WO2015112095A1

WO2015112095A1 - Smart belt for breathing and heart rate monitoring

Info

Publication number: WO2015112095A1
Application number: PCT/SG2015/050008
Authority: WO
Inventors: Xiufeng Yang; Zhihao Chen; Ser Ming Elvin CHIA; Hong Ying Janice LAM; Soon Huat Ng; Ju Teng Teo
Original assignee: Agency For Science, Technology And Research; Dso National Laboratories
Priority date: 2014-01-23
Filing date: 2015-01-23
Publication date: 2015-07-30

Abstract

A sensor member for use in a wearable device for monitoring vital signs of a user, the sensor member comprising: a substrate repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the substrate; a deformation member disposed on the substrate; and an optical fibre attached to the substrate and including a bend, the bend lying in a plane that is non-coincident with the plane of the substrate, wherein the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre.

Description

SMART BELT FOR BREATHING AND HEART RATE MONITORING

Priority Claim

The present application claims priority to Singapore Patent Application No. 201400547-4, filed 23 January, 2014.

The present invention relates to heart rate and breathing monitors. In particular, it relates to a user wearable smart belt for breathing and heart rate monitoring.

Monitoring of human vital signs such as heart beat rate, blood pressure and breathing rate is crucial for the overall health status of people, especially in risk groups such as the elderly and people with special needs. Continuous monitoring of these vital signs can help to identify heart and lung diseases such as heart failure, heart attack, stroke and apnea.

Electrical sensors have been used for vital signs monitoring. However, it has been recognized that electronic sensors are not sensitive enough to distinguish between shallow breathing and no breathing. In addition, electrical sensors are typically prone to electromagnetic interference, a significant problem in certain clinical examinations such as magnetic resonance imaging (MRI) examinations.

Electrocardiogram (ECG) sensors are also conventional devices for monitoring the heart rate utilizing detection by Electrocardiogram. Yet these devices must directly contact the skin of a patient and are very uncomfortable and disturbing to patients due to wired sensors and electrodes that must be directly attached. In order to overcome the inconvenience of directly attached sensors and electrodes, sensing beds or mattresses, pillows and cushions based on mechanical sensors, electrical sensors and fibre optical sensors have been proposed. However, most of these sensors are not wearable by the patient.

Some wearable devices have been proposed. However, those devices are generally only capable of monitoring one vital sign at a time – typically either respiratory action or cardiac rhythm. Where such wearable devices use fibre optical sensors there are also issues with accuracy due to the short length of the wearable devices and consequent short length of the optical fibres. This short length results in insufficient modulation of a signal propagated along the fibre to facilitate accurate measurement of that modulation. This short length may similarly result in low sensitivity in monitoring, for example, the respiratory and cardiac rhythms of the user.

Considering the mobility of patients, what is needed are wearable sensing and monitoring systems able to measure vital parameters such as cardiac activity, respiration action and others. More particularly, what is needed is wearable health care monitoring devices that can be incorporated into textile and garments for continuous and autonomous monitoring of vital signs of patients and elderly persons.

A smart belt is disclosed that embeds a section of optical fibre into the stretchable textile for heart beat and breathing rate monitoring. This smart belt is comfortable to wear and can be used to sense the heart rate and respiration simultaneously from various locations on the person with a single sensing belt and sensing system. The simultaneous sensing can be accomplished while the wearer is sitting or standing still, and respiration waveforms can be measured correctly even while the wearer is walking or running.

The present disclosure provides a sensor member for use in a wearable device for monitoring vital signs of a user, the sensor member comprising:
a substrate repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the substrate;
a deformation member disposed on the substrate; and
an optical fibre attached to the substrate and including a bend, the bend lying in a plane that is non-coincident with the plane of the substrate,
wherein the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre.

The term “optical fibre” is intended to include, but not be limited to, a complete optical fibre or a section of optical fibre.

The bend may form a micro bend during extension and/or retraction of the substrate. The phrase “during extension and/or retraction” is intended to mean at any point or period in time as the substrate extends and/or retracts including over the entire extension and retraction action of the substrate.

