Portable device for detecting a constriction, and system equipped with same

Abstract

The invention relates to a portable device (1) for detecting a constriction in a lumen. The portable device has a film-like substrate (S) which is arranged on an exterior of the lumen during use, wherein at least two acoustic transducers (M1, M2) are arranged on the film-like substrate (S), and each acoustic transducer (M1, M2) has at least one stack of layers. The stack of layers has at least one partially covering sequence of a first electrically conductive layer, a PVDF layer, and a second electrically conductive layer, wherein the PVDF layer is electrically polarized perpendicularly to the layer structure and has a piezo effect, and a biocompatible cover layer (DS) is additionally provided on the face facing away from the substrate. The first electrically conductive layer and the second electrically conductive layer can be connected to an analysis unit (AE).

Description

[0001] Portable device for detecting a stricture and system therewith

[0002] background

[0003] The detection of lumen narrowing is relevant in many areas. In particular, there are therapies in many areas of medicine that can result in stenosis.

[0004] In the following, further reference is made to hemodialysis, without, however, limiting the invention to this application alone.

[0005] Hemodialysis is a treatment that allows for the supplementation of kidney function in cases of acute or chronic kidney dysfunction. Typically, (arterial) blood is processed in an external bloodstream and then returned to the (venous) bloodstream.

[0006] Typically, a vascular access point on an upper extremity is used for this purpose. Commonly used vascular access points are so-called arteriovenous fistulas or central venous catheters.

[0007] This vascular access is designed to enable high flow rates to enable effective and rapid treatment.

[0008] Faulty vascular access can be detected in over 20% of hospital stays of dialysis patients - not all of them end favorably.

[0009] The most common sources of failure at or near vascular access are stenosis (vascular narrowing) or thrombosis (vascular occlusion). Therefore, monitoring the functionality of a vascular access during dialysis is a suitable measure to reduce the number of emergencies or overall mortality.

[0010] Currently, vascular access is primarily monitored using a stethoscope. However, this check is usually performed only once, so any stenosis that may occur in the meantime cannot be detected. Furthermore, such a check requires a trained ear. This means that one person may detect a (threatened) stenosis while another may not.

[0011] If an impending stenosis is detected early, it can be verified using appropriate imaging. Typical imaging techniques include (color) Doppler ultrasound examinations. These allow, for example, false-positive suspected diagnoses to be ruled out.

[0012] However, narrowings also occur elsewhere. For example, it is known in medicine that during patient treatment, narrowings can form in lumens leading to or from the patient, which can also prevent further flow. This occurs, for example, in extracorporeal blood treatments - particularly with blood sets. There can be various reasons for the narrowing. For example, a tube may be kinked or trapped or subjected to some other strain - e.g., the patient may be lying on a tube. It would also be advantageous for such facilities to provide a simple, cost-effective option and enable monitoring.

[0013] Previous approaches for continuous monitoring involve monitoring / evaluating the (venous) pump pressure or flow difference between the inflow and outflow, total flow rate, etc.

[0014] As an example, reference is made to the German patent application DE 10 2013 213 390 A1, from which such a device is known.

[0015] A disadvantage of previous approaches is that they require a complex design of the dialysis machine. This is due, for example, to the fact that devices are not intended for use by just one patient, but must be available for other patients after disinfection. Therefore, high demands are placed on disinfectability. This often means a very complex design and / or complex disinfection process.

[0016] In addition, availability is limited to newly delivered devices.

[0017] Recently, sensors based on polyvinylidene fluorides have been proposed, whose audio signals are evaluated directly, e.g. as a phonoangiogram.

[0018] However, these sensors have the disadvantage, among other things, that polyvinylidene fluorides must be conditioned using high voltage in order to achieve the desired effect.

[0019] Previous approaches, which involve bonding via silver-containing layers, frequently result in short circuits when pressure is applied, which impairs functionality. Therefore, production is expensive, and the use of such systems for the production of sound transducers has not been pursued sustainably to date.

[0020] Task

[0021] Against this background, it is an object of the invention to provide a cost-effective device that makes it possible to reliably and safely detect an (impending) stenosis.

[0022] Brief description of the invention

[0023] The object is achieved by a portable device for detecting a constriction in a lumen, wherein the portable device has a film-like substrate which, when in use, is arranged on the outside of the lumen, wherein at least two sound transducers are arranged on the film-like substrate, wherein each sound transducer has at least one stack of layers, wherein the stack of layers has at least a partially covering sequence of a first electrically conductive layer, a PVDF layer and a second electrically conductive layer, wherein the PVDF layer is electrically polarized perpendicular to the layer structure and has a piezo effect, wherein a biocompatible cover layer is further provided on the side facing away from the substrate, wherein the first electrically conductive layer and the second electrically conductive layer are connectable to an evaluation unit.

