Patent Description:
In an aspect, a radio frequency identification (RFID) tag includes, but is not limited to, a flexible substrate having a first portion and a second portion extending from the first portion, the first portion foldable between a planar configuration and a tubular configuration, the second portion foldable between a planar configuration and a folded configuration; a conductive element disposed at least on a first side of the first portion of the flexible substrate; and an RFID tag chip disposed at least on a first side of the second portion of the flexible substrate.

In an aspect, a system includes, but is not limited to, an RFID tag structured and dimensioned for ingestion by a biological subject, the RFID tag including a flexible substrate having a first portion and a second portion extending from the first portion, the first portion foldable between a planar configuration and a tubular configuration, the second portion foldable between a planar configuration and a folded configuration, a conductive element disposed at least on a first side of the first portion of the flexible substrate, and an RFID tag chip disposed at least on a first side of the second portion of the flexible substrate; and an RFID reader including a coil structured and dimensioned to interrogate the RFID tag within the biological subject.

In an aspect, a system includes, but is not limited to, an RFID tag including a flexible substrate having a first portion and a second portion extending from the first portion, the first portion foldable between a planar configuration and a tubular configuration, the second portion foldable between a planar configuration and a folded configuration, a conductive element disposed at least on a first side of the first portion of the flexible substrate, and an RFID tag chip disposed at least on a first side of the second portion of the flexible substrate; a capsule structured and dimensioned for ingestion by a biological subject, the capsule including a shell structured and dimensioned to enclose the RFID tag when the first portion of the flexible substrate is in the tubular configuration, but not when the first portion of the flexible substrate is in the planar configuration; and an RFID reader including a coil structured and dimensioned to interrogate the RFID tag within the biological subject.

In an aspect, a system includes, but is not limited to, an RFID tag including a flexible substrate foldable between a planar configuration and a tubular configuration, a conductive element disposed at least on a first side of the flexible substrate, and an RFID tag chip disposed at least on the first side of the flexible substrate electrically coupled with the conductive element; a capsule structured and dimensioned for ingestion by a biological subject, the capsule including a shell structured and dimensioned to enclose a medication for the biological subject simultaneously with the RFID tag when the flexible substrate is in the tubular configuration, but not when the flexible substrate is in the planar configuration; and a pH switch structure coupled to an exterior surface of the capsule, the pH switch configured to deactivate the RFID tag in a first configuration of the pH switch structure and to permit activation of the RFID tag in a second configuration of the pH switch structure within the biological subject.

In an aspect, a system includes, but is not limited to, an RFID tag including a flexible substrate foldable between a planar configuration and a tubular configuration, a conductive element disposed at least on a first side of the flexible substrate, and an RFID tag chip disposed at least on the first side of the flexible substrate electrically coupled with the conductive element; a capsule structured and dimensioned for ingestion by a biological subject, the capsule including a shell structured and dimensioned to enclose a medication for the biological subject simultaneously with the RFID tag when the flexible substrate is in the tubular configuration, but not when the flexible substrate is in the planar configuration; a pH switch structure coupled to an exterior surface of the capsule, the pH switch configured to deactivate the RFID tag in a first configuration of the pH switch structure and to permit activation of the RFID tag in a second configuration of the pH switch structure within the biological subject; and an RFID reader including a coil structured and dimensioned to interrogate the RFID tag within the biological subject.

In an aspect, a system includes, but is not limited to, a capsule structured and dimensioned for ingestion by a biological subject, the capsule including a shell structured and dimensioned to enclose a medication for the biological subject simultaneously with the RFID tag; the RFID tag including a flexible substrate formed in a structure for positioning within the capsule, a conductive element disposed at least on a first side of the flexible substrate, and an RFID tag chip disposed at least on a second side of the flexible substrate; and a pH switch structure coupled to an exterior surface of the capsule, the pH switch configured to deactivate the RFID tag in a first configuration of the pH switch structure and to permit activation of the RFID tag in a second configuration of the pH switch structure within the biological subject.

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the scope of the subject matter presented here.

Systems are described herein for ingestible radio frequency identification (RFID) tags, which can be utilized for tracking adherence of patients to medication protocols. For certain disease states, a patient may be directed to adhere to a medication course involving ingestion of multiple dosages per day, ingestion of multiple different drug capsules per day, ingestion of medication for multiple days, or combinations thereof. For example, treatment of tuberculosis or other infectious diseases can involve multiple doses of antibiotics over the course of multiple weeks or months. Patient compliance with a medication course can decline with long courses or complex dosages of medication. Other times, as a patient begins to feel short term benefits of the medication course, the patient may fail to complete the medication course, which can lead to failure to fully treat a disease, a risk of resurgence of the disease or disease symptoms, activation of latent bacteria, or the like. In some instances, patients may be motivated to sell the medication rather than use it for treatment of a condition as prescribed. For instance, a patient may attempt to feign taking the medication only to remove the medication from the treatment facility without ingestion.

Systems described herein include ingestible RFID tags to accompany medication as it is ingested by a patient, and associated readers positioned external to the patient to register the presence of the ingestible RFID tag within the patient, or lack thereof. These systems can be utilized by medical personnel to confirm ingestion of oral medications, for example to confirm compliance with a specific and prescribed medication regimen. The ingestible RFID tags incorporate a flexible substrate that can facilitate transition between a planar state and a cylindrical or tubular state. RFID tags in the tubular state can be positioned within a capsule (e.g., a gel-based capsule, a synthetic polymer-based capsule, etc.) while allowing space for medication within the capsule, such as within an internal region of the RFID tags in the tubular state. The flexible substrate can include a first portion for positioning of an RFID tag coil and a second portion for positioning of RFID tag chip hardware. The second portion of the flexible substrate extends from the first portion to provide a relatively large surface area for the RFID tag coil on the first portion, while retaining a form factor suitable for insertion within a medication capsule. In some embodiments, the flexible substrate includes the RFID tag chip hardware and the RFID tag coil on the same portion of the flexible substrate.

The systems described herein can include mechanisms to verify that a medication has been ingested by a patient within a recent time period. Such mechanisms can prevent detection of the RFID tag when the RFID tag is present in an environment outside the patient and permit detection when the RFID tag is present within the patient (e.g., in the stomach). For example, the RFID tag can be positioned within a capsule (e.g., in a tubular state within the capsule interior) and the capsule can include a pH switch structure that utilizes a change in pH between the environment external to the patient and the environment internal to the patient (e.g., the digestive system) to permit detection of the RFID tag within the patient. In some embodiments, the pH switch structure is coupled to an exterior surface of the capsule to shield or otherwise interfere with communications between the RFID tag within the capsule and an external RFID reader. The pH switch structure can transition between structural states in response to exposure to a specific pH range (e.g., a pH range associated with a stomach or stomach acid) to reduce shielding or mitigate interference with communications between the RFID tag within the capsule and the external RFID reader to permit identification of the RFID tag within the patient. For example, the pH switch structure can include a biocompatible metal that reacts with hydrochloric acid in the stomach to dissolve at least a portion of the pH switch structure when in the stomach and that remains intact when outside the patient.

