Optical sensing systems and methods for sensor-enabled wound dressings and systems

Abstract

In some cases, a method of coating a wound dressing includes coating a wound-facing side of a substantially flexible substrate of the wound dressing with a coating, the wound-facing side of the substrate supporting at least one optical sensor, and reducing and / or controlling the surface texture of the coating to improve detection by the at least one optical sensor. In some cases, the wound dressing includes a substantially flexible substrate supporting at least one optical sensor, the at least one optical sensor including a light source and a detector configured to detect reflected light; a void within the substrate, the void being positioned between the light source and the detector; and a coating applied to the substrate and covering the at least one optical sensor. The void can prevent light emitted by the light source from transmitting through the coating to the detector.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE Embodiments of the present disclosure relate to devices, systems, and methods for monitoring and / or treating tissue using sensor-enabled wound dressings. In some embodiments, improved optical sensing techniques are described.

[0002] 2. Description of Related Art Nearly every area of medicine could benefit from improved information about the condition of the tissue, organ, or system being treated, especially if such information could be collected in real time during treatment, and many types of treatment are still routinely performed without the use of sensor data collection. Instead, such treatments rely on visual inspection by caregivers or other limited means rather than quantitative sensor data. For example, in the case of wound treatment via dressings and / or negative pressure wound therapy, data collection is generally limited to visual inspection by caregivers, and the underlying wound tissue may often be obscured by bandages or other visual obstructions. Even intact, unbroken skin may have underlying damage invisible to the naked eye, such as compromised blood vessels or deeper tissue damage that can lead to ulcers. Similar to wound treatment, during orthopedic treatments requiring limb immobilization with a cast or other enclosure, only limited information about the underlying tissue is collected. In the case of internal tissue repairs, such as bone plates, continuous, direct, sensor-driven data collection is not performed. Additionally, braces and / or sleeves used to support musculoskeletal function do not monitor underlying muscle function or limb movement. Outside of direct treatment, common hospital room supplies such as beds and blankets could be improved by adding the ability to monitor patient parameters. Summary of the Invention [Problem to be solved by the invention]

[0003] Therefore, there is a need for improved sensor monitoring, particularly through the use of sensor-compatible substrates that can be incorporated into existing treatment regimens.

[0004] In some cases, a method of coating a wound dressing, the method comprising coating a wound-facing side of a substantially flexible substrate of the wound dressing with a coating, the wound-facing side of the substrate supporting at least one optical sensor, and at least one of reducing or controlling the surface texture of the coating to improve detection by the at least one optical sensor. Reducing or controlling the surface texture of the coating may include applying a film to the coating.

[0005] The method of any preceding paragraph or any of the methods disclosed herein may include one or more of the following features: Reducing or controlling the surface texture of the coating may include reducing the surface roughness of the coating. Coating the wound-facing side of the substantially flexible substrate of the wound dressing with the coating may include applying the coating to at least one optical sensor. The at least one optical sensor may include a light source and a detector configured to detect light reflected by the wound. Applying a film to the coating may include applying the film before the coating cures. The film may be coated with silicone. Applying a film to the coating may include applying a carrier, such as a film, at least one side of which is coated with silicone, where at least one side of the silicone-coated carrier contacts the coating, and further removing the carrier after the coating cures. The coating may be hydrophobic.

[0006] In some cases, the wound dressing may be produced by a method according to any one of the preceding claims or any of the methods disclosed herein.

[0007] In some cases, the wound dressing includes a substantially flexible substrate supporting at least one optical sensor, the at least one optical sensor including a light source and a detector configured to detect reflected light, a void within the substrate, the void being positioned between the light source and the detector, and a coating applied to the substrate and covering the at least one optical sensor, The void can prevent light emitted by the light source from transmitting through the coating to the detector.

[0008] The wound dressing of any preceding paragraph or any of the wound dressings disclosed herein may include one or more of the following features: The void may comprise a hole or slot in the material forming the substrate. The void may be formed through the entire thickness of the substrate. The distance between the light source and the detector may not exceed 10 millimeters. The coating may not fill the entire void in the substrate.

[0009] In some cases, the wound dressing described in any of the preceding paragraphs, or any of the wound dressings disclosed herein, may be produced by a manufacturing method.

[0010] In some cases, a method of manufacturing a wound dressing includes forming a void in a substantially flexible substrate that supports at least one optical sensor, the at least one optical sensor comprising a light source and a detector configured to sense reflected light, the void being positioned between the light source and the detector. The method may further include subsequently applying a coating to the substrate and covering the at least one optical sensor with the coating.

[0011] The method of any preceding paragraph or any of the methods disclosed herein may include one or more of the following features: The voids may include holes or slots in the substrate; The voids may be formed through the entire thickness of the substrate; Applying the coating may include not filling the entire voids in the substrate.

[0012] In some cases, a method of manufacturing a wound dressing includes applying a coating to a substantially flexible substrate supporting at least one optical sensor, the at least one optical sensor comprising a light source and a detector configured to sense reflected light, and covering the at least one optical sensor with the coating. The method may further include subsequently forming a void in the substrate, the void being positioned between the light source and the detector.

[0013] The method of any of the preceding paragraphs or any of the methods disclosed herein may include one or more of the following features: The voids may comprise holes or slots in the substrate. The voids may be formed through the entire thickness of the substrate. [Brief explanation of the drawings]

[0014] Embodiments of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0015] [Figure 1A] FIG. 1A illustrates a negative pressure wound therapy system according to some embodiments. [Figure 1B] FIG. 1B illustrates a wound dressing according to some embodiments. [Figure 2] FIG. 2 shows a sensor array illustrating placement of sensors integrated into a wound dressing, according to some embodiments. [Figure 3] FIG. 3 shows a flexible sensor array integrated into a perforated wound contact layer, according to some embodiments. [Figure 4] FIG. 4 shows the coating(s) of a wound dressing according to some embodiments. [Figure 5] FIG. 5 shows the coating of a wound dressing with two biocompatible coatings, according to some embodiments. [Figure 6] FIG. 6 shows the coating of a wound dressing with a biocompatible coating, according to some embodiments. [Figure 7]FIG. 7 illustrates optical sensing using a coated wound dressing according to some embodiments. [Figure 8] FIG. 8 shows the application of a film to a coating in a wound dressing, according to some embodiments. [Figure 9A] FIG. 9A shows an optical detection chart, according to some embodiments. [Figure 9B] FIG. 9B shows an optical detection chart, according to some embodiments. [Figure 10A] FIG. 10A shows voids within a substrate of a wound dressing, according to some embodiments. [Figure 10B] FIG. 10B shows voids within the substrate of a wound dressing, according to some embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0016]

[0003] The embodiments disclosed herein relate to devices and methods for at least one of monitoring and treating biological tissue using a sensor-enabled substrate. The embodiments disclosed herein are not limited to treating or monitoring a particular type of tissue or injury, but instead, the sensor-enabled technology disclosed herein is broadly applicable to any type of therapy that can benefit from a sensor-enabled substrate. Some implementations utilize sensors and data collection relied upon by medical professionals to make both diagnostic and patient management decisions.

[0017] Some embodiments disclosed herein relate to the use of sensors mounted on or embedded within substrates configured for use in the treatment of both intact and damaged human or animal tissue. Such sensors can collect information about the surrounding tissue and transmit such information to a computing device or caregiver for further treatment. In certain embodiments, such sensors can be attached to the skin anywhere on the body, including areas for monitoring arthritis, temperature, or other areas prone to problems and requiring monitoring. The sensors disclosed herein can also incorporate markers, such as radiopaque markers, to indicate the presence of the device, for example, before performing an MRI or other technique.

[0018] The sensor embodiments disclosed herein may be used in combination with clothing. Non-limiting examples of clothing for use with the sensor embodiments disclosed herein include shirts, pants, trousers, dresses, underwear, outerwear, gloves, shoes, hats, and other suitable garments. In certain embodiments, the sensor embodiments disclosed herein may be welded or laminated to a particular garment. The sensor embodiments may be printed directly onto the garment and / or embedded in fabric. Breathable and printable materials, such as microporous membranes, may also be suitable.

[0019] Sensor embodiments disclosed herein may be incorporated into cushioning or bed padding, such as in hospital beds, to monitor patient characteristics, such as any of the characteristics disclosed herein. In certain embodiments, a disposable film containing such sensors may be placed over the hospital bed and removed / replaced as needed.

[0020] In some implementations, the sensor embodiments disclosed herein may incorporate energy harvesting such that the sensor embodiments are self-sustaining. For example, energy may be recovered from a thermal energy source, a kinetic energy source, a chemical gradient, or any suitable energy source.

[0021] The sensor embodiments disclosed herein may be utilized in rehabilitation devices and treatments, including sports medicine. For example, the sensor embodiments disclosed herein may be used in braces, sleeves, wraps, supports, and other suitable items. Similarly, the sensor embodiments disclosed herein may be incorporated into sporting equipment, such as helmets, sleeves, and / or pads. For example, such sensor embodiments may be incorporated into protective helmets to monitor characteristics such as acceleration, which may be useful in concussion diagnosis.

[0022] Sensor embodiments disclosed herein can be used in conjunction with surgical devices, such as the NAVIO Surgical System by Smith & Nephew Inc. In some implementations, sensor embodiments disclosed herein can communicate with such surgical devices to guide placement of the surgical device. In some implementations, sensor embodiments disclosed herein can monitor blood flow to or away from a potential surgical site or ensure the absence of blood flow to the surgical site. Additional surgical data can be collected to assist in preventing scarring and monitor areas away from the affected area.

[0023] To further assist surgical techniques, the sensors disclosed herein can be incorporated into surgical drapes to provide information about tissue beneath the drape that may not be immediately visible to the naked eye. For example, a sensor-embedded flexible drape can have sensors strategically positioned to provide improved area-focused data collection. In certain implementations, the sensor embodiments disclosed herein can be incorporated into the boundaries or interior of the drape to create an enclosure that limits / controls the surgical theater.

[0024] Sensor embodiments disclosed herein may also be utilized for preoperative assessment. For example, such sensor embodiments can be used to gather information about potential surgical sites, such as by monitoring the skin and underlying tissue for potential incision sites. For example, perfusion levels or other suitable characteristics may be monitored at the surface of the skin and deeper in the tissue to assess whether an individual patient may be at risk for surgical complications. Sensor embodiments such as those disclosed herein may be used to assess the presence of microbial infection and provide indications for the use of antimicrobial agents. Additionally, sensor embodiments disclosed herein may gather additional information at deeper tissues, such as identifying pressure ulcer damage and / or adipose tissue levels.

[0025] Sensor embodiments disclosed herein may be utilized for cardiovascular monitoring. For example, such sensor embodiments may be incorporated into a flexible cardiovascular monitor that may be placed against the skin to monitor characteristics of the cardiovascular system and transmit such information to another device and / or a caregiver. For example, such a device may monitor pulse rate, blood oxygenation, and / or cardiac electrical activity. Similarly, sensor embodiments disclosed herein may be utilized for neurophysiological applications, such as monitoring the electrical activity of neurons.

[0026] The sensor embodiments disclosed herein may be incorporated into implantable devices such as implantable orthopedic implants, including flexible implants. Such sensor embodiments may be configured to collect information about the implant site and transmit this information to an external source. In some embodiments, an internal source may also provide power to such implants.

[0027] Sensor embodiments disclosed herein may also be utilized to monitor biochemical activity at or below the surface of the skin, such as lactose accumulation in muscle or sweat rate on the surface of the skin. In some embodiments, other properties may be monitored, such as glucose concentration, urine concentration, tissue pressure, skin temperature, skin surface conductance, skin surface resistivity, skin hydration, skin maceration, and / or skin tearing.

[0028] Sensor embodiments disclosed herein may be incorporated into ear, nose, and throat (ENT) applications. For example, such sensor embodiments may be utilized to monitor recovery from ENT-related procedures, such as wound monitoring within sinus passageways.

[0029] Sensor embodiments disclosed herein may incorporate sensor printing techniques involving encapsulation, such as encapsulation with a polymer film. Such films may be constructed using any of the polymers described herein, such as polyurethane. Encapsulation of sensor embodiments may provide waterproofing of the electronics as well as protection from local tissue, local fluids, and other sources of potential damage.

[0030] In certain embodiments, the sensors disclosed herein can be incorporated into organ protection layers. Such sensor-embedded organ protection layers can both protect the organ of interest and verify that the organ protection layer is in place and providing protection. Furthermore, sensor-embedded organ protection layers can be utilized to monitor the underlying organ, such as by monitoring blood flow, oxygenation, and other suitable markers of organ health. In some embodiments, sensor-enabled organ protection layers can be used to monitor transplanted organs, such as by monitoring the organ's fat and muscle content. Furthermore, sensor-enabled organ protection layers can be used to monitor organs during transplantation and after transplantation, such as during organ rehabilitation.

