A device that detects compression pressure

Abstract

A sensing device for sensing a compressive pressure applied by a compression bandage or garment, comprising a flexible substrate for wearing under the compression bandage or garment, comprising a compression sensor attached to the flexible substrate, the compression sensor having an input and an output and a signal path between the input and the output, the input and the output configured such that a sensor signal received by the output varies in response to a relative configuration of the input and the output and / or the signal path between the input and the output, and the input and the output configured such that the relative configuration of the input and the output varies in response to a compressive pressure applied to the compression sensor, the compressive pressure including a component perpendicular to the flexible substrate.

Description

[Technical field]

[0001] The present invention relates to a sensing device for sensing the compressive pressure exerted by a compression bandage or garment. [Background technology]

[0002] Compression therapy through the application of compression bandages (or elastic compression garments) is widely used to treat and manage circulatory disorders. This includes venous leg ulcers and venous deficiencies that can lead to deep vein thrombosis. Compression therapy also assists in the movement and removal of fluids trapped in the body's lymphatic system, helping to reduce or prevent lymphedema. Other uses for compression bandages include treating wrist and ankle sprains, muscle strains, swollen hands and feet, and contusions and bruises. Summary of the Invention [Problem to be solved by the invention]

[0003] For a compression bandage to function optimally, it must apply a certain amount of compression (pressure) to the relevant body part of the wearer. Improper application of compression can lead to uneven and insufficient compression or dangerous levels of excessive compression. In particular, improper use of compression on limbs with arterial disease has been reported to cause severe skin and tissue necrosis (in some cases requiring amputation).

[0004] Due to the different shapes and sizes of the various body parts to which a compression bandage may be applied, it is desirable to have a sensing device for sensing the actual compression pressure, e.g. the actual graduated compression pressure, exerted on the wearer by the compression bandage during use.The present invention aims to provide such a sensing device which offers various advantages over the prior art. [Means for solving the problem]

[0005] According to the present invention there is provided a sensing device for sensing a compressive pressure (e.g. a graduated compressive pressure) applied by a compression bandage (or compression garment). The sensing device comprises a flexible substrate for wearing under a compression bandage (or compression garment) and a compression sensor attached to the flexible substrate. The compression sensor has an input and an output. There is a signal path between the input and the output. The input and output are arranged such that a sensor signal received by the output varies depending on the relative configuration of the input and output and / or the signal path. The input and output are arranged such that their relative configuration varies depending on a compressive pressure applied to the compression sensor, the compressive pressure having a component normal to the substrate.

[0006] Advantageous features of the sensing device are set out in the accompanying claims. [Brief description of the drawings]

[0007] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Figure 1A] 1 is an example of a sensing device placed under a compression wrap around the wearer's leg. [Figure 1B] FIG. 1B is a top view of an example substrate of the sensing device of FIG. 1A with multiple compression sensors disposed thereon. [Diagram 2] FIG. 2 is a cross-sectional view of a first example of an optical compression sensor in a non-compressive state (a state in which no compression pressure is applied). [Diagram 3] FIG. 3 illustrates the optical compression sensor of FIG. 2 with a compressive pressure applied. [Figure 4] FIG. 11 is a cross-sectional view of a second example of an optical compression sensor in a non-compressive state (a state in which no compression pressure is applied). [Diagram 5] FIG. 5 illustrates the optical compression sensor of FIG. 4 with a compressive pressure applied. [Figure 6] FIG. 11 is a cross-sectional view of a third example of an optical compression sensor in a non-compressive state (a state in which no compression pressure is applied). [Figure 7] FIG. 7 illustrates the optical compression sensor of FIG. 6 with a compressive pressure applied. [Figure 8] FIG. 11 is a side view of a fourth example of an optical compression sensor in a non-compressed state (a state in which no compression pressure is applied). [Figure 9] FIG. 9 illustrates the optical compression sensor of FIG. 8 with a compressive pressure applied. [Figure 10] FIG. 2 is a side view showing an example of a capacitive compression sensor in a non-compressive state (a state in which no compression pressure is being applied). [Figure 11] FIG. 11 illustrates the capacitive compression sensor of FIG. 10 with a compression pressure applied. [Figure 12] FIG. 2 is a side view showing an example of a resistive compression sensor in a non-compressive state (a state in which no compression pressure is applied). [Figure 13] FIG. 1B is another example of a top view of the substrate of the sensing device of FIG. 1A, showing a single optical compression sensor disposed on the substrate. [Figure 14] FIG. 14 is a side view of the optical compression sensor of FIG. 13 in a non-compressive state (no compression pressure is applied). [Figure 15] FIG. 15 illustrates the optical compression sensor of FIGS. 13 and 14 with a compressive pressure applied. [Figure 16] FIG. 11 is a side view showing yet another example of the optical compression sensor in a non-compressive state (a state in which no compression pressure is applied). [Figure 17] FIG. 17 illustrates the optical compression sensor of FIG. 16 with a compressive pressure applied. [Figure 18] FIG. 17 illustrates a power supply and control device suitable for use in a sensing device including a compression sensor of any one of FIGS. 2-12 or FIGS. 14-17. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] The present invention relates to a sensing device for sensing a compressive pressure (e.g. graduated compression pressure) applied by a compression bandage (or compression garment). The sensing device includes a flexible substrate for wearing under the compression bandage (or compression garment) and a compression sensor attached to the flexible substrate. The compression sensor includes an input and an output. There is a signal path between the input and the output. The input and output are arranged such that a sensor signal received by the output varies depending on the relative configuration of the input and the output and / or the signal path. The input and output are arranged such that their relative configuration varies depending on a compressive pressure applied to the compression sensor, the compressive pressure having a component perpendicular to the substrate.

[0009] The sensing device is designed to have the substrate and compression sensor attached to a human or animal body underneath a compression bandage (or garment). One example is shown in FIG. 1A. More specifically, FIG. 1A shows a human leg having a knee 8, a mid-calf 10, and ankle 9. FIG. 1A also shows a flexible substrate 7 and a compression sensor 3 attached to the human leg at a location between the knee 8 and the ankle 9. The flexible substrate 7 and compression sensor 3 are attached underneath the compression bandage 1 of FIG. 1A. The flexible substrate 7 and compression sensor 3 are preferably attached over a non-elastic dressing (e.g., a bandage such as a bell band) such that a protective membrane is placed between the wearer's skin and the substrate 7.

[0010] In use, the compression bandage 1 or garment applies pressure to the leg as well as to the compression sensor 3. The tighter the compression bandage is wrapped around the leg, the greater the compression pressure on the leg. In treating venous leg ulcers, it is generally necessary to apply graduated pressure to the leg, from relatively high pressure near the ankle to relatively low pressure near the knee. Thus, compression bandages are more suitable than elastic compression garments for treating venous leg ulcers. The characteristics of typical graduated compression are described below.

[0011] An example of a sensing device is shown in Figure 1B. In Figure 1B, the sensing device 2 includes three compression sensors, namely a first compression sensor 35, a second compression sensor 50, and a third compression sensor 95. Each of the three compression sensors 35, 50, 95 is attached to a surface of a flexible substrate 7. Each of the three compression sensors 35, 50, 95 has an input and an output, respectively, with signal paths (not shown in Figure 1B) between the inputs and outputs.

[0012] The flexible substrate 7 may be made of a polymeric material. However, those skilled in the art will appreciate that other flexible materials, such as paper, are also suitable. The substrate 7 is elongated and has a length greater than its width. The length of the substrate 7 is comparable to the length of a standard adult's ankle to knee. The width of the substrate 7 is less than the circumference of a standard adult's calf. For example, the length of the substrate is about 45 cm or less and the width is about 15 cm. The thickness of the substrate is preferably 1 mm or less so as not to interfere with the wearer. However, those skilled in the art will appreciate that substrates having dimensions other than those mentioned above may be suitable and substrates of different sizes may be used for different sized legs.

[0013] The compression sensors 35, 50, 95 are spaced apart from one another. In particular, the compression sensors 35, 50, 95 are spaced apart from one another by a predetermined distance along the length of the base material 7, with the first compression sensor 35 being located near one end of the base material 7, the second compression sensor 50 being located approximately in the center of the length of the base material 7, and the third compression sensor 95 being located near the other end of the base material 7.

[0014] The overall thickness of the compression sensor 30, 50, 95 and substrate 7 is preferably less than 3 mm. Due to this very thin profile of the substrate 7 and compression sensor 30, 50, 95, they do not exert significant additional pressure on the body beyond the intended pressure exerted by the compression bandage 1. Localized pressure (i.e., a bump effect) beneath the compression sensor 30, 50, 95 is undesirable. Additionally, the very thin profile of the sensing device 2 allows the substrate 7 and attached compression sensor 30, 50, 95 to be easily attached and removed from the body without causing discomfort to the wearer.

[0015] The sensing device 2 may be positioned such that, in use, the first compression sensor 35 is located just above the wearer's ankle, the second compression sensor 50 is located at the wearer's mid-calf, and the third compression sensor 95 is located just below the wearer's knee. Such positioning is often desirable in the treatment of venous leg ulcers, and the predetermined distances between the compression sensors 35, 50, 95 may be determined by clinical recommendations to provide clinically significant graduated pressure measurements. For example, for venous leg ulcers, the target pressure profile may be 40 mmHg at the ankle, 20 mmHg at the mid-calf, and 15 mmHg below the knee. Those skilled in the art will appreciate that sensor placement may differ for other purposes, such as management of lymphedema or deep vein thrombosis.

[0016] For each compression sensor 35, 50, 95, the sensing device 2 further comprises a respective signal emitter 4a, 4b, 4c, a respective signal detector 6a, 6b, 6c, a respective input connector 20, 55, 70 extending between said respective signal emitter 4a, 4b, 4c and an input of the compression sensor, and a respective output connector 40, 80, 65 extending between the output of the compression sensor and a respective signal detector 6a, 6b, 6c.