Referring to <FIG>, an example system <NUM> for providing an ingestible RFID tag with an associated reader is shown, which can serve as context for one or more devices and/or systems described herein. The system <NUM> includes an RFID tag <NUM> having a size and shape for introduction to a digestive system <NUM> of an individual subject <NUM>, such as through ingestion of the RFID tag <NUM> by the individual subject <NUM>. The RFID tag <NUM> includes an architecture that incorporates conductive element coils that can be rolled into a cylindrical or tubular form and associated with a medication, such as being placed within a medication capsule, being formed with medicine as a medication tablet or capsule, or the like. In some embodiments, the RFID tag <NUM> is manufactured as a flexible tubular structure, such as with 3D printing. In some embodiments, the RFID tag <NUM> is manufactured as a flexible planar structure which is then rolled or folded into a cylindrical or tubular form and associated with a medication. For example, the RFID tag <NUM> includes a flexible substrate <NUM> that is foldable between a planar configuration (e.g., shown in <FIG>) and a folded or tubular configuration (e.g., shown in <FIG>). The flexible substrate <NUM> can include, but is not limited to, a polyimide material, a polyester film material (e.g., stretched polyethylene terephthalate ("Mylar")), or other material to facilitate reversible folding between the planar configuration and the folded or tubular configuration. The conductive element coils can be positioned, etched, printed, or otherwise formed on a single side of the flexible substrate <NUM> or on multiple sides of the flexible substrate <NUM>. The flexible substrate <NUM> facilitates introduction of the RFID tag <NUM> into a capsule <NUM> when in the folded or tubular configuration to accompany medication within the capsule for ingestion by the individual subject <NUM>. The system <NUM> includes an RFID reader <NUM> to identify the presence of the RFID tag <NUM> within the individual subject <NUM> through radio frequency interrogation. The system <NUM> can be utilized with human subjects (e.g., individual subject <NUM>) or non-human subjects (e.g., domesticated or non-domesticated animals) to introduce the RFID tag <NUM> to the subject, which can be utilized to track compliance with medication protocols.

Referring to <FIG>, an example RFID tag <NUM> is shown in a planar configuration. The RFID tag <NUM> includes the flexible substrate <NUM>, where the flexible substrate <NUM> includes at least two portions: a first portion <NUM> and a second portion <NUM> extending from the first portion <NUM>. The first portion <NUM> provides a relatively large surface area to support a conductive element <NUM> arranged in a rectangular coil pattern on at least a first side <NUM> of the first portion <NUM>. The conductive element <NUM> can include a metallic material, such as a metallic foil. In some embodiments, the conductive element <NUM> includes a copper material, such as a copper foil. In some embodiments, the conductive element <NUM> includes a screenprinted conductor. In some embodiments, the flexible substrate <NUM> includes a polyester film substrate (e.g., stretched polyethylene terephthalate ("Mylar")) with silver ink conductors as the conductive element <NUM> on and/or in the polyester film. The second portion <NUM> supports an RFID tag chip <NUM> on a first side <NUM> of the second portion <NUM>. The first portion <NUM> is foldable between a planar configuration (e.g., shown in <FIG>) and a tubular configuration (e.g., shown in <FIG>) to facilitate introduction of the RFID tag <NUM> into the capsule <NUM>. For example, the first portion <NUM> includes a first end <NUM> and a second end <NUM> opposing the first end <NUM>, where the first end <NUM> is positioned adjacent the second end <NUM> when the first portion <NUM> is in the tubular configuration. In some embodiments, the first end <NUM> is not coupled to the second end <NUM> when the first portion <NUM> is in the tubular configuration. For example, a gap or spacing between the first end <NUM> and the second end <NUM> can be present when the first portion <NUM> is in the tubular configuration. Alternatively or additionally, the first end <NUM> and the second end <NUM> can at least partially overlap when the first portion <NUM> is in the tubular configuration. In some embodiments, the second portion <NUM> has a surface area that is less than a surface area of the first portion <NUM>. For instance, the surface area occupied by the conductive element <NUM> in the coil pattern can be larger than the surface area occupied by the RFID tag chip <NUM> and other devices or objects positioned on the second portion <NUM>.

In some embodiments, the second portion <NUM> of the flexible substrate <NUM> includes a narrow segment <NUM> coupled to and extending from the first portion <NUM>. The narrow segment <NUM> extends into a tab segment <NUM> having a wider surface area than the narrow segment <NUM>. In some embodiments, the narrow segment <NUM> has a surface area that is less than a surface area of the tab segment <NUM>. The second portion <NUM> of the flexible substrate <NUM> is structured and dimensioned to bend at least at the narrow segment <NUM> when transitioned from the planar configuration (e.g., shown in <FIG>) to the folded configuration (e.g., shown in <FIG>). For example, a top side <NUM> of the tab segment <NUM> can be brought into position closer to the first portion <NUM> of the flexible substrate <NUM> when the second portion <NUM> of the flexible substrate <NUM> is in the folded configuration than when in the planar configuration. In some embodiments, the RFID tag chip <NUM> is disposed on the tab segment <NUM>, which can facilitate bending about the narrow segment <NUM> to transition the second portion <NUM> between the planar configuration and the folded configuration.

The folded configuration of the second portion <NUM> of the flexible substrate <NUM> can facilitate introduction of the RFID tag <NUM> into the capsule <NUM>. For example, as shown in <FIG>, the capsule <NUM> can include a tubular shell <NUM> having opposing end caps <NUM>. The capsule <NUM> is structured and dimensioned to enclose the RFID tag <NUM> when the first portion <NUM> of the flexible substrate <NUM> is in the tubular configuration, but not when the first portion <NUM> of the flexible substrate <NUM> is in the planar configuration. The tubular shell <NUM> can enclose at least a portion of the first portion <NUM> of the flexible substrate <NUM> when the first portion <NUM> is in the tubular configuration. For example, as shown in <FIG>, the tubular shell <NUM> encloses the first portion <NUM> of the flexible substrate <NUM> in the tubular configuration in an interior region <NUM> of the tubular shell <NUM> while the second portion <NUM> extends into the end cap <NUM> in the folded configuration. In some embodiments, the end cap <NUM> is structured and dimensioned to enclose the second portion <NUM> in an interior region <NUM> of the end cap <NUM> when the second portion <NUM> is in the folded configuration, but not when the second portion <NUM> is in the planar configuration. For example, by positioning the RFID tag chip <NUM> on the tab segment <NUM>, the interior region <NUM> of the end cap <NUM> can enclose the second portion <NUM> of the flexible substrate <NUM> while allowing the majority of the first portion <NUM> to be dedicated to coil configurations of the conductive elements <NUM>, which can be enclosed in the capsule <NUM> by the tubular shell <NUM>.