[0024] Such devices can be manufactured cost-effectively and allow reliable and safe detection of (impending) stenoses.

[0025] According to a further development of the invention, the first electrically conductive layer and / or the second electrically conductive layer comprises an electrically conductive plastic, in particular an electrically conductive polymer, and preferably PEDOT.PSS.

[0026] According to a further development of the invention, the film-like substrate comprises a carrier film made of PET, PU, ​​PEN, PI, or PC. Thus, a device can be provided based on different material systems that can also be combined with other devices, without this being precluded by the choice of a specific material system.

[0027] In a further development of the invention, the at least two sound transducers are pressure sensors or microphones or structure-borne sound transducers.

[0028] This means that the invention allows for a wide range of variations.

[0029] According to a further development of the invention, the stack of layers comprises several sequences of a first electrically conductive layer, a PVDF layer and a second electrically conductive layer.

[0030] This can improve sensitivity.

[0031] In yet another embodiment of the invention, the stack of layers comprises a plurality of sequences of a first electrically conductive layer, a PVDF layer and a second electrically conductive layer, wherein the second electrically conductive layer of a first sequence simultaneously also forms the first electrically conductive layer of a second sequence.

[0032] This allows the stack size to be kept small while increasing sensitivity.

[0033] According to yet another embodiment of the invention, the cover layer comprises PDMS or PET. In particular, the cover layer can provide mechanical impedance matching between the skin and an electrically conductive layer located beneath the cover layer. Alternatively and / or additionally, the cover layer can also serve as contact protection and / or corrosion protection.

[0034] According to a further development of the invention, at least the stack of layers is embedded in a non-conductive material. In particular, the non-conductive material is PET or PU.

[0035] This can also provide contact protection and / or corrosion protection as well as additional mechanical stability for the layer structure.

[0036] In yet another embodiment of the invention, the connections of the first electrically conductive layer and / or the second electrically conductive layer to the evaluation unit comprise a silver-containing layer.

[0037] This allows a secure, low-impedance connection to be provided.

[0038] According to yet another development of the invention, at least one further electrically conductive layer is arranged laterally adjacent to a stack.

[0039] By means of such additional electrical layers, shielding against interfering radiation can be provided. According to yet another embodiment of the invention, the portable device is designed to be worn on the body of a human or animal, wherein, during use, the portable device is arranged on the skin of the human or animal body to detect a stenosis in a blood vessel of the human or animal body.

[0040] The object is further achieved by a system for detecting constrictions, comprising a portable device according to the invention and an evaluation unit, wherein the evaluation unit is connected to the at least two sound transducers, wherein the signals from two sound transducers each are repeatedly differentially evaluated, wherein a stenosis is detected upon the occurrence of a significant phase shift and / or a significant signal change at only one sound transducer between a first evaluation and a second evaluation following the first. In particular, in a further development of the invention, it can be provided that a significant phase shift has a phase shift of approximately 90°.

[0041] Such systems can be manufactured cost-effectively and allow for reliable and safe detection of (impending) stenosis. In particular, the portable device can be designed as a disposable item, while the evaluation unit is reusable.

[0042] Further advantageous embodiments are the subject of the respective dependent claims, the figures and the description.

[0043] Brief description of the characters

[0044] The invention is explained in more detail below with reference to a drawing and exemplary embodiments. The drawing is a schematic representation and not to scale. The drawing does not limit the invention in any way.

[0045] They show:

[0046] Fig. 1 is a schematic representation of an embodiment of the invention,

[0047] Fig. 2 is a schematic representation of another embodiment of the invention, Fig. 3 is a schematic representation of an aspect of embodiments of the invention, and

[0048] Fig. 4 is a schematic representation of further aspects of embodiments of the invention.

[0049] Detailed description of the invention

[0050] The invention will be described in more detail below with reference to the figures. It should be noted that various aspects are described, each of which can be used individually or in combination. This means that any aspect can be used with different embodiments of the invention unless explicitly presented as a mere alternative.

[0051] Furthermore, for the sake of simplicity, reference will generally be made to only one entity in the following. Unless explicitly stated, the invention may also comprise several of the entities in question. Therefore, the use of the words "a," "an," and "another" is to be understood merely as an indication that at least one entity is used in a simple embodiment.