[0017] While the compression sensors 35, 50, 95 need to be located under the compression bandage (or garment) in use (so as to be subjected to the compression pressure applied by the compression bandage), the signal emitters 4a, 4b, 4c and signal detectors 6a, 6b, 6c do not need to be located under the compression bandage in use. Indeed, for comfort reasons in many cases it is preferable not to do so. Thus, the input connectors 20, 55, 70 and output connectors 40, 80, 65 allow the signal emitters and signal detectors to be spaced from the compression sensors so that they do not need to be located under the compression bandage (or garment) in use.

[0018] Furthermore, the signal emitters 4a, 4b, 4c and signal detectors 6a, 6b, 6c need not be attached to the substrate. Instead, they may be housed in an Electronic Control and Power Unit (ECPU, not shown in FIG. 1B) remote from the substrate. This configuration may be desirable to simplify construction and maintenance of the detector. Also, for safety reasons, it may be desirable to house active electronics remote from the substrate, especially if the substrate may become wet.

[0019] The first compression sensor 35 is arranged such that the first signal emitter 4a is connected to the first input connector 20. The first input connector 20 extends between the first signal emitter 4a and the input of the first compression sensor 35. The input of the first compression sensor 35 and the output of the first compression sensor 35 are arranged such that, in use, there is a signal path between them (e.g., if the signal is an optical signal, said signal path may be an air gap between said input and said output). The first output connector 40 extends between the output of the first compression sensor 35 and the first signal detector 6a. The first output connector 40 is therefore connected to the first signal detector 6a.

[0020] The second compression sensor 50 is disposed in a manner similar to the first compression sensor 35. The second compression sensor 50 is associated with a second input connector 55, a second output connector 65, a second signal emitter 4b, and a second signal detector 6b.

[0021] The third compression sensor 95 is disposed similarly to the first compression sensor 35 and the second compression sensor 50. The third compression sensor 95 is associated with the third input connector 70, the third output connector 80, the third signal emitter 4c, and the third signal detector 6c.

[0022] Those skilled in the art will appreciate that the sensing device 2 does not need to include a signal emitter 4a, 4b, 4c for each compression sensor 35, 50, 95, respectively, and a signal detector 6a, 6b, 6c for each compression sensor 35, 50, 95, respectively.

[0023] Alternatively, the sensing device 2 can be configured such that each compression sensor 35, 50, 95 shares a single signal emitter but has a respective signal detector 6a, 6b, 6c. Alternatively, the sensing device can be configured such that each compression sensor 35, 50, 95 shares a single signal detector but has a respective signal emitter 6a, 6b, 6c.

[0024] Those skilled in the art will appreciate that sensing device 2 can be configured with more than three compression sensors, or can be configured with less than three compression sensors.

[0025] In use, with respect to the first compression sensor 35, the input of the first compression sensor 35 and the output of the first compression sensor 35 are arranged such that the sensor signal received by the output of the first compression sensor 35 varies depending on the relative configuration of the input of the first compression sensor 35 and the output of the first compression sensor 35 and / or the signal path therebetween. Furthermore, the input of the first compression sensor 35 and the output of the first compression sensor 35 are arranged such that their relative configuration varies depending on the compression pressure (having a component perpendicular to the substrate 7) applied to the first compression sensor 35.

[0026] More specifically, a first signal emitter 4a emits an initial signal. The initial signal enters a first input connector 20. The first input connector 20 routes the initial signal to an input of a first compression sensor 35. There is a signal path between the input and an output of the first compression sensor 35. The output of the first compression sensor 35 receives a sensor signal. The sensor signal received by the output of the first compression sensor 35 is based on the initial signal from the input of the first compression sensor 35 and the relative configuration of the input of the first compression sensor 35, the output of the first compression sensor 35, and the signal path between the input and the output.

[0027] For example, in an optical sensor where the input and output are separated by an air gap, the initial signal is the amount of light emitted from the input into the air gap, and the sensor signal is the amount of light received by the output from the air gap. For example, the relative configuration of the input and output determines the angle at which light is emitted from the input and the percentage of light emitted from the input that is incident on the output. The length of the signal path also varies with the relative configuration of the input and output. Thus, the sensor signal is a portion of the initial signal that varies with the relative configuration of the input and output.

[0028] The sensor signal received by the output of the first compression sensor 35 may or may not be the same as the initial signal emitted by the first signal emitter 4a. The first output connector 40 routes the sensor signal received by the output of the first compression sensor 35 to a first signal detector 6a. The first signal detector 6a detects said sensor signal. Preferably, said sensor signal varies proportionally to the compression pressure (or inversely proportional to the compression pressure).

[0029] When no compressive pressure is applied to the first compression sensor 35, the input and output of the first compression sensor 35 and the signal path therebetween are arranged in an initial configuration. When a compressive pressure (i.e. a pressure having a component perpendicular to the substrate 7) is applied to the first compression sensor 35, the configuration of the input and output of the first compression sensor 35 and / or the signal path therebetween changes. The sensor signal received by the output of the first compression sensor 35 changes depending on the relative configuration of the input and output of the first compression sensor 35 and / or the signal path therebetween. More specifically, the change in the relative configuration of the input and output of the first compression sensor 35 compared to the initial configuration and / or the change in the signal path compared to the initial configuration depends on the amount of compressive pressure applied to the first compression sensor 35. The change from the initial configuration of the relative configuration of the input and output of the first compression sensor 35 and / or the signal path therebetween changes the sensor signal received by the output of the first compression sensor 35 and thus changes the sensor signal sensed by the first signal detector 6a.

[0030] The above-described components of the second compression sensor 50 and the third compression sensor 95 function similarly to the first compression sensor 35 .

[0031] The compression sensors 35, 50, 95 may be optical compression sensors that measure changes in an optical signal, or may be electrical compression sensors that measure changes in an electrical signal, such as electrical resistance or capacitance. Those skilled in the art will appreciate that other forms of compression sensors are possible, such as magnetic field sensing compression sensors. <Optical pressure sensor example 1>

[0032] Figure 2 illustrates an example of an optical compression sensor 103 on a substrate 2676. The optical compression sensor 103 illustrated in Figure 2 can function as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 described in Figure 1B above. The substrate 2676 forms a portion of the substrate 7 of Figure 1B.

[0033] In the case of an optical compression sensor, such as the compression sensor 103 shown in FIG. 2, the signal emitter is a light source and the signal detector is a light detector. The signal emitter may be one of the signal emitters 4a, 4b, 4c, hereinafter referred to as "light source 4a, 4b, 4c". The signal detector may be one of the signal detectors 6a, 6b, 6c, hereinafter referred to as "light detector 6a, 6b, 6c". The light source is preferably a light emitting diode (LED), e.g. an organic LED, and the light detector is preferably a photodetector or a phototransistor.

[0034] In FIG. 2, the compression sensor 103 is formed of an input section 103a and an output section 103b separated by an air gap 2354. The input section 103a includes an input optical fiber 2249 disposed (or attached) to a first portion of the substrate 2676. The input section 103a of the compression sensor 103 further includes a first portion of an upper laminating film 2243 and a lower laminating film 2565 that seal the input optical fiber 2249 and the first portion of the substrate 2676 to form a laminate structure. The input section 103a further includes a first rigid stud 2606. The output section 103b includes an output optical fiber 2255 disposed (or attached) to a second portion of the substrate 2676. The output portion 103b of the compression sensor 103 further includes a second portion of the upper laminate film 2243 and the lower laminate film 2565 that encapsulate the output optical fiber 2255 and the second portion of the substrate 2676 to form a similar laminate structure. The output portion 103b further includes a second stud 2687 and a third stud 2349. The third stud 2349 couples with a portion of the compressible foam 2374.

[0035] In the compression sensor 103 shown in FIG. 2, the input optical fiber 2249 serves as the aforementioned input connector extending between the light sources 4a, 4b, 4c and the input of the compression sensor 103. The output optical fiber 2255 serves as the aforementioned output connector extending between the output of the compression sensor 103 and the light detectors 6a, 6b, 6c. As is known, the input optical fiber and the output optical fiber each have a core surrounded by a cladding (not shown in FIG. 2). The input optical fiber 2249 has a first end and a second end. The output optical fiber 2255 has a first end and a second end. The first end of the input optical fiber 2249 is connected to the light sources 4a, 4b, 4c. The second end of the input optical fiber is the input of the compression sensor 103. Thus, the input optical fiber 2249 extends between the light sources 4a, 4b, 4c and the input of the compression sensor 103. The first end of the output optical fiber 2255 is the output of the compression sensor 103. The second ends of the output optical fibers are connected to the optical sensors 6a, 6b, 6c. Thus, the output optical fibers 2255 extend between the outputs of the compression sensor 103 and the optical sensors 6a, 6b, 6c.

[0036] 2 shows a schematic of the compression sensor 103 in the absence of applied compressive pressure. In this unstressed configuration, the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255 are substantially coaxial. The signal path between the input and output of the compression sensor 103 is from the second end of the input optical fiber 2249 through the air gap 2354 to the first end of the output optical fiber 2255.

[0037] The three rigid studs 2606, 2349, 2687 may be made of plastic. As mentioned above, the first stud 2606 is located on the input 103a of the compression sensor 103. In particular, the first stud 2606 is adjacent to the gap 2354 and is disposed below the substrate 2676 such that the substrate 2676 is sandwiched between the first stud 2606 and the input optical fiber 2249. As mentioned above, the second stud 2687 is located on the output 103b of the compression sensor 103. In particular, the second stud 2687 is disposed below the substrate 2676 at a position slightly away from the gap 2354 such that the substrate 2676 is sandwiched between the second stud 2687 and the output optical fiber 2255. As mentioned above, the third stud 2349 is also located on the output 103b of the compression sensor 103. In particular, the third stud 2349 is adjacent to the void 2354 and above the output optical fiber 2255 such that the output optical fiber 2255 is sandwiched between the third stud 2349 and the substrate 2676. The foam 2374 is sandwiched between the third stud 2349 and the output optical fiber 2255. The distance between the second stud 2687 and the void 2354 is equal to the length of the third stud 2349 such that the distal end of the third stud 2349 is approximately directly above the proximal end of the second stud 2687. Preferably, there is no overlap between the second stud 2687 and the third stud 2349.