The micro bend may be formed at least when the substrate is fully retracted. The bend may form a micro bend when the substrate is fully extended.

The deformation member may be elongate. The deformation member may extend at a non-zero angle to the direction of extension/retraction of the substrate.

The deformation member may comprise a plurality of elongate elements. The optical fibre may form a bend over each of the elongate elements. The elongate elements may be disposed in parallel. The elongate elements may be spaced at regular intervals along the substrate. The distance between neighbouring elongate elements may vary from one element to the next. The elongate elements may be fibres.

The deformation member may comprise a textile base upon which a fibre is disposed. The deformation member may comprise a textile base upon which a plurality of fibres are disposed. The plurality of fibres may be disposed in parallel. The elongate elements may be spaced at regular intervals along the substrate. The distance between neighbouring elongate elements may vary from one element to the next.

The sensor member may further comprise an opposing deformation member disposed on the substrate. The optical fibre may pass between the deformation member and the opposing deformation member. The radius of curvature of the optical fibre may change through relative movement of the deformation member and opposing deformation member with extension and retraction of the substrate.

The opposing deformation member may comprise a plurality of elongate elements. The optical fibre may form a bend under each of the elongate elements. The optical fibre may pass alternately over and under individual elements of the deformation member and opposing deformation member respectively. The elongate elements may be fibres.

The elongate elements of the opposing deformation member may be disposed in parallel. The elongate elements of the opposing deformation member may be parallel to the elongate elements of the deformation member, and the former may be offset from the latter in the direction of extension/retraction of the substrate.

The optical fibre may make multiple passes along the substrate.

The optical fibre may include a second bend in a plane parallel to the direction of extension/retraction of the substrate to enable the optical fibre to flex with extension and retraction of the substrate.

The bend may be a first bend and the optical fibre may include a second bend, wherein the radius of curvature of the second bend increases as the substrate extends so that the optical fibre extends with the substrate, and wherein the first bend pulls against the deformation member as the substrate extends thereby varying a force applied to the optical fibre to modulate a signal propagated along the optical fibre.

A sensor member for use in a wearable device for monitoring vital signs of a user, the sensor member comprising:
a substrate repeatedly extendable and retractable;
a deformation member disposed on the substrate; and
an optical fibre attached to the substrate and including a first bend and a second bend, wherein the radius of curvature of the second bend increases as the substrate extends so that the optical fibre extends with the substrate, and wherein the first bend pulls against the deformation member as the substrate extends thereby to apply force to the optical fibre to modulate a signal propagated along the optical fibre.

The first and second bends may be in respectively non-coincident planes.

The optical fibre may comprise a plurality of bends. The optical fibre may comprise a plurality of bends about the deformation member. The plurality of bends may be first bends. The optical fibre may comprise a plurality of second bends. The radius of curvature of the second bends may increase as the substrate extends so that the optical fibre extends with the substrate.

The present disclosure also provides a wearable device for monitoring vital signs of a user, the device comprising:
a support member adapted to hold the device in position on the user, the support member comprising:
a substrate repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the substrate; and
a deformation member disposed on the substrate; and
an optical fibre attached to the substrate and including a bend, the bend lying in a plane that is non-coincident with the plane of the substrate,
wherein the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre.

The present disclosure still further provides a wearable device for monitoring the vital signs of a user, the device comprising a sensor member as discussed above, wherein the substrate and deformation member are parts of a support member adapted to hold the device in position on the user.

The support member may form a belt. The support member may form a smart belt. The direction of extension/retraction of the substrate may extend along the belt. The substrate may extend along the belt over substantially less than the length of the belt.

The device may comprise an emitter transmitter for emitting the signal into the optical fibre. The device may comprise a receiver for receiving the modulated signal from the optical fibre. The device may comprise a transceiver for emitting the signal into the optical fibre and receiving the modulated signal from the optical fibre. The optical fibre has two ends, the emitter emitting the signal into one end of the optical fibre and the receiver receiving the signal from the other end of the optical fibre.

The device may comprise a transmitter for transmitting a measurement of the modulated signal to a remote device.