In some embodiments, the flexible substrate <NUM> is a continuous substrate where the first portion <NUM> and the second portion <NUM> are formed from the same substrate material as a single piece construction. In some embodiments, the first portion <NUM> and the second portion <NUM> are formed from separate substrate pieces and fused, adhered, or otherwise coupled together, such as through a coupling of the narrow segment <NUM> of the second portion <NUM> to a top side <NUM> of the first portion <NUM>.

The tab segment <NUM> of the second portion <NUM> of the flexible substrate <NUM> can include one or more tapers (e.g., tapered edges) to couple the tab segment <NUM> to the narrow segment <NUM>. For example, <FIG> shows an example RFID tag <NUM> that includes two opposing tapers <NUM>. Additional example RFID tags <NUM> including two opposing tapers <NUM> are shown in <FIG>, <FIG>, <FIG>, and <FIG>. <FIG> shows an example RFID tag <NUM> that includes one taper <NUM> that couples the tab segment <NUM> to the narrow segment <NUM>. An additional example RFID tag <NUM> including one taper <NUM> is shown in <FIG>. In some embodiments, the tab segment <NUM> supports one or more tuning capacitors <NUM> for the RFID tag <NUM>.

The RFID reader <NUM> communicates with the RFID tag <NUM> with radio frequency signals. In the use case wherein the RFID tag <NUM> is scanned while internal to an individual (e.g. for medication compliance), the radio frequency signals should be sufficient for this communication while still medically safe for the individual. In some embodiments, the RFID reader <NUM> includes a coil structured and dimensioned to generate communication signals having low frequency (e.g., on the order of <NUM>) or high frequency signals (e.g., <NUM>). In some embodiments, the coil has a width of approximately <NUM>. In some embodiments, the coil has a width of approximately <NUM>. However, the RFID reader <NUM> is not limited to the frequencies or widths provided herein and can operate with frequencies between <NUM> and <NUM> or frequencies greater than <NUM>, and can include a coil having a width of less than <NUM>, between <NUM> and <NUM>, or greater than <NUM>.

Referring to <FIG>, the example RFID tag <NUM> has the conductive element <NUM> formed into a substantially rectangular coil having a plurality of turns disposed on the first side <NUM> of the first portion <NUM> of the flexible substrate <NUM>. For the example RFID tag <NUM> in <FIG>, the coil configuration includes ten turns, however other numbers of turns can be utilized. For example, the plurality of turns can be from five turns to twenty-five turns to accommodate capsule sizes of up to size <NUM> capsules. The width of the conductive element <NUM> used to make the coil can affect the number of turns available for a given RFID tag <NUM>, dependent on the size of capsule <NUM> into which the RFID tag <NUM> is to be introduced. For example, a thicker conductive element <NUM> can be used for fewer turns as compared to a thinner conductive element <NUM> (e.g., comparing the RFID tag <NUM> of <FIG> with the RFID tag of <FIG>). In some embodiments, the spacing between turns of the conductive elements is three-thousands of an inch spacing between turns. <FIG> shows an example RFID tag <NUM> having a coil configuration with twenty-five turns. <FIG> shows an example RFID tag <NUM> having a coil configuration with ten turns. <FIG> shows an example RFID tag <NUM> having a coil configuration with five turns. <FIG> shows an example RFID tag <NUM> having a coil configuration with twenty turns. The conductive element <NUM> can include multiple coil configurations on the first side <NUM> of the first portion <NUM> of the flexible substrate <NUM>. For example, the example RFID tag <NUM> of <FIG> includes a first coil configuration <NUM> on the first side <NUM> of the first portion <NUM> and a second coil configuration <NUM> opposing the first coil configuration <NUM> on the first side <NUM> of the first portion <NUM>. In some embodiments, the first coil configuration <NUM> includes the same number of turns as the second coil configuration <NUM>. For example, in <FIG>, the first coil configuration <NUM> and the second coil configuration <NUM> each includes ten turns of the conductive element <NUM>. The RFID tag can also include a jumper set connecting the first coil configuration <NUM> and the second coil configuration between serial and parallel connections (jumper sets 404A and 404B are shown in <FIG>). The number and positioning of coils can vary based on the particular application of the RFID tag <NUM>. For example, <FIG> shows an example RFID tag <NUM> having four coils positioned around the circumference of the flexible substrate <NUM> when in a tubular configuration.

The RFID tag <NUM> can include conductive elements <NUM> on both sides of the deformable substrate <NUM> (e.g., a front surface and a rear surface) to form an RFID antenna. Referring to <FIG>, the example RFID tag <NUM> has the conductive element <NUM> formed into a first sinusoidal pattern <NUM> on a first side <NUM> of the first portion <NUM> of the deformable substrate <NUM> and the conductive element <NUM> formed into a second sinusoidal pattern <NUM> on a second side <NUM> of the first portion <NUM> of the deformable substrate <NUM>. The conductive element <NUM> can take the shape of two helixes when the first portion <NUM> of the deformable substrate <NUM> is in the tubular configuration (e.g., shown in <FIG>). The deformable substrate <NUM> is shown as transparent in <FIG> to show the layout of the first sinusoidal pattern <NUM> with respect to the second sinusoidal pattern <NUM>. The RFID tag <NUM> includes a plurality of conductive vias <NUM> through the deformable substrate <NUM> to couple at least a portion of the first sinusoidal pattern <NUM> with at least a portion of the second sinusoidal pattern <NUM> (e.g., to create a continuous conductive path through each of the first sinusoidal pattern <NUM> and the second sinusoidal pattern <NUM>).

In some embodiments, an end of a conductive element <NUM> of each of the first sinusoidal pattern <NUM> and the second sinusoidal pattern <NUM> is coupled to a trace extending from the first portion <NUM> of the flexible substrate <NUM> onto the second portion <NUM> of the flexible substrate <NUM>. For example, as shown in <FIG>, an end <NUM> of the conductive element <NUM> of the first sinusoidal pattern <NUM> is coupled to a trace <NUM> on the first side <NUM> of the deformable substrate <NUM>, where the trace <NUM> extends from the first portion <NUM> of the flexible substrate <NUM> onto the second portion <NUM> of the flexible substrate <NUM> (e.g., to electrically connect with one or more of the RFID tag chip <NUM>, tuning capacitors <NUM>, or the like). Additionally, an end <NUM> of the conductive element <NUM> of the second sinusoidal pattern <NUM> on the second side <NUM> of the first portion <NUM> is coupled to a trace <NUM> on the first side <NUM> of the deformable substrate <NUM> through a via <NUM>, where the trace <NUM> extends from the first portion <NUM> of the flexible substrate <NUM> onto the second portion <NUM> of the flexible substrate <NUM> (e.g., to electrically connect with one or more of the RFID tag chip <NUM>, tuning capacitors <NUM>, or the like). The first sinusoidal pattern <NUM> and the second sinusoidal pattern <NUM> can include the same number of turns of conductive elements <NUM> to form the respective patterns. For the example RFID tag <NUM> in <FIG>, each of the first sinusoidal pattern <NUM> and the second sinusoidal pattern <NUM> includes fifteen turns, however other numbers of turns can be utilized. For example, the plurality of turns can be from five to fifteen turns to accommodate capsule sizes of up to <NUM> capsules. <FIG> shows an example RFID tag <NUM> having dual sinusoidal configurations with nine turns.