[0052] Where procedures are described below, the individual steps of a procedure can be arranged and / or combined in any order, unless the context explicitly indicates otherwise. Furthermore, the procedures can be combined with one another, unless expressly indicated otherwise.

[0053] Numerical values ​​are generally not to be understood as exact values, but also include a tolerance of + / - 1% to + / - 10%.

[0054] Where standards, specifications, or the like are mentioned in this application, reference is always made to the standards, specifications, or the like applicable on the filing date. This means that if a standard / specification, etc., is updated or replaced by a successor, the invention is also applicable to it. Various embodiments are illustrated in the figures.

[0055] In particular, Figures 1 to 3 show parts of a wearable device 1 for detecting a narrowing in a lumen, in particular a stenosis in a blood vessel in a human or animal body.

[0056] The portable device 1 comprises a film-like substrate S which, in use, is arranged on the outside of the lumen, in particular the skin of the human or animal body.

[0057] "Film-like" means that the substrate is thin compared to its length. The material thickness can be reduced to the mechanically necessary minimum, ensuring a secure hold of the applied layers and structures while also retaining a certain degree of flexibility, allowing the wearable device 1 to conform to the outer contours of the skin at the area to be monitored, thus enabling good transmission of sound or vibrations. In particular, the substrate has a thickness of less than 0.2 mm.

[0058] At least two sound transducers M1, M2 are arranged on the foil-like substrate S.

[0059] Each transducer Ml, M2 in turn has at least one stack of layers.

[0060] These layers will now be further explained with reference to Figure 1.

[0061] To the extent that the layers have identical / similar properties, they are labeled accordingly in Figure 2 and Figure 3. In addition, layers that are shown with similar hatching in the figures also have similar electrical properties. As a rule, they then also consist of the same material, so that the number of different materials is low and thus also the processing and storage costs are low. Furthermore, in particular the layers that have a dashed frame in the figures are usually optional. The stack of layers has at least a partially covering sequence of a first electrically conductive layer LI, a PVDF layer L2 and a second electrically conductive layer L3. These represent the actual core of the sound transducer.As can be seen from Figures 1 to 3, the layers (in the sectional view) are arranged slightly offset from each other so that the layers LI and L3 can be contacted at the edge.

[0062] In particular, in embodiments of the invention it can be provided that the first electrically conductive layer LI and / or the second electrically conductive layer L3 comprise an electrically conductive plastic, in particular an electrically conductive polymer, and preferably PEDOT.PSS.

[0063] PEDOT.PSS is a polymer blend of two ionomers and is also known as poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. PVDF stands for polyvinylidene fluoride. PEDOT.PSS exhibits high conductivity and is easy to process. This makes it particularly well-suited as a material for electrically conductive layers.

[0064] Other electrically conductive polymers that can be used for the electrically conductive layers LI and L3 are, for example, PANI (polyaniline), doped PPy (polypyrrole), and doped PT (polythiophene).

[0065] The PVDF layer (L2) is electrically polarized perpendicular to the layer structure and exhibits a piezo effect.

[0066] On the side facing away from the substrate S, a biocompatible cover layer DS is further provided, wherein the first electrically conductive layer LI (e.g. made of PEDOT.PSS) and the second electrically conductive layer L3 (e.g. made of PEDOT.PSS) can be connected to an evaluation unit AE.

[0067] Such a portable device 1 can be manufactured by screen printing, in which the individual layers are applied one after the other. However, other manufacturing methods are not excluded. In particular, other printing methods, such as inkjet printers or other methods (e.g., by means of exposure processes), can also be used. It may be necessary to achieve corresponding temperatures during production. For example, the PVFD layer L2 should be heated to a temperature above the Curie temperature after application. CU of approximately 145 °C.

[0068] However, it is essential during production that the electrical polarization of the PVDF layer(s) L2 can be brought about once the respective adjacent layers LI and L3 have been applied. For this process, the material must be exposed to an external voltage. The external voltage depends on the material thickness. For a material thickness of 2 pm, for example, 150 - 300 V AC is used. The frequency of the AC voltage can be chosen appropriately, but is usually low, e.g. 1 Hz. Typically, the process does not take long, but can be completed in under a minute, in particular in less than half a minute. The polarization leads to the molecules being aligned in the desired ß-phase, i.e. an anisotropic material with a high piezoelectric coefficient is achieved.The already processed contacts K1 and K2 to the silver conductors L1 and L3 can be used as electrodes for this purpose. All sound transducers M1 ... M6 can be polarized simultaneously. In Figures 1 to 3, the completed polarization of the layers is indicated by arrows. Figure 2 shows an example of a layered structure with multiple PVDF layers. The electrical polarization of adjacent PVDF layers is (preferably) rotated by 180° relative to each other. This advantageously allows the piezoelectric voltages of the PVDF layers to be summed particularly easily when evaluating the transducers.

