A multi-modal shape sensor, method, system and use

Abstract

The invention relates to a sensor for use in a system for determining a three-dimensional surface shape of a human or animal body, the sensor comprising: a base comprising at least two sensing elements, and a deformable substrate comprising a conductive target over the base so as to provide a sensing capacitance and / or inductance across and / or resistance along the elements, wherein the sensor is adapted to change the sensing capacitance, inductance and / or resistance in response to a strain selected from: compression, stretch and bend, applied to the sensor. Also described is the use of the sensor in a system and method for determining a three-dimensional surface shape of a human or animal body, and in a stretchable material.

Description

[0001] A MULTI-MODAL SHAPE SENSOR, METHOD, SYSTEM AND USE

[0002] BACKGROUND

[0003] This invention relates to improvements in respect of shape sensors for use in systems for reproducing the three dimensional (3-D) shape of an object, in particular a patient body part for medical applications, such as custom-made orthotics and prosthetics.

[0004] In orthopaedic technology there is a need to be able to carry out a patient scan while a therapist or surgeon performs a therapeutic action on the body or while the body is resting on supporting devices. For example, a scan is taken during the straightening of a spasmic deformity of a limb in order to develop a splint for holding a straightened position. A hand of the surgeon or a support device can come into conflict with the optical scanning with the result that regions which were covered during scanning were not measured and therefore need to be reworked to provide a closed surface model to be made available for digital production of orthopaedic aids.

[0005] WO 2021 / 048538 Al discloses an extensible textile fabric with a plurality of integrated sensors of different types for evaluating and determining the 3-D shape of a body part. The fabric is in the form of a sleeve or the like to cover the surface of the body part to be measured. Each sensor type detects a particular parameter, such as strain, pressure or temperature, and detected signals from the sensors are processed to determine the 3-D surface shape of the body part.

[0006] It is an object of the invention to provide an improved sensor for use in a system to determine a surface shape of a human or animal body.

[0007] SUMMARY OF THE INVENTION

[0008] In its broadest sense, one aspect of the invention is a sensor for use in a system for determining a 3-D surface shape of a human or animal body, the sensor comprising: a base comprising at least two sensing elements, and a substrate comprising a conductive target over the base so as to provide a sensing capacitance and / or inductance across and / or resistance along the sensing elements, wherein the sensor is adapted to change the sensing capacitance, inductance and / or resistance in response to a strain type selected from two or more of: compression, stretch and bend.

[0009] In one embodiment, the sensor is adapted to change the sensing capacitance, inductance and / or resistance in response to compression and stretch, or compression and bend, or stretch and bend, or stretch, bend and compression.

[0010] The strain types applied to the sensor may be determined from the change in sensing capacitance, inductance and / or resistance. Thus, the sensor according to the invention can sense and differentiate three physical parameters, that is compression (force), stretch (elongation) and bend, as a single unit. The different strain types may be determined simultaneously or separately.

[0011] In one embodiment, the at least two sensing elements are located on an x axis, and the substrate and the base are adapted such that a normal force along an z axis towards the sensing elements causes a simultaneous increase in inductance in the sensing elements, a stretch along the x axis causes a decrease in inductance of one or more sensing elements and an increase in inductance of one or more other sensing elements, and / or a bend along the x axis causes substantially no change in inductance of one or more sensing elements and a decrease in inductance of one or more other sensing elements. The strain type and the applied strain force can be estimated well with linear function of the sum and difference of the measured inductances.

[0012] The conductive target functions as a magnetic core for the sensing elements (conductors / coils) due to the presence of a magnetic element, such as iron particles, in it. The change in sensing capacitance, inductance and / or resistance is determined by the positional relationship between the conductive target and each sensing element because the target contains an element with a high magnetic permeability. Therefore, the sensor can estimate the applied tri-axis strains by monitoring the inductance changes caused by 3-D displacement of the target.