[0031] The sensor embodiments disclosed herein may be incorporated into the treatment of wounds (disclosed in more detail below) or a variety of other applications. Non-limiting examples of additional applications for the sensor embodiments disclosed herein include monitoring and treatment of intact skin, cardiovascular applications such as monitoring blood flow, orthopedic applications such as monitoring limb movement and bone repair, neurophysiological applications such as monitoring electrical impulses, and any other tissue, organ, system, or condition that can benefit from improved sensor-enabled monitoring.

[0032] wound therapy Some embodiments disclosed herein relate to wound therapy for the human or animal body. Thus, any reference to a wound herein can refer to a wound on the human or animal body, and any reference to a body herein can refer to the human or animal body. Disclosed technology embodiments may relate to preventing or minimizing damage to physiological or biological tissue or treating damaged tissue (e.g., wounds described herein), with or without reduced pressure, including, for example, negative pressure sources and wound dressing components and devices. Devices and components, including wound overlays and packing materials, or inner layers, if present, are sometimes collectively referred to as dressings. In some embodiments, wound dressings can be provided to be used without reduced pressure.

[0033] Some embodiments disclosed herein relate to wound therapy for a human or animal body. Thus, any reference to a wound herein may refer to a wound on a human or animal body, and any reference to a body herein may refer to a human or animal body. Disclosed technology embodiments may relate to preventing or minimizing damage to physiological or biological tissue, or treating damaged tissue (e.g., wounds as described herein).

[0034] As used herein, the term "wound" may include injuries to living tissue, which may be caused by a cut, blow, or other impact, typically an impact in which the skin is cut or broken. Wounds may be chronic or acute injuries. Acute wounds occur as a result of surgery or trauma. They progress through the stages of healing within a predictable time frame. Chronic wounds typically begin as acute wounds. Acute wounds can become chronic wounds when they do not follow the healing stages, resulting in prolonged recovery. It is believed that the transition from acute to chronic wounds may be due to the patient's immunocompromised state.

[0035] Chronic wounds may include, for example, venous ulcers (such as those occurring in the legs), which account for the majority of chronic wounds and primarily affect the elderly, diabetic ulcers (e.g., foot or ankle ulcers), peripheral arterial disease, pressure ulcers, or epidermolysis bullosa (EB).

[0036] Examples of other wounds include, but are not limited to, abdominal wounds or other large or incisional wounds, whether as a result of surgery, trauma, sternotomy, fasciotomy, or other conditions, dehiscence wounds, acute wounds, chronic wounds, subacute and dehiscence wounds, traumatic wounds, flaps and skin grafts, lacerations, abrasions, contusions, burns, diabetic ulcers, pressure ulcers, stomas, surgical wounds, traumatic ulcers, and venous ulcers.

[0037] Wounds may also include deep tissue injuries, a term proposed by the National Pressure Ulcer Advisory Panel (NPUAP) to describe specific forms of pressure ulcers. These ulcers have been described by clinicians for many years with terms such as purple pressure ulcers, ulcers that may worsen, and bony prominence bruises.

[0038] Wounds can also include tissue at risk of becoming wounded, as discussed herein. For example, tissue at risk can include tissue over a bony prominence (at risk of deep tissue injury / invasiveness) or pre-operative tissue (e.g., knee tissue) that may have the potential to be amputated (e.g., for joint replacement / surgical revision / reconstruction).

[0039] Some embodiments relate to methods of treating wounds using the techniques disclosed herein in combination with one or more of advanced footwear, turning the patient, offloading (e.g., offloading of diabetic foot ulcers), treatment of infection, systemics, antimicrobials, antibiotics, surgery, tissue removal, influencing blood flow, physical therapy, exercise, bathing, nutrition, hydration, nerve stimulation, ultrasound, electrical stimulation, oxygen therapy, microwave therapy, active ozone, antibiotics, antimicrobials, and the like.

[0040] Alternatively or additionally, wounds may be treated using topical negative pressure (TNP) and / or conventional advanced wound care that is not supported by the use of applied negative pressure (which may also be referred to as non-negative pressure therapy).

[0041] Advanced wound care may include the use of absorbent dressings, occlusive dressings, antimicrobial and / or deodorant agents in wound dressings or adjuncts, padding (e.g., for cushioning such as stockings or bandages or compression therapy), and the like.

[0042] In some embodiments, the wound dressing comprises one or more absorbent layer(s), which may be foam or superabsorbent.

[0043] In some embodiments, the disclosed technology can be used with non-negative pressure dressings. A non-negative pressure wound dressing suitable for providing protection at a wound site can include an absorbent layer for absorbing wound exudate and a shielding element for at least partially shielding the view of the wound exudate absorbed by the absorbent layer during use. The shielding element can be partially translucent. The shielding element can be a masking layer.

[0044] In some embodiments, the non-negative pressure wound dressings disclosed herein comprise a wound contact layer overlying an absorbent layer, the wound contact layer may carry an adhesive moiety for forming a substantially fluid-tight seal on the wound.

[0045] In some embodiments, the wound dressings disclosed herein further comprise a layer of superabsorbent fibers, or viscose or polyester fibers.

[0046] In some embodiments, the wound dressings disclosed herein further comprise a backing layer. The backing layer may be a transparent or opaque film. Typically, the backing layer comprises a polyurethane film (typically a transparent polyurethane film).

[0047] In some cases, the foam may be an open-cell foam or a closed-cell foam, typically an open-cell foam. The foam may be hydrophilic.

[0048] The wound dressing may comprise a transmission layer, which may be a foam. The transmission layer may be a polyurethane foam laminated to a polyurethane film.

[0049] The non-negative pressure wound dressing may be a compression bandage, which is known for its use in treating edema and other venous and lymphatic disorders, for example, of the lower extremities. In some embodiments, the compression bandage may comprise a bandage system including an inner skin-facing layer and an elastic outer layer, the inner layer comprising a first ply of foam and a second ply of an absorbent nonwoven web, the inner and outer layers being sufficiently elongated to be wrapped around a patient's limb.

[0050] Negative pressure wound therapy In some embodiments, wound treatment may be performed using negative pressure wound therapy. It will be understood that embodiments of the present disclosure are generally applicable for use with TNP systems. Briefly, negative pressure wound therapy may assist in the closure and healing of many forms of "difficult-to-heal" wounds by reducing tissue edema, promoting blood flow and granulation tissue formation, and removing excessive exudate, reducing bacterial load (and therefore infection risk). In addition, treatment may reduce wound unrest, leading to faster healing. TNP treatment systems may also assist in the healing of surgically closed wounds by removing fluid and helping to stabilize tissue in an apposed position for closure. Further beneficial uses of TNP treatment may be found in grafts and flaps, where removal of excess fluid is important and graft proximity to tissue is required to ensure tissue viability.

[0051] Negative pressure therapy can be used to treat open or chronic wounds that are too large to close naturally or that otherwise do not heal with the application of negative pressure to the wound site. Topical negative pressure (TNP) therapy or negative pressure wound therapy (NPWT) involves placing a fluid-impermeable or semi-permeable cover over the wound, using various means to seal the cover against the patient's tissue surrounding the wound, and connecting a negative pressure source (e.g., a vacuum pump) to the cover in such a way that negative pressure is created and maintained beneath the cover. Such negative pressure is thought to promote wound healing by facilitating the formation of granulation tissue at the wound site and supporting normal internal inflammatory processes while simultaneously removing excess fluid, which may contain harmful cytokines or bacteria.

[0052] Some dressings used in NPWT can include many different types of materials and layers, such as gauze, pads, foam pads, or multi-layer wound dressings. One example of a multi-layer wound dressing is the PICO dressing, available from Smith & Nephew, which includes a wound contact layer and a superabsorbent layer beneath a backing layer to provide a canister-less system for treating wounds with NPWT. The wound dressing may be sealed with a suction port, providing connection to a long tube that can be used to pump fluid from the dressing or transfer negative pressure from a pump to the wound dressing. Additionally, RENASYS-F, RENASYS-G, RENASYS-AB, and RENASYS-F / AB, available from Smith & Nephew, are further examples of NPWT wound dressings and systems. Another example of a multi-layer wound dressing is the ALLEVYN Life dressing, available from Smith & Nephew, which includes a moist wound environment dressing used to treat wounds without the use of negative pressure.

[0053] As used herein, a reduced or negative pressure level, such as −X mmHg, represents a pressure level relative to normal ambient air pressure, which may correspond to 760 mmHg (or 1 atm, 29.93 inHg, 101.325 kPa, 14.696 psi, etc.). Thus, a negative pressure value of −X mmHg reflects an absolute pressure that is X mmHg lower than 760 mmHg, or in other words, an absolute pressure of (760−X) mmHg. Additionally, a negative pressure “lower” or “less” than X mmHg corresponds to a pressure closer to atmospheric pressure (e.g., −40 mmHg is lower than −60 mmHg). A negative pressure “higher” or “greater” than −X mmHg corresponds to a pressure further away from atmospheric pressure (e.g., −80 mmHg is higher than −60 mmHg). In some embodiments, the local ambient air pressure is used as a reference point, and such local air pressure need not necessarily be, for example, 760 mmHg.

[0054] In some embodiments of the wound closure devices described herein, increased wound contraction can lead to increased tissue expansion in the surrounding wound tissue. This effect can be increased, optionally in conjunction with increased tension applied to the wound by embodiments of the wound closure device, by varying the force applied to the tissue, e.g., varying the negative pressure applied to the wound over time. In some embodiments, the negative pressure can be varied over time, e.g., using a sine wave, a square wave, or synchronized with one or more physiological indicators (e.g., heart rate).

[0055] Any of the embodiments disclosed herein may be used in conjunction with any of the following patents: WO2010 / 061225, US2016 / 114074, US2006 / 0142560, and US5,703,225, which describe absorbent materials; WO2013 / 007973, which describes non-negative pressure wound dressings; GB1618298.2 (filed October 28, 2016), GB1621057.7 (filed December 12, 2016), and GB1709987.0 (filed June 22, 2017), which describe multi-layer wound dressings; EP2498829 and EP1718257, which describe wound dressings; The present invention may be used in combination with any of the features disclosed in one or more of WO 2006 / 110527, US 6,759,566, and US 2002 / 0099318, which describe compression bandages, US 8,235,955 and US 7,753,894, which describe wound closure devices, and WO 2013 / 175306, WO 2016 / 174048, US 2015 / 0190286, US 2011 / 0282309, and US 2016 / 0339158, which describe negative pressure wound therapy dressings, wound dressing components, wound treatment apparatuses, and methods, the disclosure of each of which is incorporated herein by reference in its entirety.

[0056] Overview of the NPWT System FIG. 1A shows an embodiment of a negative pressure or reduced pressure wound therapy (or TNP) system 100 including a wound cavity 110 and a wound packing material 130 disposed within the wound cavity sealed by a wound cover 120. The wound packing material 130 in combination with the wound cover 120 may be referred to as a wound dressing. A single or multiple lumen tube or conduit 140 connects the wound cover 120 to a pump assembly 150 configured to provide reduced pressure. The wound cover 120 may be in fluid communication with the wound cavity 110. In some system embodiments disclosed herein, such as the embodiment shown in FIG. 1, the pump assembly may be a canister-less pump assembly (meaning that exudate is collected in the wound dressing or conveyed via the tube 140 for collection at another location). However, some pump assembly embodiments disclosed herein may be configured to include or support a canister. Additionally, in some system embodiments disclosed herein, some pump assembly embodiments may be mounted to or supported by a covering or may be adjacent to a covering.

[0057] The wound packing 130 may be of any suitable type, such as, for example, hydrophilic or hydrophobic foam, gauze, an inflatable bag, or the like. The wound packing 130 may conform to the wound cavity 110 so that it substantially fills the cavity. The wound cover 120 may provide a substantially fluid-impermeable seal over the wound cavity 110. The wound cover 120 may have an upper surface and a lower surface, the lower surface adhesively sealing (or in any other suitable manner) the wound cavity 110. The conduit 140 or lumen or any other conduit or lumen disclosed herein may be formed from polyurethane, PVC, nylon, polyethylene, silicone, or any other suitable material.

[0058] Some embodiments of the wound cover 120 may have a port (not shown) configured to receive the end of the conduit 140. For example, the port may be a Renasys Soft Port available from Smith & Nephew. In other embodiments, the conduit 140 may otherwise pass through or beneath the wound cover 120 to supply reduced pressure to the wound cavity 110 to maintain a desired level of reduced pressure within the wound cavity. The conduit 140 may be any suitable article configured to provide at least a substantially sealed fluid flow path between the pump assembly 150 and the wound cover 120 to supply the reduced pressure provided by the pump assembly 150 to the wound cavity 110.