[0038] Studs 2606, 2687, 2349 are seen to protrude outwardly from the laminate structure, however the protrusion of studs 2606, 2687, 2349 from the laminate structure is preferably no greater than 0.5 mm in height.

[0039] The compression sensor 103 can be formed by attaching a single optical fiber to the substrate 2676 and encapsulating the single optical fiber and the substrate 2676 between the upper laminate film 2243 and the lower laminate film 2565. Heat or ultrasound can then be applied to form a laminate structure. The laminate structure can then be locally cut to form a gap 2354 between the input 103a and output 103b portions of the compression sensor 103. This cut can be performed with a sharp instrument such as a knife. It should be noted that the cut does not separate the entire substrate 7 into two separate parts. On the contrary, the cut forms a local slit in the substrate 2676 (which forms part of the substrate 7) such that the substrate 7 remains as a single piece. During construction, a portion of the lower lamination film 2565 sealing the input optical fiber 2249 can be replaced with a first stud 2606, a portion of the lower lamination film 2565 sealing the output optical fiber 2255 can be replaced with a second stud 2687, and a portion of the upper lamination film 2243 sealing the output optical fiber 2255 can be replaced with a third stud 2349 and compressible foam 2374.

[0040] In use, the light sources 4a, 4b, 4c emit an initial optical signal. The initial optical signal is incident on the input optical fiber 2249 at the first end. The input optical fiber 2249 guides the initial optical signal from the first end of the input optical fiber 2249 to the second end of the input optical fiber 2249. The initial optical signal is launched from the second end of the input optical fiber 2249 into an air gap 2354. There is a signal path between the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255. The signal path includes an air gap 2354. Typically, when the input optical fiber 2249 and the output optical fiber 2255 are arranged to be approximately coaxial (as in FIG. 2), there is a small loss of the initial signal (on the order of 20%) in transmission along the signal path due to the air gap 2354. The first end of the output optical fiber 2255 receives a sensor signal. The sensor signal is an optical signal that includes at least a portion of the initial optical signal. Output optical fiber 2255 directs the sensor signal received by the first end of output optical fiber 2255 to the second end of output optical fiber 2255. The second end of output optical fiber 2255 is connected to light sensors 6a, 6b, 6c, which sense the sensor signal.

[0041] FIG. 3 illustrates the optical compression sensor 103 of FIG. 2 in use when a compressive pressure is applied. In use, the compressive pressure may be applied by positioning the compression sensor 103 and substrate 2676 between a compression bandage (or compression garment) and a human leg, as described above with reference to FIG. 1A. The compressive pressure applied to the optical compression sensor 103 is indicated by the arrow labeled F in FIG. 3. In particular, the compressive pressure is oriented perpendicular to the substrate 2676 (or at least includes a component perpendicular to the substrate 2676). The input and output of the compression sensor 103 (i.e., the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255) are positioned such that their relative configuration changes in response to a compressive pressure applied to the compression sensor 103. In general, a change in the relative configuration of the input and output of the compression sensor 103 may include a change in the alignment of the input and output, and / or a change in the relative position of the input and output, and / or a structural deformation of the input or output. The change in the relative position of the input and output can include relative displacement in a direction perpendicular to the substrate 2676 and / or relative movement of the input and output toward and / or away from each other (i.e., parallel to the substrate 2676).

[0042] In Fig. 3, the protruding studs 2606, 2687, 2359 transmit the compressive pressure to the compression sensor 103. In particular, the third stud 2349 advantageously provides a rigid surface on which the compressive pressure can be transmitted to the output optical fiber 2255 and the substrate 2676, and the first stud 2606 and the second stud 2687 advantageously provide rigid surfaces on which compression is realized. The protrusion of the studs 2606, 2687, 2359 from the laminate structure improves the compressive pressure transmission performance of the studs 2606, 2687, 2359. The studs 2606, 2687, 2359 are arranged to transmit the compressive pressure in a non-uniform manner to the input and output of the compression sensor 103 (i.e., the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255) such that the input and output of the compression sensor 103 are affected differently by the compressive pressure. Thus, application of a compressive pressure to the compression sensor 103 changes the relative configuration of the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255. In particular, in FIG. 3, the first end of the output optical fiber 2255 has been displaced (i.e., moved) in a direction perpendicular to the substrate 2676 and is further deformed (i.e., crushed / compressed) by the application of the compressive pressure. Thus, the first optical fiber 2249 and the output optical fiber 2255 are moved out of coaxial alignment by the application of the compressive pressure. At least part of the change in configuration between FIG. 2 and FIG. 3 is due to the use of a flexible output optical fiber 2255 such that the first end of the output optical fiber 2255 is compressed by the compressive pressure. In use, when a compressive pressure is applied to the compression sensor 103, the foam 2374 is compressed. Additionally, the foam 2374 advantageously provides a restoring force and reduces hysteresis.

[0043] 3 shows a change in configuration of the first end of the output optical fiber 2255 in response to a compressive pressure, it will be appreciated that alternative configurations of studs can be used to effect a change in configuration of the second end of the input optical fiber 2249 in response to a compressive pressure. The important element is that the relative configuration of the input and output of the compression sensor 103 (i.e., the relative configuration of the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255) changes in response to the compressive pressure applied to the compression sensor 103.

[0044] The sensitivity of the compression sensor 103 depends on the material properties of the substrate 2676, the input optical fiber 2249, the output optical fiber 2255, and the soft compressible foam 2374. The sensitivity of the compression sensor 103 also depends on the relative positions of the studs 2606, 2687, 2359.

[0045] In use, the input and output of the compression sensor 103 (i.e., the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255) are arranged such that the sensor signal received by the output of the compression sensor 103 (i.e., the first end of the output optical fiber 2255) varies depending on the relative configuration of the input and output of the compression sensor 103 (i.e., the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255) and / or the signal path therebetween.

[0046] 3, the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255 are arranged such that the sensor signal varies depending on the alignment of the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255. The alignment varies depending on the compressive pressure applied to the compression sensor 103. In other words, the changes in the configuration described above include changes in the alignment.

[0047] In response to the squeezing pressure of FIG. 3, the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255 undergo a relative displacement in a direction perpendicular to the substrate 2676. The relative displacement in a direction perpendicular to the substrate 2676 changes the alignment of the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255. In other words, the change in configuration described above includes a relative displacement. Furthermore, in response to the squeezing pressure, the first end of the output optical fiber 2255 undergoes a structural deformation. This structural deformation also changes the relative configuration (and relative alignment) of the input and the output. In other words, the change in configuration described above includes a structural deformation.

[0048] Because the second end of the input optical fiber 2249 and the first end of the output optical fiber 2255 are misaligned (i.e., no longer coaxial and no longer undeformed), the amount of initial optical signal emitted from the second end of the input optical fiber 2249 and incident on the first end of the output optical fiber 2255 is smaller than in the uncompressed state of FIG. 2, where the second end of the input optical fiber and the first end of the output optical fiber are substantially coaxial and undeformed. Thus, in the uncompressed configuration of FIG. 2, a larger sensor signal is sensed by the optical detectors 6a, 6b, 6c compared to the compressed configuration of FIG. 3. Furthermore, the greater the amount of compression, the smaller the sensor signal. Thus, the sensed sensor signal varies with the amount of compression applied to the compression sensor 103. <Optical pressure sensor example 2>

[0049] Figure 4 illustrates an example of an optical compression sensor 203 on a substrate 125. The optical compression sensor 203 illustrated in Figure 4 functions as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 described in Figure 1B above. The substrate 125 forms a portion of the substrate 7 of Figure 1B.

[0050] In FIG. 4, the compression sensor 203 is formed of an input section 203a and an output section 203b. The input section 203a includes an input optical fiber 285, a first rigid spacer 326, and a compressible spacer 375. The first rigid spacer 326 and the compressible spacer 375 are disposed adjacent to each other and sandwiched between the input optical fiber 285 and the substrate 125. The input section 203a of the compression sensor 203 further includes a first portion of an optional upper laminate film 225, which encapsulates the input optical fiber 285 and the spacers 326, 375 together with the first portion of the substrate 125 to form a laminate structure. The output section 203b includes an output optical fiber 430 and a second rigid spacer 327. The second rigid spacer 327 is sandwiched between the output optical fiber 430 and the substrate 125. The output portion 203b of the compression sensor 203 further includes a second portion of the top laminating film 225 that seals the output optical fiber 430 to form a similar laminate structure with the second portion of the substrate 125. There is an air gap 410 between the input optical fiber 285 and the output optical fiber 430. The air gap 410 also extends between the first and second portions of the top laminating film 225 and between the compressible spacer 375 and the second rigid spacer 327. However, the substrate 125 is continuous (no air gaps) and supports both the input portion 203a and the output portion 203b of the compression sensor 203.

[0051] In the compression sensor 203 shown in FIG. 4, the input optical fiber 285 functions as the aforementioned input connector. The input optical fiber 285 has a core and a cladding 256 surrounding the core. The output optical fiber 430 functions as the aforementioned output connector extending between the output of the compression sensor 203 and the light detectors 6a, 6b, 6c. The output optical fiber 430 has a core and a cladding surrounding the core. The input optical fiber 285 has a first end and a second end. The output optical fiber 430 has a first end and a second end. The first end of the input optical fiber 285 is connected to the light sources 4a, 4b, 4c. The second end of the input optical fiber 285 is the input of the compression sensor 203. Thus, the input optical fiber 285 extends between the light sources 4a, 4b, 4c and the input of the compression sensor 203. The first end of the output optical fiber 430 is the output of the compression sensor 203.

