GB2627972A

GB2627972A - Sensing device for a diaper and diaper

Info

Publication number: GB2627972A
Application number: GB2303490.3A
Authority: GB
Inventors: Yasser Al Aioubi Mohamad; Ejazul Huq Syed
Original assignee: Oxford Healthtech Ltd
Current assignee: Oxford Healthtech Ltd
Priority date: 2023-03-09
Filing date: 2023-03-09
Publication date: 2024-09-11
Also published as: GB202303490D0; WO2024184542A1

Abstract

A sensing device for a diaper 1590 comprises an expandable member 2606 comprising at least a first portion 2606a configured to be fixedly attached to the external surface of the diaper, sensing circuitry 2612 arranged on the expandable member and comprising contacts for providing electrical connection with a detector unit 2604, and wherein the sensing circuitry is configured to expand in response to an expansion of the expandable member. The sensing circuitry may comprise a resistor circuit, capacitor circuit, a strain gauge pattern. The detector unit may also be provided, and coupled to the expandable member via hook and loop fastener. Also disclosed is a diaper comprising the sensing device.

Description

SENSING DEVICE FOR A DIAPER AND DIAPER

Technical field

This invention relates to a sensing device for a diaper or nappy and the like, and which is configured to determine the fullness of a diaper. The invention also relates to a diaper with a sensing device.

Background

Incontinence products such as diapers, incontinence pads and underwear allow a wearer to urinate and/or defecate without using a lavatory. The incontinence products comprise an absorbing layer to contain urine and/or faeces and prevent leakage onto outer clothing. Incontinence products can be used for children (e.g., bed wetting) as well as adults, particularly those with illnesses linked to incontinence. When a diaper, or other incontinence product, becomes soiled with urine and/or faeces, it requires changing, usually by another person (e.g., a carer). Since wearers are often unable to replace the diaper themselves, or even be unable to communicate that the diaper requires changing, the carer must manually check the diaper for soiling periodically throughout the day. This involves changing the diaper, possibly unnecessarily, thereby wasting the carer's valuable time and increasing diaper waste. On the other hand, failure to change a diaper on a sufficiently regular basis may lead to problems, such as the wearer feeling uncomfortable, a negative effect on the wearer's dignity, and/or skin problems, such as rashes, bed sores, and infections. Therefore, there is a need for an improved process for detecting the fullness of a diaper, or other incontinence products. Detecting fullness of a diaper would also be useful for babies.

WO-A-2022214807 describes an expandable member comprising one or more elastic elements extending between a plurality of attachment points, wherein the attachment points are configured to fixedly attach the expandable member to the external surface of the nappy, and wherein the one or more elastic elements are configured to stretch as the attachment points move apart such that the expandable member is configured to expand in accordance with expansion of the nappy. The sensing device further comprises a detector unit coupled to the expandable member, wherein the detector unit is configured to detect expansion of the expandable member, and is further configured to determine a nappy fullness parameter based on the detected expansion of the expandable member.

Summary

The invention provides a sensing device for a diaper, the sensing device including, an expandable member comprising at least a first portion configured to be fixedly attach to the external surface of the diaper, sensing circuitry arranged on the expandable member and comprising contacts for providing electrical connection with a detector unit, and wherein the sensing circuitry is configured to expand in response to an expansion of the expandable member.

The sensing circuitry may include at least one of, a resistor circuit, a capacitor circuit, and a strain gauge pattern.

The sensing circuitry may be formed from an electrically conductive elastomeric polymer.

The expandable member may comprises an elastomeric patch.

The expandable member may be integrated into the external surface of a diaper.

The sensing circuitry may be formed on the expandable member by one of, ink jet printing, screen printing, microcontact printing, or brush painting.

A second portion of the expandable member may be configured to reversibly attach to the external surface of the diaper.

The sensing circuitry may comprises pad connectors for connecting to electrical contacts of a detector.

The sensing device may further comprise a detector unit having electrical contacts coupled to the sensing circuitry, wherein the detector unit is configured to detect the expansion of the expandable member by measuring for a change in an electrical signal across the electrical contacts.

When the sensing circuitry comprises a variable resistor or a strain gauge pattern, the detector unit may be a resistive detector.

When the sensing circuitry comprises a variable capacitor, the detector unit may be a capacitive detector.

The detector unit may be coupled to the expandable member via a link and a loop fastener.

The invention also provides a diaper comprising a sensing device according to the invention.

The present disclosure further provides embodiments where a deformable member is fixedly or releasably attached (or attachable) to a diaper outer surface at one end and is connected to (or connectable to) a link connected to a strain or tension detector at a second end. The connection may be a hook and loop connection to allow releasable connection between the link and a loop at the second end of the expandable member.

