WO2019073261A1

WO2019073261A1 - Deformable support structure

Info

Publication number: WO2019073261A1
Application number: PCT/GB2018/052944
Authority: WO
Inventors: Panagiotis CHATZISTERGOS; Roozbeh NAEMI; Nachiappan CHOCKALINGAM
Original assignee: Staffordshire University
Priority date: 2017-10-12
Filing date: 2018-10-12
Publication date: 2019-04-18
Also published as: EP3694364A1; GB2567461B; GB201716746D0; GB2567461A

Abstract

There is disclosed a support structure for a human or animal body. The support structure has a support layer and an array of resilient upstanding members arranged over an area of the support layer. The resilient members depend from the support layer and are formed such that the resilient members resist an applied load on the support layer by reversibly collapsing in a direction towards the support layer. The resilient members soften upon repeated collapsing of the resilient members in response to cyclic loading. Each resilient member may collapse independently of other resilient members in the array.

Description

Deformable Support Structure

This disclosure concerns support structures for supporting a human or animal body. In particular, the disclosure concerns deformable and/or cushioning support structures, typically for pressure relief, and may, for example, encompass orthoses.

One technical field in which it is desirable to provide bespoke support structures is for footwear. It is generally known that the thickness and stiffness of cushioning material that is used as a shoe midsole/insole can be varied over its area to provide optimum cushioning. Whilst this approach is generally accepted for bespoke orthoses that are tailored to specific individual's needs providing this level of performance optimisation is less practical for mass-produced, standard shoe designs..

Conventional cushioning materials, such as polyuerethane foams and the like, have predetermined material properties over the area of the sole and thus, when new, provide a predetermined response to applied pressure. That is to say, the resistance to applied pressure will increase in a predictable manner as the foam material compresses down to a fully compressed condition, at which point minimal further cushioning effect is provided. The manner in which the cushioning effect is tailored is thus by changing the foam material or increasing/decreasing its thickness/depth rather than changing the nature of the material's response to applied load.

Conventional foam materials do not recover immediately when the applied load is removed. Thus repeated cyclic loading above a certain frequency results in diminished effectiveness. In order to tailor shoes for a wearer, one approach is to provide a bespoke foot orthosis in the form of an insole. Insoles may supplement the function of the midsole but will also typically degrade if using conventional compressible materials. UK Patent GB2508204 discloses a system for additive manufacturing, i.e. so- called 3D printing, of a foot orthosis in which materials of differing Shore hardness are applied in different regions, such as layers, in order to provide different compressibility.

In that example, a Computer Aided Design (CAD) system is used to alter an initial model to suit an individual for whom the orthosis is intended. However it has been found that the use of a bespoke 3D printing process that requires two materials introduces complexity to the manufacture process. Such a manufacturing technique cannot be readily widely adopted at this point in time. Furthermore, the reliance on material selection can hamper the freedom with which the insole can be customised or graded for the wearer's needs.

The applicant has a co-pending patent application, UK Patent Application No. 1621769.7 filed on 20 December 2016, the contents of which is incorporated herein by reference. That application discloses a support structure comprising a network of resilient upstanding partitions which can be tailored to undergo collapsible deformation, in use, in a manner that provides a cushioning effect. The present invention has resulted from further investigation into the behaviour of, and possible uses for, similar structures.

It is an aim of the present invention to provide a support structure or orthosis for humans or animals which mitigates one or more of the above-described problems. It may be considered an additional or alternative aim to provide a support structure which can be adapted to individuals' needs.

According to a first aspect of the present invention, there is provided a support structure for a human or animal body, the support structure comprising a support layer and an array of resilient upstanding members arranged over an area of the support layer, the resilient members depending from the support layer and being formed such that the resilient members resist an applied load on the support layer by reversibly collapsing in a direction towards the support layer, wherein the resilient members soften upon repeated collapsing of the resilient members in response to cyclic loading. The resilient members may undergo mechanical softening in response to repeated loading/unloading of the support layer. The resilient members may permanently or irreversibly soften, e.g. through repeated collapse.