Referring to <FIG>, a cross-section of an example ingestible RFID tag <NUM> in a planar configuration is shown. The RFID tag <NUM> includes the deformable substrate <NUM> having conductive elements <NUM> on opposing sides of the deformable substrate <NUM>. The conductive elements <NUM> include a top layer disposed on a first side <NUM> of the deformable substrate <NUM>, which can correspond to the first side <NUM>, the first side <NUM>, the first side <NUM>, for example. The conductive elements also include a bottom layer disposed on a second side <NUM> of the deformable substrate <NUM>, which can correspond to the second side <NUM> or a side of the deformable substrate <NUM> opposing the first side <NUM>, the first side <NUM>, or the like. The RFID tag <NUM> also includes a via (e.g., via <NUM>) through the deformable substrate <NUM>, the top layer, and the bottom layer, to electrically connect the conductive elements <NUM> of the top layer and the bottom layer. In the example shown in <FIG>, the deformable substrate <NUM> is composed of polyimide having a thickness of <NUM> and the conductive elements <NUM> of the top layer and bottom layer each have a thickness of <NUM>. The conductive elements <NUM> can be covered for protection or isolation from the external environment. For example, the RFID tag <NUM> includes a top coverlay and adhesive layer <NUM> disposed on a top surface <NUM> of the top layer and a bottom coverlay and adhesive layer <NUM> disposed on a bottom surface of the bottom layer. In embodiments, the top coverlay and adhesive layer <NUM> and the bottom coverlay and adhesive layer <NUM> each include a <NUM> thick polyimide coverlay and a <NUM> thick adhesive layer. The RFID tag <NUM> can also include a top overlay <NUM> positioned on a top surface of the top coverlay and adhesive layer <NUM>. In some embodiments, the RFID tag <NUM> includes surface pads having an electroless nickel immersion gold (ENIG) finish.

Operation of ingestible RFID tags can be affected by stomach or digestive fluids. While body tissues and fluid are substantially transparent to the magnetic signals sent between an RFID tag and RFID reader, between each turn of the conductive element coil is an electric field that extends outside the plane of the coil. The electric field should be kept separate from the stomach or digestive fluids to avoid negatively affecting the performance of the coil. In some embodiments, spacing between the coil of the RFID tag <NUM> and the stomach or digestive fluids is provided through thickness of the capsule <NUM> into which the RFID tag <NUM> is inserted, thickness of the coverlay layers or deformable substrate <NUM> (described with reference to <FIG>), or combinations thereof.

Referring to <FIG> and <FIG>, an example RFID tag <NUM> is shown in a planar configuration. The RFID tag <NUM> includes the flexible substrate <NUM> having the first portion <NUM> without the second portion <NUM> extending from the first portion <NUM>. The RFIG tag chip hardware can be electrically coupled with the conductive elements <NUM> on the first portion <NUM>. For example, <FIG> shows a top view of the RFID tag <NUM> with the conductive elements <NUM> disposed on the first side <NUM> of the flexible substrate <NUM>. The conductive elements <NUM> can be arranged in a coil pattern having an interior region <NUM> in which the RFID tag chip hardware can be seated. For example, the RFID tag <NUM> is shown with the conductive elements <NUM> arranged in a rectangular coil pattern defining the interior region <NUM> on the first side <NUM> of the flexible substrate <NUM>, where the RFID tag chip hardware (e.g., RFID tag chip <NUM>) is electrically connected to the conductive elements <NUM> within the interior region <NUM> (e.g., shown in <FIG> as connection region <NUM>).

The RFID tag <NUM> in <FIG> is shown with the conductive elements <NUM> having a plurality of turns to form the rectangular coil pattern, where the conductive elements are shown with eight turns, however the RFID tag <NUM> can include different numbers of turns. For example, the plurality of turns can be from five turns to twenty-five turns to accommodate different sizes of the capsule <NUM> (e.g., size <NUM> capsules, size <NUM> capsules, etc.). The width of the conductive element <NUM> used to make the coil can affect the number of turns available for a given RFID tag <NUM>, dependent on the size of capsule <NUM> into which the RFID tag <NUM> is to be introduced. For example, a wider conductive element <NUM> can be used for fewer turns as compared to a narrower conductive element <NUM> for the same area of the flexible substrate <NUM>. In some embodiments, the spacing between turns of the conductive elements is approximately three-thousands of an inch spacing between turns. In embodiments, the flexible substrate <NUM> is sized and dimensioned to fit within the capsule <NUM> in the tubular configuration (e.g., as shown in <FIG> and <FIG>), but not in the planar configuration (e.g., shown in <FIG>). For example, the flexible substrate <NUM> can have a length from about <NUM> to about <NUM> and can have a width from about <NUM> to about <NUM>. In an embodiment, the flexible substrate <NUM> has a length of about <NUM> and a width of about <NUM> to accommodate insertion into a <NUM> size capsule in the tubular configuration. In an embodiment, the flexible substrate <NUM> has a length of about <NUM> and a width of about <NUM> to accommodate insertion into a <NUM> size capsule in the tubular configuration.

The conductive elements <NUM> can include multiple coil configurations on the first side <NUM> of the flexible substrate <NUM>. For example, the example RFID tag <NUM> of <FIG> includes a first coil configuration <NUM> on the first side <NUM> of the flexible substrate <NUM> and a second coil configuration <NUM> opposing the first coil configuration <NUM> on the first side <NUM> of the flexible substrate. In some embodiments, the first coil configuration <NUM> includes the same pattern, number of turns, or combinations thereof, as the second coil configuration <NUM>. For example, in <FIG>, the first coil configuration <NUM> and the second coil configuration <NUM> each includes eight turns of the conductive elements <NUM> arranged in a substantially rectangular pattern.

