WO2016024216A1

WO2016024216A1 - Multipolar interconnection device for detecting and transmitting bioelectric signals

Info

Publication number: WO2016024216A1
Application number: PCT/IB2015/056102
Authority: WO
Inventors: Umberto BARONE; Roberto Merletti
Original assignee: Politecnico di Torino
Current assignee: Politecnico di Torino
Priority date: 2014-08-13
Filing date: 2015-08-11
Publication date: 2016-02-18
Anticipated expiration: 2017-02-13

Abstract

A multipolar interconnection device for detecting and transmitting bioelectric signals is described, which comprises multiwire cabling means to a first end of which first interfacing means are connected, second interfacing means being connected to a second end of said multiwire cabling means, said first interfacing means comprising a first insulating support and at least one first multipolar connector connected to said first insulating support, said at least one first multipolar connector comprising a plurality of poles and being associable with sensor means, in particular a plurality of electrodes, adapted to adhere to the skin of a person; said second interfacing means comprising a second insulating support and a second multipolar connector connected to each other, said second multipolar connector comprising a plurality of poles and being associable with a unit for acquiring and processing said bioelectric signals, said multiwire cabling means comprising a plurality of microwires adapted to transport said bioelectric signals.

Description

MULTIPOLAR INTERCONNECTION DEVICE FOR DETECTING AND TRANSMITTING BIOELECTRIC SIGNALS

DESCRIPTION

The present invention relates to a multipolar interconnection device for detecting and transmitting bioelectric signals.

It is known that muscle fibres generate bioelectric signals, also referred to as biopotentials, during the biomechanical phenomenon of spindle contraction. Muscles are the most important effector organs of the nervous system, and activate their contractile system in response to bioelectric signals sent through the nervous fibres. Such electric activity can be detected on the skin surface of the area of interest by using a technique called surface electromyography (sEMG), whereby electric signals are detected by arranging sensors made of electrically conducting material on the skin that covers the muscle.

In particular, electrodes are known which allow biopotential detection, such electrodes being connected to electric conductors at one end, while the other end can be connected to a unit for acquiring and processing said biopotentials.

Biopotentials, i.e. the signal source, are generally characterized by a weak electric potential (e.g. 20μν - 5mV), a low signal-to-noise ratio, and high internal impedance (e.g. 1-100 MOhm). In order to amplify the biopotentials, the electronic unit comprises at least one stage for analogue amplification and conditioning of biopotentials.

It is also known that biopotentials are subject to interference due to electrostatic and/or dynamic phenomena that, if not effectively removed or attenuated, will prevent biopotentials from being properly recorded, thus making it impossible to properly extract the patient's physiological information correlated thereto.

An important phenomenon of electrostatic nature is the interference of the electric grid that couples to a person's body because of the parasitic coupling capacities between the person's body and the electric cables and between the person's body and the ground reference of the electric grid. This latter high-impedance path of capacitive nature induces a common mode potential on the person's body, which shows at the sensors as noise equal to a potential difference of variable amplitude (typically in the range of 10μΥ to IV) and frequency equal to that of the electric grid plus the respective harmonic components (e.g. 50Hz, 100Hz, 150Hz, and so on). Furthermore, said noise increases with the internal impedance of the signal sources to be detected, i.e. the biopotentials. Rejection of this parasitic common mode phenomenon is usually attained by means of techniques for shielding the signal conducting cables and by means of feedback electronic circuits capable of injecting the interfering signals on the patient with reversed phase for the purpose of cancelling its global contribution on the person's body ("Drive Right Leg" circuit). These solutions, however, imply the use of heavy conducting cables and integrated circuits in proximity to the passive sensors.

On the other hand, the motion artifacts that get coupled on the conductive path of the signal between the sensors and the electronic processing unit are phenomena of dynamic nature. For example, the superimposition effect on the surface electromyographic signal causes significant degradation during dynamic measurements. Dynamic measurements refer to real-time monitoring of a person's muscular activity while executing movements that induce significant and continuous changes in the spatial position of the limbs and/or muscle groups being monitored. In particular, the piezoelectric and triboelectric effects are directly related to the dimensions and weight of the cablings, i.e. to the insulating and protective coatings of the conducting wires and to the nature of the materials they are made of.

The use of the techniques known in the art for connecting the sensors and of the above- described solutions for noise rejection implies the impossibility of effectively monitoring a person (e.g. his/her muscular activity via elecromyogram or electroencephalogram) due to the increased weight of the sensor wirings and interfaces. This weight increase mainly translates into increased electric motion artifact phenomena because the latter are related to deformation, i.e. oscillations and shocks undergone by wirings and connectors on the patient.