The support structure may be arranged to undergo non-uniform loading over the area of the support layer. The non-uniform loading may be defined by a nonuniform pressure/loading profile or distribution, e.g. a two-dimensional profile over the support layer area. The pressure/loading profile or distribution may be predetermined. The support structure may comprise a common/standard design, which adapts to an applied pressure profile through use. Alternatively the array of resilient members may be customised, e.g. upon manufacture, according to an

intended/predetermined pressure profile. In this embodiment, the resilient members may still adapt to the applied pressure profile in use.

The resilient members may each comprise a proximal end at the support layer and may extend form the support layer to a distal end or edge spaced from the support layer. The distal end/edge may be a free end/edge. The resilient member may comprise discrete resilient members. Each resilient member may be spaced from one or more adjacent member, e.g. by a gap. Each said resilient member may have a plurality of adjacent, e.g. surrounding, resilient members. The plurality of adjacent members may be spaced from said resilient member. Each resilient member may be spaced, e.g. laterally, from every adjacent or surrounding resilient member. The ability of one resilient member to deform independently of its adjacent resilient members may be beneficial in the adaptive tuning of the resilient members through use. The resilient members may resist an applied load in two modes, a first mode comprising resilient/elastic compression up to a first loading threshold and a second mode comprising reversible collapse of the resilient members beyond the first load threshold. The first mode may be considered to provide resilience to deformation primarily according to the material properties of the resilient members, e.g. elastically. In the second mode the resilient members may undergo gross deformation according to its mechanical and/or structural properties.

There may be a third mode of operation, e.g. after the applied load has passed a second threshold criterion or load value. The third mode of operation may comprise resilient compression of the collapsed resilient members.

The first threshold may comprise a pressure and/or strain threshold. The second threshold may comprise a pressure and/or strain threshold.

Any or any combination of the material properties of the resilient members (e.g. stiffness, resilience and/or elasticity), geometric properties (e.g. area, wall thickness, height, length and/or breadth) and/or arrangement within the network (e.g. number of neighbouring/adjacent members and/or density or spacing of resilient members) may be tailored to achieve a desired mechanical behaviour in response to an applied load or load distribution.

Any or any combination of said material and/or geometric properties may be uniform or equal for some or all of the resilient members of the array.

The reversible collapse of the resilient members may comprise buckling or crushing thereof. It has been found that the yielding of the resilient members in this manner can provide a beneficial additional cushioning effect for a number of applications. Furthermore it has been found that repetition of this yielding/collapse behaviour, e.g. in a cyclic/ongoing manner, causes resulting changes in the mechanical behaviour of resilient members. Unlike a conventional foam

cushioning structure which becomes compacted over repeated use (thereby losing its cushioning effect) the upstanding resilient members will still adhere to a collapsing/yielding behaviour over extended use, but will soften and thereby adapt to the loading profile applied thereto over the area of the support surface.

The array of resilient members may be tuned for predetermined loading profile, such that only some of the resilient members will undergo collapse or buckling (e.g. in the second mode of response) whereas others will not (e.g. in the first mode of resilient response).

The resilient members may undergo softening in response to the action of collapsing (e.g. in the second mode of response). The resilient members may soften according to the number of times they have undergone collapse. Thus, for a repeated loading profile in which some resilient member will collapse but others will not, the mechanical properties of the resilient members will vary over the array with ongoing use.

The array of resilient members may comprise a regular, uniform and/or evenly- spaced array, e.g. over the entire area of the support layer. Alternatively, the density of resilient members may vary over the support layer area, e.g. according a predetermined loading profile.

The resilient members may each extend in a direction or along an axis that is substantially orthogonal to a plane of the support layer.

Each resilient member may comprise a hollow, walled structure. Each resilient member may be circular or polygonal in section or plan. Each resilient member may be open-ended, e.g. at its distal end. Each resilient member may comprise a void or recess, e.g. an internal or central recess. The recess may extend in an axial direction with the resilient member. The resilient members may or may not be of substantially common cross-sectional area or profile for the height of the resilient members. Each resilient member in the array may be of common shape, e.g. in section or plan and/or a common three-dimensional shape.

Each resilient member may be of the same height.