In some embodiments, the RFID tag <NUM> includes the conductive elements <NUM> arranged on each of the first side <NUM> of the flexible substrate <NUM> and the second side <NUM> of the flexible substrate <NUM>. For example, <FIG> shows a top view of the RFID tag <NUM> with the conductive elements <NUM> disposed on the first side <NUM> of the flexible substrate <NUM>, whereas <FIG> shows a bottom view of the RFID tag <NUM> with the conductive elements <NUM> disposed on the second side <NUM> of the flexible substrate <NUM>. Throughholes or vias can electrically connect conductive elements <NUM> on the first side <NUM> to conductive elements <NUM> on the second side <NUM>. For example, <FIG> shows a first group of vias <NUM> formed with conductive elements <NUM> within the interior region <NUM> formed by the first coil configuration <NUM> and a second group of vias <NUM> formed with conductive elements <NUM> within the interior region <NUM> formed by the second coil configuration <NUM>. In embodiments, shown in <FIG>, the vias <NUM> are electrically connected with the vias <NUM> by a conductive element <NUM> that traverses the second side <NUM> of the flexible substrate (e.g., for a distance between interior regions <NUM> formed on the first side <NUM> of the flexible substrate <NUM>). The conductive elements <NUM> can further define connections for one or more tuning capacitors to tune the RFID tag <NUM>. For example, <FIG> shows a first tuning capacitor pad <NUM> coupled to the flexible substrate <NUM> within the interior region <NUM> formed by the first coil configuration <NUM> on the first side <NUM>, and <FIG> shows a second tuning capacitor pad <NUM> coupled to the flexible substrate <NUM> on the second side <NUM>.

Referring to <FIG>, a cross-section of an example ingestible RFID tag <NUM> in a planar configuration is shown. The RFID tag <NUM> includes the deformable substrate <NUM> having conductive elements <NUM> on opposing sides of the deformable substrate <NUM>. The conductive elements <NUM> include a top layer disposed on a first side <NUM> of the deformable substrate <NUM>, which can correspond to the first side <NUM>, the first side <NUM>, the first side <NUM>, for example. The conductive elements also include a bottom layer disposed on a second side <NUM> of the deformable substrate <NUM>, which can correspond to the second side <NUM> or a side of the deformable substrate <NUM> opposing the first side <NUM>, the first side <NUM>, or the like. The RFID tag <NUM> also includes a via (e.g., via <NUM>) through the deformable substrate <NUM>, the top layer, and the bottom layer, to electrically connect the conductive elements <NUM> of the top layer and the bottom layer (e.g., disposed on the first side <NUM> and the second side <NUM>). For example, the via <NUM> can represent vias <NUM> or <NUM> described with respect to <FIG> and <FIG>. In the example shown in <FIG>, the deformable substrate <NUM> is composed of a dielectric material (e.g., polyimide) having a thickness of about <NUM> and the conductive elements <NUM> of the top layer and bottom layer are composed of a conductive material (e.g., copper, aluminum, gold, silver, alloys thereof, etc.) and can have a thickness of about <NUM>. The dimensions of the components can depend on the size of the capsule <NUM> into which the RFID tag is to be positioned. The RFID tag <NUM> can also include a binder <NUM> (e.g., a paste, such as solder paste) to mount the RFID tag chip <NUM> to the conductive elements <NUM> while permitting electrical conductivity therethrough.

The system <NUM> and associated RFID tags <NUM> described herein can facilitate verification that a medication has been ingested by a patient, such as within a recent time period. For example, treatment of tuberculosis or other infectious diseases can involve multiple doses of antibiotics or other medications taken periodically (e.g., daily, weekly, etc.) over the course of multiple weeks or months. A treatment facility, healthcare staff, or other healthcare provider may monitor compliance of a medication course by tracking whether a patient ingests the medication at the treatment facility and during which period(s) of time. However, a patient may feign ingestion or other spoof the ingestion of the medication to avoid actual or prolonged ingestion. For example, the patient may hold the medication in clothing or on their person rather than swallow the medication. For instance, if location sensors are used to track individual doses of the medication, the presence of the medication in clothing or on their person may obfuscate the actual status of the medication (e.g., ingested or merely held close to the stomach). Alternatively or additionally, the patient may hold the medication in their oral cavity, esophagus, larynx, or other location to feign ingesting the medication without swallowing the medication to the stomach. In embodiments, the system <NUM> can include a structure (e.g., a pH switch structure) associated with the capsule <NUM> to interfere with communication between the RFID tag <NUM> and the RFID reader <NUM> in a first configuration and to permit or otherwise cease to interfere with communication between the RFID tag <NUM> and the RFID reader <NUM> in a second configuration that can facilitate detection of the capsule <NUM> in the stomach of the patient without detection of the capsule <NUM> outside the patient's stomach.

For example, the first configuration can be maintained while the RFID tag <NUM> and corresponding medication is located in an environment outside of the patient (e.g., in the patient's clothes, in the healthcare facility, in storage, etc.) or outside of the stomach of the patient (e.g., in the mouth, oral cavity, esophagus, larynx, or other location) to prevent communication between the RFID tag <NUM> and the RFID reader <NUM> while the medication is outside the stomach of the individual. The structure can adopt the second configuration while in the stomach, where communication between the RFID tag <NUM> and the RFID reader <NUM> is permitted to ensure that the RFID tag <NUM> and associated medication is within the stomach of the patient. For example, the RFID tag <NUM> can be positioned within the interior of the capsule <NUM> (e.g., folded into the tubular state, as shown in <FIG>, <FIG>, <FIG>), where the capsule <NUM> is fitted with a pH switch structure that utilizes a pH trigger to modify the configuration of the structure. For instance, the pH trigger can be a change in an environment of the capsule <NUM> to change the pH switch structure from the first configuration to the second configuration upon exposure to a pH associated with the stomach (e.g., having a pH of about <NUM> or less than <NUM>), but not associated with another body portion (e.g., oral cavity having a pH from about <NUM> to about <NUM>). In embodiments, the pH switch structure is formed from a biocompatible metal that can be dissolved by stomach acids to transition the structure from the first configuration, where the presence of the pH switch structure shields or otherwise prevents electromagnetic communication, to the second configuration where the absence of the pH switch structure or portions thereof permits electromagnetic communication between the RFID tag <NUM> and the RFID reader <NUM>. The pH switch structure can therefore remain intact outside the patient's body to prevent activation of the RFID tag <NUM> and can dissolve upon exposure to the stomach environment.

In embodiments, the system <NUM> utilizes materials to influence the time at which the RFID tag <NUM> is traceable by the RFID reader <NUM> following ingestion and/or the duration that the RFID tag <NUM> is traceable within the stomach of the patient by the RFID reader <NUM>. For example, the structure used to influence communications between the RFID tag <NUM> and the RFID reader <NUM> can maintain structural integrity within the stomach for a certain duration (e.g., maintaining the first configuration) to prevent communications until a sufficient duration within the stomach has passed (e.g., from about <NUM> minute to about <NUM> minutes). Alternatively or additionally, one or more components of the RFID tag <NUM> can maintain structural integrity within the stomach to permit operation of the RFID tag <NUM> during interrogation by the RFID reader <NUM> for a duration corresponding with a next dose of the medication (e.g., from about <NUM> minutes to about six hours) before structural failure of the RFID tag <NUM> within the digestive system of the patient. Such stability of the RFID tag <NUM> can ensure that if the RFID tag <NUM> is identified by the RFID reader <NUM>, the identification is associated with medication taken by the patient during that dosing period (e.g., that day) as opposed to medication taken during a prior dose that is still within the patient's digestive system, since such prior dose will no longer have a functional RFID tag <NUM>.