With these embodiments as the diaper is filling up (volume expansion) the deformable member which may be a stretchable patch is deformed in cooperation with the external surface of the diaper in at least one direction and the amount of stretch or deformation is measured by the detector, which is proportional to the volume expansion of the diaper, which is proportional to the amount of fluid in the diaper.

nstead of the expandable or defo mable member or patch, the diaper itself may nclude an expandable portion in the ou to r surface The strain gauge or tension detector can be connected to the exPandab e Portion by the hook and ',loop connection ng a loop to th by affixi e expa dable p ortion There is further disclosed an embodiment in which an expandable cord or strip is connected to a detector and the expandable cord or strip has a measurable electrical resistance that varies with expansion (stretching) of the expandable cord of strip.

In embodiments of the inventive concepts various components of the sensing device may be reused. In particular, one or more of the detector, the link, the hook, and the expandable or deformable portion..

Brief Description of the Drawings

Reference will now be made by way of example only, to the accompanying drawings in which: Figure 1 is a plan view of a diaper; and Figures 2 show schematically in a plan view a sensing device and diaper according to an embodiment; Figure 3 show schematically in a plan view a according to an embodiment; Figure 4 show schematically in a plan view a according to an embodiment; Figure 5 show schematically in a plan view a according to an embodiment; Figure 6 show schematically in a plan view a according to an embodiment.

sensing device and diaper sensing device and diaper sensing device and diaper sensing device and diaper

Detailed Description

The present disclosure relates to a sensing device for attaching to an external surface of a diaper. The sensing device comprises an expandable member, such as an elastomeric patch, which includes a first portion that is configured to fixedly attach to the external surface of the diaper. The sensing device further comprises a detector unit, which is coupled to a second portion of the expandable member, and sensing circuitry arranged on the expandable member and in electrical connection with electrical contacts of the detector unit. The sensing circuitry is configured to expand in response to an expansion of the expandable member and the detector unit is configured to detect the expansion of the expandable member by measuring a change in an electrical signal across the electrical contacts. In a specific example, the electrical signal relates to a resistance or capacitance measurement.

The present disclosure also relates to a diaper with a sensing device. An expandable member is either provided by (e.g., integrally formed) the diaper as its outermost layer, or by the sensing device which comprises such an expandable member fixedly attached to the external surface of the diaper. An example expandable member is an elastomeric patch. The sensing device at least comprises a detector unit, which is coupled to the expandable member and sensing circuitry arranged on the expandable member and in electrical connection with electrical contacts of the detector unit. The sensing circuitry is configured to expand in response to an expansion of the expandable member (in response to the volume expansion of the diaper, as it fills up) and the detector unit is configured to detect the expansion of the expandable member by measuring a change in an electrical signal across the electrical contacts. In a specific example, the electrical signal relates to a resistance or capacitance measurement.

A diaper may also be referred to herein as a nappy. A diaper is regarded as an incontinence product. The diaper may be sized to be worn by an adult person, a child or a baby, and may be of any suitable design and absorbency. The sensing device may be produced separately from the diaper, and applied to the diaper thereafter.

Alternatively, if the outermost (or "top") layer of the diaper includes a compliant portion, elements of the sensing device can be produced directly onto that portion of the top layer. Such a compliant portion can therefore serve as the expandable member. In a specific example, the sensing circuitry can be printed directly onto this compliant portion of the top layer. Other elements of the sensing device, for example, the detector unit, can be attached at a later stage of manufacturing.

The sensing devices described herein contrast to known diaper wetness/fullness sensing technologies, which typically require active sensing elements (e.g., electrical and chemical elements) inside the diaper or in physical contact with the urine absorbency layer of the diaper. Such existing sensing devices are complicated and costly to manufacture.

An example of a diaper 1600 is shown in Figure 1. Figure 1 shows a plan view of a diaper 1600, with an external surface 1590, before it is worn. The diaper 1600 includes a front 1530 connected to a waistband section 31. The front 1530 of the diaper 1600 is connected to a back 1570 of the diaper 1600 by a crotch region 1540. When the diaper 1600 is worn, the front 1530 of the diaper 1600 is positioned against the wearer's pubic region and lower abdomen, the back 1570 of the diaper 1600 is positioned against the wearer's bottom, and the crotch region 1540 of the diaper 1600 is positioned over the wearer's groin and between their legs.

The diaper 1600 has elasticated edges 1560 that extend around the top of the wearer's legs. The elasticated edges 1560 are stretchable so as to allow the diaper to be worn comfortably, and to follow the contours of the wearer's body. This mitigates leakage of fluids from the diaper 1600.

The outermost layer (or "top" layer) 1590 of the diaper 1600 is usually made of a noncompliant or "non-stretch" material. The diaper 1600 is nonetheless able to expand because of the elasticated edges 1560, and because the outermost layer 1590 is configured to be relatively loose when a wearer first puts on the diaper 1600 (i.e. when the diaper contains no faeces/urine). Creasing of the diaper material (as described below) also facilitates diaper expansion.