[0013] A stretch of the sensor causes a horizontal displacement of the conductive target, changing the area of overlap in connection with the sensing elements. A bend of the sensor causes a vertical displacement of one or more sensing elements, changing the distance between the displaced sensing element(s) and the conductive target, and no displacement of the one or more other sensing elements. A compression of the sensor causes a change in magnetic permeability in the substrate due to a decrease in thickness of the substrate and thereby the vertical distance between the target and all sensing elements. A compression strain has an approximately equal and proportionate effect on all sensing elements.

[0014] In response to a stretch or elongation force, the substrate comprising the conductive target moves linearly along a single axis over the sensing elements. In response to a bend, one sensing element moves away from the conductive target while the other sensing element does not move. The substrate material is such that it retains its shape in response to a stretch strain and to a bend strain. Thus, the substrate material does not elongate as the substrate freely moves linearly in response to a stretch strain applied to the sensor. The substrate material does not bend in response to a bend strain applied to the sensor. As will become apparent, that the substrate does not elongate and / or bend in response to stretch / bend strains is due to mechanical constraints in the sensor and / or the nature of the substrate material. The substrate material can be deformed in response to a compression strain. The substrate is preferably made of an elastomeric material. The substrate material can be suitably modified, for example by the use of fibres, additives, etc., to make it semi-rigid or so that it has the physical properties required.

[0015] These displacements of the conductive target relative to the sensing elements and the sensing elements relative to the conductive target cause a change in inductance, capacitance and / or resistance values in such a manner that the different types of strain can be differentiated and measured simultaneously at a particular region of the human or animal body.

[0016] In a preferred embodiment, the sensor comprises two sensing elements. The two sensing elements are positioned coaxially and may be located adjacent to each other. In this embodiment, a stretch along the x axis causes a decrease in inductance of one sensing element and an increase in inductance of the other sensing element. This arrangement of sensing elements ensures a proportional rise in one sensing element and a decrease in another, thereby providing a system whereby if one sensing element is affected by noise the system can still sense. A bend along the x axis causes substantially no change in inductance of one sensing element and a decrease in inductance of the other. In a bend, there is a change in position of the target on one sensing element but not on the other sensing element. The substrate is reinforced to aid the required movements in a stretch and a bend strain. The substrate is made of a soft elastomeric material that comprises mechanical constraints to prevent force dissipation and to restrict elongation to a single axis.

[0017] In one embodiment, the base of the sensor is such that it does not elongate, for example in response to a stretch strain applied to the sensor. The base may comprise a flexible portion and a rigid portion. The flexible portion may flex or bend in response to a bend strain applied to the sensor. In this embodiment, the rigid portion of the base comprises at least one sensing element and the flexible portion of the base comprises at least one other sensing element. In this way, in response to a bend strain applied to the sensor along the x axis, the sensing element(s) in the rigid portion of the base does not move / change position relative to the target with the result that there is no change in inductance of the sensing element (s) provided in the rigid portion of the base, whereas the flexible portion does move and so there is a change in inductance of the sensing element(s) provided in the flexible portion. Further, the base is preferably such that it can bend along the X and Z axes, but cannot bend or at least substantially bend in the Y axis. The base may be made of a polymer material, preferably an elastomer. The physical property of the base material can be modified according to physical requirements. Thus, for example, a harder polymer (e.g., stiffer elastomer, PVC, PEEK, etc.) may be used to achieve a rigid portion of the base and a softer polymer (e.g., softer elastomer) may be used to achieve a flexible portion of the base. The material of the base is preferably resilient. The rigid and flexible portions of the base are preferably integral.

[0018] The substrate may be a polymer material such as an elastomer, or a hydrogel. Examples of suitable elastomeric materials are Ecoflex-30™, Polydimethylsiloxane (PDMS) and RTV-528. An elastomeric material for the substrate may be suitably modified according to physical requirements by, for example, incorporation of fibre particles, such as twine or woven fabric. Further, the substrate is preferably arranged in the sensor so that it does not bend or at least does not substantially bend along the X and / or Y axis. By not stretching or bending, technical issues such as deterioration in substrate strength over time is avoided.

