Patent Publication Number: US-2023163864-A1

Title: Communication system with partial power source

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. Pat. Application No. 14/865,508 filed Sep. 25, 2015, which is a continuation of U.S. Pat. Application No. 14/341,639 filed Jul. 25, 2014, which is a continuation of U.S. Pat. Application No. 13/153,312 filed Jun. 3, 2011, now Pat. No. 8,816,847, which is a continuation of U.S. Pat. Application No. 12/564,017 filed Sep. 21, 2009, now Pat. No. 7,978,064, which is a continuation of U.S. Pat. Application No. 11/912,475 filed Jun. 23, 2008, now Pat. No. 8,847,766, which application is a 371 application of PCT Application Serial No. PCT/US06/16370 filed Apr. 28, 2006; which application pursuant to 35 U.S.C. § 119 (e), claims priority to the filing dates of: U.S. Provisional Pat. Application Serial No. 60/676,145 filed Apr. 28, 2005; U.S. Provisional Pat. Application Serial No. 60/694,078 filed Jun. 24, 2005; U.S. Provisional Pat. Application Serial No. 60/713,680 filed Sep. 1, 2005 and U.S. Provisional Pat. Application Serial No. 60/790,335 filed Apr. 7, 2006; the disclosures of which are herein incorporated by reference. 
    
    
     FIELD 
     The present invention is related to systems for detection of an event. More specifically, the present disclosure includes a system that includes a partial power source that can be activated when in contact with conductive liquid and is capable of controlling conductance to mark an event. 
     BACKGROUND 
     Ingestible devices that include electronic circuitry have been proposed for use in a variety of different medical applications, including both diagnostic and therapeutic applications. These devices typically require an internal power supply for operation. Examples of such ingestible devices are ingestible electronic capsules which collect data as they pass through the body, and transmit the data to an external receiver system. An example of this type of electronic capsule is an in-vivo video camera. The swallowable capsule includes a camera system and an optical system for imaging an area of interest onto the camera system. The transmitter transmits the video output of the camera system and the reception system receives the transmitted video output. Other examples include an ingestible imaging device, which has an internal and self contained power source, which obtains images from within body lumens or cavities. The electronic circuit components of the device are enclosed by an inert indigestible housing (e.g. glass housing) that passes through the body internally. Other examples include an ingestible data recorder capsule medical device. The electronic circuits of the disclosed device (e.g. sensor, recorder, battery etc.) are housed in a capsule made of inert materials. 
     In other examples, fragile radio frequency identification (RFID) tags are used in drug ingestion monitoring applications. In order for the RFID tags to be operational, each requires an internal power supply. The RFID tags are antenna structures that are configured to transmit a radio-frequency signal through the body. 
     The problem these existing devices pose is that the power source is internal to device and such power sources are costly to produce and potentially harmful to the surrounding environment if the power source leaks or is damaged. Additionally, having antennas extending from the device is a concern as related to the antennas getting damaged or causing a problem when the device is used in-vivo. Therefore, what is needed is suitable system with circuitry that eliminates the need for an internal power source and antennas. 
     SUMMARY 
     The present disclosure includes a system for producing a unique signature that indicates the occurrence of an event. The system includes circuitry and components that can be placed within certain environments that include a conducting fluid. One example of such an environment is inside a container that houses the conducting fluid, such as a sealed bag with a solution, which includes an IV bag. Another example is within the body of a living organism, such as an animal or a human. The systems are ingestible and/or digestible or partially digestible. The system includes dissimilar materials positioned on the framework such that when a conducting fluid comes into contact with the dissimilar materials, a voltage potential difference is created. The voltage potential difference, and hence the voltage, is used to power up control logic that is positioned within the framework. Ions or current flows from the first dissimilar material to the second dissimilar material via the control logic and then through the conducting fluid to complete a circuit The control logic controls the conductance between the two dissimilar materials and, hence, controls or modulates the conductance. 
     As the ingestible circuitry is made up of ingestible, and even digestible, components, the ingestible circuitry results in little, if any, unwanted side effects, even when employed in chronic situations. Examples of the range of components that may be included are: logic and/or memory elements; effectors; a signal transmission element; and a passive element, such as a resistor or inductor. The one or more components on the surface of the support may be laid out in any convenient configuration. Where two or more components are present on the surface of the solid support, interconnects may be provided. All of the components and the support of the ingestible circuitry are ingestible, and in certain instances digestible or partially digestible. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG.  1    shows a pharmaceutical product with an event indicator system according to the teaching of the present invention, wherein the product and the event indicator system combination are within the body. 
         FIG.  2 A  shows the pharmaceutical product of  FIG.  1    with the event indicator system on the exterior of the pharmaceutical product. 
         FIG.  2 B  shows the pharmaceutical product of  FIG.  1    with the event indicator system positioned inside the pharmaceutical product. 
         FIG.  3    is a block diagram representation of one aspect of the event indicator system with dissimilar metals positioned on opposite ends. 
         FIG.  4    is a block diagram representation of another aspect of the event indicator system with dissimilar metals positioned on the same end and separated by a non-conducting material. 
         FIG.  5    shows ionic transfer or the current path through a conducting fluid when the event indicator system of  FIG.  3    is in contact with conducting liquid and in an active state. 
         FIG.  5 A  shows an exploded view of the surface of dissimilar materials of  FIG.  5   . 
         FIG.  5 B  shows the event indicator system of  FIG.  5    with a pH sensor unit. 
         FIG.  6    is a block diagram illustration of one aspect of the control device used in the system of  FIGS.  3  and  4   . 
     