[0059] The wound cover 120 and wound packing 130 may be provided as a single item or an integral single unit. In some embodiments, no wound packing may be provided, and the wound cover may be considered a wound dressing in its own right. The wound dressing may then be connected via conduit 140 to a source of negative pressure, such as a pump assembly 150. The pump assembly 150 may be miniaturized and portable, although larger conventional such pumps may also be used.

[0060] The wound cover 120 may be positioned over the wound site to be treated. The wound cover 120 may form a substantially sealed cavity or enclosed space over the wound site. In some embodiments, the wound cover 120 may be configured with a film having high water vapor permeability to allow evaporation of excess fluid and may have a superabsorbent material contained therein to safely absorb wound exudate. It will be understood that references to wounds are made throughout this specification. In this regard, it should be understood that the term wound is to be broadly interpreted to encompass open and closed wounds where the skin is torn, incised, or perforated, or where trauma has caused a bruise, or any other surface or other condition or defect in the skin of a patient or other person who would benefit from reduced pressure treatment. A wound is therefore broadly defined as any damaged area of tissue that may or may not produce fluid. Examples of such wounds include, but are not limited to, acute wounds, chronic wounds, surgical incisions and other incisions, subacute and dehiscence wounds, traumatic wounds, flaps and skin grafts, lacerations, abrasions, contusions, burns, diabetic ulcers, pressure ulcers, stomas, surgical wounds, traumatic ulcers and venous ulcers, etc. The components of the TNP system described herein may be particularly suitable for surgical wounds that exude small amounts of wound exudate.

[0061] Some embodiments of the system are designed to operate without the use of an exudate canister. Some embodiments may be configured to support an exudate canister. In some embodiments, configuring the pump assembly 150 and tubing 140 so that the tubing 140 can be quickly and easily removed from the pump assembly 150 can facilitate or improve the process of replacing the covering or the pump, if necessary. Some pump embodiments disclosed herein may be configured with any suitable connection between the tubing and the pump.

[0062] In some implementations, pump assembly 150 may be configured to deliver a negative pressure of approximately -80 mmHg, or between about -20 mmHg and 200 mmHg. Note that these pressures are relative to normal ambient atmospheric pressure; i.e., -200 mmHg may actually be approximately 560 mmHg. The pressure range may be between about -40 mmHg and -150 mmHg. Alternatively, pressure ranges of -75 mmHg or less, -80 mmHg or less, or greater than 80 mmHg may be used. Pressure ranges below -75 mmHg may also be used. Alternatively, pressure ranges above approximately -100 mmHg or even above 150 mmHg may be provided by pump assembly 150.

[0063] In operation, the wound packing 130 is inserted into the wound cavity 110 and the wound cover 120 is placed to seal the wound cavity 110. The pump assembly 150 provides a source of negative pressure to the wound cover 120 that is transmitted through the wound packing 130 to the wound cavity 110. Fluid (such as wound exudate) may be drawn through the conduit 140 and stored in the canister. In some embodiments, the fluid is absorbed by the wound packing 130 or one or more absorbent layers (not shown).

[0064] Wound dressings that may be utilized with the pump assembly and other embodiments of the present application include Renasys-F, Renasys-G, Renasys AB, and Pico dressings available from Smith & Nephew. Further descriptions of such wound dressings and other components of negative pressure wound therapy systems that may be used with the pump assembly and other embodiments of the present application can be found in one or more of U.S. Patent Publication Nos. 2011 / 0213287, 2011 / 0282309, 2012 / 0116334, 2012 / 0136325, and 2013 / 0110058, which are incorporated by reference in their entireties. In other embodiments, other suitable wound dressings may be utilized.

[0065] Overview of wound dressings FIG. 1B shows a cross section through a wound dressing 155 according to some embodiments. FIG. 1B also shows a fluid connector 160 according to some embodiments. The wound dressing 155 may be similar to the wound dressing described in International Patent Publication No. WO 2013 / 175306(A2), which is incorporated by reference in its entirety. Alternatively, the wound dressing 155 may be any wound dressing embodiment disclosed herein or any combination of features of any number of wound dressing embodiments disclosed herein and may be positioned over the wound site to be treated. The wound dressing 155 may be placed to form a sealed cavity over the wound, such as the wound cavity 110. In some embodiments, the wound dressing 155 includes a top or cover layer, or a backing layer 220 attached to an optional wound contact layer 222, both of which are described in more detail below. These two layers 220, 222 may be joined or sealed together to define an interior space or chamber. This interior space or chamber may comprise additional structures that may be adapted to distribute or transmit negative pressure, store wound exudate and other fluids removed from the wound, and other functions that will be described in more detail below. Examples of such structures described below include a transmission layer 226 and an absorbent layer 221.

[0066] As used herein, the top, uppermost, or upper layer refers to the layer that is furthest from the surface of the skin or wound while the dressing is in use and positioned over the wound, and the bottom, lower, lowermost, or lower layer thus refers to the layer that is closest to the surface of the skin or wound while the dressing is in use and positioned over the wound.

[0067] The wound contact layer 222 may be a polyurethane layer, a polyethylene layer, or other flexible layer that has been perforated or otherwise made liquid and gas permeable, for example, via a hot pin process, laser ablation process, ultrasonic process, or some other method. The wound contact layer 222 has a lower surface 224 (e.g., facing the wound) and an upper surface 223 (e.g., facing away from the wound). Perforations 225 may comprise through-holes in the wound contact layer 222, allowing fluid to flow through the layer 222. The wound contact layer 222 helps prevent tissue ingrowth into other materials of the wound dressing. In some embodiments, the perforations are small enough to meet this requirement while still allowing fluid to flow through the perforations. For example, perforations formed as slits or holes having dimensions ranging from 0.025 mm to 1.2 mm are believed to be small enough to help prevent tissue ingrowth into the wound dressing while allowing wound exudate to flow into the dressing. In some configurations, the wound contact layer 222 may help maintain the integrity of the entire dressing 155 while also creating an airtight seal around the absorbent pad to maintain negative pressure at the wound. In some embodiments, the wound contact layer is configured to allow unidirectional, or substantially unidirectional or unidirectional, flow of fluid through the wound contact layer when negative pressure is applied to the wound. For example, the wound contact layer may allow fluid to flow away from the wound through the wound contact layer, but may not allow fluid to flow back toward the wound. In certain cases, the perforations in the wound contact layer are configured to allow such unidirectional or unidirectional flow of fluid through the wound contact layer.

[0068] Some embodiments of the wound contact layer 222 may also act as a carrier for optional upper and lower adhesive layers (not shown). For example, a lower pressure-sensitive adhesive may be provided on the lower surface 224 of the wound dressing 155, while an upper pressure-sensitive adhesive layer may be provided on the upper surface 223 of the wound contact layer. The pressure-sensitive adhesive, which may be a silicone, hot melt, hydrocolloid, or acrylic-based adhesive, or other such adhesive, may be formed on both sides of the wound contact layer, on any selected side, or on neither side of the wound contact layer. Utilizing a lower pressure-sensitive adhesive layer may help adhere the wound dressing 155 to the skin around the wound site. In some embodiments, the wound contact layer may comprise a perforated polyurethane film. The lower surface of the film may be provided with a silicone pressure-sensitive adhesive, and the upper surface may be provided with an acrylic pressure-sensitive adhesive, which may help the dressing maintain its integrity. In some embodiments, adhesive layers may be provided on both the upper and lower surfaces of the polyurethane film layer, and all three layers may be perforated.

[0069] A layer 226 of porous material may be positioned above the wound contact layer 222. This porous or permeable layer 226 allows fluids, including liquids and gases, to permeate away from the wound site and into the upper layers of the wound dressing. In particular, the permeable layer 226 can ensure that external air channels can be maintained to transmit negative pressure across the wound area, even when the absorbent layer has absorbed a significant amount of exudate. As described above, the layer 226 can remain open under the normal pressures that would be applied during negative pressure wound therapy, thereby ensuring that the entire wound site experiences equal negative pressure. The layer 226 may be formed from a material with a three-dimensional structure. For example, a knitted or woven spacer fabric (e.g., Baltex 7970 weft knit polyester) or a nonwoven fabric may be used.

[0070] In some embodiments, the transmission layer 226 comprises a 3D polyester spacer fabric layer including a top layer (i.e., the layer distal from the wound bed during use) that is 84 / 144 woven polyester, a bottom layer (i.e., the layer that lies proximal to the wound bed during use) that is 10 denier flat polyester, and a third layer sandwiched between these two layers that is a region defined by woven polyester viscose, cellulose, or similar monofilament fibers. Other materials and fibers of other linear mass densities may, of course, be used.

[0071] Throughout this disclosure, reference will be made to monofilament fibers, although it will of course be understood that multi-yarn alternatives may be utilized, and thus the top spacer fabric will have more filaments in the single yarn used to form it than the number of filaments comprising the yarn used to form the bottom spacer fabric layer.

[0072] This difference in filament count in the spaced layers helps control the flow of moisture across the transmission layer. Specifically, by having a higher filament count in the top layer, i.e., by having the top layer made from yarns having more filaments than the yarns used in the bottom layer, liquid tends to wick more along the top layer than the bottom layer. During use, this difference causes liquid to be drawn away from the wound bed and into the central region of the dressing, where the absorbent layer 221 can help contain the liquid or wick it forward toward the dressing layer where it can be released.

[0073] In some embodiments, to improve liquid flow across the transmission layer 226 (i.e., perpendicular to the channel region formed between the top and bottom spacer layers), the 3D fabric may be treated with a dry cleaning agent (such as, but not limited to, perchloroethylene) to help remove any previously applied industrial products, such as mineral oil, grease, or wax, that may interfere with the hydrophilic capabilities of the transmission layer. This may then proceed to an additional manufacturing step in which the 3D spacer fabric is washed with a hydrophilic agent (such as, but not limited to, 30 g / l Feran Ice, commercially available from the Rudolph Group). This process step helps ensure that the surface tension of the material is low enough that liquids, such as water, can penetrate the fabric immediately upon contact with the 3D knit. This step also helps control the flow of the liquid insult component of any exudate.

[0074] An absorbent layer 221 may be provided over the transmission layer 226. The absorbent, which may comprise a foam or nonwoven natural or synthetic material, and may optionally comprise a superabsorbent, forms a reservoir for fluids, particularly liquids, removed from the wound site. In some embodiments, layer 221 may also help draw fluids toward the backing layer 220.

[0075] The absorbent layer 221 material may also prevent fluid collected in the wound dressing 155 from flowing freely through the dressing and may act to contain any fluid that collects within the dressing. The absorbent layer 221 also helps distribute fluid throughout the layer by wicking, drawing fluid away from the wound site and storing it throughout the absorbent layer. This helps prevent clumping in the absorbent layer area. The absorbent capacity must be sufficient to manage the rate at which wound exudate flows when negative pressure is applied. During use, the absorbent layer experiences negative pressure, so the absorbent layer material is selected to absorb fluid under such conditions. Several materials exist that can absorb fluid when under negative pressure, such as superabsorbent materials. The absorbent layer 221 may typically be made from ALLEVYN™ foam Freudenberg 114-224-4 or Chem-Posite™ 11C-450. In some embodiments, the absorbent layer 221 may comprise a composite including superabsorbent powder, a fibrous material such as cellulose, and bonding fibers. In some embodiments, the composite is an airlaid, thermally bonded composite.

[0076] In some embodiments, the absorbent layer 221 is a layer of nonwoven cellulose fibers with superabsorbent material in the form of dry particles dispersed throughout the layer. The use of cellulose fibers introduces a fast wicking element that helps quickly and evenly distribute liquid absorbed by the dressing. The parallel arrangement of many strand-like fibers leads to strong capillary action in the fibrous pad, which helps distribute the liquid, thus efficiently delivering liquid to the superabsorbent material. The wicking action also helps bring liquid into contact with the upper cover layer, which helps increase the dressing's evaporation rate.

[0077] A gap, hole, or orifice 227 may be provided in the backing layer 220 to allow negative pressure to be applied to the dressing 155. In some embodiments, a fluid connector 160 is attached or sealed to the top of the backing layer 220 over the orifice 227 made in the dressing 155 and transmits negative pressure through the orifice 227. A long tube may be connected to the fluid connector 160 at a first end and to a pump unit (not shown) at a second end to allow fluid to be pumped from the dressing. If the fluid connector is to be adhered to the top layer of the wound dressing, the long tube may be connected at a first end of the fluid connector such that the tube or conduit extends parallel to, or substantially toward, the top surface of the dressing. The fluid connector 160 can be adhered and sealed to the backing layer 220 using an adhesive such as an acrylic, cyanoacrylate, epoxy, UV-curable, or hot-melt adhesive. The fluid connector 160 may be formed from a soft polymer, such as polyethylene, polyvinyl chloride, silicone, or polyurethane, having a hardness of 30 to 90 on the Shore A scale. In some embodiments, the fluid connector 160 may be made from a soft or compliant material.