The emitter, receiver, transceiver and/or transmitter may be attached to the support member. The emitter, receiver, transceiver and/or transmitter may be attached to the substrate.

The present disclosure yet further provides a panel for use in the manufacture of wearable devices for monitoring vital signs of a user, the panel comprising:
a sheet upon which a plurality of sensor members are formed, each sensor member comprising:
a substrate repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the substrate;
a deformation member disposed on the substrate; and
an optical fibre attached to the substrate and including a bend, the bend lying in a plane that is non-coincident with the plane of the substrate,
wherein the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre when in use.

The plurality of sensor members may be formed in a grid pattern on the sheet.

The present disclosure still further provides a method for fabricating a sensor member for use in the manufacture of a wearable device for monitoring vital signs of a user, the method comprising:
providing a sheet that is repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the sheet, wherein the sheet forms a substrate of the sensor member;
attaching a deformation member to the substrate;
attaching an optical fibre to the substrate such that the optical fibre includes a bend lying in a plane non-coincident with the plant of the sheet and the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre when in use.

Attaching the optical fibre to the substrate may include attaching the optical fibre to the deformation member and thereby to the substrate as a result of the deformation member being attached to the substrate. The optical fibre may alternatively be attached directly to the substrate.

The deformation member may comprise a textile with at least one fibre, wherein the bend in the optical fibre bends about the fibre, and attaching the deformation member to the substrate comprises attaching the textile to the substrate.

The attaching steps may comprise embroidering the deformation member and optical fibre to the substrate.

The embroidering step may comprise using a zigzag stitch. The embroidering step may comprise using Soutache embroidering. The Soutache embroidering may be performed by a computerized double-head (or two single-head) embroidery machines.

[FIG. 1A] is a block diagram of a smart belt monitoring system in accordance with a present embodiment.

[FIG. 1B] is an exploded view of a sensing sheet for the smart belt system.

[FIG. 1C] is a top planar view of the sensing sheet for the smart belt system.

[FIG. 1D] is a side planar cutaway view of the sensing sheet for the smart belt system.

[FIG. 2], comprising FIG. 2A and FIG. 2B, the smart belt and its sensing sheet, wherein FIG. 2A shows the sensing sheet and FIG. 2B shows the smart belt system including the sensing sheet.

[FIG. 3] shows heart beat and respiration measurement being taken from a user in standing position using the smart belt system of FIGs. 1A and 2B.

[FIG. 4] depicts readout of signals showing a testing result when a healthy volunteer is sitting.

[FIG. 5] depicts readout of signals showing respiration measurements of a volunteer while running.

[FIG. 6], comprising FIG. 6A, FIG. 6B and FIG. 6C, shows readouts of signals for a volunteer during different activity modes, wherein FIG. 6A depicts a readout of signals showing respiration measurements of a volunteer while standing, FIG. 6B depicts a readout of signals showing respiration measurements of a volunteer while walking, and FIG. 6C depicts a readout of signals showing respiration measurements of a volunteer while running.

[FIG. 7], comprising FIG. 7A, FIG. 7B and FIG. 7C, shows textile substrate sensing sheets in accordance with an embodiment, wherein FIG. 7A depicts a single set of textile substrate with an under-laying fibre layer, FIG. 7B depicts a first configuration of a textile fibre optic sensing sheet with under-laying, up-laying and optical fibre layers, and FIG. 7C depicts a second configuration of a textile fibre optic sensing sheet with under-laying, up-laying and optical fibre layers.

[FIG. 8], comprising FIG. 8A, FIG. 8B and FIG. 8C, shows multiple sets of textile fibre optical sensing sheets after scalable manufacturing, wherein FIG. 8A depicts multiple sets of the textile substrate with only an under-laying fibre, FIG. 8B depicts multiple sets of the textile fibre optical sensing sheets with under-laying, up-laying and optical fibre layers, and FIG. 8C depicts the multiple sets of the textile fibre optical sensing sheets of FIG. 8B with one of the sensing sheets removed and mounted on a smart belt in accordance with the system of FIG. 2B.