[0019] The conductive target is preferably embedded in the substrate. The conductive target comprises a magnetic element which may be in the form of fillers such as particles, e.g., particles of iron, nickel, cobalt or their oxides. These particles are uniformly dispersed within the substrate so that the substrate can interact with magnetic fields. At rest or before a strain force is applied to the sensor, the conductive target covers or lies over an equal area of each sensing element. For example, where there are two adjacent sensing elements, the conductive target lies at rest over 50% of the area of one sensing element and over 50% of the area of the other sensing element.

[0020] In one embodiment, the substrate comprising the conductive target moves linearly along the x axis in response to a stretch strain applied to the sensor, thereby causing a proportional change in inductance of the sensing elements. The linear movement along the x axis is preferably effected by the substrate sliding on the base. The sensor may comprise guide means to allow the substrate comprising the conductive target to move linearly, without elongation or at least without substantial elongation, in response to a strain force. The guide means may take the form of opposed walls defining a passage within which the substrate can travel along the x axis over the sensing elements provided on the base. The opposed walls may extend upwardly from the base and may be integral with the base.

[0021] Horizontal displacement of the substrate over the sensing elements may be limited by an end wall. The end wall may extend upwardly from the base and lie in a plane orthogonal to the opposed walls. The end wall and opposed walls may be integral with the base. The substrate may be connected to the end wall by means of an attachment formed of a material that allows all degrees of movement, such as an elastomer. The attachment may be comprised of the same elastomeric material as the substrate but without modification. The attachment is preferably resilient and can elongate and deform, such as bend, along any axis in response to a strain. However, movement of the attachment along certain axes is restricted by the presence of mechanical constraints, provided, for example, by the base (opposed walls, base floor, end wall).

[0022] Thus, the sensor according to the present invention is such that is allows controlled displacements of conductive target and sensing elements relative to each other in response to an applied strain with the result that different strain types can be identified and differentiated from each other.

[0023] According to another aspect, the invention is a system for determining a three- dimensional surface shape of a human or animal body, the system comprising: a sensor array with a plurality of sensors, wherein the plurality of sensors are arranged with respect to one another so as to act on the surface of the body, wherein each sensor comprises: a base comprising at least two sensing elements, and a substrate comprising a conductive target over the base so as to provide a sensing capacitance and / or inductance across and / or resistance along the sensing elements; wherein each sensor is adapted to generate a surface signal with regard to their orientation and position, where the signal is a change in sensing capacitance, inductance and / or resistance in response to an applied strain selected from one or more of: compression, stretch and bend; and a processor in electronic communication with the sensors adapted to determine the shape of the body surface from the plurality of surface signals of the plurality of sensors.

[0024] According to a further aspect, the invention is a stretchable material, comprising a plurality of sensors positioned on or in the material; wherein stretching of the material over a human or animal body positions the sensors to lie on a plurality of surface regions of the body; wherein each sensor comprises: a base comprising at least two sensing elements, and a substrate comprising a conductive target over the base so as to provide a sensing capacitance and / or inductance across and / or resistance along the sensing elements; and wherein each sensor is adapted to change the sensing capacitance, inductance and / or resistance in response to a strain applied to the sensor selected from one or more of: compression, stretch and bend.

[0025] The stretchable material preferably further comprises a computing device operatively coupled to the material and configured to receive output data from the sensors and to process the data to determine the 3-D shape of the body. Preferably, the stretchable material is in the form of a sleeve.

