Medical component with a microstructure for performing humidification and condensate management

Abstract

Components suitable for providing humidified gas to and / or removing humidified gas from a patient are provided. The microstructures 801 of the humidification chamber 129 are arranged vertically around the periphery of the humidification chamber 129, with the microstructures being perpendicular (or nearly perpendicular) to the base 705 of the chamber. The vertical microstructures carry the water 130 up the sides of the chamber, so that a larger surface area of ​​the water is exposed to the air flow within the chamber.

Description

Technical Field

[0001] Cross - Reference to Related Applications This application claims the benefit of U.S. Provisional Patent Application No. 61 / 785,895, filed on Mar. 14, 2013, and U.S. Provisional Patent Application No. 61 / 664,069, filed on Jun. 25, 2012, and incorporates them herein by reference in their entirety.

[0002] The present disclosure generally relates to components suitable for medical use, and more specifically to components suitable for delivering humidified gas to and / or removing humidified gas from a patient, such as components suitable for positive airway pressure (PAP), respirators, anesthesia methods, ventilators, and gas injection systems.

Background Art

[0003] In medical circuits, various components transport humidified gas to a patient either naturally or artificially. For example, in some respiratory circuits such as PAP and assisted breathing circuits, the gas inhaled by the patient is delivered from a heated - humidifier through an inspiratory tube to a patient interface, such as a mask. As another example, in a gas injection circuit, a tube can deliver humidified gas (usually CO2) to the abdominal cavity. This can help prevent "drying" of the patient's internal organs and can reduce the time required for recovery from surgery.

[0004] In these medical applications, the gas is preferably delivered under conditions having a humidity close to the saturation level and a temperature near body temperature (usually a temperature of 33°C to 37°C). When highly humid gas cools, condensation or "rain - out" can occur on the inner surface of the components. There is a need for components with improved humidification and condensate management in medical circuits. Therefore, the purpose of some of the components and methods described herein is to improve one or more of the problems of prior art systems or, at least, to provide useful alternatives to the general public.

Summary of the Invention

Means for Solving the Problems

[0005] Medical components having a microstructure, i.e., a micro-structure, for performing humidification and / or condensate management, and methods of manufacturing such components are disclosed in various embodiments.

[0006] In at least one embodiment, a component for use in a medical circuit includes a first region that contacts a liquid during use; a second region that is separate from the first region; and a microstructure surface that communicates with the first region and the second region and is configured to wick, i.e., draw, liquid from the first region to the second region during use, the microstructure surface including a substrate having an equilibrium contact angle of less than about π / 2 radians.

[0007] In various embodiments, the components described above have one, several, or all of the following characteristics, as well as the characteristics described elsewhere in this disclosure.

[0008] The second region can be exposed to faster air during use, and the first region can be exposed to slower air during use. The second region can be configured to communicate with a heat source. The microstructure surface can be configured to communicate with a heat source. The microstructure surface can include substantially parallel microchannels. The microchannels can be generally square in shape. The critical contact angle θ for the microchannels satisfies the equation:

Number

Number

[0009] In various embodiments, the above-described components may be incorporated into a mask. The mask may further include a drain communicating with a second region.

[0010] In various embodiments, the above-described components may be incorporated into a conduit. The component may form at least a portion of the inner wall of the conduit. The component may be an insert into the inner lumen of the conduit. The wall of the conduit may be configured to communicate with a heat source.

[0011] In at least one embodiment, a component for use in a medical circuit includes a reservoir portion configured to hold a liquid; an evaporator portion adjacent to the reservoir portion and configured to promote evaporation of the liquid; and a microstructured surface configured to transport the liquid from the reservoir portion to the evaporator portion.

[0012] In various embodiments, the above-described components have one, some, or all of the following characteristics, as well as the characteristics described elsewhere in this disclosure.

[0013] The evaporator portion may be heatable. The microstructured surface includes microchannels having a low aspect ratio near the reservoir portion and a high aspect ratio near the evaporator portion, and the aspect ratio may increase along the gradient. The microstructured surface can include a first microchannel extending substantially horizontally near the reservoir portion and a second microchannel extending substantially vertically near the evaporator portion, and the first microchannel is configured to transport the liquid to the second microchannel.

[0014] In various embodiments, the above-described components may be incorporated into a mask.