Considering the mobility of patients, great effort has been taken for the development of wearable sensing and monitoring systems able to measure vital parameters such as cardiac activity and respiration action during both passive and active activities. Optical fibre sensors are an alternative of vital signs sensor because they possess several advantageous properties, such as inherently immune from electromagnetic interference and chemical inert, for sensing and monitoring applications where non-invasiveness, risk of explosion or need for distributed measurement are concerns. Optical fibre provides significant advantages when used close to biomedical devices or in diagnostic environments because they produces no heat, they are not susceptible to electrical discharges.

Several methods and devices based on fibre optical sensors for the heart beat and breathing rate monitoring have been proposed such as (a) a vital signs monitoring system based on fibre interferometry method, (b) a smart bed for non–intrusive monitoring of respiration, heart beat and patient movement based on a statistical mode sensing and high order mode excitation using a multimode optical fibre, and (c) fibre optical based vital sign sensors embedded in pillows or cushion for heart rate, breathing rate and body movement monitoring.

Several systems also exist for vital sign monitoring systems based on multimode optical fibre intensity sensors to measure breathing rate, heart rate and/or body movement. Such optical fibres where sensing occurs in the core of the optical fibre can be developed as a yarn-like fibre for processing like standard textile yarns. Further, several textile-processing techniques, such as wrap and weft knitting, weaving and stitching, can be used to embed the sensing fibre elements into textile fabrics.

A prior art textile-based respiratory rate sensor system has been introduced which is comfortable to wear and can be located at thorax or abdomen locations due to its elastic property. However this sensor system cannot measure the heart beat signal due to the low sensitivity. A second prior art system embedded an integrated polymer optical fibre which uses the long period grating and macro bending effect of polymer optical fibres to monitor heart rate and breathing rate. This system, however, can only measure the heart beat when the breathing movement is stopped.

In accordance with a present embodiment, a smart belt is provided which embeds a section of optical fibre into a substrate, presently embodied by a stretchable textile, for heart beat and breathing rate monitoring. The smart belt in accordance with the present embodiment is very comfortable to wear and can advantageously be used to sense the heart rate and respiration simultaneously at various locations on a person with a single sensing belt and sensing system. Further, the robust smart belt in accordance with the present embodiment can be used to sense the heart rate and respiration while the wearer is sitting and while the wearer is standing still. The respiration waveform can also be accurately measured even when the wearer is walking or running.

Referring to FIG. 1A, a block diagram of a smart sensing belt measurement system 10 which can measure the heart rate and breathing rate is shown. The sensing system 10 consists of a transceiver 12 comprising a light source (e.g. optical transmitter 14), a photodetector (e.g. optical receiver 16) and a Bluetooth module 18. The sensing system 10 further comprises a substrate, embodied by a sensing sheet 20, and a computer 22. The sensing sheet 20 is incorporated into a wearable device such as a belt 48 (see FIG. 2B) to be worn by the user during measurement of vital signs of the user.

The sensing sheet 20 comprises a section of sensing optical fibre 24 and is embedded in the elastic sensing belt 10. The output light from the optical transmitter 14 is launched into one end of the optical fibre 24 and the breathing and cardiac activity of the person wearing the belt (e.g. as shown in FIG. 2B) will modulate this light as it passes through the fibre 24. The modulated light emitted from the other end of the optical fibre 24 is received by the optical receiver 16 which generates a signal in response to the modulated light which is sent to the computer 22 via the Bluetooth module 18 for signal processing and heart rate and breathing rate calculation.

The optical fibre 24 makes four passes (consecutively numbered A to D) along the sheet 20. This enables an increase in the length of the optical fibre 24 and the number of times the optical fibre is manipulated by deformation members 28, 30 (see FIG. 1B). As a result, there is a substantial increase in the amount of modulation of the light signal propagated through the optical fibre. This can be used to amplify the modulation of the signal and thus amplify the sensitivity of the device. For example, for N passes of the optical fibre along the sensing sheet 20 there may be an N-fold increase in sensitivity when compared with sensor sheet employing an optical fibre making only a single pass along the sheet.

The sheet 20 constitutes a substrate that is repeatedly extendable and retractable in a direction of extension/retraction X, X’ (see FIG. 1D). This enables the sheet 20 to stretch and contract with cardiac and respiratory motions of the user.