Each resilient member may be annular or tubular in form. In examples in which the resilient members are polygonal, the resilient members may have three, four, five, six or more sides. Each resilient member may be straight-sided, e.g. when at rest or undeformed. The resilient members may comprise one or more kink, corner, fold and/or crease when collapsed. The resilient members may be deformed out of the plane in which they extend in the first mode. The array of resilient members may comprise a regular and/or repeating pattern over the support layer area.

The width of the resilient members in the array may be equal or may vary over the array, e.g. according to a predicted pressure distribution over the support structure in use. The density of resilient members may be relatively greater, and/or the resilient member width/area relatively reduced, for regions where the applied load is expected to be higher.

A length dimension of each of said edges of the resilient members may be uniform or may vary over the area of the support layer/structure.

The support structure may comprise tens or hundreds of resilient members. The array may comprise greater than 40, 60, 80 or 100 resilient members. The wall thickness of the resilient members may be constant or may vary over the area of the support structure, for example according to the intended applied pressure distribution in use. The resilient members typically comprise a resilient polymer material. The upstanding partitions may comprise an elastomer material.

The support structure may comprise an orthosis and/or article of clothing/footwear.

The support structure may comprise a sole component of a shoe, such as an insole or mid sole.

According to a further aspect of the invention, there is provided a method of producing a support structure comprising obtaining a pressure distribution for a body to be supported in use, determining one or more material property for a support structure according to the first aspect of the invention based upon said pressure distribution and forming the support structure such that only some of the array of resilient members will collapse upon application of the pressure

distribution to the support structure in use.

The support structure may be manufactured by an additive manufacturing process.

The support structure may adapt to its intended use.

The pressure distribution may be an anatomical pressure/weight distribution for a user.

According to a further aspect of the invention, there is provided a method of customising a user support structure for an end user, the method comprising forming a support structure according to the first or second aspect and providing the support structure to the end user for use, whereby use of the support structure to support the user's weight causes one or more mechanical property of at least some of the resilient members to be permanently modified in response to said use.

According to a further aspect of the invention, there is provided a pressure distribution sensor comprising the support structure of the first aspect. Any of the optional features described in relation to any one aspect may be applied to any other aspect of the invention, where practicable.

Certain practicable examples of the present invention are described in further detail below, by way of example only, with reference to the accompanying drawings, of which:

Fig. 1 shows a three-dimensional view of a support structure according to an example of the present invention;

Fig. 2 shows a plan view of the support structure of Fig. 1 ;

Figs. 3A and 3B show respective side and three-dimensional views of a resilient member for use in an example of the invention;

Fig. 4 shows a three-dimensional view of a support structure according to a further example of the present invention;

Fig. 5 shows an example of a plot of stress against strain for a support structure according to the invention;

Fig. 6 shows a plantar pressure distribution for to be accommodated using a support structure in accordance with an example of the invention;

Figs. 7 to 9 show plots of stress against strain showing mechanical response for upstanding members that have been exposed to respective low, medium and high pressure loading over time.

In Figures 1 and 2, there is shown a structure 10 spanning an area having length and width dimensions that are substantially greater than the depth of the structure. Thus the structure takes the form of a mat, bed, pad or similar. In this example the support structure is shaped in the form of an insole for footwear, although the support structure could be used for a number of different applications as will be described below. Examples of the invention designed for footwear may be referred to as 'foot beds'. In footwear, amongst other examples of the invention, the structure may be more generally referred to as a cushioning material. The support structure 10 of Figure 1 is comprised of multiple upstanding resilient members 12 of the kind shown in the enlarged section 14. The members 12 comprise a hollow interior having a perimeter defined by one or more upstanding wall formation, which in this example takes the form of a tubular wall. In the example of a tubular member, the wall is curved in section. Oval or elliptical sectional profiles could be considered in place of a circular profile.

The wall of the resilient member is annular so as to completely enclose the hollow interior of the member when viewed in plan/section.

Whilst a constant profile, e.g. an extruded-type shape, is shown in the

macroscopic view of Figure 1 , the structure and/or surface profile of the resilient members is non-constant and/or profiled at a smaller scale as will be described below. Such shape variables may be used to tailor the behaviour/properties of the cells as desired.