[0015] In various embodiments, the above-described components may be incorporated into a chamber suitable for use with a humidifier unit. The components may form at least a portion of the inner wall of the chamber. The chamber may include a wall configured to be heated by a heater base of the humidifier unit. The chamber may include a wall configured to be heated by a heating member separate from the humidifier unit. The chamber may further include an insulating material disposed on or covering the wall of the chamber, at least in the vicinity of the evaporator portion.

[0016] In various embodiments, the above-described components may be incorporated into a conduit. The microstructured surface may form at least a portion of the inner wall of the conduit. The microstructured surface may be disposed on an insert within the inner lumen of the conduit. The wall of the conduit is configured to communicate with a heat source.

[0017] In at least one embodiment, a component of a medical circuit for use with a humidified gas includes a wall that defines a space therein, with at least a portion of the wall comprising a surface within and on a substrate having an outer surface with an equilibrium contact angle of less than about π / 2 radians and including a plurality of microchannels, the microchannels being configured to wick liquid water from a first region that holds the liquid water during use to a second region where the liquid is exposed to air flowing to or from a patient, and the microchannels including a first microchannel having a side portion and a bottom portion lower than the outer surface of the substrate, and a second microchannel having a side portion higher than the outer surface of the substrate, the side portion of the second microchannel being formed by a ridge around or between the first microchannels.

[0018] In various embodiments, the above-described medical circuit has one, several, or all of the following characteristics, as well as the characteristics described elsewhere in this disclosure.

[0019] The first microchannel may be generally square-shaped. The critical contact angle θ for the first microchannel is given by the formula:

Equation

[0020] In some embodiments, the components for use in a medical circuit include a substantially horizontal planar microstructure surface configured to disperse a liquid thereon. The microstructure surface is disposed in the path of a flowing gas, and the liquid dispenser may be configured to dispense the liquid in small amounts onto the microstructure surface.

[0021] In various embodiments, the microstructure surface includes surface irregularities.

[0022] In various embodiments, the surface irregularities include at least one of the group consisting of granules, ridges, grooves, channels, and particles.

[0023] In various embodiments, the liquid dispenser includes at least one dropper configured to dispense the liquid onto the microstructure surface one drop at a time.

[0024] In various embodiments, the liquid dispenser includes a substantially flat plate positioned at a distance above the microstructure surface, the plate including a plurality of holes through which the liquid can fall onto the underlying microstructure surface.

[0025] These and other embodiments are described in detail below.

[0026] Exemplary embodiments that implement various features of the disclosed systems and methods will now be described with reference to the drawings. The drawings and associated descriptions are provided to illustrate the embodiments and are not intended to limit the scope of the present disclosure.

Brief Description of the Drawings

[0027]

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[0028] Throughout the drawings, reference numerals are often reused to indicate correspondence between referenced (or similar) elements. Further, the first digit of each reference numeral indicates the figure number in which the element first appears.

[0029] The following detailed description discloses components of a novel medical circuit and methods of forming such components, such as components of a gas injection, anesthesia, or breathing circuit. As described above, these components include microstructures for humidification and / or condensate management. The disclosed microstructures can be incorporated into various components including tubes (e.g., inspiratory breathing tubes and expiratory breathing tubes, and other tubes between various elements of a breathing circuit such as a ventilator, humidifier, filter, water trap, sample line, connector, gas analyzer, etc.), Y connectors, catheter mounts, humidifiers, and patient interfaces (e.g., masks covering the nose and face, nasal masks, cannulas, nasal pillows, etc.), floats, probes, and sensors. A medical circuit is a broad term and its original and ordinary meaning is given to those skilled in the art (i.e., not limited to a special or customized meaning). Therefore, a medical circuit is meant to include some CPAP systems that can include an open circuit, e.g., a single inspiratory breathing tube between a ventilator / blower and a patient interface, as well as a closed circuit.

[0030] Details regarding some illustrative embodiments for implementing the apparatus and methods described herein will be described below with reference to the drawings. The present invention is not limited to these described embodiments.

[0031] Medical circuit To understand the present disclosure in more detail, first, reference is made to FIG. 1 showing a medical circuit according to at least one embodiment. More specifically, FIG. 1 shows an exemplary breathing circuit. Such a breathing circuit can be, for example, a continuous, variable, or bi-level positive airway pressure (PAP) system, or other forms of respiratory therapy. As described below, the breathing circuit includes one or more medical tubes, a humidifier, and a patient interface. Any or all of these components of the medical circuit, and other components, can incorporate microstructures for humidity and / or condensate management. The microstructures can generally be defined as structures having microscale dimensions in the range of 1 to 1000 micrometers (μm) (i.e., about 1 to 1000 μm).