For an example medication compliance regime, a patient is initially scanned with the RFID reader <NUM> to ensure no medication associated with the healthcare facility is currently in the patient's stomach. The patient is then given the capsule <NUM> containing the medication and the RFID tag <NUM>. The capsule <NUM> includes the pH switch structure to influence communications between the RFID tag <NUM> and the RFID reader <NUM> as described herein. The patient swallows the capsule <NUM> and for a period of time (e.g., from ingestion to a period of up to about <NUM> minutes), the RFID reader <NUM> is unable to record the presence of the RFID tag <NUM> within the patient (e.g., the pH switch structure is still in the first configuration, since the current duration of exposure to stomach acid is insufficient to transition the structure to the second configuration or state of dissolution). Once the capsule <NUM> is within the stomach for a sufficient duration (e.g., from about <NUM> minute to about <NUM> minutes), the stomach acid is exposed to the pH switch structure for enough time to sufficiently dissolve the pH switch structure to transition the structure to the second configuration. The second configuration can include total or partial dissolution of the pH switch structure into the stomach acid, where the structure no longer impedes the communication between the RFID tag <NUM> and the RFID reader <NUM>, thereby permitting recognition of the RFID tag <NUM> within the patient. The following day, the patient is again scanned with the RFID reader <NUM> to ensure that the prior day's RFID tag <NUM> is no longer operational. For instance, the materials of the RFID tag <NUM> has degraded within the digestive system of the patient to the extent that the RFID tag <NUM> does not sufficiently respond to interrogation by the RFID reader <NUM>. The patient is given the next dose of medication, where following the initial delay period, the RFID reader <NUM> confirms the presence of the current dose of medication. Alternatively, the patient is scanned once during each visit - after the delay period following ingestion of the medication, since the RFID tag <NUM> of the current dose is unable to communicate with the RFID reader <NUM> until after the delay period, and any RFID tags <NUM> of previous doses would be rendered sufficiently inoperable due to length of time in the patient's digestive tract.

Examples of the structure associated with the capsule <NUM> to interfere with communication between the RFID tag <NUM> and the RFID reader <NUM> are provided below. While examples used herein focus on tracking ingestion by altering communications between the RFID tag <NUM> and the RFID reader <NUM> via conditions in the stomach, the system <NUM> is not limited to such alterations occurring in the stomach. For example, other environmental conditions (e.g., different pH environments, specific chemical triggers, specific enzymatic or other biological component triggers, etc.) can be used to trigger alteration of the communications between the RFID tag <NUM> and the RFID reader <NUM>.

Referring to <FIG>, the system <NUM> can include a structure <NUM> (e.g., a pH switch structure) formed from an electrically conductive material to be placed around at least a portion of the capsule <NUM> to interfere with communication between the RFID tag <NUM> and the RFID reader <NUM>. The electrically conductive material may or may not be ferromagnetic. In operation, when the structure <NUM> is exposed to an alternating magnetic field <NUM> (e.g., via the RFID reader <NUM>), the structure <NUM> facilitates the generation of eddy currents <NUM> which in turn generate magnetic fields <NUM> opposing the alternating magnetic field <NUM>. The magnetic fields <NUM> can disrupt the interrogation signals from the RFID reader <NUM> and/or otherwise disable the functionality of the RFID tag <NUM> within the capsule <NUM> (e.g., via insufficient energy reaching the RFID tag <NUM> for power). For example, with high frequency magnetic fields <NUM>, a thin layer of structure <NUM> around an external surface of the capsule <NUM> can disable functionality of the RFID tag <NUM> within the capsule <NUM>. In embodiments, the structure <NUM> coats at least a portion the external surface of the capsule <NUM> to provide shielding of the communications between the RFID tag <NUM> and the RFID reader <NUM>. In embodiments, the structure <NUM> coats the whole external surface of the capsule <NUM> to provide shielding of the communications between the RFID tag <NUM> and the RFID reader <NUM>. The structure <NUM> can be applied to the capsule <NUM> utilizing a plating technique, including but not limited to, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), or combinations thereof. In embodiments, the structure <NUM> is applied directly to the external surface of the capsule <NUM>. In embodiments, an intervening layer is introduced between the capsule <NUM> and the structure <NUM>. For example, the capsule <NUM> can include an intervening layer on the external surface and the structure <NUM> is applied to the intervening layer utilizing a plating technique, including but not limited to, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), or combinations thereof. The intervening layer can include, but is not limited to, an acid-soluble substrate. In embodiments, the intervening layer includes an acid-soluble substrate that is dissolvable in an acidic environment having a pH at or below <NUM> and is not substantially dissolvable at a pH above <NUM>. For example, the acid-soluble substrate can include, but is not limited to, EUDRAGIT™ E PO polymer available from Evonik (Essen, Germany). The acid-soluble substrate can dissolve when exposed to the acidic environment of the stomach to remove the structure <NUM> from the external surface of the capsule <NUM>, thereby permitting activation of the RFID tag <NUM> within the capsule <NUM> when interrogated by the RFID reader <NUM>.

In embodiments, the electrically conductive material that forms the structure <NUM> is dissolvable upon exposure to chemical located in a target area for the medication (e.g., dissolvable in stomach acid for medication ingested orally). The structure <NUM> can be formed from a biocompatible metal that reacts with hydrochloric acid in the stomach. For example, the structure <NUM> can be formed from magnesium, zinc, iron, alloys thereof, or combinations thereof. The structure <NUM> is maintained in the first configuration to prevent communications between the RFID tag <NUM> and the RFID reader <NUM>, rendering the RFID tag <NUM> deactivated while the structure <NUM> is intact. Upon exposure of the structure <NUM> to chemical located in the target area (e.g., stomach acid), the structure <NUM> dissolves to transition the structure <NUM> to the second configuration. In the second configuration, the structure <NUM> permits activation of the RFID tag <NUM> upon interrogation by the RFID reader <NUM>, for example, due to the inability to generate the eddy currents <NUM> or sufficient opposing magnetic fields <NUM>. In embodiments, the structure <NUM> is formed as one or more shorted turn structures on the exterior surface of the capsule <NUM> to absorb energy transmitted between the RFID reader <NUM> to the RFID tag <NUM>. For example, referring to <FIG> and <FIG>, the structure <NUM> is formed as a pair of shorted turn structures (1000A and 1000B are shown) coupled to an exterior surface <NUM> of the capsule <NUM>. The shorted turn structures <NUM> are coupled to a portion of the exterior surface <NUM> as opposed to covering the whole exterior surface <NUM>. The shorted turn structures <NUM> are conductors each formed as a continuous circuit that disrupt the functioning of the interaction between the RFID tag <NUM> and the RFID reader <NUM>. For instance, a reader coil of the RFID reader <NUM> and a corresponding tag coil of the RFID tag <NUM> (e.g., the rectangular coils shown in <FIG>) can function as a magnetic transformer. The shorted turn structures <NUM> can absorb energy transmitted from the RFID reader <NUM> before being received by the RFID tag <NUM> in an amount sufficient to render the RFID tag <NUM> nonfunctional due to insufficient energy for power.