The support structure 12 has a support layer 14, shown in Figure 2, from which the resilient members 12 depend. The support layer 14 is a continuous layer used to hold the members 12 in a predetermined array. The support layer may comprise a simple single layer of material, which may be the same material used to form the upstanding resilient formations. In this example the support layer 14 and resilient members 12 are formed as a single, unitary structure, e.g. by a common manufacturing method. In other examples, the support layer could comprise a harder material so as to provide a support or platform, on which the resilient members can be disposed. Additionally or alternatively the support layer 14 may comprise a multi-layer structure or laminate, whereby the support layer could provide both a support for the resilient members 12 and also additional cushioning properties of itself. One or more additional layer, e.g. a foam layer, could be provided for this purpose which may or may not be of uniform thickness. In some examples, it is feasible that upstanding resilient formations 12 could be provided on both opposing sides of the support layer 14, e.g. in the same or different arrays. The support structure 10 has a peripheral wall 16 extending around the perimeter of the support layer 14. The peripheral wall is upstanding on the support layer 14 and forms a complete wall around the edge of the support structure 10. The resilient members 12 are thus enclosed by the peripheral wall 16. The peripheral wall may be formed of the same material as the resilient members 12 and/or may be formed by a common manufacturing process. The peripheral wall, support layer and resilient members 12 may comprise a unitary, e.g. homogeneous, structure.

The peripheral wall 16 serves to constrain the resilient members 12 in use. The peripheral wall 16 may deform in a collapsible manner, e.g. in a manner similar to the resilient members 12 upon loading of the support structure 10 in use.

The peripheral wall 16 is of a height similar to, or the same as, the height of the resilient members 12. The members 12 in Figures 1 and 2 are shown as being open, i.e. open-ended. Whilst the support structure may be formed as shown in Figure 1 , practical embodiments, may have a further base and/or top layer from which the upstanding members 12 may depend. The resilient members 12 and/or peripheral wall 16 may be sandwiched between suitable base later and the support layer 14. For any open cell shapes, a base and/or top layer may comprise a complete layer, e.g. as opposed to the open cells 12 of the support structure.

In other examples, the resilient members can be formed as closed cells, i.e.

having an end wall. Alternatively, the resilient members could be formed as solid finger-like structures or upstanding beams/pedestals. The support structure 10 is formed of a resiliently deformable polymer, such as a thermoplastic elastomer. The hardness of the material will be selected according to the specific weight/impact bearing properties required. The free ends/edges 18 of the upstanding walls 16 collectively define a support surface of the support structure, which can resist an applied load in use in a manner which distributes the applied load across some or all of the members 12. The structure 10 is typically oriented with the free/distal ends 18 of the members 12 facing the ground, floor or other surface (i.e. downwards) on which a body is to be supported in use. The layer 14 thus provides a continuous surface or platform on which the weight of the body can be applied in use.

Whilst the members 12 are described as being air-filled, it is not intended that the members are air tight, that is to say, it is the mechanical behaviour of the members 12 that provides the desired cushioning behaviour in response to an applied load, rather than air trapped therein.

As shown in Figures 1 and 2, the upstanding members 12 extend in a direction substantially orthogonal to the plane of the support layer 14. Each member extends in a generally parallel direction when in an at-rest or undeformed condition as shown.

The upstanding members are arranged in a regular two-dimensional array, in which upstanding members are all equidistantly arranged. The upstanding members are arranged in a series of, e.g. equally spaced, rows and columns. In this example at least eight or nine rows and/or columns are provided.

For foot bed applications, at least 80 or 100 members 12 may be provided to accommodate the variation in pressure distribution over the area of the foot bed in use.

Unlike the applicant's prior patent application, UK Patent Application No.

1621769.7, in which the support structure takes the form of interconnected walls forming a network of cells, the example structures of the present disclosure comprise an array or discrete/individual member/cells that can deform individually in response to an applied load. Turning now to Figs. 3A and 3B, there is shown an isolated resilient member 12. In this example, the resilient member is formed by a three-dimensional printing (i.e. additive manufacturing) method in which successive layers 20 of material are laid down and fused to the previous layer in a conventional manner. Various three- dimensional printing techniques are described in the art and will not be described again here, save to say that a layer deposition process is used in this example.