[0069] It should be noted that this is possible not only with PVDF but also with other polarizable materials.

[0070] However, unlike the prior art, the problem of short circuits does not arise during polarization. If one of the contacting electrically conductive layers LI (e.g., made of PEDOT.PSS) and / or L3 (e.g., made of PEDOT.PSS) shorts during polarization, the corresponding section is irreversibly damaged - unlike a section containing a metallic component - so that the resistance increases locally there and the defect location does not become apparent. In addition, the electrically conductive layers LI and / or L3 (e.g., made of PEDOT.PSS) have a significantly lower roughness than, for example, silver-containing layers, thereby maintaining the uniformity of a PVDF layer L2 even at low layer thicknesses. Such devices can be manufactured cost-effectively and allow reliable and safe detection of (impending) stenoses.

[0071] Without limiting the generality, it can be provided in embodiments of the invention that the film-like substrate S has a carrier film comprising polyethylene terephthalate (abbreviated PET), polyurethane (abbreviated PU), polyethylene naphthalate (abbreviated PEN), polyimide (abbreviated PI), polycarbonate (abbreviated PC) or paper.

[0072] Since the substrate side is not worn on the skin, it does not necessarily have to be biocompatible.

[0073] Thus, a device can be provided on the basis of different material systems which can also be combined with other devices without this being excluded by the choice of a specific material system.

[0074] In one embodiment of the invention, at least two sound transducers M1, M2 are pressure sensors or microphones or structure-borne sound transducers.

[0075] This means that the invention allows for a wide range of variations.

[0076] As shown in Figure 2, it can also be provided that the stack of layers has several sequences of a first electrically conductive layer LI, LI' (e.g. made of PEDOT.PSS), a PVDF layer L2, L2', L2" and a second electrically conductive layer L3, L3' (e.g. made of PEDOT.PSS). The stacks can be individually readable (not shown) or can be internally interconnected.

[0077] With such an arrangement, it is possible to utilize the effect of an external force (sound / shock wave / deflection) on the same surface, thus achieving greater sensitivity. The piezoelectrically generated charge, and thus the measured signal, can be increased by alternating electrically conductive layers (e.g., PEDOT.PSS) and PVDF layers. This multiplies the effectively utilized sensor area per layer, thus also increasing the absolute generated charge and thus the sensor's sensitivity.

[0078] It is particularly advantageous if the second electrically conductive layer (e.g. made of PEDOT.PSS) of a first sequence simultaneously forms the first electrically conductive layer (e.g. made of PEDOT.PSS) of a second sequence.

[0079] This allows the stack size to be kept small while increasing sensitivity.

[0080] According to yet another embodiment of the invention, the cover layer DS comprises polydimethylsiloxane (abbreviated PDMS) or PET.

[0081] In particular, the cover layer can provide mechanical impedance matching between the skin and an electrically conductive layer (e.g., made of PEDOT.PSS) located beneath the cover layer. Alternatively and / or additionally, the cover layer can also serve as contact protection and / or corrosion protection. Both PDMS and PET are biocompatible and can be in non-invasive contact with the skin.

[0082] According to a further development of the invention, at least the stack of layers is embedded in a non-conductive material FL. In particular, the non-conductive material is PET or PU.

[0083] This can also provide contact protection and / or corrosion protection as well as additional mechanical stability for the layer structure.

[0084] In yet another development of the invention, the connections K1, K2 of the first electrically conductive layer (e.g. made of PEDOT.PSS) and / or the second electrically conductive layer (e.g. made of PEDOT.PSS) with the evaluation unit AE comprise a silver-containing layer.

[0085] This allows a secure, low-impedance connection to be provided. According to yet another embodiment of the invention, adjacent to the side - as shown in Figure 3

[0086] - at least one further electrically conductive layer K3, K4 is arranged to form a stack.

[0087] Such additional electrical layers K3, K4 can provide shielding against interference, particularly against mains hum. For this purpose, the corresponding electrically conductive layers K3 and K4 can be connected to a ground potential of the evaluation unit AE.

[0088] In yet another embodiment of the invention, the electrically conductive layers K3 and K4 comprise silver.