    
    
     DETAILED DESCRIPTION 
     The present disclosure includes multiple embodiments for indicating the occurrence of an event. As described in more detail below, a system of the present invention is used with a conducting fluid to indicate the event marked by contact between the conducting fluid and the system. For example, the system of the present disclosure may be used with pharmaceutical product and the event that is indicated is when the product is taken or ingested. The term “ingested” or “ingest” or “ingesting” is understood to mean any introduction of the system internal to the body. For example, ingesting includes simply placing the system in the mouth all the way to the descending colon. Thus, the term ingesting refers to any instant in time when the system is introduced to an environment that contains a conducting fluid. Another example would be a situation when a non-conducting fluid is mixed with a conducting fluid. In such a situation the system would be present in the non-conduction fluid and when the two fluids are mixed, the system comes into contact with the conducting fluid and the system is activated. Yet another example would be the situation when the presence of certain conducting fluids needed to be detected. In such instances, the presence of the system, which would be activated, within the conducting fluid could be detected and, hence, the presence of the respective fluid would be detected. 
     Referring again to the instance where the system is used with the product that is ingested by the living organism, when the product that includes the system is taken or ingested, the device comes into contact with the conducting liquid of the body. When the system of the present invention comes into contact with the body fluid, a voltage potential is created and the system is activated. A portion of the power source is provided by the device, while another portion of the power source is provided by the conducting fluid, which is discussed in detail below. 
     Referring now to  FIG.  1   , an ingestible product  14  that includes a system of the present invention is shown inside the body. The product  14  is configured as an orally ingestible pharmaceutical formulation in the form of a pill or capsule. Upon ingestion, the pill moves to the stomach. Upon reaching the stomach, the product  14  is in contact with stomach fluid  18  and undergoes a chemical reaction with the various materials in the stomach fluid  18 , such as hydrochloric acid and other digestive agents. The system of the present invention is discussed in reference to a pharmaceutical environment. However, the scope of the present invention is not limited thereby. The present invention can be used in any environment where a conducting fluid is present or becomes present through mixing of two or more components that result in a conducting liquid. 
     Referring now to  FIG.  2 A , a pharmaceutical product  10 , similar to the product  14  of  FIG.  1   , is shown with a system  12 , such as an ingestible event marker or an ionic emission module. The scope of the present invention is not limited by the shape or type of the product  10 . For example, it will be clear to one skilled in the art that the product  10  can be a capsule, a time-release oral dosage, a tablet, a gel cap, a sub-lingual tablet, or any oral dosage product that can be combined with the system  12 . In the referenced embodiment, the product  10  has the system  12  secured to the exterior using known methods of securing micro-devices to the exterior of pharmaceutical products. Example of methods for securing the micro-device to the product is disclosed in U.S. Provisional Application No. 61/142,849 filed on Jan. 1, 2009 and entitled “HIGH-THROUGHPUT PRODUCTION OF INGESTIBLE EVENT MARKERS” as well as U.S. Provisional Application No. 61/177,611 filed on May 12, 2009 and entitled “INGESTIBLE EVENT MARKERS COMPRISING AN IDENTIFIER AND AN INGESTIBLE COMPONENT”, the entire disclosure of each is incorporated herein by reference. Once ingested, the system  12  comes into contact with body liquids and the system  12  is activated. The system  12  uses the voltage potential difference to power up and thereafter modulates conductance to create a unique and identifiable current signature. Upon activation, the system  12  controls the conductance and, hence, current flow to produce the current signature. 
     There are various reasons for delaying the activation of the system  12 . In order to delay the activation of the system  12 , the system  12  may be coated with a shielding material or protective layer. The layer is dissolved over a period of time, thereby allowing the system  12  to be activated when the product  10  has reached a target location. 
     Referring now to  FIG.  2 B , a pharmaceutical product  20 , similar to the product  14  of  FIG.  1   , is shown with a system  22 , such as an ingestible event marker or an identifiable emission module. The scope of the present invention is not limited by the environment to which the system  22  is introduced. For example, the system  22  can be enclosed in a capsule that is taken in addition to/independently from the pharmaceutical product. The capsule may be simply a carrier for the system  22  and may not contain any product. Furthermore, the scope of the present invention is not limited by the shape or type of product  20 . For example, it will be clear to one skilled in the art that the product  20  can be a capsule, a time-release oral dosage, a tablet, a gel capsule, a sub-lingual tablet, or any oral dosage product. In the referenced embodiment, the product  20  has the system  22  positioned inside or secured to the interior of the product  20 . In one embodiment, the system  22  is secured to the interior wall of the product  20 . When the system  22  is positioned inside a gel capsule, then the content of the gel capsule is a non-conducting gel-liquid. On the other hand, if the content of the gel capsule is a conducting gel-liquid, then in an alternative embodiment, the system  22  is coated with a protective cover to prevent unwanted activation by the gel capsule content. If the content of the capsule is a dry powder or microspheres, then the system  22  is positioned or placed within the capsule. If the product  20  is a tablet or hard pill, then the system  22  is held in place inside the tablet. Once ingested, the product  20  containing the system  22  is dissolved. The system  22  comes into contact with body liquids and the system  22  is activated. Depending on the product  20 , the system  22  may be positioned in either a near-central or near-perimeter position depending on the desired activation delay between the time of initial ingestion and activation of the system  22 . For example, a central position for the system  22  means that it will take longer for the system  22  to be in contact with the conducting liquid and, hence, it will take longer for the system  22  to be activated. Therefore, it will take longer for the occurrence of the event to be detected. 