[0026] According to a yet further aspect, the invention is a method of determining a 3-D shape of a human or animal body surface, comprising: placing a plurality of sensors on a plurality of surface regions of the body surface; wherein each sensor comprises: a base comprising at least two sensing elements, and a substrate comprising a conductive target over the base so as to provide a sensing capacitance and / or inductance across and / or resistance along the sensing elements, wherein each sensor is adapted to change the sensing capacitance, inductance and / or resistance in response to an applied strain selected from one or more of: compression, stretch and bend; generating a plurality of signals belonging to the surface regions in response to a strain applied to the sensor selected from: force, stretch and bend; and determining the surface shape of the body surface from the plurality of signals of the sensors by using a signal processing unit.

[0027] In one embodiment of the method, the sensors are mounted in or on a textile material which is placed on a body surface in such a way that the plurality of sensors come to lie on a plurality of surface regions of the body surface.

[0028] In one embodiment, a digital data set of a peripheral surface of a human or animal body surface is created from the plurality of sensor signals.

[0029] According to another aspect, the invention is a method for providing a customized orthotic product, the method comprising: providing a stretchable material, comprising a plurality of sensors positioned on or in the material, each sensor comprising: a base comprising at least two sensing elements, and a substrate comprising a conductive target over the base so as to provide a sensing capacitance and / or inductance across and / or resistance along the sensing elements, wherein each sensor is adapted to change the sensing capacitance, inductance and / or resistance in response to an applied strain selected from one or more of: compression, stretch and bend; providing a processor in electronic communication with the sensors; placing the material over the body part so that the plurality of sensors lie on a plurality of surface regions of the body; determining the surface shape of the body from the plurality of surface signals of the plurality of sensors by use of the processor; and using the determined surface shape of the body to design a customized orthotic product.

[0030] In one embodiment, the method further comprises displaying the 3-D shape of the body or part thereof on a display. In one embodiment of the method, the 3-D image of the shape of the body is used to design a customized orthotic product by (1) fabricating the body part in 3-D form and designing the orthotic product using the fabricated body part, or (2) designing the orthotic product using the 3-D image of the body part, and fabricating the orthotic product in 3-D form from the designed image of the orthotic product.

[0031] In one embodiment, the method further comprises reading output from sensors at one or more target regions of the body part where force or deformation pressure is applied to hold, manipulate and / or correct the body part; and using the output to design the orthotic product.

[0032] The sensors may be integrated or embedded within the material and / or positioned onto the material surface. In one embodiment, the sensors are provided in channels, pockets, or the like, formed in the material. In another embodiment, the sensors are laminated onto or incorporated in an elastomeric material. For example, the sensors may be laminated onto an elastomeric sheet, where the sheet may be in the form of a strip. The elastomeric material may comprise silicone, polyurea, polyether, polyurethane, or the like, or any combination thereof.

[0033] In one embodiment, the material is a textile and the sensors are positioned on, or integrated or embedded within, the fibres or yarn of the textile. The stretchable material may comprise natural fibres, such as wool, cotton, etc. and / or synthetic fibres, such as elastane (a polyether-polyurea copolymer). By having the sensors positioned on or within the yarn, conventional textile manufacturing methods, like knitting and weaving, can be used to fabricate the article.

[0034] A flexible cover may be provided over the sensors on the material. Preferably, the flexible cover provides a moisture / water-resistant / proof protective layer. In one embodiment, the flexible cover is a non-textile, and preferably the flexible cover is itself covered with textile fibres. In another embodiment, the sensors are coated or embedded in a water-proof material, for example, silicone. In this way, the article can be washed and re-used multiple times.

[0035] In one embodiment, two dimensions of the sensor, such as height or thickness, are less than about 10 mm and another dimension of the sensor, such as width, is less than about 35 mm, preferably less than about 10 mm.

[0036] In one embodiment, the article is in the form of a sleeve adapted to snugly fit over a part of the object, for example a body part, such as a limb of a patient. In this embodiment, the plurality of sensors may comprise one or more closed loops of sensors. The sensors may arranged in an array or matrix. Thus, rows and columns of sensors may be provided in or on the article material.