The detailed view B in Fig. 3A shows the edge of successive layers 20 in further detail, where it can be seen that the successive layers of the resilient member form a non-smooth or textured surface/edge profile. The edge of each layer may be rounded thereby forming a discontinuity, trough or recess at the interface between adjoining layers. The layers 20 are shaped according to a desired cross sectional profile and stacked on a common axis so as to form the desired height of the upstanding member. In any examples of the invention the resilient members may be elongate in form.

Fig. 4 shows a further example of support structure in which the resilient members 12A are polygonal, rather than circular in plan/section. The resilient members 12A are hexagonal in plan/section in this example. A regular hexagonal shape has been used, although other regular or irregular polygonal shapes could be used.

Upon application of a load/pressure onto the support surface of the structure 10, the members 12 or 12A exhibit mechanical behaviour that can be divided into three distinct modes or zones, (i), (ii) and (iii) as shown in the schematic

stress/strain graph of Figure 5. It is to be noted that whilst Figure 5 shows a stress/strain graph, a similarly shaped plot (i.e. a similar response) would be seen for a force/displacement graph and any of the below description of Figures 5 and/or 7-9 may also apply to such a graph. In zone (i) the support structure 10 behaves like many other resiliently deformable materials, such that the support structure undergoes elastic compression, wherein the internal stress within the material resists the force applied thereto, e.g. in a generally linear manner. The gradient of this portion of the graph is thus due to the Young's Modulus of the support structure material.

However in zone (ii) the stress/strain or force/displacement relationship changes. In zone (ii), the behaviour can be described as strain softening. That is to say, beyond a predetermined value of strain, i.e. beyond a corresponding value of applied load, the upstanding members 12 will buckle or collapse so as to cause a second type or mode of mechanical response. The members 12 will thus yield under compressive stress and will deform out of the plane of the wall structure when at rest. This causes the height of the walls to reduce more rapidly than the compression that occurs in zone (i).

The pressure/loading magnitude that triggers the aforementioned sudden and drastic change in geometry (i.e. collapse) and the associated instantaneous change mechanical behaviour will be referred to simply as critical load/pressure.

In Figure 5, it can be seen that in zone (ii) the shape of the graph changes and the gradient reduces significantly before increasing again in zone (iii). The graph thus changes from a concave to a convex form by way of an inflexion. In different examples of the invention, according to selection of relevant properties for the support structure, such as the hardness/softness of the material, the wall thickness, the cell size/are, and the wall height, the gradient may either approach zero, become zero, or become negative within zone (ii). In the latter example of a negative gradient, the graph will achieve a zero gradient at two spaced points of the curve, a first point at which the gradient is reducing and a second point at which the gradient is increasing. Once the upstanding members 12 have collapsed, increasing strain further will cause a positive gradient in zone (iii). The collapsed structure will thus be compressed further and the rate of elastic deformation of the members in this form will decrease as the structure approaches its elastic limit, i.e. its compressive strength.

When the applied pressure is released, the members 12 typically revert back to their upstanding condition very quickly, e.g. akin to 'snapping' back to an un- deformed condition. This can occur more quickly than a conventional foam material which will typically expand more slowly as it approaches its un-deformed condition.

Whilst collapse of the members 12 causes a reversible instantaneous mechanical response of the members, it has been found that repeatedly loading and unloading the resilient members in a manner that results in collapse (i.e. according to zones (ii) and (iii) of Fig. 5), causes a permanent and/or irreversible change in the mechanical behaviour of the members 12, e.g. including their response to further/future loading. Ongoing research and development work stemming from this realisation has demonstrated that support structures of the type disclosed herein age very differently when they are subjected to repetitive loading depending on whether the loading is below, at or above the structure's critical pressure. This makes it possible to design a structure that changes its mechanical characteristics in a predictable and controllable way in response to its loading in use. Additionally it opens the way for structures that adapt to loading so as to tune their mechanical properties for enhanced performance.

