Patent Application
20090272814
This invention relates to a passive transponder adapted to be embedded in fabrics. This invention also relates to an item, for example an absorbent fabric for medical purposes, provided with at least one passive transponder adapted to be attached to, embedded in, or integrated into the item.
Absorbent fabrics are normally used to stop internal bleeding, for instance during surgery in hospitals, and there is a potential risk that the absorbent fabrics are left inside a patient's body after surgery is completed, which may cause the patient to be sick, or even die, from this mistake. Thus, there is a need to determine if the absorbent fabrics have been removed after surgery, and preferably before the wound is closed by stitches.
A way to determine if the absorbent fabrics have been removed is to keep track of how many pieces of absorbent fabric have been put into the patient, and then count how many have been removed. This is very impractical and a solution that may verify that all have been removed is more desirable.
A solution to this problem is to use any type of transmitting antennas, such as disclosed in U.S. Patent Application Publications No. US 2006/0161225, by Sormann et al. and No. US 2005/0095197 by Tuszynski et al., embedded in absorbent fabrics, since it is easy to detect any absorbent fabric unintentionally left inside a human body after surgery. An article from “Threadless @ Virginia Tech” with the title “News and Notes for our Industrial partners” (Dec. 12, 2006) discloses patch antennas that can be embroidered into fabric with a conductive thread.
However, it is not desirable to embed transmitting antennas into an absorbent fabric intended to be used during surgical procedures. A passive component that does not emit any signals until the detection takes place is desirable.
Passive transponders that, when hit by RF power of a first frequency f1, retransmit RF power of a second harmonic frequency f2, are known from U.S. Pat. No. 6,456,228. However, these are large in size and less flexible than is needed in order to be able to attach them to an arbitrarily shaped surface or embed them into a fabric.
Therefore, there is a need to provide a new type of passive transponders.
An object of the present invention is to provide passive transponders that are smaller and more flexible than prior art passive transponders.
That object can be achieved by a passive transponder, comprising an antenna having two electrically conductive parts, a diode connected between the electrically conductive parts, and a transmission line connected to the antenna and to the diode. The transmission line is adapted to match the impedance of the diode to an impedance of the antenna. The passive transponder, when hit by RF power of a first frequency f1, retransmits RF power of a harmonic frequency nf1, where n=2, 3, 4 . . . . Each electrical conductive part of the antenna comprises at least one flexible, electrically conductive, thread.
Another object of the present invention is to provide an item having a surface, adapted to be secured to an article with an arbitrary shape, to which surface a passive transponder can be attached, or in which surface a passive transponder can be embedded.
That object can be achieved by an item provided with at least one passive transponder with deformable properties attached to, or embedded in, the surface.
An object of a preferred embodiment is to provide a fabric that can be detected by a detector when the fabric is immersed in an electrically conductive environment, such as a human body.
That object can be achieved by a fabric provided with at least one passive transponder embedded in or integrated into the fabric.
An advantage of the present invention is that the passive transponder does not include a power source and thus does not transmit RF power until a detector activates the passive transponder by transmitting RF power of the correct frequency.
Another advantage of the present invention is that RF power of a harmonic second frequency will be detected by the detector only if a passive transponder is present in the area under investigation.
A further advantage of the present invention is that the item (or fabric) can be handled in any way, e.g., by folding, crumpling up, etc., without jeopardizing the function of the passive transponder due to the flexible design.
Further objects and advantages will be apparent to a skilled person from this description and the drawings.
The several features, objects, and advantages of the invention will be understood by reading this description in conjunction with the drawings, in which:
Passive transponders preferably need to be adapted to a desired receiving frequency and a transmitting frequency, which normally is twice as high as the receiving frequency, but any harmonic frequency will be sufficient for the passive transponder to work properly. The procedure to adapt the passive transponders is described in U.S. Pat. No. 6,456,228, which is incorporated here by reference.
A passive transponder may be as small as 1 mm×10 mm, but is preferably 2 mm×30 mm, and encapsulated in a material with a high dielectric constant, such as silicone. An important property of the passive transponder is that a piece of conducting material is attached to each side of a diode, and a transmission line is arranged between each side of the diode. The process of adapting the passive transponder to react to RF power of a desired frequency and to retransmit RF power of a harmonic frequency is readily apparent for a skilled person from the detailed description of U.S. Pat. No. 6,456,228.
The electrically conductive material of the antenna and the transmission line of the passive transponders is preferably a highly flexible material that can be folded without damaging the electrical properties of the material, e.g., insulated metal wires, or conductive threads as illustrated in connection with
It is of course possible to fasten a pre-manufactured passive transponder, such as illustrated in any of
The fabric 50 may be formed into an arbitrary shape adapted for a product, e.g., a compress for absorbing fluids or a tamponade for flow stoppage of blood, used during medical treatment or surgery.
In order to be able to detect a piece of fabric, provided a passive transponder is attached to the fabric, radio frequency (RF) power of a first frequency f1 needs to be transmitted from a detector. The transponder will then retransmit RF power of a harmonic frequency fh, i.e., a multiple of the first frequency f1, where fh=nf1, n=2, 3, 4, . . . . The retransmitted RF power of the harmonic frequency fh, preferably the second harmonic frequency f2, is detected by the detector and the presence of the passive transponder is verified. If no RF power of the harmonic frequency is detected, there are no passive transponders present, and thus no fabric.
A detector, such as those commercially available from Recco AB, is preferably swept over an object, such as a living body of a patient, at a close distance to detect the presence of any passive transponders. The sweeping procedure is preferably performed prior to completion of the surgical operation, but it is also possible to verify the non-presence of passive transponders after the patient has left the operating room.
Although
Item 60 is preferably a label (as illustrated in
The artisan will understand that this invention can be embodied in many different forms, not all of which are described above, and all such forms are contemplated to be within the scope of the invention. The particular embodiments described above are merely illustrative and should not be considered restrictive in any way. The scope of the invention is determined by the following claims, and all variations and equivalents that fall within the range of the claims are intended to be embraced therein.
It is emphasized that the terms “comprises” and “comprising”, when used in this application, specify the presence of stated features, integers, steps, or components and do not preclude the presence or addition of one or more other features, integers, steps, components, or groups thereof.
This application claims the benefit of the filing date of U.S. Provisional Patent Application No. 61/050,339, which was filed on May 5, 2008, and which is incorporated here by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61050339 | May 2008 | US |