FIG. 1B depicts an exploded view of a sensor member, presently embodied by the sensing sheet 20 (e.g. an embroidered optical fibre micro bend sensing sheet), of the smart belt system which includes the embedded section of optical fibre. The sheet 20 includes a deformation member 28 disposed on a substrate 30, the substrate being repeatedly extendable and retractable in a direction of extension/retraction X, X’. The sheet further includes an optical fibre 24 attached to the substrate 30 and including a plurality of bends 32 as best seen in FIG. 1D.

Deformation member 28 comprises a plurality of parallel fibres 38. The fibres 38 are disposed between the optical fibre 24 and sheet 30 and are thus referred to as under-laying fibres. Conversely, opposing deformation member 30 comprises a plurality of parallel fibres 40 that lay on top of the fibre 24 with respect to the sheet 30 and are thus referred to as over-laying or up-laying fibres. The optical fibre 24 is therefore sandwiched between the

fibres

38, 40 of the

deformation members

28, 30.

The opposing deformation member 30 may in fact not be necessary in some embodiments provided the requisite micro bend in the optical fibre 24 and the adjustment of the radius of curvature of that bend (i.e. lengthening and shortening of the period as shown in FIG. 1D) are achieved as discussed below.

The optical fibre 24 connects with the transceiver 12 through lead sections 39 of the optical fibre 24. The signal is transmitted into one of the lead sections 39 and is received from the other lead section 39.

FIG. 1C is a top planar view of the embroidered optical fibre micro bend sensing sheet 20.In this embodiment the under-laying fibres 38 are pre-sewn/stitched as segmented strips before positioning of the optical fibre 24 on the sheet 20. The optical fibre 24 is then laid on top of the under-laying fibres 38 in a serpentine or sinusoidal pattern. The up-laying fibres 40 are then post-sewn/stitched as a segmented strip after positioning of the optical fibre 24 on the sheet 20.

FIG. 1D is a side planar cutaway view of the embroidered optical fibre micro bend sensing sheet in accordance with the present embodiment. The cross-sectional view of FIG. 1D emphasizes the passage of the optical fibre alternately over and under the fibres of the deformation members. The short radius of curvature of the optical fibre about the fibres of the deformation members highlights the manner in which the micro bending effect of the multimode optical fibre of the sensing sheet is achieved.

The optical fibre 24 is sewn or stitched (see stitches 42) to the sheet 20 to hold it in place on the sheet 20. As the sheet 20 extends in the extension/retraction direction X, X’ the optical fibre 24 will pull against the

fibres

38, 40. To facilitate this bending action the under-laying fibres 38 are offset from the up-laying fibres 40 in the direction of extension/retraction of the sheet 20. Thus the optical fibre 24 assumes a generally sinusoidal form (when viewed in cross-section per FIG. 1D) about the

fibres

38, 40. Incidentally, the optical fibre 24 also assumes a sinusoidal shape in the plane of the sheet 20 as shown in FIG. 1C. In other words, when viewed in cross-section the optical fibre forms two sinusoidal shapes in non-coincidental and non-parallel planes – one of the sinusoids being exhibited in FIG. 1C and the other in FIG. 1D.

Micro bends may be formed in the optical fibre 24 as the sheet extends. Micro bends may also, or alternatively, be formed as the sheet 20 contracts/retracts as the optical fibre 24 will need to assume a more sinusoidal shape than the flatter shape achieved during extension of the sheet 20.

Thus extension and retraction of the substrate or sheet 20 changes a radius of curvature of the bends 32 in the optical fibre 24 about the

fibres

38, 40 of the

deformation members

28, 30. This change in radius of curvature modulates a signal propagated along the optical fibre 24.

The bends 32 lie in a plane 34 that is non-coincident with a plane of the sheet 20 (i.e. in the plane of the page). Thus as the sheet 20 extends the fibre 24 is pulled against the

fibres

38, 40. This applies force to the fibre 24 that can be measured as a modulation of the light signal propagated through the fibre 24.