     Referring now to  FIG.  3   , in one embodiment, the systems  12  and  22  of  FIGS.  2 A and  2 B , respectively, are shown in more detail as system  30 . The system  30  can be used in association with any pharmaceutical product, as mentioned above, to determine when a patient takes the pharmaceutical product. As indicated above, the scope of the present invention is not limited by the environment and the product that is used with the system  30 . For example, the system  30  may be placed within a capsule and the capsule is placed within the conducting liquid. The capsule would then dissolve over a period of time and release the system  30  into the conducting liquid. Thus, in one embodiment, the capsule would contain the system  30  and no product. Such a capsule may then be used in any environment where a conducting liquid is present and with any product. For example, the capsule may be dropped into a container filled with jet fuel, salt water, tomato sauce, motor oil, or any similar product. Additionally, the capsule containing the system  30  may be ingested at the same time that any pharmaceutical product is ingested in order to record the occurrence of the event, such as when the product was taken. 
     In the specific example of the system  30  combined with the pharmaceutical product, as the product or pill is ingested, the system  30  is activated. The system  30  controls conductance to produce a unique current signature that is detected, thereby signifying that the pharmaceutical product has been taken. The system  30  includes a framework  32 . The framework  32  is a chassis for the system  30  and multiple components are attached to, deposited upon, or secured to the framework  32 . In this embodiment of the system  30 , a digestible material  34  is physically associated with the framework  32 . The material  34  may be chemically deposited on, evaporated onto, secured to, or built-up on the framework all of which may be referred to herein as “deposit” with respect to the framework  32 . The material  34  is deposited on one side of the framework  32 . The materials of interest that can be used as material  34  include, but are not limited to: Cu or Cul. The material  34  is deposited by physical vapor deposition, electrodeposition, or plasma deposition, among other protocols. The material  34  may be from about 0.05 to about 500 µm thick, such as from about 5 to about 100 µm thick. The shape is controlled by shadow mask deposition, or photolithography and etching. Additionally, even though only one region is shown for depositing the material, each system  30  may contain two or more electrically unique regions where the material  34  may be deposited, as desired. 
     At a different side, which is the opposite side as shown in  FIG.  3   , another digestible material  36  is deposited, such that materials  34  and  36  are dissimilar. Although not shown, the different side selected may be the side next to the side selected for the material  34 . The scope of the present invention is not limited by the side selected and the term “different side” can mean any of the multiple sides that are different from the first selected side. Furthermore, even though the shape of the system is shown as a square, the shape maybe any geometrically suitable shape. Material  34  and  36  are selected such that they produce a voltage potential difference when the system  30  is in contact with conducting liquid, such as body fluids. The materials of interest for material  36  include, but are not limited to: Mg, Zn, or other electronegative metals. As indicated above with respect to the material  34 , the material  36  may be chemically deposited on, evaporated onto, secured to, or built-up on the framework. Also, an adhesion layer may be necessary to help the material  36  (as well as material  34  when needed) to adhere to the framework  32 . Typical adhesion layers for the material  36  are Ti, TiW, Cr or similar material. Anode material and the adhesion layer may be deposited by physical vapor deposition, electrodeposition or plasma deposition. The material  36  may be from about 0.05 to about 500 µm thick, such as from about 5 to about 100 µm thick. However, the scope of the present invention is not limited by the thickness of any of the materials nor by the type of process used to deposit or secure the materials to the framework  32 . 
     According to the disclosure set forth, the materials  34  and  36  can be any pair of materials with different electrochemical potentials. Additionally, in the embodiments wherein the system  30  is used in-vivo, the materials  34  and  36  may be vitamins that can be absorbed. More specifically, the materials  34  and  36  can be made of any two materials appropriate for the environment in which the system  30  will be operating. For example, when used with an ingestible product, the materials  34  and  36  are any pair of materials with different electrochemical potentials that are ingestible. An illustrative example includes the instance when the system  30  is in contact with an ionic solution, such as stomach acids. Suitable materials are not restricted to metals, and in certain embodiments the paired materials are chosen from metals and non-metals, e.g., a pair made up of a metal (such as Mg) and a salt (such as CuCl or Cul). With respect to the active electrode materials, any pairing of substances - metals, salts, or intercalation compounds - with suitably different electrochemical potentials (voltage) and low interfacial resistance are suitable. 
     Materials and pairings of interest include, but are not limited to, those reported in Table 1 below. In one embodiment, one or both of the metals may be doped with a non-metal, e.g., to enhance the voltage potential created between the materials as they come into contact with a conducting liquid. Non-metals that may be used as doping agents in certain embodiments include, but are not limited to: sulfur, iodine and the like. In another embodiment, the materials are copper iodine (Cul) as the anode and magnesium (Mg) as the cathode. Embodiments of the present invention use electrode materials that are not harmful to the human body. 
     