Figure 2 is a schematic illustration of a sensing device 2402 attached to a diaper 1600. The diaper is described in detail in relation to Figure 1. The sensing device 2402 comprises a detector unit 2404 mounted on the waistband 31 of the diaper, and an deformable and/ or expandable member in the form of a patch 2406 which is coupled to the detector unit 2404 via a link 2410.

The patch 2406 in Figure 2 is shown as being rectangular and being positioned centrally across a substantial area of the front 1530, the crotch region 1540, and the back 1570 of the diaper 1600. The skilled reader will understand that the patch 2406 can be any suitable shape, such as a square, circle, oval or the like. If the patch 2406 is a circle or oval, references to an "end portion" of the patch should be interpreted merely as "a portion" of that patch.

The patch 2406 may be sized and shaped so that it covers an area of the diaper 1600. More specifically, the patch covers a part of each or one of the front of the diaper, the back of the diaper, the crotch region of the diaper, the elasticated edges of the diaper, or a combination thereof.

The patch 2604 may be made of an elastomeric material. Example materials include rubbers such as, Nitrile, Neoprene, silicone, or ethylene propylene diene monomer EPDM), or the like. Such materials have a low stiffness (i.e., Young's modulus) and high strain to failure. The stiffness of the patch is chosen such that it functions in accordance with the diaper material. That is, such that the patch 2406 closely follows the volume expansion of the diaper, i.e. in response to the volume expansion of the diaper, as it fills up. Every diaper, irrespective of the top surface material, will expand when it is filling up. The fixedly attached (at one point) stretchable patch sensor, connected to a detector, via a Link, is a convenient way of capturing the volume expansion.

The patch 2406 comprises a first end portion 2406a and a second end portion 2406b. The first and second end portions 2406a, 2406b include respective means for attaching the patch to the external surface of the diaper. Example means for attaching the first end portion to the diaper include glues, adhesives (including water based, solvent based and hot melt), stitching, hook and loop type fasteners (such as Velcro®), poppers, magnets or the like. The external surface of the diaper may be provided with a complementary fastener type to allow attachment of the patch, for example, if a hook and loop type fastener is used. Such example means allow the first end portion 2406a to fixedly couple to the external surface of the diaper. In the context of the disclosure, a fixed coupling between two components should be interpreted to mean that, to a first approximation, there can be no relative movement between the two components in normal use. The skilled reader will understand that there are other suitable means for fixedly attaching the end portion 2406a of patch 2406 to the diaper.

The means for attaching the second end portion to the diaper is of lesser importance. Its purpose is principally to avoid "flapping" of the patch 2406 and link 2410, when the sensing device is attached to a diaper during transmit. Attaching the second end potion to the diaper is not therefore essential. However, without this secondary attachment to the diaper, which limits free movement of the second end portion of the patch, damage could be caused to the sensing device 2402. Generally, although not necessarily, the second end portion 2406b is detached from the diaper prior to being worn. The means for attaching the second end portion 2406b to the diaper allows for reversible attachment and detachment of the patch 2406 to the diaper. In an example, the means for attaching the second end portion 2406b to the diaper is a hook and loop type fastener, such as Velcro®. As has already been noted, when using such a fastener, the diaper is provided with the complimentary fastener so that the reversible attachment can be made. Other reversible attachment means are possible.

As shown in Figure 2, the link 2410 is attached to the detector unit 2404 at a first end.

The link 2410 terminates with a fastener in the form of a loop 2408 at an opposing second end. In use (i.e., when the diaper is worn by a wearer), the second end portion 2406b of the expandable member is fixedly attached to the loop. In this way, any tension in the patch 2406 can be transferred to the detector unit 2404 via the loop 2408 and link 2410. The patch 2406 is conveniently expandable, i.e. elastic, so that an initial tension can be maintained when connected to the detector.

The general working principle of the sensing device 2402 is now described.

In use, the wearer invariably defecates and/or urinates in the diaper 1600. The diaper absorbs fluid contained in the faeces and/or urine or is otherwise caused to expand.

As the diaper 1600 expands, the first end portion 2406a of the patch, which is fixedly attached to the diaper, moves in accordance with the diaper and hence further away from the detector unit 2404. As the second end portion 2406b of the patch is coupled to the detector unit 2404, the first and second end portions are urged apart from one another during expansion of the diaper. Accordingly, the patch 2406 is caused to expand into a state of tension as the diaper expands during use. The tension in the patch 2406 is transferred through to the detector unit 2404 via the link 2410 and the loop fastener 2408.

The detector unit is configured to measure this tension or "pulling force" using any suitable means. The detector unit 2404 of figure 2, may be a tension meter, tension sensor or tension gauge, for example. In an example, the detector unit is an off-theshelf displacement or strain detector. More sophisticated detector units, as, for example, described in WO-A-2022214807 are possible. In particular, the optical detectors described in Figures 9a-9d, 10, 11a, 11b, 12 and 13 and the conductive detectors described in Figures 16 to 17 from WO-A-2022214807 are all suitable detector units. These detectors are incorporated herein by reference.