With reference to both FIGs. 1C and 1D it will be noted that the fibre 24 includes a plurality of first bends 44 and second bends 32. The first bends 44 lie in one plane (i.e. that of the sheet 20) and the second bends 32 lie in a non-coincident plane 34.

The first bends 44 facilitate extension and retraction of the fibre 24 with extension and retraction of the sheet 20. It is appreciated that the fibre does not physically lengthen or shorten to any appreciable degree and in this sense “extend” and “retract” are intended to convey the length of the sheet 20 over which the fibre 24 extends.

The second bends 32 have greater influence on the modulation of the signal propagating along the fibre 24 as they have a considerably sharper radius of curvature that is adjusted with extension and retraction of the sheet 20. The radius of curvature is sufficiently sharp that it forms a micro bend over part of the extension and retraction action of the sheet 20 (e.g. when fully extended and/or retracted) and may even form a micro bend during the entirety of that extension and retraction action. Thus changes in the radius of curvature of the fibre 24 about the deformation member(s) modulates the signal and it is this modulation that can have greatest influence over the signal ultimately measured to determine respiratory and cardiac rhythms of the user.

The micro bending effect which captures the heart rate and breathing rate and converts them into optical signals is summarized mathematically in equations Math. 1 and Math. 2 below.

where the term on the left of the equation is the critical period length of the deformed optical fibre, n _o is the refractive index of the core of the optical fibre, a is the radius of the core and N.A. is the numerical aperture.

where the heart beat exerts a force F to the bent fibre, Χ is the amplitude of the bent fibre, T is the transmission coefficient of light through the bent fibre, Kf is the bent fibre force constant, and A _s , Y _s and l _s are the cross-sectional area, Young’s modulus, and length of the deformer, respectively.

FIG. 2A depicts the sensing sheet which includes the multimode optical fibre in accordance with the present embodiment and FIG. 2B shows a wearable device, presently embodied by smart belt 48, that includes the sensing sheet 10. The smart belt 48 shown in FIG.2B includes one optical transceiver which includes an optical transmitter, an optical receiver and a Bluetooth communication module. The belt can be divided into two parts: a sensing area and a non-sensing area, where the sensing optical fibre in the middle section of belt is the sensing area. The sensing area occupies substantially less than the length of the belt. The emitter 14, receiver 16 and transmitter 18 of FIG. 1A may be attached to the belt in, for example, the non-sensing area. The belt can wrap around the upper body (chest or abdomen position) of a person with the sensing area on either the person’s back, chest or abdomen to measure their cardiac and breathing activity. The mechanical activities of cardiac muscle and respiration apply force on the sensing optical fibre in the belt thereby modulating the light in the fibre. The light received by one optical receiver reflects both the heart beat and the respiration action.

The sensing belt in accordance with the present embodiment was tested on healthy adults to measure the heart and respiration activity. Referring to FIG. 3 a heart beat and respiration measurement of a person in a standing position and using the smart belt system is depicted. The sensing belt is wrapped around the upper body of the person and this person can sit, stand, walk or run within the range of the Bluetooth receiver. In FIG. 3, the sensing part of the smart belt is on the back of the standing person. In this example, the length of the belt is about 70cm, though the smart belt in accordance with the present embodiment is not limited to this length. During testing of the smart belt, measurements were done with the wearer in four positions: sitting, standing, walking and running. When the wearer was standing or sitting, the heart beat and respiration waveform were monitored and the heart rate and breathing rate were measured as 61bpm and 15bpm, respectively. In order to determine whether the measurements were correct, the heart rate was also measured using a commercial SpO2 device–the two results were the same. For breathing rate verification, breaths were counted–these two results were also the same.

FIG. 4 depicts readout of signals showing a testing result when a smart belt wearer is sitting and FIG. 5 depicts readout of signals showing respiration measurements while the smart belt wearer is running. In this measurement, the sensing part of the smart belt is located on the chest of the volunteer. It can clearly be seen that the heart rate and breathing rate are 74bpm and 19bpm, respectively. The displaying period of ballistocardiograph and respiratory waveform patterns are six seconds and twenty seconds, respectively. After verification, it was determined that both the heart rate and the breathing rate were correctly measured.