The mechanical behaviour in zone (ii) is markedly different from the foam

materials, which maintain a strongly positive gradient throughout the compression process. In contrast, the upstanding wall structure can maintains the initial gradient for longer in zone (i), e.g. closer to a linear stress/strain relationship, than the foam material. Thus the support structure 10 will resist small loads to a greater degree and will provide a relatively firm support prior to collapse in zone (ii). The support structure according to the present invention can significantly alter the response to different loading conditions, whereby applied pressure can be offloaded in an effective manner. Thus the support structure can be tuned in advance and various properties of the support structure may be modified to suit a particular application, such as any or any combination of the following parameters:

- Hardness/resilience of the material used to create the support structure

- Upstanding member size/area, density and/or count

- Upstanding member shape (e.g. in plan or section), including circular,

triangular, quad, etc, for example including variations of regular or irregular shapes and/or a mixture of different shapes within different portions of a common support structure

- Wall thickness (constant or variable for different regions of the support bed)

- Wall orientation or shape, including straight, planar walls that may be

vertical or angled walls/faces, e.g. according to whether the upstanding member section is constant or variable with height.

- Upstanding member height (constant or variable)

- Support structure covering

Whilst such features allow a particularly customisable support structure, it has been found that a further key benefit is the ability of the structure to react to loading in use and thereby allow self-customisation. In particular, it has been found that the mechanical properties of the individual upstanding members 12, and thus the structure as a whole, change over time based on repeated loading and unloading of the upstanding members. Rather than this being a negative quality resulting in degradation of mechanical properties, e.g. as attributed to reduced performance of conventional foams over time, the changes in mechanical properties can beneficially modify the cushioning effect for an individual user.

Turning to Figure 6, there is shown an example plantar pressure distribution 22 for a single foot of an individual. The plantar pressure distribution 22 indicates different pressure applied to different plantar regions and is non-uniform, indicating regions 24 of higher loading in contrast to other regions 26 of lower or minimal loading. Such a pressure distribution could be obtained from a static/standing condition but will more typically be obtained by analysis of transient pressure distribution during movement (i.e. walking, jogging and/or running). Individual pressure distributions taken at different times during movement can be

added/overlaid to achieve an overall pressure distribution/profile for an individual.

Knowing the maximum and minimum pressures to be accommodated, a support structure can be provided as a foot bed in which some, but typically not all, upstanding members will collapse according to zone (ii) of Fig. 5 when loaded under the pressure profile.

Therefore, rather than having to provide a foot bed that is perfectly adapted to the individual user in advance for optimal offloading of pressure, a foot bed can be provided that is approximately correct and then allowed to adapt further to the user over time by wearing/use of the foot bed. This may alleviate the need for accurate biomechanical measurements for a subject in order to provide a suitable foot bed. This may be important when it is considered that obtaining detailed biomechanical measurements is usually costly and time consuming processes.

Furthermore, even if you get a subject to walk around with suitable pressure sensing equipment as part of a test, it is not simple to predict the actual pressure distribution over a period of time of 'normal' (i.e. highly variable) use.

Instead of detailed biomechanical measurement, the invention may allow a foot bed to be prescribed based on a very simple plantar pressure measurement and/or based on other information such as the subject's body weight (BW), shoe size, level of physical activity etc.

Figures 7-9 show some representative results of tests of sample support structures 10. The initial mechanical behaviour of the samples and their critical load was assessed under compression. The mechanical aging on the quasi-static mechanical response of samples having an infill density of 10% was assessed. The samples were subjected to 100,000 cycles of mechanical aging (e.g.

simulating 6 weeks of continuous use for walking) at different loading magnitudes. The effect or repetitive loading was assessed by comparing their final mechanical response to compression to their original response (i.e. response before

mechanical aging). Three different scenarios of loading magnitude were tested, which correlate to the results of Figs. 7-9 as follows:

• Fig. 7 (low pressure): applied load equal to critical load

• Fig. 8 (medium pressure): applied load equal to minimum needed to

generate 50% compression

· Fig. 9 (high pressure): applied load 50% higher than for Fig. 8.