[0037] According to a further aspect, the present invention is a method for determining a stretch, bend and / or compression applied to an article, comprising: providing a sensor as described in contact with the article; determining a stretch by detecting an increase in inductance of one sensing element and a decrease in inductance of the other sensing element; determining a bend by detecting substantially no change in inductance of one sensing element and a decrease in inductance of the other sensing element; and / or determining a compression by detecting a simultaneous increase in inductance of the two sensing elements.

[0038] Definitions

[0039] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art.

[0040] Within this specification, the terms "comprises" and "comprising" are interpreted to mean "includes, among other things". These terms are not intended to be construed as "consists of only". The term "coil" is generally understood to be an electrical conductor and may be a wire that is in the shape of a coil. An electric current is passed through the wire of the coil to generate a magnetic field. Alternatively, a magnetic field through the interior of the coil generates a voltage in the conductor. Various coil shapes and configurations are possible, including square, rectangular, spiral with any number of turns etc., planar, helical and complex 3-dimensional. The condition to meet is that the area covered and changed by the substrate on the coils are equal and proportionate, respectively. For example, the substrate with conductive target covers 50% of the area initially and as it moves linearly where the area on one coil changes by A% the area on the other coil changes by +A%.

[0041] Within this specification embodiments have been described in a way which enables a clear and concise specification to be written. The following is a non-restrictive description of preferred embodiments of the invention, provided for the purpose of exemplification only, with reference to the accompanying drawings. It is intended and will be appreciated that embodiments may be variously combined or separated without parting from the invention.

[0042] BRIEF DESCRIPTION OF THE FIGURES

[0043] Figure 1 shows a side view of a sensor according to one embodiment of the invention;

[0044] Figures 2 (a), (b) and (c) show front view, side view and top view, respectively, of a base of the sensor according to the one embodiment of the invention;

[0045] Figures 3 (a), (b) and (c) show front view, side view and top view, respectively, of the base of Figure 2 with first and second sensing elements in position according to the one embodiment of the invention;

[0046] Figures 4 (a) and (b) show a front view and a side view, respectively, of a substrate of the sensor according to the one embodiment of the invention; and Figure 5 shows a schematic overview of a system involved in using a sensor according to the invention to measure a structure such as a human body part.

[0047] DETAILED DESCRIPTION

[0048] An embodiment of the invention will now be described with reference to the accompanying figures.

[0049] With reference to figure 1, a sensor (10) comprises a base (12), two sensing elements or coils (SCI, SC2) on the base, and a substrate (14) consisting of three parts (XI, X2, X3) over the base (10) and the two coils (SCI, SC2). A conductive target is provided in one part (X2) of the substrate (14). The dimensions of this sensor are: 30 mm x 8 mm x 8 mm.

[0050] The base (12) of the sensor (10) is shown in figure 2 to be rectangular in shape and is formed of a single piece of material. The base has a cut-out portion (16) for the placement of the clip (14) and two coils (SCI, SC2). The base (12) has opposed side walls (18, 20) and an end wall (22). The base is 27 mm (I) x 8 mm (h) x 8 mm (w) and the cut-out portion is 25 mm (I) x 5.5 mm (h) x 5 mm (w). The base (12) is made of an elastomeric material that is mechanically reinforced to prevent elongation of the base in all axes (X, Y and Z) and bending in the Y-axis. The base is allowed to bend in the X and Z axes.

[0051] The base is formed of Ecoflex™ with no additives and is mechanically reinforced with twine or woven fabric that is strategically placed to prevent various movements as described.