In use, power is supplied to the detector unit 2404 by an electronic control and power supply unit (not shown). The electronic control and power supply unit may be an internal or external power supply, such as a battery.

Advantageously, the changes in the electrical signal measured by the detector unit 2404 are proportional to the change in volume of the diaper caused by urination and/or defecation by the wearer. This is in contrast to existing approaches, where the diaper fullness is estimated using a moisture sensor inside the diaper, or using a pressure sensor to sense increased radial pressure between the wearer and the diaper, or using a pressure sensor to sense increased radial pressure between the wearer and the diaper.

Figure 3 is a schematic illustration of a sensing device 2502 attached to a diaper 1600. The sensing device 2502 differs from the sensing device of Figure 2 in that the expandable member takes the form of an elasticated cord 2506, such as a Spandex® cord. The working principle of the alternative sensing device 2502 is the same as described immediately above in relation to Figure 2. Corresponding reference numerals are used to denote each component part of the sensing device 2502.

In an alternative embodiment, with reference to figure 3, the elasticated cord 2506 is replaced with a conductive elastomer cord with a finite, predetermined or known resistance. As the cord is stretched the resistance increases and this is recorded in the detector 2404 using several options including a Wheatstone Bridge.

Figure 4 is a schematic illustration of an alternative sensing device 2602 attached to a diaper 1600 according to an embodiment. The sensing device may comprise a detector unit 2604 mounted for example, in or on the waistband 31 of the diaper, and an expandable member in the form of a patch 2606. Sensing circuitry 2612 is integrally formed onto the patch 2606. In figures 4 and 5, as with Figures 2 and 3, the patch 2606 is shown coupled to the detector unit 2604 via a link 2610 and a fastener 2608 (e.g., a loop fastener). However, the patch 2606 can be connected to the outer surface 1590 of the diaper as well as or instead of the physical connection to the detector 2604. Conveniently the patch 2606 is fixedly or releasably attached to the diaper at the second end 2606b nearest the detector as well as at the first end 2606a. In figures 4, 5 and 6, multiple connection points to the diaper outer surface are permissible. Example means for attaching the second end portion 2606b to the diaper include glues, adhesives (including water based, solvent based and hot melt), stitching, hook and loop type fasteners (such as Velcro®), poppers, magnets or the like. Other reversible and non-reversible attachment means are possible As shown, the sensing circuitry 2612 comprises an electrically conductive polymer, elastomer, which acts as a variable resistor 2614. The variable resistor is in electrical connection with respective leads or electrical contacts 2616a, 2616b of the detector unit 2604. Conveniently, the electrical contacts 2616a, 2616b of the detector are connected to pad connectors 2617 of the sensing circuitry 2612. The pad connectors may conveniently be formed on the expandable member 2606 as shown in Figure 6. Alternatively, the sensing circuitry may include leads or other extension that connect to pads on the outer surface of the diaper or directly to the electrical contacts 2616a, 2616b. Examples of the pad connectors on the expandable member are shown in figure 6 and described briefly below. The polymer 2612a is made from a compliant material so that it is able to stretch/expand with the patch 2606. The electrical resistance of the resistor 2614 changes in response to a stress and/or strain applied to it. Suitable polymer materials include conductive or semiconductive polymers, and composite materials including a polymer material impregnated with conductive material such as conductive carbon particles, suitable materials include conductive polyacetylene, polyaniline, polypyrrole, and polyethylenedioxythiothene. The detector unit 2604 of Figure 4 is configured to measure a change in resistance of the variable resistor caused by the expansion of the patch 2606. The fullness of the diaper can be determined from this change in resistance.

More specifically, the detector unit 2604 is configured to detect expansion of the patch 2606 by measuring a change in resistance of the resistor 2614 caused by the patch changing its length. To a first approximation, the resistance R of the resistor 2614 is given by: R = PL (1) where p is the resistivity of the electrically conductive polymer, L is the total path length of the electrically conductive polymer, and A is the cross-sectional area of the electrically conductive polymer. As the electrically conductive polymer are stretched (due to expansion of the diaper 1600), the path length L increases, thereby increasing the resistance R of the variable resistor. The change in resistance can be detected in the detector unit using a standard Wheatstone bridge circuit. The change in resistance R is proportional to the volume increase of the diaper 1600. In other words, the resistance of the variable resistor varies in dependence on the volume of urine and/or faeces inside the diaper 1600. Such a Wheatstone bridge circuit is described and shown in Figure 18 of WO-A-2022214807.

Instead of the resistor being created on a separate stretchable patch, the resistor may be printed (inkjet printing, screen printing, microcontact and brush painting) directly on the diaper outer layer, which has been modified to create a stretchable patch. A conductive ink may be, for example, Poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT/PSS) composite ink, or DOT-PEDOT (DOT stands for drop-on-textile) ink is capable of providing highly stretchable electrodes. PEDOT/PSS composite film exhibit electrical conductivity up to 1000S/cm. PEDOT/PSS composites may also be used as interconnects.