       
         
          TABLE 1
           
               
               
               
            
               
                   
                 Anode 
                 Cathode 
               
               
                 Metals 
                 Magnesium, Zinc Sodium (†) Lithium (†) Iron 
                   
               
               
                 Salts 
                   
                 Copper salts: iodide, chloride, bromide, sulfate, formate, (other anions possible) Fe 3+  salts: e.g. orthophosphate, pyrophosphate, (other anions possible) Oxygen (††) on platinum, gold or other 
               
               
                   
                   
                 catalytic surfaces 
               
               
                 Intercalation compounds 
                 Graphite with Li, K, Ca, Na, Mg 
                 Vanadium oxide Manganese oxide 
               
            
           
         
       
     
     Thus, when the system  30  is in contact with the conducting liquid, a current path, an example is shown in  FIG.  5   , is formed through the conducting liquid between material  34  and  36 . A control device  38  is secured to the framework  32  and electrically coupled to the materials  34  and  36 . The control device  38  includes electronic circuitry, for example control logic that is capable of controlling and altering the conductance between the materials  34  and  36 . 
     The voltage potential created between the materials  34  and  36  provides the power for operating the system as well as produces the current flow through the conducting fluid and the system. In one embodiment, the system operates in direct current mode. In an alternative embodiment, the system controls the direction of the current so that the direction of current is reversed in a cyclic manner, similar to alternating current. As the system reaches the conducting fluid or the electrolyte, where the fluid or electrolyte component is provided by a physiological fluid, e.g., stomach acid, the path for current flow between the materials  34  and  36  is completed external to the system  30 ; the current path through the system  30  is controlled by the control device  38 . Completion of the current path allows for the current to flow and in turn a receiver, not shown, can detect the presence of the current and recognize that the system  30  has been activate and the desired event is occurring or has occurred. 
     In one embodiment, the two materials  34  and  36  are similar in function to the two electrodes needed for a direct current power source, such as a battery. The conducting liquid acts as the electrolyte needed to complete the power source. The completed power source described is defined by the physical chemical reaction between the materials  34  and  36  of the system  30  and the surrounding fluids of the body. The completed power source may be viewed as a power source that exploits reverse electrolysis in an ionic or a conduction solution such as gastric fluid, blood, or other bodily fluids and some tissues. Additionally, the environment may be something other than a body and the liquid may be any conducting liquid. For example, the conducting fluid may be salt water or a metallic based paint. 
     In certain embodiments, these two materials are shielded from the surrounding environment by an additional layer of material. Accordingly, when the shield is dissolved and the two dissimilar materials are exposed to the target site, a voltage potential is generated. 
     In certain embodiments, the complete power source or supply is one that is made up of active electrode materials, electrolytes, and inactive materials, such as current collectors, packaging, etc. The active materials are any pair of materials with different electrochemical potentials. Suitable materials are not restricted to metals, and in certain embodiments the paired materials are chosen from metals and non-metals, e.g., a pair made up of a metal (such as Mg) and a salt (such as Cul). With respect to the active electrode materials, any pairing of substances - metals, salts, or intercalation compounds - with suitably different electrochemical potentials (voltage) and low interfacial resistance are suitable. 
     A variety of different materials may be employed as the materials that form the electrodes. In certain embodiments, electrode materials are chosen to provide for a voltage upon contact with the target physiological site, e.g., the stomach, sufficient to drive the system of the identifier. In certain embodiments, the voltage provided by the electrode materials upon contact of the metals of the power source with the target physiological site is 0.001 V or higher, including 0.01 V or higher, such as 0.1 V or higher, e.g., 0.3 V or higher, including 0.5 volts or higher, and including 1.0 volts or higher, where in certain embodiments, the voltage ranges from about 0.001 to about 10 volts, such as from about 0.01 to about 10 V. 