[0052] With reference to figure 3, first and second coils (SCI, SC2) are integrated on the floor (24) of the base (12) in the cut-out portion (16). The coils (SCI, SC2) are planar and rectangular. Each coil is 10 mm (I) x 5 mm (w) x 0.12 mm (d). The clip (X2) comprising a conductive target is surrounded on either side by the opposed side walls (18, 20) when in position on the base over the coils (SCI, SC2). The clip (X2) is a movable component and has a magnetic element embedded therein which the coils (SCI, SC2) present in the base (12) sense. As shown in figure 4, the clip is made of three distinct parts (XI, X2 and X3). The three parts of the clip are joined together to form the finished clip (14). As with the base (12), the clip material is provided with mechanical reinforcements that prevent or limit certain movements.

[0053] Details of the three parts of the clip are provided below.

[0054] XI:

[0055] XI is the part that affixes to the end wall (22) of the base (12). It is the only part of the sensor that does not have any mechanical reinforcement and it is allowed all degrees of movement. Movement of XI is restricted by the surrounding reinforced side walls and end wall and so this part of the clip does have some restrictions in movement.

[0056] Material: Ecoflex™ with no additives

[0057] Mechanical Reinforcement: None

[0058] Dimensions: 5 mm x 5 mm x 5 mm

[0059] X2:

[0060] X2 is the only part of the sensor that is magnetically sensitive. It forms the central core of the coil. This part of the clip lies over the coils SCI and SC2. The movement of this core is detected by the coils. This part is mechanically reinforced.

[0061] Material: Ecoflex™ with ferrous additives.

[0062] Mechanical Reinforcement: Axial Reinforcement. Elongation is not allowed. Y axis bend is not allowed.

[0063] Dimensions: 20 mm x 5 mm x 5 mm

[0064] X3:

[0065] X3 serves only a mechanical function, providing an arm for the clip to connect to external features or another similar sensor. This part has mechanical reinforcement. Material: Ecoflex™ with ferrous additives.

[0066] Mechanical Reinforcement: Axial Reinforcement. Elongation is not allowed. Y axis bend is not allowed.

[0067] Dimensions: 15 mm x 5 mm x 5 mm

[0068] The three parts of the clip are joined together with a bonding agent, such as Ecoflex™, to form the full clip (Figures 1 and 4). The dimensions of the fully assembled clip are: 30 mm x 5 mm x 5 mm.

[0069] The final sensor (10) is assembled by placing the clip (14) in the indent (16) provided in the base (12). The clip is secured onto the base (12) by attaching clip part (XI) to the end wall (22) of the base (12) as shown in figure 1. At rest, the magnetic part of the clip (X2) covers exactly 50% area of both coils (SCI and SC2).

[0070] The sensor (10) operates on inductance (L) measurement of the coils (SCI and SC2). The inductance henceforth is referred to as LI and L2 for SCI and SC2, respectively.

[0071] • LI and L2 increase if X2 is placed on top of it and decreases if X2 is removed.

[0072] • The change in LI and L2 is proportional to the area of the coil covered by the area.

[0073] • LI and L2 also increase / decrease if the magnetic property of X2, a factor called permeability (p) changes.

[0074] • X2 covers 50% area of both SCI and SC2 at rest and LI and L2 have similar values.

[0075] The change in LI and L2 is utilized to identify the three parameters: elongation, bending and force.

[0076] The changes that occur during each of the three parameters are described below.

[0077] Elongation:

[0078] X2 slides on the two coils (SCI, SC2) since X2 cannot stretch. This results in X2 moving away from one coil (SCI) and moving towards the other coil (SC2). This causes L2 to increase and LI to decrease. Bend:

[0079] The whole sensor (10) can bend, and bend detection only occurs in the X axis. The type of bend is a cantilever bend. Bend causes no movement in the X2, however one coil (SC2) slips and moves away from X2 causing a decrease in L2, and LI remains constant as there is no movement in X2 and the other coil (SCI).

[0080] Force:

[0081] An applied normal force changes the magnetic property of X2. This in turn changes the area covered by both coils (SCI, SC2) in the same way. As a result, both LI and L2 increase in the same proportions.