Figure 5 is a schematic illustration of another sensing device 2702 attached to a diaper 1600. The sensing device comprises a detector unit 2704 mounted in the waistband of the diaper, and an expandable member in the form of a patch 2706. A sensing circuitry 2712 is integrally formed onto the patch 2706. As with Figures 2, 3 and 4, the patch 2706 is fixedly attached at a first end portion 2706a to the diaper and coupled to the detector unit 2704 via a link 2710 and a fastener 2708 (e.g., a loop fastener).

The sensing circuitry 2712 comprises a variable capacitor 2714. The capacitor is formed from a first 2714a and a second set of electrodes 2714b which are spaced apart from one another. Each set of electrodes is in electrical connection with an electrical contact 2716a, 2716b of the detector unit 2704. Each set of electrodes is formed from an electrically conductive polymer. Example polymers include suitable materials include conductive polyacetylene, polyaniline, polypyrrole, and polyethylenedioxythiothene.

The capacitor is in electrical connection with respective leads or electrical contacts 2716a, 2716b of the detector unit 2704. Conveniently, the electrical contacts 2716a, 2716b of the detector are connected to pad connectors 2717 of the sensing circuitry 2712. The pad connectors may conveniently be formed on the expandable member 2706 as shown in Figure 6. Alternatively, the sensing circuitry may include leads or other extension that connect to pads on the outer surface of the diaper or directly to the electrical contacts 2716a, 2716b. Examples of the pad connectors on the expandable member are shown in figure 6 and described briefly below.

In the example shown, the first and second set of electrodes 2714a, 2714b form an inter-digitated pattern 2716, i.e., a first digitated pattern spaced apart and overlapping with a second digitated pattern. The inter-digitated pattern 2716 is oriented so that the digits of each pattern extend away or towards the detector unit 2704. The first digitated pattern may be a mirror image of the second digitated pattern but shifted laterally to one another so as to stagger the digits of each of the patterns.

The first and second digitated patterns may cover a substantial portion of the diaper. For example, the inter-digitated pattern may extend between the elasticated edges 1560 of the diaper 1600 and beyond the centreline of the diaper 1600, and/or a substantial portion of the front, crotch region and back of the diaper 1600.

As mentioned above, the first and second patterns (or electrodes 1714a, 2714b) are spaced apart. This spacing forms gaps between the digits in each of the patterns.

These gaps restrict the flow of current across the each set of electrodes 2714a, 2714b and forms the dielectric of the variable capacitor 2714.

The capacitor may be created on a separate elastomeric patch on an acrylic base or polyethylene terephthalate PET. The patch material may be silicone elastomer or similar having good stretchability, high elongation limit (greater than 100%) and being non-toxic to human body). The silicone elastomer fills the areas between the electrodes and form the dielectric of the capacitor. To increase the dielectric constant of the elastomer, ceramic particles or similar may be added to the elastomer. The conducting electrodes may be formed on the elastomer by screen-printing thin metal film (e.g. copper or silver or similar) or a similar technique.

The capacitance of the interdigitated capacitive sensor is described as: CL = (n-1) 8. Br Wt Where CL represents the capacitance value; a and Br are primitives associated with free space and dielectric layer respectively; W and d are the overlapped length of electrodes and the distance separating the two electrodes respectively; t is the thickness of the conductive electrode and n is the number of interdigital electrodes within the structure.

In an alternative method, the interdigital capacitor electrodes may be produced directly on the outer layer of the diaper using inkjet printing using a Poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT/PSS) conductive ink or thermally curable silver inkjet printable conductive ink or similar. The outer layer of the diaper may be a modified stretchable integrated patch of a suitable polymer such as silicone and having appropriate dielectric property (as stated above) or printable strontium titanate based dielectric nanocomposite in a polyvinylpyrrolidone (PVP) matrix. The inkjet printing of such polymers is known but not on a diaper.

The set of electrodes 2714a, 2714b are compliant so that they can stretch/expand in accordance with the patch 2706. The capacitance of the variable capacitor 2714 changes in response to this expansion because (i) the total area of overlap between the first and second digitated patterns changes; and/or (h) the spacing (or gap size) between the first and second digitated patterns changes. A change in capacitance is representative of a change in diaper fullness.

The capacitor may be operated in a high frequency mode (up to 10 MHz) in a capacitance bridge circuit.

The detector unit 2704 is configured to detect expansion of the patch 2706 by measuring a change in capacitance of across the sensing circuitry 2702. As the patch 2706 expands in accordance with the diaper and the change in capacitance is proportional to the expansion of the patch, the change in capacitance of the capacitor is proportional to the volume change of the diaper. That is, the change in capacitance of the capacitor is proportional to the amount of urine and/or faeces inside the diaper 1600. The change in capacitance can be detected using a capacitance bridge circuit, for example. Such a capacitance bridge circuit is described and shown in Figure 19 of WO-A-2022214807.