     Referring again to  FIG.  3   , the materials  34  and  36  provide the voltage potential to activate the control device  38 . Once the control device  38  is activated or powered up, the control device  38  can alter conductance between the materials  34  and  36  in a unique manner. By altering the conductance between materials  34  and  36 , the control device  38  is capable of controlling the magnitude of the current through the conducting liquid that surrounds the system  30 . This produces a unique current signature that can be detected and measured by a receiver (not shown), which can be positioned internal or external to the body. In addition to controlling the magnitude of the current path between the materials, non-conducting materials, membrane, or “skirt” are used to increase the “length” of the current path and, hence, act to boost the conductance path, as disclosed in the U.S. Pat. Application Serial No. 12/238,345 entitled, “In-Body Device with Virtual Dipole Signal Amplification” filed Sep. 25, 2008, the entire content of which is incorporated herein by reference. Alternatively, throughout the disclosure herein, the terms “non-conducting material”, “membrane”, and “skirt” are interchangeably with the term “current path extender” without impacting the scope or the present embodiments and the claims herein. The skirt, shown in portion at  35  and  37 , respectively, may be associated with, e.g., secured to, the framework  32 . Various shapes and configurations for the skirt are contemplated as within the scope of the present invention. For example, the system  30  may be surrounded entirely or partially by the skirt and the skirt maybe positioned along a central axis of the system  30  or off-center relative to a central axis. Thus, the scope of the present invention as claimed herein is not limited by the shape or size of the skirt. Furthermore, in other embodiments, the materials  34  and  36  may be separated by one skirt that is positioned in any defined region between the materials  34  and  36 . 
     Referring now to  FIG.  4   , in another embodiment, the systems  12  and  22  of  FIGS.  2 A and  2 B , respectively, are shown in more detail as system  40 . The system  40  includes a framework  42 . The framework  42  is similar to the framework  32  of  FIG.  3   . In this embodiment of the system  40 , a digestible or dissolvable material  44  is deposited on a portion of one side of the framework  42 . At a different portion of the same side of the framework  42 , another digestible material  46  is deposited, such that materials  44  and  46  are dissimilar. More specifically, material  44  and  46  are selected such that they form a voltage potential difference when in contact with a conducting liquid, such as body fluids. Thus, when the system  40  is in contact with and/or partially in contact with the conducting liquid, then a current path, an example is shown in  FIG.  5   , is formed through the conducting liquid between material  44  and  46 . A control device  48  is secured to the framework  42  and electrically coupled to the materials  44  and  46 . The control device  48  includes electronic circuitry that is capable of controlling part of the conductance path between the materials  44  and  46 . The materials  44  and  46  are separated by a non-conducting skirt  49 . Various examples of the skirt  49  are disclosed in U.S. Provisional Application No. 61/173,511 filed on Apr. 28, 2009 and entitled “HIGHLY RELIABLE INGESTIBLE EVENT MARKERS AND METHODS OF USING SAME” and U.S. Provisional Application No. 61/173,564 filed on Apr. 28, 2009 and entitled “INGESTIBLE EVENT MARKERS HAVING SIGNAL AMPLIFIERS THAT COMPRISE AN ACTIVE AGENT”; as well as U.S. Application No. 12/238,345 filed Sep. 25, 2008 and entitled “IN-BODY DEVICE WITH VIRTUAL DIPOLE SIGNAL AMPLIFICATION”; the entire disclosure of each is incorporated herein by reference. 
     Once the control device  48  is activated or powered up, the control device  48  can alter conductance between the materials  44  and  46 . Thus, the control device  48  is capable of controlling the magnitude of the current through the conducting liquid that surrounds the system  40 . As indicated above with respect to system  30 , a unique current signature that is associated with the system  40  can be detected by a receiver (not shown) to mark the activation of the system  40 . In order to increase the “length” of the current path the size of the skirt  49  is altered. The longer the current path, the easier it may be for the receiver to detect the current. 
     Referring now to  FIG.  5   , the system  30  of  FIG.  3    is shown in an activated state and in contact with conducting liquid. The system  30  is grounded through ground contact  52 . The system  30  also includes a sensor module  74 , which is described in greater detail with respect to  FIG.  6   . Ion or current paths  50  between material  34  to material  36  and through the conducting fluid in contact with the system  30 . The voltage potential created between the material  34  and  36  is created through chemical reactions between materials  34 / 36  and the conducting fluid.  FIG.  5 A  shows an exploded view of the surface of the material  34 . The surface of the material  34  is not planar, but rather an irregular surface. The irregular surface increases the surface area of the material and, hence, the area that comes in contact with the conducting fluid. 