[0052] A second end of the output optical fiber 430 is connected to the optical detectors 6a, 6b, 6c. Thus, the output optical fiber 430 extends between the output of the compression sensor 203 and the optical detectors 6a, 6b, 6c.

[0053] 4 shows a schematic of the compression sensor 203 in the absence of applied compressive pressure. In this unstressed configuration, the second end of the input optical fiber 285 and the first end of the output optical fiber 430 are generally coaxial. The signal path between the input and output of the compression sensor 203 is from the second end of the input optical fiber 285 through the air gap 410 to the first end of the output optical fiber 430.

[0054] The second rigid spacer 327 is disposed adjacent to the gap 410. The compressible spacer 375 is disposed adjacent to the gap 410 and opposite the second rigid spacer 327. The first rigid spacer 326 is disposed adjacent to the compressible spacer 375. Thus, the compression sensor 203 includes a compressible member (in the form of the compressible spacer 375) between the substrate 125 and the input of the compression sensor 203 (i.e., between the substrate and the second end of the input optical fiber 285). In an alternative configuration (not shown), the compressible spacer 375 can be included at the output portion 203b rather than the input portion 203a. In this alternative configuration, the compression sensor includes a compressible member (in the form of a compressible spacer) between the substrate 125 and the output portion (i.e., between the substrate and the first end of the output optical fiber 430).

[0055] The compression sensor 203 can be formed by attaching a single optical fiber to a spacer 326, 375, 327 disposed on (or attached to) the substrate 125, and encapsulating the single optical fiber and the spacer 326, 375, 327 between the upper laminate film 225 and the substrate 125. Heat or ultrasound can then be applied to create a laminate structure in which the substrate 125 serves as the lower laminate film. The laminate structure can then be locally cut to form a gap 410 between the input 203a and output 203b portions of the compression sensor 203. No cut is made through the substrate 125, so that the input 203a and output 203b portions are connected by the common substrate 125 (the first and second portions of the substrate 125 are the areas of the common substrate 125 that are located under the input optical fiber 285 and the output optical fiber 430, respectively). The cut can be made using a sharp instrument such as a knife.

[0056] In use, the light sources 4a, 4b, 4c emit initial optical signals. The initial optical signals emitted by the light sources 4a, 4b, 4c enter the input optical fiber 285 at a first end. The input optical fiber 285 guides the initial optical signals from the first end of the input optical fiber 285 to the second end of the input optical fiber 285. The initial optical signals are emitted from the second end of the input optical fiber 285 into the air gap 410. There is a signal path between the second end of the input optical fiber 285 and the first end of the output optical fiber 430. The signal path passes through the air gap 410. Typically, when the input optical fiber 285 and the output optical fiber 430 are arranged to be substantially coaxial, there is a small loss (in the range of 20%) of the initial signal when transmitting through the signal path through the air gap 410. The first end of the output optical fiber 430 receives a sensor signal. The sensor signal is an optical signal that includes at least a portion of the initial optical signal. The output optical fiber 430 guides the sensor signal received by the first end of the output optical fiber 430 to the second end of the output optical fiber 430. A second end of the output optical fiber 430 is connected to the light detectors 6a, 6b, 6c, which detect the sensor signal.

[0057] FIG. 5 shows the optical compression sensor 203 of FIG. 4 when a compression pressure is applied during use.

[0058] In use, a compressive pressure may be applied by disposing the compression sensor 203 and substrate 125 between a compression bandage (or compression garment) and the human leg, as described above with reference to FIG. 1A. As with the previous example of FIG. 3, the compressive pressure is oriented perpendicular to the substrate 125 (or at least includes a component perpendicular to the substrate 125). The input and output of the compression sensor 203 (i.e., the second end of the input optical fiber 285 and the first end of the output optical fiber 430) are positioned such that their relative configuration changes in response to the compressive pressure applied to the compression sensor 203. Preferably, the relative configuration of the input and output changes proportionally (or inversely) to the compressive pressure applied to the compression sensor 203.

[0059] When a compressive pressure (i.e., a pressure having a component perpendicular to the substrate) is applied to the compressive sensor 203, the compressible spacer is compressed. As a result, the second end of the input optical fiber 285 (attached to the compressible spacer 375) is displaced downward toward the substrate. In contrast, the first end of the output optical fiber 430 is not displaced downward by the compressive pressure because it is attached to the second rigid spacer 327 (which is not compressed).

[0060] Although not shown, the second end of the input optical fiber 285 and / or the first end of the output optical fiber 430 can additionally or alternatively be adapted to deform in shape under compression.

[0061] As shown in FIG. 5, the input 285 and output 430 optical fibers are moved out of coaxial alignment by the application of compressive pressure.

[0062] 5 illustrates a change in configuration of the second end of the input optical fiber 285 in response to a compressive pressure, it will be appreciated that alternative configurations of spacers can be utilized to effect a change in configuration of the first end of the output optical fiber 430 in response to a compressive pressure. The key requirement is that the relative configuration of the input and output of the compression sensor 203 (i.e., the relative configuration of the second end of the input optical fiber 285 and the first end of the output optical fiber 430) change in response to a compressive pressure applied to the compression sensor 203.

[0063] Those skilled in the art will appreciate that the first rigid spacer 326 is optional and may be removed. However, the first rigid spacer 326 is effective because it inhibits the displacement of the input optical fiber 285 in the region of the input optical fiber 285 located above the first rigid spacer 326. As a result, when a compressive pressure is applied to the compression sensor 203, the second end of the input optical fiber 285 (attached to the compressible spacer 375) is displaced in a direction perpendicular to the substrate 125 more than it would be if the first rigid spacer 326 were not present. Thus, the first rigid spacer 326 increases the sensitivity of the compression sensor 203.

[0064] Those skilled in the art will appreciate that the second rigid spacer 327 can be replaced with a second compressible spacer having different material properties and compressibility different from that of the compressible spacer 375 to produce the aforementioned changes in the relative configuration of the inputs and outputs. However, the second rigid spacer 327 is preferably stiff to increase the sensitivity of the compression sensor 203. The sensitivity of the compression sensor 203 depends on the material properties of the compressible spacer 375. <Optical pressure sensor example 3>

[0065] Figure 6 illustrates an example of an optical compression sensor 303 on a substrate 3777. The optical compression sensor 303 illustrated in Figure 6 may function as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 described in Figure 1B above. The substrate 3777 forms a portion of the substrate 7 of Figure 1B.

[0066] In FIG. 6, the compression sensor 303 is formed of an input section 303a and an output section 303b. The input section 303a includes an input optical fiber 3439, a first rigid layer 3450, and a flexible layer 3543. The first rigid layer 3450 is sandwiched between the input optical fiber 3439 and the flexible layer 3543. The flexible layer 3543 is sandwiched between the first rigid layer 3450 and a first portion of the substrate 3777. The input section 303a of the compression sensor 303 further includes a first portion of an optional upper laminate film 3230, which seals the input optical fiber 3439, the first rigid layer 3450, and the flexible layer 3543 together with the first portion of the substrate 3777 to form a laminate structure. The output section 303b includes an output optical fiber 3449, a compressible layer 3850, and a second rigid layer 3620. The compressible layer 3850 is sandwiched between the output optical fiber 3449 and the second rigid layer 3620. The second rigid layer 3620 is sandwiched between the compressible layer 3850 and a second portion of the substrate 3777. The output section 303b of the compression sensor 303 further includes a second portion of the upper laminate film 3250, which, together with the second portion of the substrate 3777, is sealed to form a laminate structure similar to that of the input section 303a. There is an air gap 3111 between the input optical fiber 3439 and the output optical fiber 3449. Air gaps 3111 also extend between the first and second portions 3230, 3250 of the top laminate film, between the compressible layer 3850 and the first rigid layer 3450, and between the flexible layer 3543 and the second rigid layer 3620. However, the substrate 3777 is continuous (without air gaps) and supports both the input portion 303a and the output portion 303b of the compression sensor 303.

[0067] In the compression sensor 303 shown in FIG. 6, the input optical fiber 3439 functions as the input connector described above. The input optical fiber 3439 has a core and a cladding 3434 surrounding the core. The output optical fiber 3449 functions as the aforementioned output connector extending between the output of the compression sensor 303 and the light detectors 6a, 6b, 6c. The output optical fiber 3449 has a core and a cladding surrounding the core. The input optical fiber 3439 has a first end and a second end. The output optical fiber 3449 has a first end and a second end. The first end of the input optical fiber 3439 is connected to the light sources 4a, 4b, 4c. The second end of the input optical fiber 3439 is the input of the compression sensor 303. Thus, the input optical fiber 3439 extends between the light sources 4a, 4b, 4c and the input of the compression sensor 303. The first end of the output optical fiber 3449 is the output of the compression sensor 303. A second end of the output optical fiber 3449 is connected to the optical detectors 6a, 6b, 6c. Thus, the output optical fiber 3449 extends between the output of the compression sensor 303 and the optical detectors 6a, 6b, 6c.

[0068] 6 shows a schematic of the compression sensor 303 in the absence of applied compression pressure. In this unstressed configuration, the second end of the input optical fiber 3439 and the first end of the output optical fiber 3449 are substantially coaxial. The signal path between the input and output of the compression sensor 303 is from the second end of the input optical fiber 3439 through the air gap 3111 to the first end of the output optical fiber 3449.