[0078] In some embodiments, the absorbent layer 221 includes at least one through-hole 228 positioned to underlie the fluid connector 160. The through-hole 228 may, in some embodiments, be the same size as the opening 227 in the backing layer, or may be larger or smaller. As shown in FIG. 1B, a single through-hole may be used to create an opening under the fluid connector 160. It will be understood that multiple openings may alternatively be utilized. Additionally, if one or more ports are to be utilized in accordance with certain embodiments of the present disclosure, one or more openings may be made in the absorbent and shielding layers in registration with each respective fluid connector. While not required for certain embodiments of the present disclosure, the use of through-holes in the superabsorbent layer may provide a fluid flow path that remains unobstructed, particularly when the absorbent layer is near saturation.

[0079] 1B , a gap or through-hole 228 may be provided in the absorbent layer 221 below the orifice 227 such that the orifice directly connects to the permeable layer 226. This allows negative pressure applied to the fluid connector 160 to be transmitted to the permeable layer 226 without passing through the absorbent layer 221. This ensures that negative pressure applied to the wound site is not inhibited by the absorbent layer as it absorbs wound exudate. In other embodiments, no gap may be provided in the absorbent layer 221, or alternatively, multiple gaps may be provided below the orifice 227. In further alternative embodiments, additional layers, such as another permeable layer, or a shielding layer such as those described in International Patent Application Publication No. WO 2014 / 020440, the entire contents of which are incorporated by reference, may be provided above the absorbent layer 221 and below the backing layer 220.

[0080] The backing layer 220 may be gas-impermeable but moisture-permeable and may extend across the width of the wound dressing 155. For example, the backing layer 220 may be a polyurethane film (e.g., Elastollan SP9109) with a pressure-sensitive adhesive on one side. The backing layer 220 is impermeable to gases; therefore, it covers the wound and acts to seal the wound cavity over which the wound dressing is placed. In this manner, an effective chamber is created between the backing layer 220 and the wound site, within which a negative pressure can be established. The backing layer 220 may be sealed to the wound contact layer 222 at a boundary area around the periphery of the dressing, for example, by adhesive or welding techniques, ensuring that air is drawn through the boundary area. The backing layer 220 protects the wound from external bacterial contamination (a bacterial barrier) and allows liquid from wound exudate to migrate through the layer and evaporate from the outer surface of the film. The backing layer 220 may include two layers: a polyurethane film and an adhesive pattern spread over the film. The polyurethane film may be breathable and may be made from a material that increases its water transmission rate when wet. In some embodiments, the breathability of the backing layer increases when the backing layer becomes wet. The breathability of the wet backing layer may be up to about 10 times greater than the breathability of the dry backing layer.

[0081] The absorbent layer 221 may be of a larger area than the transmission layer 226 so that the absorbent layer overlaps the edges of the transmission layer 226, thereby ensuring that the transmission layer does not contact the backing layer 220. This provides an outer channel in the absorbent layer 221 that is in direct contact with the wound contact layer 222, aiding in more rapid absorption of exudate into the absorbent layer. Furthermore, this outer channel ensures that fluid cannot pool around the perimeter of the wound cavity, which could otherwise seep through the seal around the dressing and lead to the formation of a leak. As shown in FIG. 1B, the absorbent layer 221 may define a perimeter that is smaller than the perimeter of the backing layer 220, such that a border or boundary area is defined between the edge of the absorbent layer 221 and the edge of the backing layer 220.

[0082] 1B, one embodiment of the wound dressing 155 includes a gap 228 in the absorbent layer 221 that underlies the fluid connector 160. During use, therefore, for example, when negative pressure is applied to the dressing 155, the wound-facing portion of the fluid connector may contact the transmission layer 226 and therefore may help transmit negative pressure to the wound site even when the absorbent layer 221 is filled with wound fluid. In some embodiments, the backing layer 220 may be at least partially adhered to the transmission layer 226. In some embodiments, the gap 228 is at least 1-2 mm larger than the diameter of the wound-facing portion or orifice 227 of the fluid connector 160.

[0083] For example, in embodiments with a single fluid connector 160 and through-hole, it may be preferable for the fluid connector 160 and through-hole to be located in an off-center position. Such a location may allow the dressing 155 to be positioned on the patient such that the fluid connector 160 is elevated relative to the remainder of the dressing 155. In such a positioning, the fluid connector 160 and filter 214 may be less likely to come into contact with wound fluid that could prematurely block the filter 214 to reduce the transmission of negative pressure to the wound site.

[0084] Referring now to the fluid connector 160, some embodiments include a sealing surface 216, a bridge 211 including a proximal end (closer to the negative pressure source) and a distal end 140, and a filter 214. The sealing surface 216 may form an applicator that is sealed to the top surface of the wound dressing. In some embodiments, the bottom layer of the fluid connector 160 may include the sealing surface 216. The fluid connector 160 may further include an upper surface spaced vertically from the sealing surface 216, which in some embodiments is defined by a separate upper layer of the fluid connector. In other embodiments, the upper and lower surfaces may be formed from the same piece of material. In some embodiments, the sealing surface 216 may include at least one gap 229 therein to communicate with the wound dressing. In some embodiments, the filter 214 may be positioned across or may span the opening 229 in the sealing surface. The sealing surface 216 may be configured to seal the fluid connector to the cover layer of the wound dressing and may comprise an adhesive or a weld. In some embodiments, the sealing surface 216 may be placed over an orifice in the cover layer, with an optional spacer element 215 configured to create a gap between the filter 214 and the transmission layer 226. In other embodiments, the sealing surface 216 may be positioned over an orifice in the cover layer and a gap in the absorbent layer 220, allowing the fluid connector 160 to provide airflow through the transmission layer 226. In some embodiments, the bridge 211 may comprise a first fluid passageway 212 in communication with a negative pressure source, the first fluid passageway 212 comprising a porous material that may be the same as or different from the porous layer 226 described previously, such as a 3D knitted material. The bridge 211 can be encapsulated by at least one flexible film layer 208, 210 having a proximal end and a distal end and configured to surround the first fluid passageway 212, the distal end of the flexible film connecting to the sealing surface 216. The filter 214 is configured to substantially prevent wound exudate from entering the bridge, and the spacer element 215 is configured to prevent the fluid connector from contacting the transmission layer 226. These elements are described in more detail below.

[0085] Some embodiments may further include an optional second fluid passageway positioned above the first fluid passageway 212. For example, some embodiments may provide an air leak configured to provide an air path into the first fluid passageway 212 and the dressing 155, possibly located at the proximal end of the top layer, similar to the suction adapter described in U.S. Pat. No. 8,801,685, which is incorporated by reference in its entirety.

[0086] In some embodiments, the fluid passageway 212 is constructed from a compliant material that is flexible and also allows fluid to pass through even when the spacer is twisted or folded. Suitable materials for the fluid passageway 212 include, but are not limited to, foams, including open-cell foams, such as polyethylene or polyurethane foam, meshes, 3D knits, nonwoven materials, and fluid channels. In some embodiments, the fluid passageway 212 may be constructed from materials similar to those described above with respect to the transmission layer 226. Advantageously, such materials used for the fluid passageway 212 may not only allow for greater patient comfort, but may also provide greater kink resistance so that the fluid passageway 212 can still move fluid from the wound toward the source of negative pressure while twisting or bending.

[0087] In some embodiments, the fluid passageway 212 may be comprised of a wicking fabric, such as a knitted or woven spacer fabric (such as polyester knitted 3D fabrics like Baltex 7970® or Gehring 879®), or a nonwoven fabric. These selected materials can be positioned to direct wound exudate away from the wound, transmit negative pressure or expelled air to the wound site, and may also provide some kink resistance or occlusion resistance to the fluid passageway 212. In some embodiments, the wicking fabric may have a three-dimensional structure, which may, in some cases, aid in wicking fluid or transmitting negative pressure. In certain embodiments including a wicking fabric, these materials remain open and can transmit negative pressure to the wound area under typical pressures used in negative pressure therapy, e.g., −40 to −150 mmHg. In some embodiments, the wicking fabric may comprise several layers of material stacked or laminated on top of each other, which, in some cases, may be useful in preventing the fluid passageway 212 from collapsing under negative pressure conditions. In other embodiments, the wicking fabric used in the fluid passageway 212 may be 1.5 mm to 6 mm thick, and more preferably, the wicking fabric may be 3 mm to 6 mm thick and may consist of one or several individual wicking fabric layers. In other embodiments, the fluid passageway 212 may be between 1.2 mm and 3 mm thick, and preferably greater than 1.5 mm. Some embodiments, such as suction adapters used with dressings that retain liquids, such as wound exudate, may use a hydrophobic layer in the fluid passageway 212, allowing only gas to move through the fluid passageway 212. Additionally, as previously described, the materials used in the system can be compliant and soft, which may help avoid pressure sores and other complications that can result from wound treatment systems exerting pressure against a patient's skin.

[0088] In some embodiments, the filter element 214 is impermeable to liquids but permeable to gases, providing a liquid barrier to ensure that liquids cannot escape the wound dressing 155. The filter element 214 may also function as a bacterial barrier. Typically, the pore size is 0.2 μm. Suitable materials for the filter element 214 include 0.2 micron Gore™ expanded PTFE, PALL Versapore™ 200R, and Donaldson™ TX6628 from the MMT range. Larger pore sizes can also be used, but these may require a secondary filter layer to ensure complete biocontamination containment. Because wound fluid contains lipids, it is preferable, though not required, to use an oleophobic filter membrane, such as 1.0 micron MMT-332 followed by 0.2 micron MMT-323. This prevents lipids from blocking the hydrophobic filter. The filter element can be attached or sealed to a port or cover film over the orifice. For example, the filter element 214 may be molded into the fluid connector 160 or may be glued to one or both of the top of the cover layer and the bottom of the suction adapter 160 using an adhesive, such as, but not limited to, a UV-curable adhesive.

[0089] It will be appreciated that other types of materials can be used for the filter element 214. More broadly, a microporous membrane can be used, which is a thin, flat sheet of polymer material containing billions of tiny pores. Depending on the membrane chosen, these pores can range in size from 0.01 micrometers to greater than 10 micrometers. Microporous membranes are available in both hydrophilic (water filtering) and hydrophobic (water repellent) forms. In some embodiments, the filter element 214 comprises a support layer and an acrylic copolymer membrane formed on the support layer. In some embodiments, the wound dressing 155 according to certain embodiments uses a microporous hydrophobic membrane (MHM). Numerous polymers can be used to form the MHM. For example, the MHM can be formed from one or more of PTFE, polypropylene, PVDF, and acrylic copolymers. Any of these polymers can be treated to obtain specific surface properties, which can be both hydrophobic and oil-repellent. These will repel low surface tension liquids such as multivitamin injections, lipids, surfactants, oils and organic solvents.

[0090] The MHM blocks liquids while allowing air to flow through the membrane. It is also a highly efficient air filter, eliminating potentially infectious aerosols and particles. The single piece MHM is a popular option for replacing mechanical valves or vents. Therefore, the incorporation of the MHM can reduce product assembly costs and improve profits and the cost / benefit ratio for the patient.

[0091] The filter element 214 may also include an odor-absorbing material, such as activated carbon, carbon fiber cloth, or Vitec Carbotec-RT Q2003073 foam, or the like. For example, the odor-absorbing material may form a layer of the filter element 214 or may be sandwiched between hydrophobic microporous membranes within the filter element. The filter element 214 therefore allows gas to escape through the orifices. However, liquids, particulates, and pathogens are contained within the coating.

[0092] The wound dressing 155 may include a spacer element 215 in conjunction with the fluid connector 160 and the filter 214. The addition of such a spacer element 215 may support the fluid connector 160 and the filter 214 so that they do not come into direct contact with the absorbent layer 220 or the transmission layer 226. The absorbent layer 220 may also act as an additional spacer element to prevent the filter 214 from contacting the transmission layer 226. Thus, such a configuration may concomitantly minimize contact between the filter 214 and the transmission layer 226 and wound fluids during use.