     In one embodiment, at the surface of the material  34 , there is chemical reaction between the material  34  and the surrounding conducting fluid such that mass is released into the conducting fluid. The term “mass” as used herein refers to protons and neutrons that form a substance. One example includes the instant where the material is CuCl and when in contact with the conducting fluid, CuCl becomes Cu (solid) and Cl -  in solution. The flow of ions into the conduction fluid is depicted by the ion paths  50 . In a similar manner, there is a chemical reaction between the material  36  and the surrounding conducting fluid and ions are captured by the material  36 . The release of ions at the material  34  and capture of ion by the material  36  is collectively referred to as the ionic exchange. The rate of ionic exchange and, hence the ionic emission rate or flow, is controlled by the control device  38 . The control device  38  can increase or decrease the rate of ion flow by altering the conductance, which alters the impedance, between the materials  34  and  36 . Through controlling the ion exchange, the system  30  can encode information in the ionic exchange process. Thus, the system  30  uses ionic emission to encode information in the ionic exchange. 
     The control device  38  can vary the duration of a fixed ionic exchange rate or current flow magnitude while keeping the rate or magnitude near constant, similar to when the frequency is modulated and the amplitude is constant. Also, the control device  38  can vary the level of the ionic exchange rate or the magnitude of the current flow while keeping the duration near constant. Thus, using various combinations of changes in duration and altering the rate or magnitude, the control device  38  encodes information in the current flow or the ionic exchange. For example, the control device  38  may use, but is not limited to any of the following techniques namely, Binary Phase-Shift Keying (PSK), Frequency modulation, Amplitude modulation, on-off keying, and PSK with on-off keying. 
     As indicated above, the various embodiments disclosed herein, such as systems  30  and  40  of  FIGS.  3  and  4   , respectively, include electronic components as part of the control device  38  or the control device  48 . Components that may be present include but are not limited to: logic and/or memory elements, an integrated circuit, an inductor, a resistor, and sensors for measuring various parameters. Each component may be secured to the framework and/or to another component. The components on the surface of the support may be laid out in any convenient configuration. Where two or more components are present on the surface of the solid support, interconnects may be provided. 
     As indicated above, the system, such as system  30  and  40 , control the conductance between the dissimilar materials and, hence, the rate of ionic exchange or the current flow. Through altering the conductance in a specific manner the system is capable of encoding information in the ionic exchange and the current signature. The ionic exchange or the current signature is used to uniquely identify the specific system. Additionally, the systems  30  and  40  are capable of producing various different unique exchanges or signatures and, thus, provide additional information. For example, a second current signature based on a second conductance alteration pattern may be used to provide additional information, which information may be related to the physical environment. To further illustrate, a first current signature may be a very low current state that maintains an oscillator on the chip and a second current signature may be a current state at least a factor of ten higher than the current state associated with the first current signature. 
     Referring now to  FIG.  6   , a block diagram representation of the control device  38  is shown. The device  30  includes a control module  62 , a counter or clock  64 , and a memory  66 . Additionally, the device  38  is shown to include a sensor module  72  as well as the sensor module  74 , which was referenced in  FIG.  5   . The control module  62  has an input 68 electrically coupled to the material  34  and an output  70  electrically coupled to the material  36 . The control module  62 , the clock  64 , the memory  66 , and the sensor modules  72 / 74  also have power inputs (some not shown). The power for each of these components is supplied by the voltage potential produced by the chemical reaction between materials  34  and  36  and the conducting fluid, when the system  30  is in contact with the conducting fluid. The control module  62  controls the conductance through logic that alters the overall impedance of the system  30 . The control module  62  is electrically coupled to the clock  64 . The clock  64  provides a clock cycle to the control module  62 . Based upon the programmed characteristics of the control module  62 , when a set number of clock cycles have passed, the control module  62  alters the conductance characteristics between materials  34  and  36 . This cycle is repeated and thereby the control device  38  produces a unique current signature characteristic. The control module  62  is also electrically coupled to the memory  66 . Both the clock  64  and the memory  66  are powered by the voltage potential created between the materials  34  and  36 . 