Figure 6 shows another example of the sensing circuitry 2812 and detector 2804. In the embodiment of figure 6, the sensing circuitry 2812 comprises a strain gauge pattern 2814. The strain gauge pattern 2814 is formed by printing a zig zag or meandering pattern as shown in figure 6, however, any suitable pattern may be used, so long as the distortion of the pattern caused by the volume expansion of the diaper, which will deform the pattern causing a change in the measured resistance. Each end of the strain gauge pattern 2814 terminates in conductive pads 2813. The detector which is, for example a wheatstone bridge type detector, includes respective leads, wires or electrical contacts 2816a, 2816b having pads 2817, shown connected to the conductive pads 2813. The pads 2817 and 2813 are connected to each other before use.

The sensing circuitry 2812 including the strain gauge pattern 2814 may be printed directly onto an expandable member 2806 and may be printed using inkjet printing or screen printing or similar using conductive ink or a conductive paste. Conductive paste or ink may contain carbon, silver or PEDOT: PSS composite conductive materials or similar as discussed above in relation to figures 4 and 5. Example polymers include suitable materials include conductive polyacetylene, polyaniline, polypyrrole, and polyethylenedioxythiothene.

The expandable member 2806 of figure 6 may, as for figures 4 and 5, be a separate patch, which is fixedly or reversibly attached to the outer surface of the diaper 1590 as discussed above, or the expandable member 2806 may be a part of an expandable area of the outer surface of the diaper itself that is formed during manufacture of the diaper (for example by pleating). The patch 2806 may comprise a stretchable polymer such as silicone rubber, natural polyisoprene, polybutadiene, nitrile rubber, polyethylene terephthalate (PET) etc. As the diaper volume expands due to urine and or feces ingress, a curved surface is created. The stretchable polymer patch and consequently the strain gauge also curves accordingly. The electrical resistance change of the strain-gauge under bending may be measured using the Whetstone bridge located inside the detector.

The strain on the printed pattern induced by bending is described by the equation Gf = (AR/RO)/E, E=c/p where Gf, c, c, p, AR, RO are the gauge factor, the strain, half the substrate thickness, the bending curvature, the change in resistance and the initial resistance, respectively.

Variants modifications are possible within the scope of the invention, as will be clear to the skilled reader. At least the following variants are possible.

Referring to Figures 4 and 5, the sensing circuitry 2612, 2712 can be integrally formed to the external surface of the diaper. This is possible if the outermost layer of the diaper or a part thereof is made from a compliant material, such as a polymer. As has been described above, such a top layer can be created by creasing and/or selectively modifying the non-stretch top layer of conventional diapers.

In such a case, the sensing device does not need the expandable member (i.e., the patches 2606, 2706), link 2610, 2710 or fastener element 2608, 2708, shown in Figures 4 and 5. This is because the expandable member is provided by the diaper itself and the coupling to the detector unit is provided by the electrical contacts. This advantageously reduces materials cost and plastic waste. Conveniently, the sensing circuitry can then be printed directly onto the diaper. This approach greatly improves ease of manufacturing, especially if the printing step is incorporated into the production line of the diaper.

A technical advantage of replacing the patch 2606, 2706 with the outermost layer of the diaper is that the expansion of the diaper measured corresponds to those areas of the diaper in which the variable resistor or capacitor is disposed. This means that the fullness of the diaper can be determined with a higher degree of spatial sensitivity.

On the other hand, a technical advantage of using a patch 2606, 2706, attached to the external surface of the diaper and having a variable resistor or capacitor integrally formed thereto, is that any expansion of the diaper between the detector unit and the first end portion of the patch can be measured by the detector unit. This means that the sensing device can more reliably measure the fullness of the diaper. It is less sensitive, for example, to spatial variations in the volume expansion of the diaper.

In the above embodiments, for example as shown in figures 4 and 5, the electrical patterns e.g. the sensing circuitry 2612, 2712 are shown in a particular orientation. However, the orientation is not essential since any orientation will be exposed to the volume increase of the diaper. The sensing circuitry 2612, 2712, could be disposed at, for example, 90 degrees to that shown.

In the examples described above, a single sensing device is shown as being attached to a diaper. It will be understood by the skilled reader that any suitable number of sensing devices may be used on the same diaper.

In some examples, the diaper comprises one or more additional sensing devices. The sensing device and the one or more additional sensing devices are configured to detect expansion at different locations on the external surface of the diaper by being fixedly attached to different regions of the diaper. In a specific example, a first sensing device is used to measure expansion on the front 1530 of the diaper 1600, a second sensing device is used to measure expansion of the crotch region 1540 of the diaper 1600 and a third sensing device is used to measure expansion on the back 1570 of the diaper 1600.

Printing the sensing circuitry directly onto the compliant top layer of the diaper is a convenient way of incorporating multiple sensing devices without complicating manufacturing significantly.