[0069] As described above, the compression sensor 303 includes a compressible layer 3850 sandwiched between the output optical fiber 3449 and the second rigid layer 3620 (which is attached to and disposed above the substrate 3777). Thus, the compression sensor 303 includes a compressible member (in the form of the compressible layer 3850) between the substrate 3777 (and, indirectly, the second rigid layer 3620) and the output of the compression sensor 303 (i.e., the first end of the output optical fiber 3449). In an alternative configuration (not shown), the compressible layer 3850 can be included in the input portion 303a rather than the output portion 303b. In this alternative configuration, the compression sensor 303 includes a compressible member (in the form of the compressible layer) between the substrate 3777 and the input portion (i.e., the second end of the input optical fiber 3449).

[0070] The compression sensor 303 can be formed by attaching a single optical fiber to the first rigid layer 3450 and the compressible layer 3850. The first rigid layer 3450 and the compressible layer 3850 are then placed (or attached) on the flexible layer 3543 and the second rigid layer 3620 such that a) the first rigid layer 3450 is sandwiched between the input optical fiber 3439 and the flexible layer 3543, and b) the compressible layer 3850 is sandwiched between the output optical fiber 3449 and the second rigid layer 3620. The flexible layer 3543 and the second rigid layer 3620 are then attached (or placed on) the substrate 3777. The optical fiber 3439, 3449 and the compressible layer 3850, the flexible layer 3543 and the rigid layers 3450, 3620 are encapsulated between the top lamination film 3230, 3250 and the substrate 3777. Heat or ultrasound can then be applied to create a laminate structure in which the substrate 3777 acts as the lower laminate film. The laminate structure can then be locally cut to form an air gap 3111 between the input 303a and output 303b portions of the compression sensor 303. No cut is made through the substrate 3777, so that the input 303a and output 303b portions are connected by the common substrate 3777 (the first and second portions of the substrate 3777 are areas of the common substrate 3777 that underlie the input and output optical fibers 3439 and 3449, respectively). The cut can be made using a sharp instrument such as a knife.

[0071] In use, the light sources 4a, 4b, 4c emit an initial optical signal. The initial optical signal emitted by the light sources 4a, 4b, 4c enters the input optical fiber 3439 at a first end. The input optical fiber 3439 guides the initial optical signal from the first end of the input optical fiber 3439 to the second end of the input optical fiber 3439. The initial optical signal is emitted from the second end of the input optical fiber 3439 into the air gap 3111. There is a signal path between the second end of the input optical fiber 3439 and the first end of the output optical fiber 3449. The signal path passes through the air gap 3111. Typically, when the input optical fiber 3439 and the output optical fiber 3449 are arranged to be substantially coaxial, there is a small loss (in the range of 20%) of the initial signal when transmitting through the signal path due to the air gap 3111. The first end of the output optical fiber 3449 receives the sensor signal. The sensor signal is an optical signal that includes at least a portion of the initial optical signal. The output optical fiber 3449 directs the sensor signal received by the first end of the output optical fiber 3449 to a second end of the output optical fiber 3449. The second end of the output optical fiber 3449 is connected to the light sensors 6a, 6b, 6c. The light sensors 6a, 6b, 6c sense the sensor signal.

[0072] FIG. 7 shows the optical compression sensor 303 of FIG. 6 when a compression pressure is applied during use.

[0073] In use, a compressive pressure can be applied by disposing the compression sensor 303 and substrate 3777 between a compression bandage (or compression garment) and the human leg, as described above with reference to FIG. 1A. The compressive pressure of the compression sensor 303 is illustrated by the arrow labeled F in FIG. 7. As with the previous examples of FIG. 5 and FIG. 3, the compressive pressure is in a direction perpendicular to the substrate 3777 (or at least includes a component in a direction perpendicular to the substrate 3777). The input and output of the compression sensor 303 (i.e., the second end of the input optical fiber 3449 and the first end of the output optical fiber 3439) are arranged such that their relative configuration changes in response to the compressive pressure applied to the compression sensor 303. Preferably, the relative configuration of the input and output changes proportionally (or inversely) to the compressive pressure applied to the compression sensor 303.

[0074] When a compressive pressure (i.e., a pressure that has a component perpendicular to the substrate) is applied to the compression sensor 303, the compressible layer 3850 is compressed. As a result, the first end of the output optical fiber 3449 (attached to the compressible layer 3850) is displaced downward toward the substrate. In contrast, the second end of the input optical fiber 3439 is not displaced downward under the compressive pressure because the first end of the output optical fiber 3439 is attached to the first rigid layer 3450 (which does not compress).

[0075] Although not shown, the second end of the input optical fiber 3439 and / or the first end of the output optical fiber 3449 may additionally or alternatively deform in shape under compression.

[0076] As shown in FIG. 7, the input 3439 and output 3449 optical fibers are moved out of coaxial alignment by the application of compressive pressure.

[0077] 7 illustrates a change in configuration of the first end of the output optical fiber 3449 in response to a compressive pressure, it will be appreciated that alternative configurations of the compressible layer 3850, stiff layers 3450, 3620 and flexible layer 3543 can instead be used to cause a change in configuration of the second end of the input optical fiber 3439 in response to a compressive pressure. The important element is that the relative configuration of the input and output of the compression sensor 303 (i.e., the relative configuration of the second end of the input optical fiber 3439 and the first end of the output optical fiber 3449) changes in response to a compressive pressure applied to the compression sensor 303.

[0078] The sensitivity of the compression sensor 303 depends on the material properties of the compressible layer 3850 . One skilled in the art will appreciate that the first rigid layer 3450 can be replaced with a second compressible layer having different material properties, different compressibility than the compressible layer 3850, or removed entirely. However, the first rigid layer 3450 is advantageous because it inhibits the displacement of the input optical fiber 3439. As a result, when a compressive pressure is applied to the compression sensor 303, the displacement of the first end of the output optical fiber 3449 relative to the second end of the input optical fiber 3439 is greater than if the first rigid layer 3450 were not present or rigid. Thus, the first rigid layer 3450 increases the sensitivity of the compression sensor 303.

[0079] Those skilled in the art will appreciate that the second rigid layer 3620 is optional, but aids in achieving compression of the compressible layer 3850 by forming a rigid surface against which the compressible layer 3850 can be compressed, thus increasing the sensitivity of the compression sensor 303.

[0080] Moreover, one skilled in the art will appreciate that the flexible layer 3543 is optional. The flexible layer advantageously acts as a compensation layer to level the compression sensor 303 such that in the unstressed state, the input optical fiber 3439 and the output optical fiber 3449 are substantially coaxial. In an alternative example (not shown), the combined first rigid layer 3450 and flexible layer 3543 can be replaced with a thicker first rigid layer 3450. <Optical pressure sensor example 4>

[0081] Figure 8 illustrates an example of an optical compression sensor 403. The optical compression sensor 403 illustrated in Figure 8 may function as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 described in Figure 1B above.

[0082] In FIG. 8, the compression sensor 403 is composed of an input optical fiber 120 and an output optical fiber 210. The compression sensor 403 further comprises guide members in the form of a first microtube 135, a second microtube 140 and a third microtube 150. The input optical fiber 120 has a first end and a second end. The output optical fiber 210 has a first end and a second end. The input optical fiber 120 passes through the first microtube 135 and the second microtube 140 into the third microtube 150, and the second end of the input optical fiber 120 is enclosed within the third microtube 150. The first end of the output optical fiber 210 is also enclosed within the third microtube 150 such that the second end of the input optical fiber 120 and the first end of the output optical fiber 210 and the signal path therebetween are located within the third microtube 150. There is an air gap between the second end of the input optical fiber 120 and the first end of the output optical fiber 210. The signal path passes through the gap. The compression sensor 403 further comprises a first spacer 180 and a second spacer 195.

[0083] A first spacer 180 connects the first microtube 135 to the substrate 110. A second spacer 195 connects the third microtube 150 to the substrate 110. A second microtube 140 floats above the substrate 110 and is not connected to the substrate 110.

[0084] In the compression sensor 403 shown in FIG. 8, the input optical fiber 120 functions as the input connector described above. The input optical fiber 120 has a core and a cladding (not shown) surrounding the core. The output optical fiber 210 functions as the aforementioned output connector extending between the output of the compression sensor 403 and the light detectors 6a, 6b, 6c. The output optical fiber 210 has a core and a cladding (not shown) surrounding the core. A first end of the input optical fiber 120 is connected to the light sources 4a, 4b, 4c. A second end of the input optical fiber 120 is the input of the compression sensor 403. Thus, the input optical fiber 120 extends between the light sources 4a, 4b, 4c and the input of the compression sensor 403. A first end of the output optical fiber 210 is the output of the compression sensor 403. A second end of the output optical fiber 210 is connected to the light detectors 6a, 6b, 6c. Thus, the output optical fiber 210 extends between the output of the compression sensor 403 and the optical detectors 6a, 6b, 6c.

[0085] 8 shows a schematic of the compression sensor 403 in the absence of applied compression pressure. In this unstressed configuration, the second end of the input optical fiber 120 and the first end of the output optical fiber 210 are substantially coaxial and separated by an initial distance in the form of an air gap. The signal path between the input and output of the compression sensor 403 is from the second end of the input optical fiber 120, through the air gap, to the first end of the output optical fiber 210.

[0086] The microtubes 135 , 140 , 150 preferably have an inner diameter that is just slightly larger than the outer diameter of the input and output optical fibers 120 , 210 to constrain movement of the input and output optical fibers 120 , 210 to be coaxial within the microtubes 135 , 140 , 150 .

[0087] The microtubes 135, 140, 150 may be made of metal, plastic, ceramic, or other suitable materials. Preferably, the second microtube 140 has a length of up to 2 cm, and the first microtube 135 and the third microtube 150 have a length of up to 5 cm.

[0088] The first spacer 180 and the second spacer 195 are preferably 1 mm thick or less to make the compression sensor compact, and therefore comfortable for the wearer.