[0093] Similar to the wound dressing embodiments described above, some wound dressings include a perforated wound contact layer with a silicone adhesive on the skin-contacting surface and an acrylic adhesive on the backside. Above this bordered layer is a transmission layer or 3D spacer cloth pad. Above the transmission layer is an absorbent layer. The absorbent layer may include a superabsorbent nonwoven (NW) pad. The absorbent layer may contact the transmission layer approximately 5 mm beyond the perimeter. The absorbent layer may have gaps or perforations toward one edge. The gaps may be approximately 10 mm in diameter. Above the transmission and absorbent layers is a backing layer. The backing layer may be a high moisture vapor transmission rate (MVTR) film that is patterned and coated with an acrylic adhesive. The high MVTR film and wound contact layer encapsulate the transmission and absorbent layers, creating a peripheral boundary of approximately 20 mm. The backing layer may have a 10 mm gap that overlaps the gap in the absorbent layer. Above the hole, a fluid connector may be coupled, comprising a liquid-impermeable, gas-permeable semi-permeable membrane (SPM) or filter that overlies the aforementioned gap.

[0094] Sensor-equipped wound dressing Wound dressings incorporating several sensors can be utilized to monitor wound characteristics as the wound heals. Collecting data from wounds that are healing well and from wounds that are not healing well can provide useful insights in identifying measurements to indicate whether the wound is on a healing trajectory.

[0095] In some implementations, several sensor technologies may be used in a wound dressing or one or more components forming part of the entire wound dressing device. For example, as shown in FIGS. 2 and 3, which depict wound dressings 250 and 320 including sensor arrays according to some embodiments, one or more sensors may be incorporated on or in the wound contact layer, which may be a perforated wound contact layer as shown in FIG. 3. While the wound contact layer in FIGS. 2 and 3 is shown as having a square shape, it will be understood that the wound contact layer may have other shapes, such as a rectangle, a circle, an oval, etc. In some embodiments, the sensor-integrated wound contact layer may be provided as a separate layer of material placed over the wound area and then covered by the wound dressing device or a component of the wound dressing device, such as gauze, foam or other wound packing material, a superabsorbent layer, a drape, a fully integrated dressing such as Pico or Allevyn Life dressing, etc. In other embodiments, the sensor-integrated wound contact layer may be part of a single-unit dressing, as described herein.

[0096] The sensor-integrated wound contact layer can be placed in contact with the wound and will allow fluid to pass through the contact layer with little or no damage to the tissue in the wound. The sensor-integrated wound contact layer can be made from a flexible material such as silicone and may incorporate antimicrobial agents or other therapeutic agents known in the art. In some embodiments, the sensor-integrated wound contact layer may incorporate an adhesive that adheres to wet or dry tissue. In some embodiments, the sensor(s) may be incorporated into or encapsulated within other components of the wound dressing, such as the absorbent layer or spacer layer described above.

[0097] As shown in Figures 2 and 3, five sensors can be used, including sensors for temperature (e.g., 25 thermistor sensors in a 5x5 array with approximately 20 mm pitch), oxygen saturation or SpO2 (e.g., four or five SpO2 sensors with a 10 mm pitch in a single line from the center to the edge of the wound contact layer), tissue color (e.g., 10 optical sensors in a 2x5 array with approximately 20 mm pitch; it is not necessary for all five sensors to be aligned per column of the array), pH (e.g., by measuring the color of a pH-sensitive pad, optionally using the same optical sensor as for tissue color), and conductivity (e.g., nine conductive contacts in a 3x3 array with approximately 40 mm pitch). As shown in Figure 3A, the SpO2 sensors can be arranged in a single line from the center or near the center of the wound contact layer to the edge of the wound contact layer. The linearity of the SpO2 sensor may allow the sensor to take measurements in the center of the wound, at the edge or wound, or on intact skin to measure changes between various regions. In some embodiments, the wound contact layer or sensor array may be larger than the size of the wound to cover not only the entire surface area of the wound but also the surrounding intact skin. A larger size wound contact layer and / or sensor array and multiple sensors may provide more information about the wound area than if sensors were placed only in the center of the wound or only in one area at a time.

[0098] Sensors may be incorporated onto flexible circuit substrates formed from flexible polymers including polyamide, polyimide (PI), polyester, polyethylene naphthalate (PEN), polyetherimide (PEI), various fluoropolymers (FEP) and copolymers, or any material known in the art. The sensor array may be incorporated into a two-layer flexible circuit. In some embodiments, the circuit board may be a multi-layer flexible circuit board. In some embodiments, these flexible circuits may be incorporated into any layer of the wound dressing. In some embodiments, the flexible circuit may be incorporated into a wound contact layer. For example, the flexible circuit may be incorporated into a wound contact layer similar to the wound contact layer described with reference to FIG. 1B. The wound contact layer may have cutouts or slits that allow one or more sensors to protrude from the lower surface of the wound contact layer and directly contact the wound area.

[0099] In some embodiments, the sensor-integrated wound contact layer can include first and second wound contact layers, with a flexible circuit board sandwiched between these two layers of wound contact layer material. The first wound contact layer has a lower surface intended to contact the wound and an upper surface intended to contact the flexible circuit board. The second wound contact layer has a lower surface intended to contact the flexible circuit board and an upper surface intended to contact the wound dressing or one or more components forming part of the entire wound dressing device. The upper surface of the first wound contact layer and the lower surface of the second wound contact layer can be glued together with the flexible circuit board sandwiched between these two layers.

[0100] In some embodiments, one or more sensors on the flexible circuit board can be completely encapsulated or covered by the wound contact layer to prevent contact with moisture or fluids in the wound. In some embodiments, the first wound contact layer can have cutouts or slits that allow one or more sensors to protrude from the underside and directly contact the wound area. For example, one or more SpO2 sensors, as shown in FIG. 3, are shown protruding from the bottom surface of the wound contact layer. In some embodiments, the SpO2 sensors can be mounted directly on the underside of the first wound contact layer. Some or all of the sensors and electrical or electronic components can be embedded or encapsulated (e.g., waterproof or liquid-proof) with a polymer, such as a silicone or epoxy-based polymer. The polymer encapsulation can prevent fluid ingress and chemical leaching from the components. In some embodiments, the wound contact layer material can seal the components to prevent water ingress and chemical leaching.

[0101] In some embodiments, gathering and processing wound-related information may utilize three components, including a sensor array, a control and processing module, and software, which are described in more detail herein.

[0102] In any one or more of the embodiments of FIG. 2 or FIG. 3, the sensor array portion may include multiple portions extending either about the periphery of a wound dressing component, such as a wound contact layer, or inward from the outer edge of the wound dressing component. For example, the illustrated embodiment includes multiple linearly extending portions that are parallel to the edges of the wound dressing component and, in some embodiments, may trace the entire periphery of the wound dressing component. In some embodiments, the sensor array portion may comprise a first plurality of parallel linearly extending portions that are perpendicular to a second plurality of parallel linearly extending portions. These linearly extending portions may also have different lengths and may extend inward to different locations within the interior of the wound dressing component. The sensor array portion preferably does not cover the entire wound dressing component, thereby forming gaps between the multiple portions of the sensor array. As shown in FIG. 2, this allows some, and possibly most, of the wound dressing component to be exposed by the sensor array. For example, for a perforated wound contact layer such as that shown in Figures 2 and 3, the sensor array portion may not block the majority of the perforations in the wound contact layer. In some embodiments, the sensor array may also be perforated or shaped to match the perforations in the wound contact layer to minimize the blockage of the perforations to fluid flow.

[0103] 3 shows a flexible sensor array integrated into a perforated wound contact layer 320, according to some embodiments. As shown, the sensor array may be sandwiched between two films or wound contact layers. The wound contact layer may have perforations formed as slits or holes, as described above, that are small enough to allow wound exudate to flow into the dressing while helping to prevent tissue ingrowth into the wound dressing. In some embodiments, the wound contact layer may have one or more slits, which increase the flexibility of the wound contact layer with the integrated sensor array. In some embodiments, one of the wound contact layers may have an extra cutout to accommodate the sensor so that the sensor can directly contact the skin.

[0104] In some embodiments, one or more of a thermistor, a conductivity sensor, an SpO2 sensor, or a color sensor can be used in a sensor array to provide information about the condition of the wound. The sensor array and individual sensors can assist clinicians in monitoring wound healing. One or more sensors can operate individually or in conjunction with each other to provide data related to wound and wound healing characteristics.

[0105] The temperature sensor may use a thermocouple or thermistor to measure temperature. The thermistor may be used to measure or track the temperature of the underlying wound or the thermal environment within the wound dressing. The temperature measurement sensor may be calibrated, and data obtained from the sensor may be processed to provide information about the wound environment. In some embodiments, an ambient sensor measuring ambient air temperature may also be used to help eliminate problems associated with environmental temperature shifts.

[0106] Optical sensors can be used to measure wound appearance using a light sensor or detector, such as an RGB sensor, with a light source or illumination source. In some embodiments, both the RGB sensor and the illumination source will be pressed against the skin, resulting in light penetrating into the tissue and exhibiting the spectral signature of the tissue itself.

[0107] Light propagation through tissue can be governed by two main phenomena: scattering and attenuation. For attenuation, as light passes through tissue, the intensity of the light can be lost due to absorption by various components of the tissue. Blue light tends to be highly attenuated, while light at the red end of the spectrum tends to be least attenuated.

[0108] Scattering processes can be more complex and can have various "regimes" that must be considered. The first aspect of scattering is based on the size of the scattering center compared to the wavelength of the incident light. If the scattering center is much smaller than the wavelength of light, Rayleigh scattering can be assumed. If the scattering center is on the order of the wavelength of light, the more detailed formulation of Mie scattering must be considered. Another factor that contributes to scattered light is the distance between the entry and exit of the scattering medium. If the mean free path of light (the distance between scattering events) is much longer than the distance traveled, ballistic photon transport is assumed. In the case of tissue, scattering events are approximately 100 microns apart, so a 1 mm path distance would effectively randomize the direction of the photons and the system would enter the diffusive regime.

[0109] The light source may be a light-emitting diode (LED), such as one or more of a white LED, an RGB LED, a UV LED, etc. In some cases, an ultra-bright LED, an RGB sensor, and a polyester optical filter can be used as components of an optical sensor to measure tissue color differences. For example, since surface color can be measured from reflected light, color can be measured from light that first passes through the tissue for a given shape. This can include sensing color from an LED in contact with the skin from diffusely scattered light. In some embodiments, an LED can be used in conjunction with a nearby RGB sensor to detect light diffused through the tissue. The optical sensor can image diffused internal light or surface reflected light.

[0110] Additionally, optical sensors can be used to measure autofluorescence. Autofluorescence is used because tissue absorbs light at one wavelength and emits at another. Additionally, dead tissue cannot autofluoresce, so this can be a very clear indicator of whether the tissue is healthy or not. It can be very useful to have a nearby red-sensitive photodiode (or some other wavelength-shifting frequency band) with UV light to act as a binary test for healthy tissue, for example, where blue light (or even UV light) with such a shallow penetration depth will autofluoresce at a very specific wavelength.

[0111] Conductivity sensors can be used to determine the difference between live and dead tissue or to indicate changes in impedance due to an open wound in diseased tissue. Conductivity sensors may include Ag / AgCl electrodes and an impedance analyzer. Conductivity sensors can be used to measure changes in impedance in wounded areas by measuring the impedance of the surrounding tissue / area. In some embodiments, a sensor array may utilize conductivity sensors to measure changes in conductivity on surrounding electrodes due to changes in wound size or shape. In some embodiments, conductivity sensors may be used in the wound bed or around the wound.

[0112] In some embodiments, a pH-changing pad can be used as a pH sensor. A spectrometer and a broadband white light source can be used to measure the spectral response of the pH dye. Illumination and imaging can be provided on the surface of the wound dressing in contact with the wound and on the bottom surface on the same side as the fluid application. Alternatively, in some embodiments, illumination and imaging sources can be provided on a surface of the wound dressing opposite the bottom surface and away from the fluid application, or on the top surface of the dressing.

[0113] In some embodiments, a pulse oximetry SpO2 sensor can be used. Pulsatile blood flow can be monitored to measure how oxygenated the blood is. Pulse oximetry works by measuring the time-resolved absorption / transmission of light in tissue at two different wavelengths of light. When hemoglobin is oxygenated, its absorption spectrum changes relative to deoxygenated blood. By measuring at two different wavelengths, a measure of how oxygenated the blood is is obtained.

