). Each possesses a central atom in a cubic unit cell having a dipole moment. These molecules switch between these two stable states based on the application of an electric field to the molecule. Since these cells rely on electrical fields, rather than charge storage, memories utilizing this mechanism are far less susceptible to gamma and other types of radiation than traditional semiconductor memory structures. Ferro-electric devices are well known and are described in more detail in U.S. Pat. No. 3,728,694, issued to Rohrer. 
     Another example of a memory device that does not utilize charge as the storage mechanism is MRAM, also known as magnetoresistive or simply magnetic RAM. These memory devices utilize ferromagnetic material, often in the form of Hall sensors, to store the state of the bit. Further details are provided in U.S. Pat. No. 6,140,139. Since magnetic fields are utilized, rather than capacitive charge, these memory devices are also much less susceptible to gamma radiation. 
     As stated above, memory devices that do not utilize charge as the storage mechanism are less susceptible to corruption due to radiation, particularly gamma radiation, thereby making them particularly advantageous in certain applications. RFID and other remotely readable tags that must pass through x-ray machines, such as airport screening machines, or tags that are used in the pharmaceutical and drug industries, can function when assembled using these memory devices. 
     In one experiment, shown in  FIG. 1 , RFID tags  10  utilizing a ferroelectric memory device  20 , and several tags  30  utilizing conventional memory technology  40 , were subjected to repeated exposure of gamma radiation  50 . Each was subjected to a standard 25 kGray dosage. Thereafter, each was read. All of the tags  30  utilizing the conventional memories  40  were unreadable, while those tags  10  utilizing the ferroelectric memory devices  20  were functional. A test pattern was then written to each of the functioning devices  10  and they were then subjected to a second dose of radiation  50 . The tags were then retested and the test pattern was readable in each. 
     Based on this, it is possible to develop a sophisticated pharmaceutical asset management system. In one embodiment, the pharmaceutical components, such as filtration devices and the like, have a remotely readable tag affixed to them, such as an RFID tag. This tag contains device specific information, such as, but not limited to device specific information (such as serial number, date of manufacture, etc.), device specifications (such as upper and lower pressure limits), and device test parameters. Customers could use this information in a variety of ways. For example, an automated instrument setup and calibration procedure can be established. By using an RFID or equivalent reader, the customer could determine calibration values, upper and lower limits, units of measure and/or the data exchange protocol. 
     These tags can also be used in conjunction with remote sensors, such as pressure, temperature and concentration sensors. The use of these types of sensors is described in U.S. patent applications Ser. Nos. 11/402,737, 11/402,437, and 11/402,438, the disclosure of each is hereby incorporated by reference. In this case, information obtained by the sensors can be stored in the RFID tags and read by the customer at a later time. 
     Finally, the ability to utilize a remotely readable asset management tag is beneficial for pharmaceutical consumables, such as filters, bags, tubes and process instruments. Currently, the pharmaceutical industry is exploring the possibility of disposable technology. In this scenario, the customer could configure their required system using at least some disposable components (such as filters, bags, hoses, etc). This allows the customer to customize their configuration as necessary and also eliminates the costly cleaning operations that must currently be performed. To improve the efficiency and predictability of using disposable components, RFID tags can be affixed to these components. Such tags allow for the wireless automated identification of components, including such information as catalog number, serial number, and date of manufacture. These tags also allow a secure automated method of transferring unit specific specification to the customer as noted above. Using the information contained within these tags, a GAMP compliant method of transferring unit specific test procedure information to an automated integrity tester can be created. The memory devices described above are beneficial in this application, since these disposable components must be irradiated to insure sterilization.