The darker plots in Figs. 7-9 show the original mechanical response, whereas the lighter plots show the aged response. As can be seen the mechanical 'aging' process is significantly affected by the magnitude of the applied repetitive loading. The results indicated that repetitive loading lower or equal to the sample's critical one has little effect on its mechanical response. However higher loading can lead to substantial softening. When critical pressure is exceeded the collapse of the upstanding members' structure causes the development of significant localised stresses and strains, which in turn lead to localised micro damage. Micro-damage is accumulated as result of repetitive loading and this accumulation is stronger in areas where loading is higher leading to measurable softening. Areas where pressure is above the critical threshold will develop some softening while areas that are loaded below this threshold will not. Moreover, within the areas where changes occurs, softening will increase with loading magnitude.

Previous tests have also demonstrated that the initial mechanical properties of thin wall structures, including their critical load, can be easily controlled and adapted by changing the size, shape of the members, the thickness of the walls and the material used (or any of the other parameters described above). In the case of the 3D printed samples presented here, the manufacturing process also contributes to the repeatability of the aforementioned mechanism. More specifically the deposition of layer onto layer of material provides a guide for the accumulation of micro-damage which makes the mechanical aging process very repeatable.

However 3D printing is not the only manufacturing technique that could lead to the desired effects. For example, staking, laying down of thin sheets of material that are cut to the cross-sectional shape of the array or individual upstanding members. Other examples of applying successive layers could be considered. Discontinuities or lines of weakness could be provided in the upstanding member in other ways if desired, e.g. by pre-forming the upstanding members 12 of a suitably texture/profiled material and applying them to the support layer.

Whilst the layered structure of the upstanding members described above has been particularly apt for the self-customising of mechanical behaviour over time, it is possible that other structures, textures and or mechanical features of the upstanding members could result in a similar effect. For example, forming of the upstanding formations with a profile that varies in a macroscopic scale, e.g. by virtue of a corner, indent, line(s) of weakness or similar, may achieve the same repeatability in mechanical aging. This may allow non-layered structures and associated manufacturing methods, e.g. conventional moulding methods, to be used for manufacture of the support structures.

Mass production of a range of support structures could thus be enabled instead of bespoke individual structures using 3D printing.

According to aspects of the invention, there may be provided a support structure with upstanding members each having one or more geometric feature to promote a stress concentration during collapse, e.g. and thereby cause predictable mechanical aging of the upstanding members in a desirable manner. Unlike conventional foams, which become flattened/compressed with increase compressive loading, the upstanding members under collapse will 'snap' back to their original height once the load is removed and would thus look generally undeformed after repeated use but would soften based on the mechanical aging process described herein.

In many examples of the invention, it is desired that the upstanding members are not affected or minimally affected by bending, such that the upstanding members are deformed predominantly, or entirely, in compression. The upstanding members may have low or minimal bending stiffness.

According to the above disclosure, it is possible to manufacture a foot bed with mechanical properties and critical load that is tailored for specific applications and/or individuals. When this foot bed goes in use, areas of high loading will age differently compared to areas where loading is medium or low. Regions of the foot bed that undergo high loading (substantially above the critical loading) will become softer enhancing the uniform distribution of plantar loads and the reduction of plantar pressure. The same foot bed product will adapt differently to optimise performance on an individual basis when given to two different individuals provided that some or all of the upstanding members are consistently/repeatedly loaded to above their critical loading condition in use.

Use of the support structure has yielded additional unexpected benefits and/or applications. It has been found that the support structure can be used as a device to assess plantar loading during activities of daily living without the need for complicated or intrusive electronic sensors. In such a use a foot bed insert/insole is given to a patient and can be fitted within their normal shoes. The patient returns to their daily activities and uses the shoes with the footbed for a predefined period of time. Assessing changes in the mechanical properties of the insert will enable identification of the areas of the foot that are most heavily loaded during the patient's actual daily activities. This can provide some useful real-life information that may differ from information obtained by asking the same patient to undertake constrained biomechanical assessment, e.g. by walking in a straight line in a gait lab. This information can enhance prescription and ultimately the clinical management of certain conditions, including diabetic foot disease.