The electrode wiring solutions known in the art are based on active or passive shields that cause a considerable increase in the rigidity and weight of the conducting cables in use. In addition, the materials employed in the above-mentioned solutions have dielectric properties that do not make the cabling immune from motion artifact effects. The necessity of connecting a plurality of electrodes to a multichannel measurement unit is an important technical problem in real applications, where wearable devices need to be used, which must be light and miniaturized, for monitoring physiological parameters in real time through non-invasive multichannel techniques. Furthermore, a plurality of electrodes requires a large number of conducting cables, resulting in more evident dynamic interference on the bioelectric signals.

It is therefore the object of the present invention to provide a multipolar interconnection device for detecting and transmitting bioelectric signals, which allows rejection of parasitic phenomena of electrostatic and dynamic nature.

In brief, the following will describe a multipolar interconnection device for detecting and transmitting bioelectric signals which comprises multiwire cabling means to a first end of which first interfacing means are connected, second interfacing means being connected to a second end of said multiwire cabling means; the first interfacing means comprise a first insulating support and at least one first multipolar connector connected to said first insulating support; at least one first multipolar connector comprises a plurality of poles and is associable with sensor means, in particular a plurality of electrodes, adapted to adhere to a person's skin. The second interfacing means comprise a second insulating support and a second multipolar connector connected to each other; said second multipolar connector comprises a plurality of poles and is associable with a unit for acquiring and processing said bioelectric signals; finally, the multiwire cabling means comprise a plurality of microwires adapted to transport the bioelectric signals. The device according to the invention allows monitoring a person's muscular activity also in dynamic conditions, ensuring high rejection of noise caused by electric grid interference and motion artifacts.

Further features of the invention are set out in the appended claims, which are intended to be an integral part of the present description.

The above objects will become more apparent from the following detailed description of a multipolar interconnection device for detecting and transmitting bioelectric signals according to the present invention, with particular reference to the annexed drawings, wherein:

- Figure 1 shows a multipolar interconnection device according to the present invention;

- Figure 2 illustrates in detail the multipolar interconnection device of Fig. 1;

- Figure 3 illustrates in detail some characteristics of a first part of the device according to the invention;

- Figure 4 shows an implementation of an electric connection in the device according to the invention;

- Figure 5 illustrates a multiwire distribution of the device according to the invention;

- Figure 6 shows in detail a second part of the device according to the invention.

In the present description, the terms bioelectric signal(s) and biopotential(s) have the same meaning.

With reference to Figures 1 and 2, there is shown a multipolar interconnection device 1 according to the present invention, said device 1 comprising multiwire cabling means 5 to a first end of which first interfacing means 3 are connected, second interfacing means 7 being connected to a second end of said multiwire cabling means 5.

Considering a source side LS of the device 1, i.e. that side of the device 1 on which biopotentials are detected, the first interfacing means 3 comprise a first insulating support 9 and at least one first multipolar connector 11 connected to the first insulating support 9. At least one first multipolar connector 11 comprises a plurality of poles and is associable with sensor means 13, in particular a plurality of non-invasive electrodes comprising an electrically conducting surface, which adhere to the skin C of a person. Considering a measurement side LM of the device 1, i.e. that side on which biopotentials are acquired and processed, the second interfacing means 7 comprise a second insulating support 15 and a second multipolar connector 17 connected to each other. Said second multipolar connector 17 comprises a plurality of poles and is associable with a unit 19 for acquiring and processing biopotentials.

More in detail, with reference to Fig. 3, the first interfacing means 3 preferably comprise the sensor means 13 and a third insulating support 23, on which the sensor means 13, i.e. the electrodes, are installed. The third insulating support 23 allows interconnecting the sensor means 13 with at least one first multipolar connector 11. In particular, the sensor means 13 are of the passive type, i.e. they do not require the use of analogue electronics arranged in proximity to the skin C of the person (therefore not requiring the presence of any power sources and/or connections for supplying power to electronic circuits close to the source of the bioelectric signals to be measured), and may be in any number N (where N is an integer number), e.g. 32. The N sensors 13 are thus adapted to simultaneously detect N biopotentials (SI, S2, S_N). In addition, the sensor means 13 comprise two further sensors: one for detecting a first reference signal "G", i.e. a signal detected at one point of the skin C where no particular subcutaneous sources of bioelectric signals are present, and the other for detecting a second reference signal "P" used for collecting the common mode potential being distributed on the person's body (this point may coincide or be adjacent to the point where the first reference signal "G" is detected). As a whole, there are N+2 sensors; hence, N+2 bioelectric signals are detected on the skin C of the person.

Preferably, the first interfacing means 3 comprise two first multipolar connectors 1 1 , one for detecting the first and second reference signals "G" and "P", and the other one for detecting the N biopotentials.