Each sensing device may be coupled to a detector unit via a respective link and fastener.

Although, as has already been noted, a link and fastener is not required if the sensing circuitry is integral to the top layer of the diaper.

In some examples, each sensing device is coupled to the same detector unit. Alternatively, a detector unit can be shared amongst a plurality of the sensing devices. If a plurality of detector units are used, each detector unit can be mounted to the waistband of the same diaper. The use of multiple sensing devices improves the accuracy of the diaper fullness indication. Different measurement readings from different regions of the diaper can be used to determine whether the diaper is filled primarily with liquid (e.g., urine in the crotch region of the diaper) or solids (e.g., faeces in the back region of the diaper).

Although the detector unit has been described as being mounted in the waistband of the diaper, it may be mounted on any other suitable part of the external surface 1590 of the diaper 1600, such as the front 1530 of the diaper 1600, or near the waistband 31.

In figures 4, 5 and 6, there is a single resistor, capacitor and strain gauge shown, however, there could be two or more of each. For example there could be a plurality of resistors or stain gauge patterns connected in series. For example there may be a plurality of capacitors connected in a parallel.

Body movement Movement of a diaper wearer's body (for example, getting up, walking around, and lying down) may affect the sensing capabilities of the sensing device. The body movement may cause changes to the detected signal, thereby leading to inaccurate expansion measurements. A MEMS (micro electro mechanical system) capacitor-based gyroscope or an accelerometer may be used in the detector unit to record any movement in the body of the diaper wearer. Appropriate corrections may then be applied electronically and/or in the software to differentiate between the actual signal (due to urine and/or faeces ingress and consequent volume expansion) and any signal changes caused by the body movement.

An example MEMS gyroscope and MEMS accelerometer are described in detail in relation to Figures 23a and 23b of PCT/GB2022/050862. The referenced gyroscope and accelerometer can be used in any of the sensing devices described above.

Power supply An electronic control and power supply unit may be used with any example of the sensing device described above. The control and power supply unit may house the detector units described above.

The control and power supply unit may comprise signal amplifiers, an analogue-to-digital converter, a microcontroller or other processor, memory, a data logger, a wireless transmission system (e.g. BluetoothTm), discrete or integrated electronic components, FPGAs, DSPs, ASICs, etc. The electronic control and power supply may have a digital display which is configured to display instantaneous volume readings. The electronic control and power supply unit may also comprise an audio indicator, e.g. for signalling an alert if the volume of the urine and/or faeces inside the diaper is outside a target range. The entire electronic control and power supply may be contained within a housing of the unit.

Measurements determined by the sensing device can be captured at intervals and stored in the data logger prior to processing in the microprocessor. Measurements may be taken and recorded in the data logger as frequently as desired -e.g. every minute or every hour. Data from the data logger or the microprocessor may be transmitted by the transmission system to a remote device or server. This may be a smartphone, laptop, pager or other device. The remote device can keep a record of liquid volume data that can be used for clinical evaluation. This data logging may be used by clinicians to monitor the level of incontinence in a patient.

The electronic control and power supply unit may further comprise a rechargeable coin cell for supplying electrical power to the sensing device and the electrical components of the electronic control and power supply unit. The electronic control and power supply unit may supply a voltage of 5V or less. The electronic control and power supply unit further comprises a USB port by which data may be retrieved from the data logger.

The electronic control and power supply unit may be attached to a diaper via adhesive pads, a hook-and-loop connecting mechanism or similar, or it may be integrated into a housing or casing of the sensing device. Alternatively, the electronic control and power supply unit may be communicatively coupled to the sensing device. For example, the electronic control and power supply unit may be connected by a cable, or other suitable wired or wireless power and communication link, and be located remotely from the sensing device -e.g., in a pocket of clothing worn by the wearer, or on a bedside trolley.

Analytics Using the sensing device of any of the previously described examples, the detected signal may be used to generate volume vs. time data. From this data, diaper fullness parameters, such as a) the total volume of urine and/or faeces, b) flow rate of the urine, and c) frequency of the discharge, may be calculated using an analytical method, e.g. a definite integral. This is very useful for incontinence assessment.

The volume of urine inside the diaper may be calculated using an empirical method, as follows. Multiple experiments are performed on a range of diapers of different sizes and absorption capacities. Known quantities of liquid (e.g., saline water) are injected into the diaper and the output signal of the detector unit recorded. The quantity of liquid may be up to several litres. Software is used to convert the output signal into the amount of liquid inside the diaper. The result is displayed as a volume. The output signal (e.g., mV) is converted into a volume (e.g., ml) of liquid (using the empirical method stated above), volume vs time data collected, and a volume vs time graph may be generated. Using a definite integral, the volume of urine discharged by the wearer in any given time period can be deduced from the area under the curve. The flow rate (dmi/dt) of the discharge can also be determined at any instance during the use of the diaper. This is particularly useful for incontinence assessment of a patient, which is currently done manually.