[0114] Components in the sensor array may be connected by multiple connections. In some embodiments, the thermistors may be arranged in five groups. Each thermistor is nominally 10 kΩ, and each group of five has a common ground. There are five groups of thermistors, providing a total of 30 connections. In some embodiments, there may be nine conductive terminals. Each conductive terminal requires one connection, providing a total of nine connections. In some embodiments, there may be five SpO2 sensors. Each SpO2 sensor requires three connections in addition to power and ground (which are covered separately), providing a total of 15 connections. In some embodiments, there may be ten color sensors. Each color sensor includes an RGB LED and an RGB photodiode. Each color sensor requires six connections, five of which are common to all sensors, providing a total of 15 connections. Power and installation are considered separately. In some embodiments, there may be five pH sensors. The pH sensors may be color-changing disks and may be detected using the color sensors described above. Therefore, the pH sensor does not require any additional connections. There are three power rails and seven ground return signals, which may provide a total of 10 common connections. In some embodiments, the sensor array may include 25 thermistors (Murata NCP15WB473E03RC), 9 conductive terminals, 5 SpO2 (ADPD144RI), 10 RGB LEDs (such as KPTF-1616RGBC-13), 10 RGB color sensors, 10 FETs, a printed circuit board (PCB), and assembly.

[0115] Although the use of an RGB sensor and an LED is described in the specific example, any light sensor and illumination source can be used.

[0116] A control module can be used to interface with the sensor array (wirelessly or via one or more wired connections). In some embodiments, the control module may include a power source, such as a battery, and electronics to power the sensors. The control module may include one or more processors, as described herein. The control module may also log data at appropriate intervals and enable data transfer to an external computing device, such as a personal computer (PC). The control module may be customized with various features depending on the sensors used in the sensor array and the data collected by the sensors. In some embodiments, the control module may be comfortable and compact enough to be worn continuously for several weeks. In some embodiments, the control module may be located near or on the wound dressing. In some embodiments, the control module may be located remotely from the wound dressing and associated sensor array. Whether the control module is located on, near, or remote from the dressing, it may communicate with the sensor array and wound dressing via electrical wires or wireless communication. In some embodiments, the control module may be adaptable for use with different sensor arrays, allowing for easy replacement of the sensor array.

[0117] In some embodiments, the control module may include various requirements and combinations of features, including but not limited to the features listed in Table 1 below. [Table 1]

[0118] The control module may include a controller or microprocessor. Features of the control module may include a real-time clock (RTC), status LEDs, a USB connector, serial flash, and a debug connector.

[0119] In some embodiments, the microprocessor may have one or more of the following features: a 2.4 GHz or another suitable frequency radio (either integrated or external), a supplied Bluetooth software stack, an SPI interface, USB (or UART for external USB drivers), I2C, a 3-channel PWM, 32 GPIOs, or a 6-channel ADC. In some embodiments, the device may require at least 48 I / O pins, or possibly more, due to scaling limitations. A Bluetooth stack typically requires less than 20 kB of on-board flash, so a minimum of 32 kB may be required. In some embodiments, 64 kB may be required if complex data processing is considered. The processor core may be an ARM Cortex M4 or similar processor core. In some embodiments, parts may include ST's STM32L433LC or STM32F302R8, which may require an external radio or NXP's Kinetis KW class with an integrated radio.

[0120] In some embodiments, the control module can include a memory component, with the amount of local storage depending on the sample rate and resolution of the sensor. For example, an estimated data requirement of 256 Mb (32 MB) can be met by using serial flash devices from several manufacturers (Micron, Spansion).

[0121] The control module may utilize one or more analog switches. In some embodiments, analog switches with good on-resistance and reasonable bandwidth may be used. For example, Analog Devices' ADG72 or NXP's NX3L4051HR may be used. Based on the initial system architecture, eight of these will be required.

[0122] The control module may incorporate a power source such as a battery. For example, a 300 mWh / day battery may be used. For 7 days, 2100 mWh is provided. This may be provided by a 10-day supply of non-rechargeable ER14250 (14.5 mm diameter x 25 mm) LiSOCl2 cells, or a 7-day supply of rechargeable Li 14500 (14.5 mm diameter x 500 mm) Li-Ion cells.

[0123] The control module may incorporate a real-time clock (RTC). The RTC may be selected from any RTC device with a crystal. The control module may also include various resistors, capacitors, connectors, charge controllers, and other power supplies.

[0124] The control module PCB can be a four-layer board approximately 50mm x 20mm or 25mm x 40mm. The type of PCB used can be driven in large part by the connection requirements to the sensor array.

[0125] The control module housing may be a two-part molded piece with clip features that allow easy access for charging the sensor array or battery.

[0126] Data collected through the sensor array passes through the control module and may be processed by host software. The software may run on a processing device. The processing device may be a PC, tablet, smartphone, or other computer capable of running the host software. The processing device running the software may communicate with the control module through electrical wires or wirelessly. In some embodiments, the software may be configured to provide access to data stored on the control module rather than perform big data analytics. The host software may include an interface to the control module via Bluetooth or USB. In some embodiments, the host software may read the status of the control module, download log data from the control module, upload sample rate control to the control module, convert control module data into a format suitable for processing by a big data analytics engine, or upload data to the cloud for processing by the analytics engine.

[0127] The software may be developed for PC (Windows / Linux), tablet or smartphone (Android / iOS), or multiple platforms.

[0128] In some embodiments, some or all of the other components of the local negative pressure system, such as the negative pressure source (e.g., a pump), and power source(s), sensor(s), connector(s), user interface component(s) (e.g., button(s), switch(es), speaker(s), screen(s), etc.), and the like, may be integrated with the wound dressing. In some embodiments, components may be integrated below, within, on top of, or adjacent to the backing layer. In some embodiments, the wound dressing may include a second cover layer or a second filter layer for positioning over the wound dressing layer and any of the integrated components. The second cover layer may be the top layer of the dressing or may be a separate outer skin that surrounds the integrated components of the local negative pressure system.

[0129] As used herein, the top, uppermost, or upper layer refers to the layer that is furthest from the surface of the skin or wound while the dressing is in use and positioned over the wound, and the bottom, lower, lowermost, or lower layer thus refers to the layer that is closest to the surface of the skin or wound while the dressing is in use and positioned over the wound.

[0130] Positioning of components In some cases, electrical or electronic components, such as sensors, connections, etc., can be placed on, positioned on, or embedded within one or more wound dressing components, which can be placed in or on the wound, the skin, or both the wound and the skin. For example, one or more electronic components can be positioned on a substrate, such as on a side facing the wound. The substrate can be integrated with a wound contact layer as described herein (e.g., one or more electronic components can be positioned on or proximal to the lower surface 224 of the wound contact layer 222 in FIG. 1B). The substrate can be flexible, elastic, or stretchable, or substantially flexible, elastic, or stretchable, to conform to or cover the wound. For example, the substrate may be made from a stretchable or substantially stretchable material such as one or more of polyurethane, thermoplastic polyurethane (TPU), silicone, polycarbonate, polyethylene, polyimide, polyamide, polyester, polyethylene tetraphthalate (PET), polybutalene threaphthalate (PBT), polyethylene naphthalate (PEN), polyetherimide (PEI), along with various fluoropolymers (FEP) and copolymers, or another suitable material. In some cases, one or more electronic components may alternatively or additionally be disposed on or positioned on or embedded within any one or more of the transmission layer, absorbent layer, backing layer, or any other suitable layer of the wound dressing.

[0131] The electronic components (e.g., 402 in FIGS. 4-6 ) may be one or more of any electronic components described herein, such as a sensor (e.g., an LED, a temperature sensor, an optical sensor, etc.), a light source, a controller, or a processor (e.g., a communications processor). One or more of the electronic components may be connected by electronic connections, which may be tracks printed on a substrate, such as conductive copper, a conductive ink (such as silver ink, graphite ink, etc.), or the like. At least a portion of the electronic connections may be flexible or stretchable, or substantially flexible or stretchable. Connectors may be configured to electronically connect the electronic components to the electronic connections, which may in turn be connected to other electronic components located on the substrate, on or in other components of the wound dressing, or external to the wound dressing. Connectors may be pins, leads, bumps, etc. Additionally or alternatively, sockets may be used to support and electronically connect the electronic components.

[0132] In some implementations, it may be desirable for the wound contact layer to be stretchable to better conform to or cover the wound, but at least a portion of the electronic components may not be stretchable or flexible. In such cases, when the wound is covered with a wound dressing and the wound contact layer is positioned in or on the wound, undesirable or excessive localized strain or stress may be exerted on one or more electronic components, such as the support area or mounting portion of the electronic components. For example, such stress may be due to patient movement, changes in the shape or size of the wound (e.g., due to wound healing), etc. Such stress may cause one or more electronic components to move, fall off, or malfunction (e.g., creating an open circuit due to a pin or another connector being disconnected). Alternatively or additionally, it may be desirable to maintain the position of one or more electronic components, such as one or more sensors, in the same or substantially the same location or area on the wound contact layer relative to the wound (e.g., in contact with the wound) so that measurements collected by the one or more electronic components accurately capture changes over time in the same or substantially the same location or area of the wound. For example, as the patient moves, the surface of the stretchable wound contact layer may move, yet it may be desirable to position one or more electronic components in the same location or area relative to the wound.

[0133] In some cases, the substrate may be perforated to allow fluids, such as wound exudate, to pass through the substrate. Perforation may be achieved using one or more of cold pin perforation, hot pin perforation, laser ablation perforation, ultrasonic or ultrasonic perforation, etc., to render the wound contact layer permeable to liquids and gases. In some implementations, one or more utilized perforation processes may produce a flat or substantially flat substrate around the perforations, rather than an uneven surface (such as a donut-shaped surface). Having a flat or substantially flat substrate can help produce a uniform layer when the conformal coating is applied (such as via a spray, brush, etc., as described herein). Furthermore, using a perforation process that leaves an uneven or substantially flat surface of the substrate may pose a greater risk of one or more components, such as electronic connections or electronic component 2, becoming dislodged when perforations are made around the components.

[0134] In some cases, a coating can be applied to the substrate. The coating can be a conformal coating configured to encapsulate or coat the substrate or one or more components supported by the substrate, such as electronic connections or components. The coating can provide biocompatibility and shield or protect the electronics from contact with fluids and the like. The coating can be one or more of a suitable polymer, an adhesive such as 1072-M UV, light, or heat curable or hardening adhesive, Optimax adhesive (e.g., NovaChem Optimax 8002-LV), parylene (e.g., Parylene C), silicone, epoxy, urethane, acrylated urethane, or another suitable biocompatible and stretchable material. The coating can be thin, such as about 100 microns thick, less than about 100 microns thick, or more than about 100 microns thick. The coating can be applied and cured using one or more of UV, light, or heat curing. In some implementations, particularly if the substrate is not impermeable to fluids, the coating can be applied to the opposite side of the substrate (or the side facing away from the wound).

[0135] Any of the embodiments described herein can be used in conjunction with any of the features described in International Publication No. WO2018 / 189265, entitled "Component Stress Relief for Sensor Enabled Negative Pressure Wound Therapy Dressings," which is incorporated by reference in its entirety.

[0136] Component encapsulation and stress relief As described herein, a biocompatible coating can be applied to the wound contact layer or electronic components positioned on the wound contact layer. In some cases, the wound contact layer includes a thin, flexible substrate that conforms to the wound. For example, the substrate can be made of a stretchable or substantially stretchable material or film, such as polyurethane, TPU, silicone, polycarbonate, polyethylene, polyimide, polyamide, polyester, PET, PBT, PEN, PEI, or the like, along with various FEP and copolymers, or another suitable material. The substrate may not be biocompatible. The coating can be flexible. The coating can include one or more suitable polymers, adhesives such as 1072-M adhesive (e.g., Dymax 1072-M), 1165-M adhesive (Dymax 1165-M, etc.), parylene (such as Parylene C), silicone, epoxy, urethane, acrylated urethane, acrylated urethane substitute (such as Henkel Loctite 3381), or other suitable biocompatible and substantially stretchable materials. The coating may be thin, e.g., from about 80 microns or less up to several millimeters or more. As described herein, the coating may be applied by lamination, adhesive, welding (e.g., ultrasonic welding), and cured by one or more of light, UV, heat, etc. The coating may be transparent or substantially transparent to allow optical detection. The coating may retain its bond strength when subjected to sterilization, such as EtO sterilization. The coating may have a hardness of less than about A100, A80, A50, or less. The coating may have an elongation at break of greater than about 100%, 200%, 300%, or more. The coating may have a viscosity of about 8,000 to 14,500 centipoise (cP). In some cases, the coating may have a viscosity as high as about 3,000 cP. In some cases, the coating may have a viscosity less than about 3,000 cP. The coating may be fluorescent.

[0137] When the substrate and electronic components are intended to be positioned on or in the body, it may be desirable for the substrate and the electronic components supported by the substrate to be conformable. One aspect of conformability is the extensibility of the coating material, as the electronic components may need to be separated from the wound. The coating applied to the substrate may need to have the ability to stretch with the substrate (if the substrate is stretchable or substantially stretchable). Combining the elongation properties of both the substrate and the coating can maximize the desired properties of the device. In some examples, the substrate may be formed from a TPU film. The coating may be formed from an acrylated urethane, such as 1165-M Dymax, 1072-M Dymax, or another suitable material described herein.