[0089] A first end of the output optical fiber 210 is preferably fixed in place adjacent one end of the third microtube 150 such that it cannot move relative to the third microtube 150. A second end of the input optical fiber 120 is unfixed and is therefore free to move coaxially within the third microtube 150.

[0090] In use, the light sources 4a, 4b, 4c emit initial optical signals. The initial optical signals emitted by the light sources 4a, 4b, 4c enter the input optical fiber 120 at a first end. The input optical fiber 120 guides the initial optical signals from the first end of the input optical fiber 120 to the second end of the input optical fiber 120. The initial optical signals are emitted from the second end of the input optical fiber 120 into the air gap. There is a signal path between the second end of the input optical fiber 120 and the first end of the output optical fiber 210. The signal path passes through the air gap. Typically, when the compression sensor 403 is in the uncompressed state of FIG. 8, there is a small loss (in the range of 20%) of the initial signal in transmission along the signal path due to the initial distance in the air gap. The first end of the output optical fiber 210 receives a sensor signal. The sensor signal is an optical signal that includes at least a portion of the initial optical signal. The output optical fiber 210 guides the sensor signal received by the first end of the output optical fiber 210 to the second end of the output optical fiber 210. A second end of the output optical fiber 210 is connected to the light detectors 6a, 6b, 6c, which detect the sensor signal.

[0091] FIG. 9 shows the optical compression sensor 403 of FIG. 8 when a compression pressure is applied during use. In use, a compressive pressure is applied by positioning the compression sensor 403 and substrate 110 between a compression bandage (or compression garment) and the human leg, as described above with reference to FIG. 1A. As with the previous examples of FIGS. 7, 5, and 3, the compressive pressure is in a direction perpendicular to the substrate 110 (or at least includes a component in a direction perpendicular to the substrate 110). The input and output of the compression sensor 403 (i.e., the second end of the input optical fiber 120 and the first end of the output optical fiber 210) are positioned such that their relative configuration changes in response to the compressive pressure applied to the compression sensor 403. Preferably, the relative configuration of the input and output changes the compressive pressure applied to the compression sensor 403.

[0092] When a compressive pressure (i.e., a pressure having a component perpendicular to the substrate) is applied to the compression sensor 403, the second microtube 140 is displaced downwards towards the substrate 110. As a result, the portion of the input optical fiber 120 threaded through the second microtube 140 is displaced (along with the second microtube 140) towards the substrate 110. Because the input optical fiber 120 is inelastic, the downward displacement of the portion of the input optical fiber 120 threaded through the second microtube 140 partially pulls the input optical fiber 120 out of the third microtube 150. In particular, the second end of the input optical fiber 120 is displaced axially along the third microtube 150 from the fixed first end of the output optical fiber 210. The axial displacement (which is in a direction parallel to the substrate 110) changes the relative configuration of the second end of the input optical fiber 120 and the first end of the output optical fiber 210 (i.e., changes the relative configuration of the input and output of the compression sensor 403). In other words, the change in configuration described above involves a displacement of the input and output of the compression sensor in a direction parallel to the substrate 110.

[0093] For example, if the second end of the input optical fiber 120 is displaced axially away from the first end of the output optical fiber 210, the gap, and signal path, between the second end of the input optical fiber 120 and the first end of the output optical fiber 210 increases from a first distance in Figure 8 to a second distance, as shown in Figure 9. As a result, the amount of initial optical signal emitted from the second end of the input optical fiber 120 and incident on the first end of the output optical fiber 210 is lower than in the unstressed state of Figure 8, where the second end of the input optical fiber 120 and the first end of the output optical fiber 210 are located closer together.

[0094] Preferably, the sensor signal varies inversely proportional to the compression pressure.

[0095] As described above, the first end of the output optical fiber 210 is fixed in place so that it is not displaced by the compressive pressure. However, one skilled in the art will appreciate that instead of fixing the first end of the output optical fiber 210, the second end of the input optical fiber 120 can be fixed in place. In this alternative, the first end of the output optical fiber 210 is free to move axially. The important factor is that the relative configuration of the input and output of the compression sensor 403 (i.e., the relative configuration of the second end of the input optical fiber 120 and the first end of the output optical fiber 210) changes in response to the compressive pressure applied to the compression sensor 403.

[0096] Those skilled in the art will appreciate that the spacers 180, 195 are optional, but are beneficial because they increase the range of possible displacement of the second microtube 140, and therefore the sensitivity of the compression sensor 403. Those skilled in the art will similarly appreciate that the first microtube 135 and the second microtube 140 are optional. <Example of a capacitance type compression sensor>

[0097] Figure 10 illustrates an example of a capacitive compression sensor on a substrate 110. The capacitive compression sensor illustrated in Figure 10 may function as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 described in Figure 1B above. The substrate 110 forms a portion of the substrate 7 of Figure 1B.

[0098] The capacitive compression sensor shown in FIG. 10 is an example of an electrical compression sensor. In an electrical compression sensor such as the capacitive compression sensor shown in FIG. 10, the signal emitter is an electrical signal emitter / generator such as a coil, and the signal detector is an electrical signal detector such as a coil or a MEMS sensor. The signal emitter may be any of the signal emitters 4a, 4b, and 4c, and will be referred to hereinafter as "electrical signal generators 4a, 4b, and 4c." The signal detector may be any of the signal detectors 6a, 6b, and 6c, and will be referred to hereinafter as "electrical signal detectors 6a, 6b, and 6c." In the case of the capacitive compression sensor shown in FIG. 10, the electrical signal generator is an AC electrical signal generator, and the electrical signal detector is an AC electrical signal detector.

[0099] The structural arrangement of the compression sensor shown in FIG. 10 is similar to that of the optical compression sensor shown in FIG. 8 in terms of the substrate 110 and the microtubes 135, 140, 150. Similarly, the spacers 580, 595 of FIG. 10 are equivalent to the spacers 180, 195 of FIG. 8. However, FIG. 10 differs from FIG. 8 in that the input conductive line 520 replaces the input optical fiber 120 of FIG. 8 and the output conductive line 200 replaces the output optical fiber 210 of FIG. 8. The compression sensor of FIG. 10 further includes a variable capacitor formed between the first plate 167 at the second end of the input conductive line 520 and the second plate 175 at the first end of the output conductive line 200. The signal path passes between the capacitor plates 167, 175. The capacitance can be made variable by changing the distance between the capacitor plates 167, 175.

[0100] In the compression sensor shown in FIG. 10, the input conductive wire 520 functions as the aforementioned input connector extending between the electrical signal generator 4a, 4b, 4c and the input of the compression sensor. More specifically, a first end of the input conductive wire 520 is connected to the electrical signal generator 4a, 4b, 4c, and a second end of the input conductive wire is connected to the first capacitor plate 167. The input of the compression sensor is the first capacitor plate 167. The output conductive wire 200 functions as the aforementioned output connector extending between the output of the compression sensor and the electrical signal detector 6a, 6b, 6c. More specifically, a first end of the output conductive wire 200 is connected to the second capacitor plate 175, and a second end of the output conductive wire is connected to the electrical signal detector 6a, 6b, 6c. The output of the compression sensor is the second capacitor plate 175.

[0101] 10 shows a schematic of the compression sensor with no applied compression pressure. In this uncompressed configuration, the signal path between the input and output of the compression sensor is from the first capacitor plate 167 through the air gap 280 to the second capacitor plate 175. The air gap 280 therefore corresponds to the distance between the plates 167, 175 of the variable capacitor.

[0102] The second capacitor plate 175 is preferably fixed in place such that it cannot move relative to the third microtube 150. The first capacitor plate 167 is unfixed and is free to move within the third microtube 150 in an axial direction that is a direction parallel to the substrate 110.

[0103] In an alternative embodiment, rather than a simple two plate 167, 175 device with an air gap 280, the variable capacitor can be a more advanced MEMS type capacitor. That is, the capacitor plates can be thin film MEMS type micromachined capacitor plates. The capacitor plates can be comprised of interleaved projections (e.g., interdigitated fingers). In this case, the capacitance varies depending on the degree of interleaving of the projections (e.g., finger interdigitation). In this interleaving example, the capacitor plates can be arranged in a common plane. In particular, the capacitor plates can have interdigitated fingers arranged to lie in a common plane. Such an interdigitated finger arrangement can help keep the compression sensor thin and out of the way of the wearer of the sensing device.

[0104] In use, the electrical signal generators 4a, 4b, 4c apply a voltage between the plates 167, 175 of the variable capacitor, and the electrical signal detectors 6a, 6b, 6c sense the capacitance between the plates 167, 175. The voltage can be considered as the output electrical signal, and the capacitance can be considered as the sensed electrical signal. The capacitance of the variable capacitor varies with the distance between the plates 167, 175. In the uncompressed state of FIG. 10, it is assumed that there is a first distance between the plates 167, 175.

[0105] FIG. 11 shows the application of a compression pressure when using the capacitive compression sensor of FIG. In use, a compressive pressure is applied by placing a compression sensor and substrate 110 between a compression bandage (or garment) and the human leg, as described above with reference to Figure 1A. As with the previous examples of Figures 9, 7, 5 and 3, the compressive pressure is in a direction perpendicular to the substrate 110 (or at least includes a component in a direction perpendicular to the substrate 110). The input and output of the compression sensor (i.e., plates 167, 175 of the variable capacitor) are positioned such that their relative configuration changes in response to the compressive pressure applied to the compression sensor. Preferably, the distance 280 between the plates 167, 175 changes in proportion to the compressive pressure applied to the compression sensor.