[0082] Table I below shows the change in inductances with the relevant physical parameter. An algorithm acquires LI and L2 in real time, the computation is carried out, and the physical parameter is ascertained. The physical parameter values are obtained from calibration data of the sensor.

[0083] Table 1

[0084] Examples of the working range and the theoretical range for elongation in stretch, force and bend sensing are provided below.

[0085] Stretch Sensing:

[0086] Force Sensing: Bend Sensing:

[0087] The sensor (10) measures three parameters. Elongation sensing is acquired through the movement of the conductive target over the coils (SCI, SC2). The movement is typically in the range of few millimetres. Force sensing is achieved through change in the magnetic property of the material and has an equal and proportionate effect on all the coils (SCI, SC2). Bend sensing is achieved through change in the position of the magnetic core (X2) on one coil (SC2) but not on the other coil (SCI). The value L2is obtained from a calibration curve. The difference in value of L2corresponds to the bend in the system.

[0088] The system of the invention can include a personal computer system, image computer, mainframe computer system, workstation, network appliance, internet appliance, or other device. The system may also include any suitable processor known in the art, such as a parallel processor. In addition, the system may include a platform with high speed processing and software, either as a standalone or a networked tool. The processor can, for example, run a machine learning algorithm or other software for the sensing techniques. The processor can be in electronic communication with the sensors.

[0089] There may be a regression analysis or another fitting method to provide a model linking tensile strain to inductance. This can be calibrated by initial measurements for a given device geometry and frequency.

[0090] A selected body surface is effectively scanned from, for example, a textile sleeve to generate a three-dimensional data set representing the body part surface geometry. With reference to figure 5, a selected body part (30) is covered with a sleeve (32) comprising integrated stretchable sensors (34) so that each sensor (34) lies proximate to a surface region of the body part (30). Force, bend and elongation data (36, 38, 40) from the sensor (34) are captured and relayed to a computer (42) as sleeve data (44). Custom software and a specific processing algorithm (46, 48) reconstruct the data into an on-screen accurate digital geometric shape and replica three-dimensional image (50) of the original three-dimensional body part, with measured data information, to an on-screen monitor (52) of a computer device. The sleeve (32) may have a connection for an integrated or external attached power supply. Wireless or wired technology may be used for data transfer from the sleeve to a computer / laptop / smart device. For example, yarns may be connected to a BluetoothTM-enabled interface hardware circuit that will condition the output signals and transmit them to smartphones or laptops for further processing.

[0091] The computing device includes a display for displaying the three-dimensional image of the body part. The computing device may be operatively coupled to a three- dimensional printer, a Computer Numerical Control (CNC) machine or a robot multiaxis carver, to provide a three-dimensional mould of the body part image and / or an orthotic product. The computing device preferably comprises a processor and storage. Stored instructions may be executed by the processor to perform an action. For example, stored instructions may be executed by the processor to perform an action on a three-dimensional printer responsive to input from a sensor.

[0092] It should be understood that various changes and modifications to the presently preferred embodiments described herein will be apparent to those skilled in the art. For example, the invention has been described with reference to measurement of strain based on inductance measurement. It will be apparent that capacitance and / or resistance measurement can be measured in addition or as an alternative to inductance with the invention by suitable adjustments. Such changes and modifications can be made without departing from the scope of the present invention and without diminishing its attendant advantages. It is therefore intended that such changes and modifications are covered by the appended claims.

Claims

Claims1. A sensor for use in a system for determining a three-dimensional surface shape of a human or animal body, the sensor comprising: a base comprising at least two sensing elements, and a deformable substrate comprising a conductive target over the base, so as to provide a sensing capacitance and / or inductance across and / or resistance along the elements, wherein the sensor is adapted to change the sensing capacitance, inductance and / or resistance in response to a strain selected from: compression, stretch and bend, applied to the sensor.