[0138] The substrate may need to be uniformly and comprehensively coated (e.g., the substrate may be encapsulated with a biocompatible coating). The substrate (e.g., TPU) may be hydrophilic and therefore may need to be encapsulated with a hydrophobic coating to create a hydrophobic dressing to be placed on or in a wound. As used herein, biocompatible may mean complying with one or more applicable standards, such as ISO 10993 or USP Class VI.

[0139] FIG. 4 shows coating(s) of a wound dressing, according to some embodiments. As described herein, one of the sides of the substrate 530 of the wound dressing may include multiple electronic components 402 protruding from the surface. As shown in FIG. 4, a coating 440A may be applied to the side of the substrate that supports the electronic components. As described herein, the coating 440A may be biocompatible. The coating 440A may be hydrophobic. The coating 440A may be substantially stretchable or expandable.

[0140] As shown in FIG. 4, coating 440B can be applied to the opposite side of the substrate. This can be advantageous if the substrate is not biocompatible or hydrophobic. Coating 440B can be biocompatible. Coating 440B can be hydrophobic. Coating 440B can be substantially stretchable or expandable. Coatings 440A and 440B can be the same or different. As shown in FIG. 4, substrate 530 can be encapsulated with a coating. Although not shown, the left and right sides of substrate 530 are also encapsulated with a coating.

[0141] FIG. 5 illustrates coating of a wound dressing with two biocompatible coatings, according to some embodiments. Electronic components 402 supported by a substrate 530 may be coated with coating 640A, particularly if substrate 530 is stretchable or substantially stretchable. As described herein, coating 640A may be non-stretchable or substantially non-stretchable to provide stress relief to the electronic components (which may include electronic modules or electronic connections). Coating 640A may be applied over and around the electronic components. Coating 640A may be biocompatible. Coating 640A may be hydrophobic.

[0142] The non-stretchable or substantially non-stretchable coatings described herein, such as coating 640A, can be formed from acrylated urethane materials or modified urethane materials (e.g., Henkel Loctite 3211). For example, the coating can be one or more of Dymax 1901-M, Dymax 9001-E, Dymax 20351, Dymax 20558, Henkel Loctite 3211, or another suitable material. The coating can have a viscosity of about 13,500 cP to 50,000 cP before curing, or a viscosity of about 3,600 cP to about 6,600 cP before curing. In some cases, the coating can have a viscosity of about 50,000 cP or less. The coating can have a hardness of about D40 to about D65 and / or a linear shrinkage of about 1.5 to 2.5%. The coating can be transparent or substantially transparent to allow for optical detection. The coating may be colorless or substantially colorless. Coating 640A may be fluorescent. The coating may retain its bond strength when subjected to sterilization, such as EtO sterilization.

[0143] As shown, coating 640B can be applied to the remaining surface of the side of the substrate that supports the electronic components. Coating 640B can also be applied to the opposite side of the substrate. Although not shown, the left and right sides of substrate 530 are also encapsulated with a coating. Coating 640B can be biocompatible. Coating 640B can be hydrophobic. Coating 640B can be substantially stretchable or expandable. Coating 640B can be similar to any one or more of the flexible or substantially flexible coatings described herein. For example, coating 640B can be formed from an acrylated urethane or its substitute, such as 1165-M Dymax, 1072-M Dymax, Henkel Loctite 3381, or another suitable material.

[0144] In some cases, a non-elastic or substantially non-elastic coating may not be biocompatible. As shown in FIG. 6 , electronic components 402 supported by a substrate 530 are coated with a non-elastic or substantially non-elastic coating 740A that is not biocompatible. A second coating 740B may be applied to the side of the substrate 530 that supports the electronic components. Coating 740B may be applied over coating 740A. Coating 740B may also be applied to the opposite side of the substrate. Although not shown, the left and right sides of the substrate 530 are also encapsulated with coating 740B. Coating 740B may be biocompatible. Coating 740B may be hydrophobic. Coating 740B may be substantially elastic or expandable.

[0145] Coating a thin, flexible substrate with a biocompatible material can be challenging because the substrate may need to be coated on both the side where the electronic components are located and the opposite side, and the substrate may need to be coated uniformly and comprehensively (e.g., the substrate may be encapsulated by the biocompatible coating).

[0146] Any of the embodiments described herein may be used with any of the features described in International Application No. PCT / EP2018 / 069883, entitled "Biocompatible Encapsulation and Component Stress Relief for Sensor Enabled Negative Pressure Wound Therapy Dressings," which is incorporated by reference in its entirety.

[0147] Controlling the surface roughness of coatings In some cases, the surface finish of a coating can affect the accuracy of optical detection. This can be due, for example, to a rougher surface scattering more light than a smoother surface. For example, when considering the optical path from a light source (such as an LED) through the coating and the return path of the light through the coating toward a light sensor or detector, it may be desirable to reduce light scattering at the coating. For example, the path of light emitted by the light source may be at a particular angle relative to the wound, and the path of light reflected by the wound may be at the same or a different angle. Surface roughness can affect at least the refractive index of the coating, which in turn can affect the angle at which the light travels and the accuracy of optical detection or sensing of one or more aspects of the wound, such as color. Therefore, it may be desirable to reduce or control the surface roughness of a coating (or any other aspect of the surface finish).

[0148] In some scenarios, a particular coating may have desirable properties (such as biocompatibility, hydrophobicity, extensibility, etc.), but the surface roughness of the coating may be undesirable to facilitate the accuracy of optical detection. A secondary material (such as a film) may be applied to the coating to control or reduce the surface roughness. The secondary material may have a smoother surface, thereby controlling or reducing the surface roughness of the resulting coating. In some cases, the secondary material may be applied before curing the coating (using any of the curing methods described herein). It may be desirable to apply a hydrophobic secondary material. In such cases, the use of a hydrophilic secondary material, such as a polyurethane (PU) film, may be undesirable. The secondary material may be optically clear or transparent, such as an optically clear film.

[0149] In some cases, a high viscosity liquid or gel can be used as the secondary material. The secondary material can be viscoelastic and / or hydrophobic. For example, a silicone grease, such as high vacuum grease, can be used. As another example, fats, lipids, oils, vegetable oils, greases (synthetic or natural), etc. can be used.

[0150] In some cases, a film coated with a silicone finish can be used as the secondary material. The silicone-coated side of the film can be placed facing the wound, with the uncoated side of the film in contact with the coating. In some scenarios, the silicone-coated side of the film can be placed in contact with the coating. In certain cases, both sides of the film can be coated with silicone. The silicone coating can provide the desired hydrophobicity when applied to a hydrophilic material, such as a PU film. The silicone coating can also be optically transparent.

[0151] In some scenarios, other coatings can be applied to the secondary material (such as a film) in addition to or instead of silicone. For example, polytetrafluoroethylene (PTFE), polyethylene (PE), PET, nylon, other hydrophobic hydrocarbon-based polymer films (such as cling film or plastic wrap), lacquers, varnishes, etc. can be used. The coating can be optically clear. The coating can be hydrophobic.

[0152] Any of the secondary materials described herein may be one or more of optically clear or substantially optically clear, hydrophobic or substantially hydrophobic, or expandable or stretchable or substantially expandable or stretchable.

[0153] The use of a coating on a secondary material, such as a silicone coating, can provide several advantages. For example, the coating can modify the surface hydrophobicity of the secondary material to a desired level. As another example, it can improve light transmission efficiency. For example, the coating can provide an intermediate refractive index layer between the secondary material and the fluid (such as air, water, exudate, blood, sweat, or other aqueous liquids), thereby reducing optical scattering and improving the light transmission efficiency of an otherwise uncoated secondary material (such as a PU film). As yet another example, the coating may be suitable for direct contact with biological tissue.

[0154] FIG. 7 illustrates optical sensing using a coated wound dressing, according to some embodiments. As described herein, one of the sides of the substrate 530 of the wound dressing can include multiple electronic components protruding from the surface. Such components can include a light source 802A and a photodetector 802B. As shown, these components are positioned on the side of the substrate 530 facing the wound. The electronic components, including 802A and 802B, are coated with a coating 842, which can be similar to coating 440A described herein. A secondary material 844 can be applied to coating 842 to control or reduce the surface roughness of the coatings described herein. As shown, light emitted from light source 802A passes through coating 842, is reflected from the wound, passes through coating 842, and is detected by photodetector 802B. As shown, using a secondary material to control or reduce the surface roughness of coating 842 can reduce the coating's interference with light propagation and improve the accuracy of optical detection.

[0155] For ease of understanding, Figure 7 shows a cleft between the substrate and the wound, but one or more sensors supported by substrate 530 may be positioned in contact with the wound. Light may travel into the tissue and reflect back toward photodetector 802B. In some cases, fluid (such as wound exudate) may be present in the path of the light.

[0156] In some cases, a secondary material may alternatively or additionally be applied to the side of coating 842 that faces away from the wound. In some cases, an additional coating may be included, such as a substantially non-stretchable coating (e.g., 740A), as described herein.

[0157] In certain cases, the secondary material can be applied to the coating using a carrier, which may be removable. FIG. 8 illustrates the application of a secondary material, such as a film, to a coating in a wound dressing, according to some embodiments. A release carrier 940 (shown as the top of FIG. 8 ) includes a coated region 944 (e.g., a silicone-coated film region) and a release liner or handle 942, which may be removable. The coated region 944 may be applied to a coating 902 applied to a substrate described herein. The coated region 944 may be applied to one or more of the coatings applied to the wound-facing or non-wound-facing side of the substrate. This may be done before the coating 902 cures. The release handle 942 may be removed after the application of the coated region to the coating 902, such as after curing. The release handle 942 may be rigid or substantially rigid. For example, the release handle 942 may be made from cardboard or corrugated cardboard.

[0158] Although the foregoing describes, in some cases, one or more sensors being positioned on the wound-facing side of the substrate, the foregoing approach may be used with substrates that additionally or alternatively support sensors on the non-wound-facing side of the substrate.

[0159] Prevents light bleeding and saturation The accuracy of optical detection can depend on the optical clarity or optical transparency of the coating(s). Because a transparent material allows light (of a particular wavelength or wavelengths) to be transmitted through the material without light absorption or reflection, it may be desirable to use a substantially transparent coating (of a particular wavelength or wavelengths, such as IR-UV wavelengths).

[0160] In some cases, the use of an optically transparent coating may unnecessarily direct light emitted from the light source directly to the light sensor or detector. The internal reflectivity of the coating allows a light pipe or guide to be formed within the coating, directing light through the coating directly from the light source to the detector. This may undesirably prevent the light from being directed toward the wound. Additionally, the guided light may saturate the detector, especially if the spacing between the light source and the detector is small, such as less than about 10 mm, less than about 15 mm, less than about 20 mm, or another suitable value.

[0161] 9A shows the red, green, and blue values detected by an RGB detector in an uncoated substrate in response to the emission of light of a particular color, such as dark red. The detected normalized RGB values are plotted on the y-axis, and the sensor number is plotted on the x-axis (there are nine sensors in the embodiment shown). A sufficient separation is shown between the R value at the top and the G and B values at the bottom. Such separation indicates accurate detection of the color of the emitted light.

[0162] Figure 9B shows the red (R), green (G), and blue (B) values detected by an RGB detector within the coated substrate. In contrast to Figure 9A, there is not enough separation between the R, G, and B values detected by the optical detector because light is directed directly from the light source to the detector, saturating the detector. This leads to inaccurate detection (e.g., the detected color is gray and dark red is not emitted).

[0163] To address these issues, a void can be formed in the substrate between the light source and the detector. The void can be a hole, a slot, or the like. The void can be formed by one or more of laser drilling (e.g., laser ablation drilling), cold pin drilling, hot pin drilling, pin punch drilling, ultrasonic or ultrasonic drilling, or the like. The void can be formed through the thickness of the substrate material, for example, through the entire thickness. The void can disrupt the light guide formed in the coating between the light source and the detector, regardless of the orientation of light emission by the light source (e.g., vertically emitted, laterally emitted, etc.). The void can be formed before or after application of the coating to the substrate. In cases where the void is formed before application of the coating, the coating can be applied such that it does not fill the void when applied to the substrate. For example, the coating may flow through the void, thereby not filling or only partially filling the void. The void can create an internal reflective wall in the coating, thereby eliminating or minimizing any light-guiding effects formed in the coating.

[0164] 10A shows a void 1002A in substrate 530, according to some embodiments. Void 1002A is shown as a hole formed through substrate 530 and is located between light source 845 and light detector 846.

[0165] 10B shows a void 1002B in substrate 530, according to some embodiments. The void 1002B is shown as a slot formed through substrate 530 and is located between light source 845 and light detector 846.