If the shorted turn structures <NUM> no longer maintain the continuous circuit structure, the shorted turn structures <NUM> can no longer form short circuits for the energy transferred from the RFID reader <NUM>, thereby permitting functioning of the RFID tag <NUM>. The shorted turn structures <NUM> can therefore operate as a pH switch structure by removing all or portions of the structure <NUM> upon exposure to a pH-specific environment, such as the stomach of the patient. For example, in embodiments, one or more shorted turn structures <NUM> are applied directly to the exterior surface <NUM> of the capsule <NUM> utilizing a plating technique, including but not limited to, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), or combinations thereof. In some embodiments, capsule <NUM> can include an intervening layer on the external surface <NUM> with the shorted turn structure <NUM> applied to the intervening layer utilizing a plating technique, including but not limited to, dip coating, chemical vapor deposition (CVD), physical vapor deposition (PVD), or combinations thereof. <FIG> illustrates shorted turn structures 1000A and 1000B coupled to intervening layer <NUM> which in turn is coupled to the exterior surface <NUM> of the capsule <NUM>. The intervening layer <NUM> can include, but is not limited to, an acid-soluble substrate. In embodiments, the intervening layer <NUM> includes an acid-soluble substrate that is dissolvable in an acidic environment having a pH at or below <NUM> and is not substantially dissolvable at a pH above <NUM>. For example, the acid-soluble substrate can include, but is not limited to, EUDRAGIT™ E PO polymer available from Evonik (Essen, Germany). The acid-soluble substrate can dissolve when exposed to the acidic environment of the stomach to remove the shorted turn structure <NUM> from the external surface <NUM> of the capsule <NUM>, thereby permitting activation of the RFID tag <NUM> within the capsule <NUM> when interrogated by the RFID reader <NUM>.

The shorted turn structure <NUM> can be formed from a single conductive material or multiple conductive materials to provide energy absorption functionality. For single material shorted turn structures <NUM>, a portion of the shorted turn structure can have a material thickness (e.g., normal to the external surface <NUM>) that is thinner than the other portions of the shorted turn structure. The thinner portion can fully dissolve to break the continuous circuit structure when exposed to the acidic environment of the patient before the other portions of the shorted turn structure <NUM> due to less material needing to dissolve before the continuous circuit structure is broken. For example, the thinner portion can act as an acid-reactive fuse to disable the shorted turn structure <NUM> upon reacting with stomach acid. The thicker portions of the shorted turn structure <NUM> can keep resistance of the shorted turn structure <NUM> low to provide improved shielding effectiveness as compared to a shorted turn structure <NUM> with the whole continuous circuit structure having thickness of the thinner portion. Similarly, for shorted turn structures <NUM> formed from multiple materials, a portion of the shorted turn structure can have a material thickness (e.g., normal to the external surface <NUM>) that is thinner and formed from a first material with the other portions of the shorted turn structure having greater material thickness formed from one or more different electrically conductive materials. In embodiments, the thinner portion of the shorted turn structure <NUM> is formed from a first electrically conductive material and the thicker portion of the shorted turn structure <NUM> is formed from a second electrically conductive material. In embodiments, the first electrically conductive material includes at least one of magnesium, zinc, or iron, or an alloy thereof and the second electrically conductive material includes at least one of gold, silver, or copper, or an alloy thereof. The first electrically conductive material can be a material having a higher reactivity with stomach acid to cause failure of the shorted turn structure <NUM> at the thinner portion as compared to the material reactivity with stomach acid of the second electrically conductive material.

Experiments were performed to determine the read range of various RFID tag configurations (having the RFID chip hardware located on the tab segment <NUM>, such as shown in <FIG>) placed internally in cadaver animals utilizing two different RFID reader configurations. Example results are shown in <FIG>. For each test, the RFID tag (e.g., RFID tag <NUM>) was positioned into the folded or tubular configuration (e.g., as shown in <FIG>) and placed inside a capsule (of a <NUM> or a <NUM> size). The capsule was placed inside a PVC cylinder (<NUM> diameter, with <NUM> between an end of the cylinder and an end of the capsule) for implantation into a swine belly. Five different RFID tag configurations were utilized: a ten turn coil configuration for a <NUM> capsule (e.g., shown in <FIG> in a planar configuration), a twenty turn coil configuration for a <NUM> capsule (e.g., shown in <FIG> in a planar configuration), a ten turn coil configuration for a <NUM> capsule (e.g., shown in <FIG> in a planar configuration), a twenty-five turn coil configuration for a <NUM> capsule (e.g., shown in <FIG> in a planar configuration), and a fifteen turn helix or sinusoidal coil for a <NUM> capsule (e.g., shown in <FIG> in a planar configuration). The tags were selected for the ex vivo experiment on the basis of data generated during bench experiments (data shown with respect to <FIG>). Two different RFID readers were utilized: a <NUM> wide coil (e.g., shown in <FIG>) and a <NUM> wide coil. Each RFID tag was interrogated by each RFID reader from two different orientations: orientation A and orientation B, where the respective orientation for the RFID tags is shown with respect to FIGS. 10A (for the planar-coil tags (e.g., ten turn for <NUM> capsule, twenty turn for <NUM> capsule, ten turn for <NUM> capsule, and twenty-five turn for <NUM> capsule)) and 10B (for the helix or sinusoidal coil (e.g., fifteen turn helix for <NUM> capsule)). The read range for tag orientation B for the ten turn for <NUM> capsule, the ten turn for <NUM> capsule, and the twenty-five turn for <NUM> capsule tag configurations is displayed as zero, where the thickness of the swine belly may have been wider than the minimum read range for each of the tag configurations. Bench experiments provide additional read range measurements for the example RFID tags in air and saline environments, with example data shown in <FIG> described further herein.

Experiments were performed to determine the read range of various RFID tag configurations (having the general configuration of <FIG> and <FIG>) placed internally in sedated animals utilizing different RFID reader configurations. A pig model was used for the testing, where the pig was sedated during the testing. A small diameter tube was placed down the esophagus to facilitate placement of capsules containing RFID tags in the tubular configuration inside the stomach of the pig. The capsule was carefully introduced down the tube until it entered the stomach. A fluoroscope was used to verify the location of the capsule in the stomach. The fluoroscope was also used to determine the physical distance from the outside skin to the RFID tag. Two distances were measured: (<NUM>) from the back of the pig to the RFID tag; and (<NUM>) from the side of the pig to the RFID tag). Reader-antenna performance (e.g., ability and/or capability to detect the RFID tags) was measured at both back and side positions, which are generally aligned along orientations A and B shown in <FIG> (e.g., short axis orientations).