     The control module  62  is also electrically coupled to and in communication with the sensor modules  72  and  74 . In the embodiment shown, the sensor module  72  is part of the control device  38  and the sensor module  74  is a separate component. In alternative embodiments, either one of the sensor modules  72  and  74  can be used without the other and the scope of the present invention is not limited by the structural or functional location of the sensor modules  72  or  74 . Additionally, any component of the system  30  may be functionally or structurally moved, combined, or repositioned without limiting the scope of the present invention as claimed. Thus, it is possible to have one single structure, for example a processor, which is designed to perform the functions of all of the following modules: the control module  62 , the clock  64 , the memory  66 , and the sensor module  72  or  74 . On the other hand, it is also within the scope of the present invention to have each of these functional components located in independent structures that are linked electrically and able to communicate. 
     Referring again to  FIG.  6   , the sensor modules  72  or  74  can include any of the following sensors: temperature, pressure, pH level, and conductivity. In one embodiment, the sensor modules  72  or  74  gather information from the environment and communicate the analog information to the control module  62 . The control module then converts the analog information to digital information and the digital information is encoded in the current flow or the rate of the transfer of mass that produces the ionic flow. In another embodiment, the sensor modules  72  or  74  gather information from the environment and convert the analog information to digital information and then communicate the digital information to control module  62 . In the embodiment shown in  FIG.  5   , the sensor modules  74  is shown as being electrically coupled to the material  34  and  36  as well as the control device  38 . In another embodiment, as shown in  FIG.  6   , the sensor module  74  is electrically coupled to the control device  38  at connection  78 . The connection  78  acts as both a source for power supply to the sensor module  74  and a communication channel between the sensor module  74  and the control device  38 . 
     Referring now to  FIG.  5 B , the system  30  includes a pH sensor module  76  connected to a material  39 , which is selected in accordance with the specific type of sensing function being performed. The pH sensor module  76  is also connected to the control device  38 . The material  39  is electrically isolated from the material  34  by a non-conductive barrier  55 . In one embodiment, the material  39  is platinum. In operation, the pH sensor module  76  uses the voltage potential difference between the materials  34 / 36 . The pH sensor module  76  measures the voltage potential difference between the material  34  and the material  39  and records that value for later comparison. The pH sensor module  76  also measures the voltage potential difference between the material  39  and the material  36  and records that value for later comparison. The pH sensor module  76  calculates the pH level of the surrounding environment using the voltage potential values. The pH sensor module  76  provides that information to the control device  38 . The control device  38  varies the rate of the transfer of mass that produces the ionic transfer and the current flow to encode the information relevant to the pH level in the ionic transfer, which can be detected by a receiver (not shown). Thus, the system  30  can determine and provide the information related to the pH level to a source external to the environment. 
     As indicated above, the control device  38  can be programmed in advance to output a pre-defined current signature. In another embodiment, the system can include a receiver system that can receive programming information when the system is activated. In another embodiment, not shown, the switch  64  and the memory  66  can be combined into one device. 
     In addition to the above components, the system  30  may also include one or other electronic components. Electrical components of interest include, but are not limited to: additional logic and/or memory elements, e.g., in the form of an integrated circuit; a power regulation device, e.g., battery, fuel cell or capacitor; a sensor, a stimulator, etc.; a signal transmission element, e.g., in the form of an antenna, electrode, coil, etc.; a passive element, e.g., an inductor, resistor, etc. 