[0106] Similar to the optical example of FIG. 9, when a compressive pressure is applied to the compressive sensor of FIG. 11, the second microtube 140 is displaced downwards towards the substrate 110. As a result, the input conductive line 520 is partially pulled out of the third microtube 150 such that the first capacitor plate 167 is further away from the second capacitor plate 175 (i.e., the first capacitor plate 167 is displaced axially (relative to the third microtube 150) in a direction parallel to the substrate 110). In other words, the distance 280 between the plates 167, 175 increases. The displacement of the first capacitor plate 167 changes the relative configuration of the inputs and outputs of the variable capacitor. In other words, the change in the configuration includes a displacement in a direction parallel to the substrate 110. The change in the configuration of the inputs and outputs of the variable capacitor results in a change in capacitance. The sensor signal received by the electrical signal detectors 6a, 6b, 6c changes according to the capacitance of the variable capacitor.

[0107] As discussed above, the first ends of the output conductive wires 200 are fixed in place so that they are not displaced by the compressive pressure. However, one skilled in the art will appreciate that instead of fixing the first ends of the output conductive wires 200, the second ends of the input connecting wires 520 can be fixed in place. In this alternative, the first ends of the output conductive wires 200 are free to move axially. The important factor is that the relative configuration of the input and output of the compression sensor (i.e., the relative configuration of the capacitor plates 167, 175) changes in response to the compressive pressure applied to the compression sensor.

[0108] Those skilled in the art will appreciate that spacers 580, 595 are optional, but may be advantageously included since they increase the possible range of displacement of second microtube 140, and therefore the sensitivity of compression sensor 403. Those skilled in the art will similarly appreciate that first microtube 135 and second microtube 140 are optional. <Example of a resistive compression sensor>

[0109] An example of a resistive compression sensor is shown in Figure 12. The resistive compression sensor shown in Figure 12 can function as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 described in Figure 1B above.

[0110] 10 and 11, except that the variable capacitor is replaced by a variable resistor 157 connected between the second end of the input conductive line 520 and the first end of the output conductive line 200. The resistance of the variable resistor 157 varies depending on the distance between the input and output of the variable resistor (i.e., the distance between the second end of the input conductive line 520 and the first end of the output conductive line 200).

[0111] Variable resistor 157 is a displacement sensitive resistor such as a strain gauge, a conductive polymer, a piezo-resistive element, or the like.

[0112] Those skilled in the art will appreciate that the variable resistor example of Figure 12 can be easily modified to incorporate magnetic field sensors. In such an example, the electrical signal generators 4a, 4b, 4c can be replaced with magnetic field emitters, the signal detectors 6a, 6b, 6c can be replaced with magnetic field detectors (which may be, for example, Hall effect or Lorentz effect sensors, MEMS sensors), and the variable resistors can be replaced with magnets. <Optical pressure sensor example 5>

[0113] FIG. 13 illustrates an optical compression sensor 465 similar to that described with respect to FIGS. 8 and 9. Like the examples illustrated in FIGS. 8 and 9, the example of FIG. 13 includes a substrate 400, an input optical fiber 425, and an output optical fiber 450. The input optical fiber 425 extends between a light source 495 and an input of the compression sensor 465. The output optical fiber 450 extends between an output of the compression sensor 465 and a light detector 510. The example illustrated in FIG. 13 differs from the examples illustrated in FIGS. 8 and 9 because the input optical fiber 425 and the output optical fiber 450 are not coaxial. Instead, the input optical fiber 425 and the output optical fiber 450 are parallel and adjacent to one another. A second end of the input optical fiber 425 is adjacent to a first end of the output optical fiber 450.

[0114] Figure 14 shows a cross-section of the optical compression sensor 465 of Figure 13 in a plane perpendicular to the substrate. The structural arrangement of the compression sensor 465 is similar to that of the optical compression sensor shown in Figure 8 in terms of the substrate 400 and the microtubes 135, 140, 150. Similarly, the spacers 180, 195 of Figure 14 are equivalent to the spacers 180, 195 of Figure 8. Additionally, similar to Figure 8, the input of the compression sensor 465 is the second end of the input optical fiber 425 and the output of the compression sensor 465 is the first end of the output optical fiber 450.

[0115] In FIG. 14 , the input optical fiber 425 extends through the first microtube 135 and into the third microtube 150. The input optical fiber 425 does not extend through the second microtube 140. Instead, the input optical fiber 425 extends parallel to and adjacent to the second microtube 140 (shown by a dashed line). Meanwhile, the output optical fiber 450 extends through all three microtubes 135, 140, 150. Neither the second end of the input optical fiber 425 nor the first end of the output optical fiber 450 is fixed to a position within the third microtube 150. Instead, both the second end of the input optical fiber 425 and the first end of the output optical fiber 450 are free to move axially (i.e., in a direction parallel to the substrate 400) within the third microtube 150.

[0116] 14 further comprises a signal reflector 185 (i.e., an optical reflector) disposed in the signal path between the second end of the input optical fiber 425 (i.e., the input of the compression sensor 465) and the first end of the output optical fiber 450 (i.e., the output of the compression sensor 465). Thus, the signal path includes: (a) an air gap between the second end of the input optical fiber 425 and the signal reflector; (b) the signal reflector 185 itself; and (c) The air gap between the signal reflector and the first end of the output optical fiber 450. The signal reflector 185 is a mirror, such as a micromirror. Both the second end of the input optical fiber 425 and the first end of the output optical fiber 450 are a short initial distance away from the mirror 185 in the unstressed state of FIG.

[0117] In use, the light source emits an initial optical signal 495. The initial optical signal emitted by the light source 495 enters the input optical fiber 425 at a first end. The input optical fiber 425 guides the initial optical signal from the first end of the input optical fiber 425 to a second end of the input optical fiber 425. The initial optical signal is emitted from the second end of the input optical fiber 425 towards the air gap. There is a signal path between the second end of the input optical fiber 425 and a first end of the output optical fiber 450. The signal path passes through the air gap and involves reflection from the mirror 185. The first end of the output optical fiber 450 receives a sensor signal. The sensor signal is an optical signal that includes at least a portion of the initial optical signal. The output optical fiber 450 guides the sensor signal received by the first end of the output optical fiber 450 to a second end of the output optical fiber 450. The second end of the output optical fiber 450 is connected to a light sensor. The light sensor detects the sensor signal.

[0118] Figure 15 illustrates the application of a compressive pressure in use of the optical compression sensor 465 of Figure 14. In use, a compressive pressure is applied by placing the compression sensor 465 and substrate 400 between a compression bandage (or compression garment) and a person's leg, as described above with reference to Figure 1A.

[0119] 11, 9, 7, 5 and 3, the compressive pressure is in a direction perpendicular to the substrate 400 (or at least includes a component in a direction perpendicular to the substrate 400). The input and output of the compression sensor 465 (i.e., the second end of the input optical fiber 425 and the first end of the output optical fiber 450) are positioned such that their relative positions change in response to the compressive pressure applied to the compression sensor 465.

[0120] When a compressive pressure is applied to the compression sensor 465, the second microtube 140 is displaced downwards towards the substrate 400. As a result, the portion of the output optical fiber 450 that extends through the second microtube 140 is displaced (along with the second microtube 140) towards the substrate 400. Because the output optical fiber 450 is inelastic, the downward displacement of the portion of the output optical fiber 450 that extends through the second microtube 140 partially pulls the output optical fiber 450 out of the third microtube 150. In particular, the first end of the output optical fiber 450 is displaced axially along the third microtube 150 away from the fixed mirror 185. The axial displacement (which is in a direction parallel to the substrate 400) changes the relative configuration of the second end of the input optical fiber 425 and the first end of the output optical fiber 450, and the signal path therebetween. In particular, the length of the signal path between the second end of the input optical fiber 425 and the first end of the output optical fiber 450 increases due to the increased distance between the first end of the output optical fiber 450 and the mirror 185). In other words, the change in configuration described above includes a displacement of the output of the compression sensor 465 in a direction parallel to the substrate 400. The axial displacement (which is in a direction parallel to the substrate 400) also changes the relative configuration of the first end of the output optical fiber 450 and the mirror 185. Thus, the second end of the input optical fiber 425 and the first end of the output optical fiber 450 are configured such that, in response to a compression pressure, at least one of the second end of the input optical fiber 425 and the first end of the output optical fiber 450 undergoes a relative displacement with respect to the signal reflector 185 to change the signal path. Due to the change in the length of the signal path, the amount of the initial optical signal emitted from the second end of the input optical fiber 425 and incident on the first end of the output optical fiber 450 is lower under compression (as in FIG. 15) than in the non-compressed state of FIG. 14.

[0121] Of note, the input optical fiber 425 (not extending through the second microtube 140) may also be somewhat affected by the squeeze pressure. In particular, the input optical fiber 425 may also be displaced downward toward the substrate 400 such that the second end of the input optical fiber 425 is pulled further away from the mirror 185, thereby further increasing the signal path. However, the downward displacement of the output optical fiber 450 is enhanced by the presence of the microtube 140, so that the downward displacement of the input optical fiber 425 is less than the downward displacement of the output optical fiber 450. In an alternative arrangement, both optical fibers 425, 450 may extend through the second microtube 140, making the squeeze sensor 465 more sensitive. Those skilled in the art will appreciate that instead of the output optical fiber 450 extending through the second microtube 140, the input optical fiber 425 may also extend through the second microtube 140. In yet another option, the end of the optical fiber that does not extend through the second microtube 140 can be fixed in place in the third microtube 150 relative to the mirror 185 . <Optical pressure sensor example 6>

[0122] FIG 16 illustrates an example of an optical compression sensor. The optical compression sensor 103 illustrated in FIG 16 is not directly suitable to function as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 described above in FIG 1B because there is no input connector connecting a light source to the input of the compression sensor and there is no output connector connecting the output of the compression sensor to a light sensor. Instead, in the compression sensor illustrated in FIG 16, the input of the compression sensor is a light source 616 and the output of the compression sensor is a light sensor 625. Thus, the light source 616 and the light sensor 625 are coupled to the substrate 690 in FIG 16, rather than being disposed outside the substrate as illustrated in FIG 1B.