As an alternative, the first interfacing means 3 comprise only one first multipolar connector 1 1 for detecting the first and second reference signals "G" and "P" as well as the N biopotentials.

All of the N+2 sensors are connected to the two first multipolar connectors 1 1 via electric connections 25.

A plurality of microwires are connected to the first insulating support 9 through at least one electric connection 21 , in particular a spot weld.

More specifically, N microwires are adapted to transport the N biopotential signals (S I , S2, . . . , S_N). Preferably, the N microwires are insulated, and each one has a diameter not exceeding 0. 1 mm and an insulating coating having a thickness not exceeding 50 μηι. The microwire material may be, for example, copper, silver-coated copper, graphene or stainless steel. The insulating coating must preferably ensure an insulation capacity of at least 100 V/μηι, and it may be made, for example, of a polyurethane-based material. The first reference signal "G" and the second reference signal "P" are replicated over a plurality of microwires (whether insulated or not), each having a diameter not exceeding 0. 1 mm. More specifically, K microwires transport the second reference signal "P", and J microwires transport the first reference signal "G" according to a star configuration 12. K and J may be any integer number. The star configuration 12 refers to the method of connection between the K and J microwires and the electric connections 21 on the insulating support 9; in other words, J microwires branch out from one welding spot on the insulating support 9 whereat the first reference signal "G" arrives, and, likewise, K microwires branch out from one welding spot on the insulating support 9 whereat the second reference signal "P" arrives.

With reference to Fig. 4, the following will describe the implementation of a closed conducting loop 10, also referred to as "Guard Ring". Both surfaces of the first insulating support 9 comprise a loop 10. Said loop 10 is polarized by the first reference signal "G" and allows the points of contact between the microwires and the first insulating support 9 to be immunized from the effect of the surface leak currents of electrostatic nature that may be present on the first insulating support 9.

Likewise, the closed conducting loop 10 can also be installed on the second insulating support 15.

As a whole, K+J+N microwires are obtained at the output of the first interfacing means 3, which are then inserted into the multiwire cabling means 5. In other words, the multiwire cabling means 5 comprise a plurality of microwires adapted to transport bioelectric signals.

Each insulated microwire may, in its turn, be coated with a film (not thicker than 50 μπι) comprising highly electrically conducting nanoparticles, e.g. made of graphite, silver, gold or graphene, in order to further reduce the triboelectric and piezoelectric effect during the mechanical deformations of the microwire itself.

Fig. 5 shows a cross-sectional view of the multiwire cabling means 5. The set of microwires (for the first and second reference signals "G" and "P" and the N biopotentials S) inserted in the multiwire cabling means 5 is grouped and braided by using a stranding technique that can ensure the utmost cohesion among the microwires in accordance with a distribution of the signals such that the microwires transporting the first reference signals "G" are never contiguous to those transporting the second reference signals "P", except along the perimeter of the bundle of microwires, i.e. of the multiwire cabling means 5.

The multiwire cabling means 5 comprising the whole bundle of microwires may in turn be coated with a braid 27 made from textile yarn, e.g. silk, which can compact the microwire structure resulting from the stranding process. The yarn braid 27 is made conductive or semi-conductive by means of a doping treatment using electrically conducting nanoparticles, the material of which may be silver, graphene, gold or graphite, or a combination thereof. Such a treatment makes the multiwire cabling means 5 more immune from parasitic noise of electrostatic and dynamic nature. The multiwire cabling means 5 are preferably 1.5 metres long, but different lengths may also be obtained. Therefore, the electronic acquisition and processing unit 19 can advantageously be arranged at a comfortable distance from the signal source (i.e. the sensor means 13), since it must not necessarily be placed on the person's body.

In fact, the peculiarities of the device 1 described so far allow obtaining a length of the cabling means 5 of the order of metres, just because said peculiarities allow rejection of interference from the electric grid and interference due to motion of the microwires included in the cabling means 5 (it is known, in fact, that motion of the microwires causes artifacts on the bioelectric signals).

Finally, Fig. 6 shows the measurement side LM, wherein the multiwire cabling means 5 are connected to the second interfacing means 7.

The features of the present invention, as well as the advantages thereof, are apparent from the above description.

A first advantage of the multipolar interconnection device according to the invention is that it allows monitoring a person's muscular activity also in dynamic conditions, ensuring high rejection of noise caused by electric grid interference and motion artifacts.

A second advantage of the multipolar interconnection device according to the invention is that it has a lower weight, higher flexibility and smaller dimensions than prior art devices, thus further reducing artifacts on biopotentials due to mechanical motion of the device itself.