2. A sensor according to claim 1, wherein the sensing elements are located on an x axis, and the substrate and the base are adapted such that a force along the z axis causes a simultaneous increase in inductance in the at least two sensing elements, a stretch along the x axis causes a decrease in inductance of one or more sensing elements and an increase in inductance of the other one or more sensing elements, and a bend along the x axis causes substantially no change in inductance of one or more sensing elements and a decrease in inductance of the other one or more sensing elements.

3. A sensor according to claim 1 or claim 2, wherein the substrate is arranged in the sensor so that it moves linearly along a single axis in response to a stretch so as to cause a proportional change in inductance of the at least two sensing elements.

4. A sensor according to claim 3, wherein the substrate is arranged in the sensor to slide on the base in response to a stretch.

5. A sensor according to any one of the preceding claims, comprising guide means allowing movement of the substrate along a single axis over the sensingelements in response to a stretch, optionally wherein the guide means comprise opposed walls of the base.

6. A sensor according to any one of the preceding claims, wherein the base unit comprises a rigid portion and a flexible portion, wherein one sensing element is provided in the rigid portion and the other sensing element is provided in the flexible portion.

7. A sensor according to claim 6, wherein the flexible portion of the base is such that it allows bend along the x axis and the z axis, and / or substantially no bend along the y axis.

8. A sensor according to any one of the preceding claims, wherein the base is such that it does not elongate in response to stretch force applied to the sensor.

9. A sensor according to any one of the preceding claims, wherein the substrate is structured and arranged such that it does not bend along the x and / or y axis, and / or it does not elongate in response to a strain applied to the sensor.

10. A system for determining a three-dimensional surface shape of a human or animal body, which comprises a sensor array with a plurality of sensors, arranged with respect to one another so as to act on the surface of the body; wherein each sensor is as defined in any one of the preceding claims 1 to 9; and wherein the sensors are adapted to generate a surface signal with regard to their orientation and position in the magnetic field of an associated surface region; and a processor in electronic communication with the sensors adapted to determine the shape of the body surface from the plurality of surface signals of the plurality of sensors.

11. A stretchable material, comprising a plurality of sensors positioned on or in the material; wherein each sensor is as defined in any one of claims 1 to 9, whereinstretching of the material over a human or animal body positions the sensors to lie on a plurality of surface regions of the body; and wherein the sensors detect a strain selected from: compression, stretch and bend, at an associated surface region.

12. The material of claim 11, further comprising a computing device operatively coupled to the material and configured to receive output data from the sensors and to process the data to determine the three-dimensional shape of the body.

13. A method of determining a three-dimensional shape of a human or animal body surface, comprising: placing a plurality of sensors on a plurality of surface regions of the body surface; wherein each sensor is as defined in any one of claims 1 to 9; generating a plurality of signals belonging to the surface regions in response to strain selected from: compression, stretch and bend, applied to each sensor; and determining the surface shape of the body surface from the plurality of signals of the sensors by using a signal processing unit.

14. The method according to claim 13, wherein the sensors are mounted in or on a textile material which is placed on a body surface in such a way that the plurality of sensors come to lie on a plurality of surface regions of the body surface, the sensors signaling according to a position and orientation of an associated surface region in response to a strain selected from: compression, stretch and bend.

15. A method for providing a customized orthotic product, comprising: providing a system according to claim 10; providing a material according to claim 11; placing the material over the body part so that the material is stretched, at least in part;reading output from the sensors, and determining the three- dimensional shape of the body part based on the output from the sensors; and using the determined three-dimensional shape of the body part to design a customized orthotic product.

16. A method for determining a stretch, bend and / or compression applied to an article, comprising: providing a sensor according to any one of claims 1 to 9 in contact with the article; determining a stretch by detecting an increase in inductance of one sensing element and a decrease in inductance of another sensing element; determining a bend by detecting substantially no change in inductance of one sensing element and a decrease in inductance of another sensing element; and / or determining a compression by detecting a simultaneous increase in inductance of the two or more sensing elements.

Images