[0166] In some scenarios, one or more voids formed in the substrate may further allow fluids such as wound exudate, blood, etc. to pass through the substrates described herein. Advantageously, the location of the void between the light source and the photodetector may allow detection of one or more optical properties of the wound exudate passing through the void, such as the color of the exudate, the presence of blood, the properties of the blood (e.g., level of oxygenation), etc.

[0167] In some cases, redundant electrical or mechanical components can be installed between the optical sensor and the detector in place of an air gap, which can act to eliminate or minimize any light-induced effects in the coating.

[0168] In some situations, lenses can be used to shape or direct the light emitted by the light source. The lenses can be used to collimate the emitted light beam, improve color uniformity, improve color distribution, and / or the like. For example, the lenses can be reflectors or reflectors with total internal reflection (TIR) lenses. In some cases, a light guide through the coating can be created by placing a lens within the coating. A light guide (rather than a photodetector as described herein) can be used to direct the emitted light toward the wound. The photodetector can be configured to ignore noise from light sources other than the light source associated with the photodetector (e.g., to eliminate or reduce crosstalk between adjacent light sources). For example, light having an intensity below a threshold can be ignored by the detector as noise. The light guide formed through the coating can be used to focus the light emitted by the light source, thereby improving detection accuracy, at least in part.

[0169] Any of the embodiments described herein may be used in conjunction with any of the features described in one or more of International Application No. PCT / EP2018 / 075815, entitled "Sensor Positioning and Optical Sensing for Sensor Enabled Wound Therapy Dressings and Systems," International Application No. PCT / EP2018 / 069883, entitled "Biocompatible Encapsulation and Component Stress Relief for Sensor Enabled Wound therapy Dressings," and International Application No. PCT / EP2018 / 078374, entitled "Fluid Management for Sensor Enabled Wound Therapy Dressings and Systems," each of which is incorporated by reference in its entirety.

[0170] Other variations In some embodiments, one or more electronic components may be located on the side of the wound contact layer opposite the wound-facing side, and the systems and methods described herein are equally applicable to such wound contact layers.

[0171] Although certain embodiments described herein relate to wound dressings, the systems and methods disclosed herein are not limited to wound dressings or medical applications. The systems and methods disclosed herein are generally applicable to electronic devices in general, such as electronic devices that can be worn or applied by a user.

[0172] Any values, such as thresholds, limits, time periods, etc., provided herein are not intended to be absolute values and may therefore be approximate. In addition, any thresholds, limits, time periods, etc. provided herein may be fixed or variable, either automatically or by a user. Furthermore, as used herein, terms expressing a relative degree, such as greater than, over, or less than, relative to a reference value, are intended to encompass equality with the reference value. For example, exceeding a positive reference value can encompass being equal to or greater than the reference value. In addition, as used herein, terms expressing a relative degree, such as greater than, over, or less than, relative to a reference value, are intended to encompass the inverse of the disclosed relationship, such as less than, under, or over, relative to the reference value. Furthermore, although various process blocks may be described with respect to determining whether a value meets or does not meet a particular threshold, the blocks may equally be understood with respect to, for example, whether a value (i) is less than or exceeds a threshold, or (ii) meets or does not meet a threshold.

[0173] It should be understood that a feature, material, characteristic, or group described in connection with a particular aspect, embodiment, or example can be applied to any other aspect, embodiment, or example described herein, unless it is inconsistent with the other aspect, embodiment, or example. All features disclosed in this specification (including any accompanying claims, abstract, and drawings), or all steps of any similarly disclosed method or process, may be combined in any combination, except combinations in which at least some of such features or steps are mutually exclusive. Protection is not limited to the details of any of the foregoing embodiments. Protection extends to any novel, or any novel combination, of features disclosed in this specification (including any accompanying claims, abstract, and drawings), or any novel, or any novel combination of steps of any similarly disclosed method or process.

[0174] While certain embodiments have been described, these embodiments are presented by way of example only and are not intended to limit the scope of the protected subject matter. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Additionally, various omissions, substitutions, and changes may be made in the form of the methods and systems described herein. Those skilled in the art will appreciate that, in some embodiments, the actual steps performed in the illustrated or disclosed processes may differ from those shown in the figures. In some embodiments, certain of the steps described above may be omitted, or others may be added. For example, the actual steps or order of steps performed in the disclosed processes may differ from those shown in the figures. In some embodiments, certain of the steps described above may be omitted, or others may be added. For example, various components illustrated in the figures may be implemented as software or firmware on a processor, controller, ASIC, FPGA, or dedicated hardware. Hardware components, such as controllers, processors, ASICs, FPGAs, and the like, may include logic circuitry. Furthermore, the features and characteristics of the specific embodiments disclosed above may be combined in different ways to form additional embodiments, all of which fall within the scope of the present disclosure.

[0175] While the present disclosure includes certain specific embodiments, examples, and applications, those skilled in the art will recognize that the present disclosure extends beyond the specifically disclosed embodiments to other alternative embodiments or uses, and obvious variations and equivalents thereof, including embodiments that may not provide all of the features and advantages described herein. Accordingly, the scope of the present disclosure is not intended to be limited by the specific disclosure of preferred embodiments herein, but may be defined by the claims presented herein or hereafter.

[0176] Conditional language such as "can," "could," "might," or "may," unless specifically stated otherwise or interpreted otherwise within the context of use, is typically intended to convey that certain embodiments include certain features, elements, or steps, while other embodiments do not. Thus, such conditional language is not generally intended to imply that features, elements, or steps are required in any way for one or more embodiments, or that one or more embodiments necessarily include logic for determining, with or without user input or instruction, whether those features, elements, or steps are included in or should be performed in any particular embodiment. Terms such as "comprise," "include," and "have" are synonymous and used in an inclusive, open-ended manner and do not exclude additional elements, features, acts, operations, etc. Also, the term "or" is used in an inclusive sense (as opposed to an exclusive sense), such that, for example, when used to connect a list of elements, the term "or" means one, some, or all of the elements in the list. Further, the term "each," as used herein, in addition to having its ordinary meaning, can also refer to any subset of the list of elements to which the term "each" is applied.

[0177] Conjunctive phrases such as "at least one of X, Y, and Z," unless specifically stated otherwise, are to be construed otherwise in accordance with the context in which they are generally used to suggest that an item, term, etc. may be either X, Y, or Z. Thus, such conjunctive phrases are generally not intended to suggest that a particular embodiment requires the presence of at least one X, at least one Y, and at least one Z.

[0178] As used herein, degree-expressing phrases, such as "approximately," "about," "generally," and "substantially," refer to values, amounts, or characteristics that approximate a given value, amount, or characteristic that still performs a desired function or produces a desired result. For example, the terms "approximately," "about," "generally," and "substantially" can refer to an amount that is within 10%, 5%, 1%, 0.1%, and 0.01% of a given amount. As another example, in certain embodiments, the terms "generally parallel" and "substantially parallel" refer to values, amounts, or characteristics that deviate from exactly parallel by 15 degrees or less, 10 degrees or less, 5 degrees or less, 3 degrees or less, 1 degree or less, or 0.1 degrees or less.

[0179] The scope of the present disclosure is not intended to be limited by the specific disclosure of preferred embodiments in this section or elsewhere herein, but may be defined by the claims set forth in this section or elsewhere herein, or set forth hereafter. The claim language is to be interpreted broadly based on the language used in the claims, and is not limited to the examples described herein or described during the prosecution of this application, which examples are to be construed as non-exclusive. [Additional note 1] 1. A method of coating a wound dressing, said method comprising: coating a wound-facing side of a substantially flexible substrate of the wound dressing with a coating, the wound-facing side of the substrate supporting at least one optical sensor; and at least one of reducing or controlling the surface texture of the coating by applying a film to the coating to improve detection by the at least one optical sensor. [Additional note 2] 10. The method of claim 1, wherein reducing or controlling the surface texture of the coating comprises reducing the surface roughness of the coating. [Additional note 3] 3. The method of any one of clauses 1 or 2, wherein coating the wound-facing side of the substantially flexible substrate of the wound dressing with the coating comprises applying the coating to the at least one optical sensor. [Additional note 4] 4. The method of any one of clauses 1 to 3, wherein the at least one optical sensor comprises a light source and a detector configured to detect light reflected by the wound. [Additional note 5] 5. The method of any one of claims 1 to 4, wherein applying the film to the coating comprises applying the film before the coating has cured. [Additional note 6] 6. The method according to any one of appended items 1 to 5, wherein the film is coated with silicone. [Additional note 7] 7. The method of any one of clauses 1 to 6, wherein applying the film to the coating comprises applying a carrier coated on at least one side with silicone, wherein the at least one side of the silicone coated carrier contacts the coating, and the method further comprises removing the carrier after the coating has cured. [Additional note 8] 8. The method according to any one of appended items 1 to 7, wherein the coating is hydrophobic. [Additional note 9] A wound dressing produced by the method according to any one of appendixes 1 to 8. [Additional Note 10] 1. A wound dressing comprising: a substantially flexible substrate supporting at least one optical sensor, the at least one optical sensor comprising a light source and a detector configured to sense reflected light; a gap in the substrate, the gap being positioned between the light source and the detector; a coating applied to the substrate and covering the at least one optical sensor; A wound dressing, wherein the gap prevents light emitted by the light source from transmitting through the coating to the detector. [Additional Note 11] 11. The wound dressing of claim 10, wherein the voids comprise holes or slots in the material forming the substrate. [Additional Note 12] 12. The wound dressing according to claim 10 or 11, wherein the voids are formed throughout the thickness of the substrate. [Additional Note 13] 13. The wound dressing according to any one of claims 10 to 12, wherein the distance between the light source and the detector is 10 millimeters or less. [Additional Note 14] 14. The wound dressing according to any one of claims 10 to 13, wherein the coating does not fill the entire voids in the substrate. [Additional Note 15] 1. A method of making a wound dressing, comprising: forming an air gap in a substantially flexible substrate supporting at least one optical sensor, the at least one optical sensor comprising a light source and a detector configured to sense reflected light, the air gap being positioned between the light source and the detector; subsequently applying a coating to the substrate and covering the at least one optical sensor with the coating. [Additional Note 16] 16. The method of claim 15, wherein the void comprises a hole or a slot in the substrate. [Additional Note 17] 17. The method of any one of claims 15 or 16, wherein the voids are formed throughout the thickness of the substrate. [Additional Note 18] 18. The method of any one of appended items 15 to 17, wherein applying the coating includes not filling the entire void in the substrate. [Additional Note 19] 1. A method of making a wound dressing, comprising: applying a coating to a substantially flexible substrate supporting at least one optical sensor and covering the at least one optical sensor with the coating, the at least one optical sensor comprising a light source and a detector configured to sense reflected light; Subsequently, forming a cavity in the substrate, the cavity being positioned between the light source and the detector. [Additional Note 20] 20. The method of claim 19, wherein the void comprises a hole or slot in the substrate. [Additional Note 21] 21. The method of any one of claims 19 to 20, wherein the voids are formed throughout the thickness of the substrate.

Claims

1. 1. A wound dressing comprising: a substantially flexible substrate supporting at least one optical sensor, the at least one optical sensor comprising a light source and a detector spaced apart from the light source and configured to sense reflected light; a gap in the substrate, the gap being positioned between the light source and the detector; a coating applied to the substrate and covering both the light source and the detector that constitute the at least one optical sensor; A wound dressing wherein the voids create internal reflective walls within the coating that prevent light emitted by the light source from transmitting through the coating to the detector.

2. The wound dressing of claim 1 , wherein the voids comprise holes or slots in the material forming the substrate.

3. 3. The wound dressing of claim 1, wherein the voids are formed through the entire thickness of the substrate.

4. A wound dressing according to any one of claims 1 to 3, wherein the distance between the light source and the detector is 10 millimeters or less.

5. A wound dressing according to any preceding claim, wherein the coating does not fill the entire void within the substrate.

6. 1. A method of making a wound dressing, comprising: forming an air gap in a substantially flexible substrate supporting at least one optical sensor, the at least one optical sensor comprising a light source and a detector spaced apart from the light source and configured to sense reflected light, the air gap being positioned between the light source and the detector; Subsequently, applying a coating to the substrate, the coating covering both the light source and the detector that form the at least one optical sensor; Including, The method wherein the air gap creates an internal reflective wall within the coating that prevents light emitted by the light source from transmitting through the coating to the detector.

7. The method of claim 6 , wherein the voids comprise holes or slots in the substrate.

8. The method of claim 6 or 7, wherein the voids are formed through the entire thickness of the substrate.

9. The method of any one of claims 6 to 8, wherein applying the coating comprises not filling all of the voids in the substrate.

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