     In certain embodiments, the ingestible circuitry includes a coating layer. The purpose of this coating layer can vary, e.g., to protect the circuitry, the chip and/or the battery, or any components during processing, during storage, or even during ingestion. In such instances, a coating on top of the circuitry may be included. Also of interest are coatings that are designed to protect the ingestible circuitry during storage, but dissolve immediately during use. For example, coatings that dissolve upon contact with an aqueous fluid, e.g. stomach fluid, or the conducting fluid as referenced above. Also of interest are protective processing coatings that are employed to allow the use of processing steps that would otherwise damage certain components of the device. For example, in embodiments where a chip with dissimilar material deposited on the top and bottom is produced, the product needs to be diced. However, the dicing process can scratch off the dissimilar material, and also there might be liquid involved which would cause the dissimilar materials to discharge or dissolve. In such instances, a protective coating on the materials prevents mechanical or liquid contact with the component during processing can be employed. Another purpose of the dissolvable coatings may be to delay activation of the device. For example, the coating that sits on the dissimilar material and takes a certain period of time, e.g., five minutes, to dissolve upon contact with stomach fluid may be employed. The coating can also be an environmentally sensitive coating, e.g., a temperature or pH sensitive coating, or other chemically sensitive coating that provides for dissolution in a controlled fashion and allows one to activate the device when desired. Coatings that survive the stomach but dissolve in the intestine are also of interest, e.g., where one desires to delay activation until the device leaves the stomach. An example of such a coating is a polymer that is insoluble at low pH, but becomes soluble at a higher pH. Also of interest are pharmaceutical formulation protective coatings, e.g., a gel cap liquid protective coating that prevents the circuit from being activated by liquid of the gel cap. 
     Identifiers of interest include two dissimilar electrochemical materials, which act similar to the electrodes (e.g., anode and cathode) of a power source. The reference to an electrode or anode or cathode are used here merely as illustrative examples. The scope of the present invention is not limited by the label used and includes the embodiment wherein the voltage potential is created between two dissimilar materials. Thus, when reference is made to an electrode, anode, or cathode it is intended as a reference to a voltage potential created between two dissimilar materials. 
     When the materials are exposed and come into contact with the body fluid, such as stomach acid or other types of fluid (either alone or in combination with a dried conductive medium precursor), a potential difference, that is, a voltage, is generated between the electrodes as a result of the respective oxidation and reduction reactions incurred to the two electrode materials. A voltaic cell, or battery, can thereby be produced. Accordingly, in embodiments of the invention, such power supplies are configured such that when the two dissimilar materials are exposed to the target site, e.g., the stomach, the digestive tract, etc., a voltage is generated. 
     In certain embodiments, one or both of the metals may be doped with a non-metal, e.g., to enhance the voltage output of the battery. Non-metals that may be used as doping agents in certain embodiments include, but are not limited to: sulfur, iodine and the like. 
     It is to be understood that this invention is not limited to particular embodiments or aspects described, as such may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims. 
     Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limit of that range and any other stated or intervening value in that stated range, is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included in the smaller ranges and are also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention. 
     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. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention, representative illustrative methods and materials are now described. 
     All publications and patents cited in this specification are herein incorporated by reference as if each individual publication or patent were specifically and individually indicated to be incorporated by reference and are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited. The citation of any publication is for its disclosure prior to the filing date and should not be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed. 
     It is noted that, as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. It is further noted that the claims may be drafted to exclude any optional element. As such, this statement is intended to serve as antecedent basis for use of such exclusive terminology as “solely,” “only” and the like in connection with the recitation of claim elements, or use of a “negative” limitation. 
     As will be apparent to those of skill in the art upon reading this disclosure, each of the individual embodiments described and illustrated herein has discrete components and features which may be readily separated from or combined with the features of any of the other several embodiments without departing from the scope or spirit of the present invention. Any recited method can be carried out in the order of events recited or in any other order which is logically possible. 
     Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity of understanding, it is readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims. 
     Accordingly, the preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present invention is embodied by the appended claims.