[0123] Light source 616 is not directly attached to substrate 690, and light sensor 625 is not directly attached to substrate 690. Instead, one end of light source 616 is separated from substrate 690 by a first rigid spacer 675, and one end of light sensor 625 is separated from substrate 690 by a compressible spacer 630. The other ends of light source 616 and light sensor 630 are arranged to overlap.

[0124] The compression sensor includes a compressible member (i.e., in the form of a compressible spacer 630) between the substrate 690 and the light detector 625. In an alternative configuration, the compressible spacer 630 and the rigid spacer 675 can be interchanged such that the compression sensor includes a compressible member between the substrate 690 and the light source 616.

[0125] The sensing device further includes an input contact 645 and an output contact 660. The contacts 645, 660 connect the optical compression sensor to an electronic control and power supply. Preferably, the contacts 645, 660 are conductive wires.

[0126] In use, the light source 616 emits an initial light signal. A portion of the initial light signal emitted by the light source 616 is directly sensed as a sensor signal by the light detector 625. Thus, a signal path exists between the light source 616 and the light detector 625.

[0127] The light source 616 and the light detector 625 are positioned such that the sensor signal received by the light detector 625 varies depending on the relative positioning of the light source 616 and the light detector 625. In particular, the sensor signal varies depending on the degree of overlap between the light source 616 and the light detector 630. The light source 616 and the light detector 625 are positioned such that their relative positioning (i.e., their overlap) varies depending on the compressive pressure applied to the compression sensor.

[0128] When no compressive pressure is applied to the compression sensor (ie, as shown in FIG. 16), the light source 616 and the light detector 625 and the signal path therebetween are arranged in an initial, uncompressed configuration.

[0129] 17 shows the compression sensor when a compressive pressure (i.e., a pressure that has a component perpendicular to the substrate) is applied. The compressive pressure compresses the compressible spacer 630 in a direction perpendicular to the substrate. As a result, the signal detector 625 is displaced relative to the signal emitter 675.

[0130] The light source 616 and the light sensor 625 may additionally or alternatively change shape in response to the compressive pressure.

[0131] The aforementioned displacement or deformation changes the relative configuration of the light source 616 and the light sensor 625. In particular, the degree of overlap between the light source 616 and the light sensor 625 changes. The greater the overlap, the greater the sensor signal received by the light sensor 625. The smaller the overlap, the smaller the sensor signal received by the light sensor 625.

[0132] The sensitivity of the compression sensor depends on the material properties of the compressible spacer 630 .

[0133] One skilled in the art will appreciate that rigid spacer 675 can be replaced with a second compressible spacer having different material properties and different compressibility than compressible spacer 630. However, rigid spacer 675 is preferably rigid to increase the sensitivity of the compression sensor.

[0134] Those skilled in the art will appreciate that the arrangement shown in Figure 1B can be adapted such that the compression sensor shown in Figures 16 and 17 is suitable to function as at least one of the first compression sensor 35, the second compression sensor 50, and the third compression sensor 95 of Figure 1B. For example, the input connector can be replaced with the first contact 645 and the output connector can be replaced with the second contact 660. Additionally, as illustrated in Figure 16, the signal emitter and signal detector of Figure 1B can be moved to form part of the compression sensor. <Power and Control Devices>

[0135] FIG. 18 illustrates a schematic of an electronic control and power unit 1520 that can be used with any of the embodiments of the sensing device described above. The electronic control and power unit 1520 can be comprised of signal amplifiers, analog-to-digital converters, microcontrollers or other processors, memory, data loggers, wireless transmission systems (e.g., Bluetooth™), discrete or integrated electronic components, FPGAs, DSPs, ASICs, and the like. The microcontroller or other processor can be configured to determine an estimate of the pressure applied to the sensing device based on the sensor signal. The electronic control and power unit may include a digital display 1530 configured to display an instantaneous reading of the estimate of the pressure applied to the sensing device. The electronic control and power unit 1520 can also include an audio indicator 1500 to sound an alarm if the estimate of the pressure applied to the sensing device is outside of a target range, for example, if a pressure bandage (or garment) is applied too tightly or too loosely to the wearer. The entire electronic control and power unit 1520 can be contained within a housing.

[0136] The measurements determined by the sensing device can be captured at intervals and stored in a data logger before being processed by a microprocessor. Measurements can be taken as frequently as desired, for example, every minute, hour, etc., and recorded in the data logger. Data from the data logger or microprocessor is transmitted by a transmission system to a remote device or server. This can be a smartphone, laptop, pager, or other device. The remote device can keep a record of an estimate of the pressure applied to the sensing device that can be used for clinical evaluation. This data record can be used by clinicians for clinical monitoring of patients wearing the sensing device.

[0137] The electronic control and power unit 1520 may further include a rechargeable coin cell battery for powering the sensing device and the electrical components of the electronic control and power unit 1520. The electronic control and power unit 1520 provides a voltage of 5V or less. The electronic control and power unit 1520 further includes a USB port 1500 through which data can be retrieved from the data logger.

[0138] The electronic control and power unit 1520 may be attached to the compression bandage (or garment) via an adhesive pad, hook-and-loop fastener attachment mechanism, or the like, or may be integrated into the housing or casing of the sensing device. Alternatively, the electronic control and power unit 1520 may be communicatively coupled to the sensing device. For example, the electronic control and power unit 1520 may be connected by a cable, or other suitable wired or wireless power and communication link, and located remotely from the sensing device (e.g., in a pocket of a garment worn by the wearer, or on a bedside trolley). The electronic control and power unit 1520 may be configured to estimate pressures in the range of 2 mmHg to 100 mmHg.

Claims

1. 1. A sensing device for sensing a compression pressure exerted by a compression bandage or garment, the sensing device comprising: a flexible substrate for wearing under the compression bandage or compression garment; a compression sensor attached to the flexible substrate; The compression sensor includes: an input and an output, and a signal path between the input and the output; the input and the output are arranged such that a sensor signal received by the output changes in response to a change in the relative configuration of the input and the output and / or a signal path between the input and the output; the input and the output are arranged to change their relative configuration in response to the compressive pressure applied to the compressive sensor, the compressive pressure having a component perpendicular to the flexible substrate; A sensing device comprising:

2. the input and the output are arranged such that the sensor signal varies in response to alignment of the input and the output; The alignment changes in response to the compressive pressure applied to the compression sensor.

2. The sensing device of claim 1 .

3. The input and the output are configured such that, in response to the compressive pressure, at least one of the input and the output undergoes a displacement in a direction perpendicular to the flexible substrate, the displacement in a direction perpendicular to the flexible substrate changing the alignment of the input and the output.

3. The sensing device of claim 2.

4. The input and the output are configured such that in response to the compressive pressure, at least one of the input and the output undergoes a structural deformation, the structural deformation changing the relative configuration of the input and the output. A sensing device according to any one of claims 1 to 3, characterized in that

5. the input and the output are configured such that in response to the compressive pressure, at least one of the input and the output undergoes a displacement in a direction parallel to the flexible substrate; and The displacement in a direction parallel to the flexible substrate changes the relative configuration of the input and the output.

5. The sensing device of claim 4.

6. The compression sensor further comprises one or more guide members arranged to restrict movement of the input and output to a particular direction parallel to the flexible substrate.

5. The sensing device of claim 4.

7. the compression sensor further comprising a signal reflector disposed in the signal path between the input and the output, the input and the output being configured such that in response to the compression pressure, at least one of the input and the output undergoes a displacement relative to the signal reflector such that the signal path is altered.

2. The sensing device of claim 1 .

8. the compression sensor further comprising a compressible member between the flexible substrate and one of the input and the output, the compressible member configured to compress in response to the compressive pressure applied to the compression sensor, and the relative configuration of the input and the output and / or the signal paths between the input and the output changing in response to compression of the compressible member.

2. The sensing device of claim 1 .

9. and a processor configured to determine an estimate of the compressive pressure applied to the sensing device based on the sensor signal.

2. The sensing device of claim 1 .

10. a digital display configured to display the estimate of the compressive pressure applied to the sensing device; or an audio indicator configured to output an audible alarm if the estimate of the compressive pressure applied to the sensing device is outside a predetermined range; Further comprising at least one of 10. The sensing device of claim 9.

11. Further comprising a signal emitter and a signal detector; the signal emitter is a light source and the signal detector is a light detector; The sensing device further comprises: an input optical fiber extending between the light source and the input of the compression sensor; an output optical fiber extending between the output of the compression sensor and the optical detector; Having 2. The sensing device of claim 1 .

12. the input is a signal emitter and the output is a signal detector; the signal emitter and the signal detector overlap; The sensor signal varies in response to an overlapping amount between the signal emitter and the signal detector, and the overlapping amount varies in response to the compressive pressure.

2. The sensing device of claim 1 .

13. Further comprising a signal emitter and a signal detector, the signal emitter is an electrical signal generator and the signal detector is an electrical signal detector; The sensing device further comprises: a first conductive line extending between the electrical signal generator and the input of the compression sensor; and a second conductive line extending between the output of the compression sensor and the electrical signal detector.

2. The sensing device of claim 1 .

14. The compression sensor further includes a variable resistor electrically connected between the input and the output, or a variable capacitor electrically connected between the input and the output.

14. The sensing device of claim 13.

15. the compression sensor being one of a plurality of compression sensors mounted on the flexible substrate, spaced apart from one another, and having a respective input and a respective output; 2. The sensing device of claim 1 .

16. For each of the plurality of compression sensors, the respective output is arranged to transmit a respective sensor signal to a respective signal detector; and / or for each of said plurality of compression sensors, said respective input being arranged to receive a respective signal emitted by a respective signal emitter; 16. The sensing device of claim 15,

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