A further advantage of the multipolar interconnection device according to the invention is that it allows obtaining a length of the multiwire cabling means of the order of metres. A fourth advantage of the device according to the invention is that it makes it possible to easily sensorize tissues by means of passive sensors distributed over large surfaces and then interconnected with an electronic unit in accordance with the technique described herein.

The multipolar interconnection device for detecting and transmitting bioelectric signals may be subject to many possible variations without departing from the novelty spirit of the inventive idea; it is also clear that in the practical implementation of the invention the illustrated details may have different shapes or be replaced with other technically equivalent elements.

It can therefore be easily understood that the present invention is not limited to a multipolar interconnection device for detecting and transmitting bioelectric signals, but may be subject to many modifications, improvements or replacements of equivalent parts and elements without departing from the novelty spirit of the inventive idea, as clearly specified in the following claims.

Claims

1. Multipolar interconnection device (1) for detecting and transmitting bioelectric signals, comprising multiwire cabling means (5) to a first end of which first interfacing means (3) are connected, second interfacing means (7) being connected to a second end of said multiwire cabling means (5), said first interfacing means (3) comprising a first insulating support (9) and at least one first multipolar connector (11) connected to said first insulating support (9), said at least one first multipolar connector (11) comprising a plurality of poles and being associable with sensor means (13), in particular a plurality of electrodes, adapted to adhere to the skin (C) of a person; said second interfacing means (7) comprising a second insulating support (15) and a second multipolar connector (17) connected to each other, said second multipolar connector (17) comprising a plurality of poles and being associable with a unit (19) for acquiring and processing said bioelectric signals, said multiwire cabling means (5) comprising a plurality of microwires adapted to transport said bioelectric signals.

2. Device (1) according to claim 1, wherein said first interfacing means (3) comprise said sensor means (13) and a third insulating support (23) on which said sensor means

(13) are installed, said third insulating support (23) being adapted to interconnect said sensor means (13) with said at least one first multipolar connector (11).

3. Device (1) according to claim 1 or 2, wherein said sensor means (13) comprise N sensors for detecting N bioelectric signals, where N is an integer number, a sensor for detecting a first reference signal ("G") collected at one point of said skin (C) where there is no significant presence of any subcutaneous sources of bioelectric signals, and a sensor for detecting a second reference signal ("P") for collecting the common mode potential being distributed on said person's body.

4. Device (1) according to one or more of the preceding claims, wherein said first interfacing means (3) comprise at least one first multipolar connector (1 1) for detecting said first reference signal ("G"), said second reference signal ("P") and said N bioelectric signals.

5. Device (1) according to one or more of the preceding claims, wherein each microwire belonging to said plurality of microwires is insulated by an insulating coating having a thickness not exceeding 50 μηι, and said each microwire has a diameter not exceeding 0.1 mm.

6. Device (1) according to claim 5, wherein the material of said plurality of microwires comprises one or more elements from the group including: copper, graphene, silver-coated copper, and stainless steel.

7. Device (1) according to one or more of the preceding claims, wherein said insulating coating ensures an insulation capacity of at least 100 V/μιη.

8. Device (1) according to one or more of the preceding claims, wherein said insulating coating is made of a polyurethane-based material.

9. Device (1) according to one or more of the preceding claims, wherein said first reference signal ("G") and said second reference signal ("P") are replicated over said plurality of microwires.

10. Device (1) according to one or more of the preceding claims, wherein the microwires associated with said first reference signal ("G") and said second reference signal ("P") are not insulated.

11. Device (1) according to one or more of the preceding claims, wherein each insulated microwire is coated with a film comprising highly electrically conducting nanoparticles and having a maximum thickness of 50 μτη.

12. Device (1) according to claim 11, wherein the material of said film comprises one or more elements from the group including: graphite, graphene, silver, and gold.

13. Device (1) according to one or more of the preceding claims, wherein said first insulating support (9) comprises, on both of its surfaces, a closed conducting loop (10) polarized by said first reference signal ("G").

14. Device (1) according to one or more of the preceding claims, wherein said plurality of microwires inserted in said multiwire cabling means (5) are grouped and braided by using a stranding technique in accordance with a distribution of said bioelectric signals such that the microwires associated with said first reference signal ("G") are never contiguous to the microwires associated with said second reference signal ("P"), except along the perimeter of said multiwire cabling means (5).

15. Device (1) according to one or more of the preceding claims, wherein said multiwire cabling means (5) are coated with a braid (27) made from textile yarn, in particular silk.

16. Device (1) according to claim 15, wherein said textile-yarn braid (27) is made conductive or semi-conductive by means of a doping treatment using electrically conducting nanoparticles.

17. Device (1) according to claim 16, wherein the material of said conducting nanoparticles comprises one or more elements from the group including: silver, gold, graphene, and graphite.