[0089] Likewise, an adaptation layer SL can be provided for adaptation between the substrate S and a first layer, e.g. for contacting Kl / K2.

[0090] The object of the invention is further achieved by a system W for detecting stenoses, comprising a portable device according to the invention and an evaluation unit AE, wherein the evaluation unit AE is connected to at least two sound transducers M1, M2.

[0091] For example, the evaluation unit can be connected to the portable device 1 via a plug connection. The evaluation unit AE can also provide a ground connection for shielding purposes.

[0092] The signals from two transducers M1, M2 are repeatedly differentially evaluated during operation. If a significant phase shift and / or a significant signal change occurs at only one of the transducers M1, M2 between a first evaluation and a second evaluation following the first, a stenosis is detected. The sampling rate can be selected to resolve a typical range that is still perceptible to the human ear using a stethoscope. An example sampling frequency is 5 kHz.

[0093] The evaluation unit AE can also provide (analog) filtering, particularly a low-pass filter. It can also be provided that certain frequencies, such as mains hum, are filtered out (analog or digital) using a (notch) filter.

[0094] The evaluation unit AE can also provide amplification, e.g., through a transimpedance amplifier. This is typically connected to a sound transducer (via K1 and K2) using the shortest possible connection cable.

[0095] The evaluation unit AE can, for example, be equipped with a power supply (inductive / battery / energy harvesting) as well as a corresponding processing unit (CPU), e.g., a microcontroller or a suitably programmed circuit that activates a local error reporting device (DIS) in the event of a (threatened) stenosis being detected and / or sends a signal to an external monitoring unit (not shown) via a wireless interface (ANT). For example, the evaluation unit AE can provide a wireless connection via Bluetooth / Bluetooth LowEnergy, ULE, or WLAN, etc.

[0096] In particular, a further development of the invention can provide for a significant phase shift of approximately 90°. The differential pressure changes of two transducers can be compared. In particular, the change in blood sounds (both high-frequency and low-frequency phase shift) before and after the stenosis is measurable and can be used to predict a constriction between two sensors.

[0097] Without limiting the generality, as shown in Figure 5, the portable device 1 can also be provided with a plurality of sound transducers M1...M6, whereby the number can be suitably selected. Then, two sound transducers at a time can be read differentially. Preferably, the sound transducers M1...M6 are all of the same size and are preferably also located at the same distance d from one another, e.g., 10...15 mm.

[0098] Although the transducers M1...M6 are depicted as square in the figures, this is not necessary. Rather, the transducers could also be rectangular, elliptical, or round. The size of the transducers M1...M6 should roughly correspond to the dimensions of the vascular system being examined. For example, the sensor can have a diameter / edge length of 5...10 mm.

[0099] For example, transducers M1 and M2 can be read differentially. Transducers M3 and M4 can be read simultaneously or subsequently. Transducers M5 and M6 can be read differentially, simultaneously or subsequently.

[0100] Alternatively, it can also be provided that the transducers M1 and M4 are read differentially. The transducers M2 and M5 can be read simultaneously or subsequently. The transducers M3 and M6 can be read differentially, simultaneously or subsequently.

[0101] Such an arrangement with multiple transducers offers the advantage that the lumen, e.g., the corresponding vascular access (shunt vein), can be monitored over a longer distance, e.g., more than half of the forearm (or possibly also the upper arm). This allows the occurrence of a narrowing / stenosis to be monitored over a longer section of the lumen, e.g., a longer segment of the vein.

[0102] Preferably, the transducers are arranged in a line and thus approximately replicate the course of the corresponding vascular access (shunt vein).

[0103] According to the invention, an arrangement with at least two sound transducers M1, M2 is used for detection. This enables differential evaluation of the measurement signals, which greatly improves the sensitivity of the arrangement and also produces more robust measurement results (i.e., fewer false positive detections). Such systems can be manufactured cost-effectively and allow for reliable and safe detection of (impending) stenoses. In particular, the portable device can be designed as a disposable item, while the evaluation unit can be reused.

[0104] Without limiting its generality, it can also be provided that the wearable device 1 is arranged on a garment or is part of a garment. The garment could, for example, be a sleeve / stocking, in which case the device described above is preferably arranged on the inside.

[0105] The evaluation unit AE can be housed in a durable housing. Typically, the evaluation unit AE is designed to withstand mechanical stress and is designed as a reusable product.

[0106] The portable device 1 can be used once or multiple times. However, it should be noted that during heat disinfection, polarization may need to be performed again.