Several RFID reader configurations were tested, with different reader models and antenna sizes evaluated. The RFID reader assemblies included a commercial reader module (Andea M20 Reader Assembly with <NUM>. 5W power rating; Andea M202 Reader Assembly with <NUM>. 5W power rating) with a battery power subsystem housed inside an off-the-shelf enclosure. The reader assemblies incorporated a standard connector that permitted switching between the different antenna sizes that were evaluated. Four antenna sizes were used during the in vivo testing: <NUM> re-tuned antenna, <NUM> antenna, <NUM> antenna, <NUM> antenna.

Two capsule-tag configurations were used during testing: (<NUM>) an RFID tag having the configuration of <FIG> and <FIG> placed in the tubular configuration within a <NUM> size capsule coated in epoxy; and (<NUM>) an RFID tag having the configuration of <FIG> and <FIG> placed in the tubular configuration within a <NUM> size capsule, which in turn is placed within a <NUM> size capsule coated in epoxy.

In a first test, a capsule with the first capsule-tag configuration was introduced to the stomach. Fluoroscope evaluation indicated that the capsule was located in stomach, and that the internal distance from tag to skin (side direction) was approximately <NUM>. Results of the initial analyses are shown in Table <NUM>.

Observations were made that the capsule appeared to be slightly rotating within the stomach, so several readings were reanalyzed. As an example, the M20 reader with a <NUM> retuned antenna detected the tag from the side position at approximately <NUM> from the skin and from the back position at the skin surface.

The capsule positioning was reevaluated with the fluoroscope, which indicated that the capsule was located in the stomach, but had slightly shifted in position, with the internal distance from the tag to skin in the side direction was approximately <NUM> and from the tag to skin in the back direction was approximately <NUM>. Results of analyses with this positioning is shown in Table <NUM>.

In a second test, a capsule with the second capsule-tag configuration (<NUM> capsule in <NUM> capsule) was introduced to the stomach. Fluoroscope evaluation indicated that the capsule was located in the stomach next to the capsule from the first test previously described. It was observed that when the tags from the capsules were next to each other, the communication field between tag and reader was disrupted resulting in lowered read range. Water (<NUM>) was added to the stomach, which caused the capsules to move apart and perpendicular to one another. Read range improved as compared to when the capsules were positioned next to each other and returned to previous performance results. The tag within the capsule was detected from the side position for two reader configurations: M20 reader with <NUM> retuned antenna and M20 reader with <NUM> antenna.

In a third test, a capsule including the folded RFID tag having the configuration of <FIG> and <FIG> was introduced to the stomach, where fluoroscope evaluation indicated that the capsule was located to another capsule in the stomach. An additional <NUM> of water was added to the stomach, which caused the capsules to move approximately <NUM> apart. The tag within the capsule was detected from the side position and from the back position for two reader configurations: M20 reader with <NUM> retuned antenna and M20 reader with <NUM> antenna. Tag detection was videoed and showed to be robust. The tag within the capsule was also detected from the side position at a range of approximately <NUM> from skin with an M20 reader with <NUM> antenna. An additional <NUM> of water to the stomach, which caused the capsules to move approximately <NUM> or greater apart. The tag within the capsule was then detected from the side position at a range of approximately <NUM> from skin with an M20 reader with <NUM> antenna and from the side position at a range of approximately <NUM> from skin with an M20 reader with <NUM> retuned antenna.

In a fourth test, a capsule including a tether and the folded RFID tag having the configuration of <FIG> and <FIG> was introduced into the stomach via an esophagus tube. Fluoroscope evaluation indicated that the capsule slowly rotated on axis as the tether was twisted. The tag within the capsule was detected from the side position with an M20 reader with <NUM> retuned antenna, where it was observed that rotating the tag resulted in changing detection. The tag and the three other tags previously introduced to the stomach were detected from the side position at approximately <NUM> from skin.

The in vivo tests resulted in successful detection of all tests tags for all reader-antenna combinations. Referring to <FIG>, a chart showing read ranges from the back position and from the side position for various antenna sizes are shown for an example reader (M20). The read range data is similar to read range tests of the same RFID capsule during bench experiments in air with different combinations of reader types and antenna types, with example results shown in <FIG> (with antenna types on the y-axis (from bottom to top: <NUM> bespoke, <NUM> bespoke, DLP-RFID-ANT Original, DLP-RFID-ANT retuned, DLP-RFID-ANT, FEIG ISC. ANT100/<NUM>) and for each series the reader types from top to bottom are Andea M20, Andea M202, FEIG CPR74, FEIG MR102, and GAO-RFID <NUM>). The in vivo tests demonstrated that tag orientation impacts read range. The in vivo tests also suggested that tag proximity to another in vivo tag can reduce read range through interference.

Experiments were performed to determine the read range of various RFID tag configurations in a planar configuration and with some of the RFID tags also in a folded or tubular configuration (e.g., as shown in <FIG>). Example results are shown in <FIG>, where rows labeled <NUM> represent commercially available tags, rows labeled <NUM> represent example RFID tags described herein, and rows labeled <NUM> represent example RFID tags described herein tested in both planar configurations ("Measured (VNA) Flat") and folded or tubular configurations ("Measured (VNA) Curved"). The read range was measured according to one or more orientations of coaxial, right-angle long-axis rotation, or right-angle radial rotation. Examples of the orientations for RFID tags measured in the folded or tubular configurations are shown with respect to <FIG> (for the planar-coil tags) and 15B (for the helix or sinusoidal tags).

Claim 1:
A radio frequency identification, RFID, system (<NUM>), comprising:
an RFID tag (<NUM>) including
a flexible substrate (<NUM>) foldable between a planar configuration and a tubular configuration,
a conductive element (<NUM>) disposed at least on a first side (<NUM>) of the flexible substrate, and
an RFID tag chip (<NUM>) disposed at least on the first side of the flexible substrate electrically coupled with the conductive element;
a capsule (<NUM>) structured and dimensioned for ingestion by a biological subject, the capsule including a shell (<NUM>) structured and dimensioned to enclose a medication for the biological subject simultaneously with the RFID tag when the flexible substrate is in the tubular configuration, but not when the flexible substrate is in the planar configuration; and
a pH switch structure coupled to an exterior surface of the capsule, the pH switch configured to deactivate the RFID tag in a first configuration of the pH switch structure and to permit activation of the RFID tag in a second configuration of the pH switch structure within the biological subject,
characterized in that
the pH switch structure includes an electrically conductive material having a shorted turned structure coupled to the exterior surface of the capsule, wherein a portion of the shorted turn structure has a material thickness that is thinner than the other portions of the shorted turn structure, and wherein the shorted turn structure configured to absorb energy transmitted between an RFID reader and the RFID tag.