FIG. 6 shows readouts of signals for the smart belt wearer during different activity modes, where FIG. 6A depicts a readout of signals showing respiration measurements while the smart belt wearer is standing, FIG. 6B depicts a readout of signals showing respiration measurements while the smart belt wearer is walking, and FIG. 6C depicts a readout of signals showing respiration measurements while the smart belt wearer is running.

When the wearer was walking or running as in FIGs. 6B and 6C, the heart beat waveform was damaged by a large artifact motion and could not be monitored or displayed correctly. But the breathing waveform and breathing rate is still testable (for example, in FIG. 6C the breathing rate was up to 67bpm when the smart belt wearer was running). From the signal readouts of FIG. 6A, it can be seen that the breathing waveform is clear and uniform in the standing position. When the smart belt wearer is walking or running, the breathing waveforms (FIGs. 6B and 6C) are still clear although they are not so uniform as that in the standing or sitting cases of FIG. 6A.

FIG. 7, comprising FIGs. 7A, 7B and 7C, shows textile substrate sensing sheets, where FIG. 7A depicts a single set of textile substrates with under-laying fibre which is represented by the equal spaced parallel straight lines. FIGs. 7B and 7C depict two configurations of a textile fibre optic sensing sheet with under-laying, up-laying and optical fibre layers in accordance with the present embodiment, the parallel straight lines represent the under-laying and up-laying fibre, and the curve lines represent the layout of the optical fibre. The difference between the two configurations is the layout of the optical fibre although both are sinusoidal or U-shaped patterns. The curve lines of the optical fibre can be parallel or non-parallel curves.

FIGs. 8A, 8B and 8C, show multiple sets of textile fibre optical sensing sheets after manufacturing. Manufacturing in accordance with the present embodiment as shown in these figures advantageously provides a highly scalable manufacturing process.

FIG. 8A depicts a panel 50 for use in the manufacture of wearable devices for monitoring vital signs of a user. The panel 50 is shown in position on a machine bed 52 and comprises a sheet or elastic substrate 54 from which the sheets 20 are formed. Multiple sensor members are formed on a single elastic substrate in order to facilitate upscaling of the manufacture of the wearable devices.

In the embodiment shown in FIG. 8A the deformation member comprises a textile base 56 on which under-laying fibres 58 are formed or disposedfibre (as seen in FIG. 7A). FIG. 8B depicts multiple sets of the textile fibre optical sensing sheets 20 with under-laying fibres 58, up-laying fibres 60 and optical fibre layers 24. Each of these sets of the textile fibre optical sensing sheets 20 can be used to manufacture a smart belt in accordance with the present embodiment. FIG. 8C depicts the multiple sets of the textile fibre optical sensing sheets of FIG. 8B with one of the sensing sheets 20’ removed (e.g. by cutting) and mounted on the smart belt 62 in accordance with the present embodiment.

A typical method for fabricating a sensor member 20 for use in the manufacture of a wearable device 62 for monitoring vital signs of a user may include:

providing a sheet, such as elastic substrate 54, that is repeatedly extendable and retractable in a direction of extension/retraction X, X’, the direction of extension/retraction lying in a plane of the sheet, wherein the sheet forms a substrate of the sensor member 20;

attaching a deformation member (comprising textile 56 and fibres 58) to the substrate 54;

attaching an optical fibre 24 to the substrate 54 such that the optical fibre 24 includes a bend lying in a plane non-coincident with the plane of the substrate and the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre when in use.

The step of attaching the deformation member (56, 58) to the substrate 54 involves attaching the textile to the substrate. The fibre 24 can then be attached on top of the deformation member (56, 58) and thereby be secured, directly or indirectly, to the substrate 54.

The attaching steps can involve adhesion but more likely will comprise embroidering the deformation member (56, 58) and optical fibre 24 to the substrate 54. The embroidery used in the present embodiment is Soutache embroidery.