[0107] By means of the invention it is therefore possible to monitor lumens of various types, particularly in a medical context.

[0108] Another example of monitoring a lumen - in addition to monitoring stenoses in blood vessels - is the detection of narrowings in a tube, e.g. for extracorporeal blood treatment during treatment.

[0109] For example, a tube could be narrowed by kinking or pressure (pinching, patient sitting on the tube).

[0110] The device according to the invention can also be used here, in which the corresponding lumen "carries" the portable device 1, e.g. by placing the portable device 1 around a tube / lumen. The portable device 1 or its evaluation unit AE can be connected to a blood treatment machine; likewise, the portable device 1 can be part of a blood treatment machine or a separate device that, for example, sends data about a detected narrowing / stenosis as a (digital) signal. Such a (digital) signal can, for example, be transmitted to an external server, a portable device, such as a smartphone or a smartwatch, a treatment machine, etc.

[0111] List of designations

[0112] 1 wearable device

[0113] S film-like substrate

[0114] Ml ... 6 transducers

[0115] L1,L3;L1',L3' electrically conductive layer (e.g. made of PEDOT.PSS)

[0116] L2,L2',L2" PVDF layer

[0117] DS top layer

[0118] AE evaluation unit

[0119] FL non-conductive material

[0120] Kl, K2 connection

[0121] K3, K4 further electrically conductive layer

[0122] CPU processing unit

[0123] ANT wireless interface d distance

Claims

Claims A device (1) that can be worn on the body for detecting a constriction in a lumen, the wearable device comprising a film-like substrate (S) that, when in use, is arranged on an outer side of the lumen, at least two sound transducers (M1, M2) being arranged on the film-like substrate (S), each sound transducer (M1, M2) comprising at least one stack of layers, the stack of layers comprising at least a partially covering sequence of a first electrically conductive layer (L1), a PVDF layer (L2), and a second electrically conductive layer (L3), the PVDF layer (L2) being electrically polarized perpendicular to the layer structure and having a piezoelectric effect, a biocompatible cover layer (DS) being provided on the side facing away from the substrate (S), the first electrically conductive layer and the second electrically conductive layer being connectable to an evaluation unit (AE).Device according to claim 1, characterized in that the film-like substrate (S) has a carrier film comprising PET, PU, ​​PEN, PI, or PC. Device according to claim 1 or 2, characterized in that the at least two sound transducers (M1, M2) are pressure sensors or microphones or structure-borne sound transducers. Device according to one of the preceding claims, characterized in that the stack of layers comprises several sequences of a first electrically conductive layer (L1), a PVDF layer (L2, L2', L2"), and a second electrically conductive layer (L3). Device according to one of the preceding claims, characterized in that the cover layer (DS) comprises PDMS or PET. Device according to one of the preceding claims, characterized in that the cover layer (DS) provides a mechanical impedance match between the skin and an electrically conductive layer located beneath the cover layer (DS). Device according to one of the preceding claims, characterized in that the stack of layers has a plurality of sequences of a first electrically conductive layer, a PVDF layer and a second electrically conductive layer, wherein the second electrically conductive layer of a first sequence simultaneously also forms the first electrically conductive layer of a second sequence. Device according to one of the preceding claims, characterized in that at least the stack of layers is embedded in a non-conductive material (FL). Device according to claim 8, that the non-conductive material is PET or PU. Device according to one of the preceding claims, characterized in that the connections (K1, K2) of the first electrically conductive layer and / or the second electrically conductive layer to the evaluation unit (AR) have a silver-containing layer.Device according to one of the preceding claims, characterized in that at least one further electrically conductive layer (K3, K4) is arranged laterally adjacent to a stack. Device according to one of the preceding claims, characterized in that the first electrically conductive layer (LI) and the second electrically conductive layer (L3) comprise PEDOT.PSS. Device according to one of the preceding claims, characterized in that the portable device is designed to be worn on the body of a human or animal body, wherein in use the portable device is arranged on the skin of the human or animal body in order to detect a stenosis in a blood vessel of the human or animal body. System for detecting narrowings, comprising a device according to one of the preceding claims and an evaluation unit (AE), wherein the evaluation unit (AE). to which at least two sound transducers (M1, M2) are connected, wherein the signals from each of two sound transducers are repeatedly differentially evaluated, wherein a stenosis is detected if a significant phase shift and / or a significant signal change occurs at only one sound transducer between a first evaluation and a second evaluation following the first. System according to claim 14, characterized in that a significant phase shift has a phase shift of approximately 90°.

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