Due to the ingress of urine and/or faeces, the expanding diaper applies a pressure to the expandable member or sensing circuitry. This pressure can be computed as: P = - (2)

A

where P is the pressure on the expandable member or sensing circuitry, F is the force on them and A is the total area through which the force acts. The force F can be detected using a force detector. Using the empirical method described above, the pressure P can be related to the volume of the liquid inside the diaper. The empirical method involves the injection of a known quantity of liquid (up to several litres) inside the diaper. This provides an alternative method of detecting the volume inside the diaper at any given instance, during use. An appropriate software may be compiled based on this method to generate and display a digital value of the volume of the urine and/or faeces inside the diaper.

A filtering algorithm may be used to avoid false detections caused by movement of the wearer. For example, time sampling may be used to remove unwanted signals due to movement by wearer. The sensing device is configured to process the output signal from the detector unit so as to remove transient features caused by movement of the wearer, for example when walking around, or turning in bed. Sensor data may be logged over time and processed to determine the frequency, flow rate, and/or volume of the wearer's urination.

The sensing device may also comprise an output device for providing an indication of fullness of the diaper, such as a speaker, a display, or a light-emitting component (e.g. an LED). The output device may comprise electronic circuitry, such as a radio transmitter, configured to transmit a signal, e.g. to a smartphone e.g. of a parent, guardian or carer. The indication may be binary (e.g. full or not full), or may indicate a degree of fullness of the diaper.

The sensing device may be configured to determine when the detected displacement in the diaper exceeds a predetermined threshold. The output device may be configured to provide an indication, e.g. transmit a signal, in response to determining that the detected displacement exceeds the predetermined threshold. In this way, the sensing device may be used to provide an alert to a parent, guardian or carer that a diaper, e.g. worn by a baby, infant, toddler, child, adult or animal, has been filled, e.g. by urine or faeces, and needs to be replaced.

A first expansion of the expandable member is measured before or soon after the diaper has been put on, or is preconfigured. This first expansion is representative of the state or stretch in the diaper 1600 when the diaper 1600 is in an unsoiled 'empty' state, i.e., the unexpanded state. Over time, the sensing device records, at intervals, further measurements of the expansion. Each further measurement of expansion can be compared with the first expansion measurement. If the sensing device records an expansion measurement that is greater than the first expansion measurement by a predetermined threshold, indicating a significant expansion of the diaper, the sensing device determines that the diaper is filling up or has been filled, e.g. by urine and/or faeces. Consequently, the sensing device may be arranged to issue an alert to the parent or carer that the diaper has been soiled and therefore requires changing -e.g. by sending a radio message to a baby monitor device, or to an app on a phone belonging to the parent or carer. In some examples, more complex processing of the expansion measurement may be performed, e.g. to filter out changes arising due to movement of the wearer.

Claims

CLAIMS: 1. A sensing device for a diaper, the sensing device comprising: an expandable member comprising at least a first portion configured to be fixedly attach to the external surface of the diaper; sensing circuitry arranged on the expandable member and comprising contacts for providing electrical connection with a detector unit, wherein, the sensing circuitry is configured to expand in response to an expansion of the expandable member.
2. The sensing device of claim 1, wherein the sensing circuitry includes at least one of, a resistor circuit, a capacitor circuit, and a strain gauge pattern.
3. The sensing device of claim 1 or 2, in which the sensing circuitry is formed from an electrically conductive elastomeric polymer.
4. The sensing device of any one of claims 1 to 3, wherein the expandable member comprises an elastomeric patch.
5. The sensing device of any one of claims 1 to 4, wherein the expandable member is integrated into the external surface of a diaper.
6. The sensing device of any one of claims 1 to 5, wherein the sensing circuitry is formed on the expandable member by one of, ink jet printing, screen printing, microcontact printing, or brush painting.
7. The sensing device of any one of claims 1 to 6, in which a second portion of the expandable member is configured to reversibly attach to the external surface of the diaper.
8. The sensing device of any one of claims 1 to 7, wherein the sensing circuitry comprises pad connectors for connecting to electrical contacts of a detector.
9. The sensing device of any one of claims 1 to 8, further comprising a detector unit having electrical contacts coupled to the sensing circuitry, wherein the detector unit is configured to detect the expansion of the expandable member by measuring for a change in an electrical signal across the electrical contacts.
10. The sensing device of claim 9, wherein the sensing circuitry comprises a variable resistor or a strain gauge pattern, and the detector unit is a resistive detector.
11. The sensing device of claim 9, wherein the sensing circuitry comprises a variable capacitor and the detector unit is a capacitive detector.
12. The sensing device according to any one of claims 9, 10 or 11, wherein the detector unit is coupled to the expandable member via a link and a loop fastener.
13. A diaper comprising a sensing device, wherein the sensing device is a sensing device according to any one of claims 1 to 12.