The smart sensing belt in accordance with the present embodiment can be used to measure heart rate and breathing rate simultaneously while the smart belt is wrapped around the upper body when the wearer sits or is standing still. In addition, the breathing waveform and breathing rate can advantageously be measured correctly even when the wearer is walking or running. This means that artifact motion has little effect on the breathing waveform. The simple arrangement and elasticity enable the sensing belts to be low cost and suitable enough or comfortable enough for continuous monitoring of the vital signs of the wearer during daily life activities such as sitting, standing, walking and running. In this manner, the sensing belt in accordance with the present embodiment has various beneficial applications for elderly persons and people in special needs.

Thus it can be seen that motion artifacts during walking or running have little effect on the final result of breathing rate of the smart sensing belt in accordance with the present embodiment. In addition, the smart sensing belt is comfortable to wear and a computerized double (or two single-head) Soutache embroidery stitching method well-known by those skilled in the textile arts can be used to fabricate multiple sets of sensing sheet in a highly scalable fabrication process which has high potential for mass production.

It will be appreciated by a person skilled in the art that numerous variations and/or modifications may be made to the present invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects to be illustrative and not restrictive.

Claims

A sensor member for use in a wearable device for monitoring vital signs of a user, the sensor member comprising:
a substrate repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the substrate;
a deformation member disposed on the substrate; and
an optical fibre attached to the substrate and including a bend, the bend lying in a plane that is non-coincident with the plane of the substrate,
wherein the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre.
The sensor member according to claim 1, wherein the bend forms a micro bend during extension and/or retraction of the substrate.
The sensor member according to claim 2, wherein the micro bend is formed at least when the substrate is fully retracted.
The sensor member according to claim 2, wherein the bend forms a micro bend when the substrate is fully extended.
The sensor member according to claim 1, wherein the deformation member is elongate and extends at a non-zero angle to the direction of extension/retraction of the substrate.
The sensor member according to claim 1, further comprising an opposing deformation member disposed on the substrate such that the optical fibre passes between the deformation member and the opposing deformation member and the radius of curvature of the optical fibre changes through relative movement of the deformation member and opposing deformation member with extension and retraction of the substrate.
The sensor member according to claim 1, wherein the optical fibre includes multiple passes along the substrate.
The sensor member according to claim 1, wherein the bend is a first bend and the optical fibre includes a second bend, wherein the radius of curvature of the first bend increases as the substrate extends so that the optical fibre extends with the substrate, and wherein the second bend pulls against the deformation member as the substrate extends thereby varying a force applied to the optical fibre to modulate a signal propagated along the optical fibre.
The sensor member according to claim 8, wherein the first and second bends are in respectively non-coincident planes.
A wearable device for monitoring vital signs of a user, the device comprising:
a support member adapted to hold the device in position on the user, the support member comprising:
a substrate repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the substrate; and
a deformation member disposed on the substrate; and
an optical fibre attached to the substrate and including a bend, the bend lying in a plane that is non-coincident with the plane of the substrate,
wherein the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre.
The wearable device for monitoring the vital signs of a user, the device comprising a sensor member according to claim 1, wherein the substrate and deformation member are parts of a support member adapted to hold the device in position on the user.
The wearable device according to claim 10, wherein the support member forms a belt.
The wearable device according to claim 10, further comprising at least one of:
an emitter for emitting the signal into the optical fibre;
a receiver for receiving the modulated signal from the optical fibre;
a transceiver for emitting the signal into the optical fibre and receiving the modulated signal from the optical fibre; and
a transmitter for transmitting a measurement of the modulated signal to a remote device.
A panel for use in the manufacture of wearable devices for monitoring vital signs of a user, the panel comprising:
a sheet upon which a plurality of sensor members are formed, each sensor member comprising:
a substrate repeatedly extendable and retractable in a direction of extension/retraction, the direction of extension/retraction lying in a plane of the substrate;
a deformation member disposed on the substrate; and
an optical fibre attached to the substrate and including a bend, the bend lying in a plane that is non-coincident with the plane of the substrate,
wherein the deformation member is disposed between the bend and substrate so that extension and retraction of the substrate changes a radius of curvature of the bend about the deformation member thereby modulating a signal propagated along the optical fibre when in use.
The panel according to claim 14, wherein the plurality of sensor members are formed in a grid pattern on the sheet.