In addition to the clinical and surgical footwear market, the support structures disclosed herein can have applications in performance as well as safety footwear. The support structures could be used for other footwear components, such as midsoles, arch plugs, metatarsal beams/pads, heel plugs, or shoe uppers, e.g. for protective footwear. Furthermore the support structures are not only limited to foot bed applications but can be applied to any cushioning or supporting surface for clinical or commercial applications, e.g. for other support structures for the human or animal body. Types of orthoses include, by way of example only, hand orthoses, or parts of a neck brace, or a knee brace, or other types of lower limb orthotic, such as night splints, or surgical shoe components.

There have been determined a number of other shock-absorbing or pressure- distributing applications for which the present invention may be well suited, including cushioned and/or padded garments. Other examples include helmets, body armour, seat covers, saddles, mats (including floor mats or yoga mats), grips and the like which are designed to relieve pressure or distribute impact or weight.

Claims

Claims:

1 . A support structure for a human or animal body, the support structure comprising:

a support layer, and

an array of resilient upstanding members arranged over an area of the support layer,

the resilient members depending from the support layer and oriented such that the resilient members resist an applied load on the support layer by reversibly collapsing in a direction towards the support layer,

wherein the mechanical characteristics of the resilient members change upon repeated collapsing of the resilient members in response to cyclic loading such that the support structure adapts through use to an applied load distribution over the area of the support layer.

2. A support structure according to claim 1 wherein the resilient members permanently or irreversibly soften through repeated collapse.

3. A support structure according to claim 1 or 2, wherein the resilient members each comprise a proximal end at the support layer and extend from the support layer to a distal end spaced from the support layer wherein the distal end is a free end.

4. A support structure according to any preceding claim, wherein the resilient members of the array are discrete resilient members, each being spaced from one or more adjacent resilient member.

5. A support structure according to any preceding claim, wherein the array is a two-dimensional array and each resilient member of the array has a plurality of adjacent resilient members.

6. A support structure according to any preceding claim, wherein each resilient member may individually deform in response to a non-uniform applied load distribution.

7. A support structure according to any preceding claim, wherein the resilient members resist an applied load in two modes, a first mode comprising

resilient/elastic compression up to a first loading threshold and a second mode comprising reversible collapse of the resilient members beyond the first load threshold.

8. A support structure according to claim 7, wherein the resilient members soften upon repeated collapsing of the resilient members according to a

magnitude of applied load above the first loading threshold.

9. A support structure according to any preceding claim, wherein the resilient members each extend in a direction that is substantially perpendicular to a plane of the support layer.

10. A support structure according to any preceding claim, wherein each resilient member is hollow.

1 1 . A support structure according to claim 10, wherein an end of the resilient member is open.

12. A support structure according to any preceding claim, wherein each resilient member is tubular in form.

13. A support structure according to any preceding claim, wherein each resilient member is shaped so as to define one or more feature part way along its length to promote resilient collapse of the resilient member in use at the feature.

14. A support structure according to claim 13, wherein the feature comprises a notch or groove.

15. A support structure according to claim 13 or 14, wherein each resilient layer comprises a plurality of layers and the feature comprises an interface between adjacent layers.

16. A support structure according to any preceding claim, wherein the height of each resilient member in the array is substantially equal.

17. A support structure according to any preceding claim, wherein the array comprises greater than 60, 80 resilient members.

18. A support structure according to any preceding claim, wherein the resilient members comprise an elastomer material.

19. A support structure according to any preceding claim, wherein the support structure is a unitary 3D printed structure.

20. An orthosis according to the support structure of any preceding claim.

21 . An article of footwear or foot bed comprising the support structure of any preceding claim.

22. A method of customising a user support structure for an end user, the method comprising forming a support structure according to any preceding claim and providing the support structure to the end user for use, whereby repeated loading of the support structure in use according to a loading profile caused by the user's weight distribution on the support structure causes one or more mechanical property of at least some of the resilient members to be permanently modified in response to said use.

23. The use of a support structure according to any one of claims 1 -21 as a mechanical sensor for recording a loading profile applied to the support structure by the relative hardness/stiffness of the resilient members in the array after use.