[0032] Gas can be transported through the circuit of FIG. 1 as follows. Dry gas passes from the ventilator / blower 105 to the humidifier 107 that humidifies the dry gas. In some embodiments, the ventilator / blower 105 can be integrated with the humidifier 107. The humidifier 107 is connected via port 111 to the inlet 109 (the end that receives the humidified gas) of the inspiratory tube 103, thereby supplying the humidified gas to the inspiratory tube 103. The inspiratory tube is a tube configured to deliver breathing gas to a patient. The gas flows through the inspiratory tube 103 to the outlet 113 (the end that discharges the humidified gas), and then flows through the patient interface 115 connected to the outlet 113 to the patient 101. In this example, the outlet 113 is a Y-piece adapter. The expiratory tube 117 is also connected to the patient interface 115. The expiratory tube is a tube configured to move the exhaled humidified gas away from the patient. Here, the expiratory tube 117 returns the humidified gas exhaled from the patient interface 115 to the ventilator / blower 105. The inspiratory tube 103 and / or the expiratory tube 117 according to at least one configuration may include a microstructure. These tubes (or others) will be described in detail below.

[0033] In this example, dry gas enters the ventilator / blower 105 through the vent 119. The fan 121 can improve the flow of gas flowing into the ventilator / blower by sucking air or other gas through the vent 119. The fan 121 may be, for example, a variable-speed fan, and the electronic control device 123 controls the fan rotation speed. In particular, the function of the electronic control device 123 can be controlled by the main electronic control device 125 in response to an input from the main control device 125 and a predetermined required value (default value) of pressure or fan rotation speed set by the user via the dial 127.

[0034] Humidifier 107 includes a humidification chamber 129 containing a quantity of water 130 or other suitable humidifying liquid. Preferably, the humidification chamber 129 is removable from the humidifier 107 after use. By being removable, the humidification chamber 129 can be more easily sterilized or discarded. However, the portion of the humidification chamber 129 of the humidifier 107 can be of an integral structure. The body of the humidification chamber 129 can be formed from a non-conductive glass or plastic material. However, the humidification chamber 129 can also include conductive components. For example, the humidification chamber 129 can include a high thermal conductivity base (e.g., an aluminum base) that contacts or is associated with the heating plate 131 of the humidifier 107. By way of example, the humidifier 107 can be either a stand-alone humidifier, such as any of the humidifiers in the respiratory humidification range of Fisher & Paykel Healthcare Limited (Auckland, New Zealand). An exemplary humidification chamber 129 is described in U.S. Patent No. 5,445,143 to Sims, which is incorporated herein by reference in its entirety.

[0035] The humidification chamber 129 according to at least one embodiment can include a microstructure and is described in more detail herein.

[0036] The humidifier 107 can also include electronic control. In this example, the humidifier 107 includes an electronic, analog or digital main controller 125. Preferably, the main controller 125 is a microprocessor-based controller that executes commands of computer software stored in an associated memory. In response to inputs of humidity and temperature values set by the user via the user interface 133, for example, and other inputs, the main controller 125 determines when (or to what level) to energize the heating plate 131 to heat the water 130 within the humidification chamber 129.

[0037] Any suitable patient interface 115 can be incorporated. The patient interface is a broad term and is given its original and ordinary meaning to those skilled in the art (i.e., not limited to a special or customized meaning), and includes, but is not limited to, masks (e.g., tracheal masks, face masks, and nasal masks), cannulas, and nasal pillows. A temperature probe 135 can be connected to the inspiratory tube 103 near the patient interface 115 or to the patient interface 115. The temperature probe 135 monitors the temperature near or at the patient interface 115. A heating filament (not shown) associated with the temperature probe is used to adjust the temperature of the patient interface 115 and / or the inspiratory tube 103 to raise the temperature of the inspiratory tube 103 and / or the patient interface 115 above the saturation temperature, thereby reducing the chance of unwanted condensation occurring.

[0038] The patient interface 115 according to at least one embodiment can include a microstructure and is described in detail below.

[0039] In FIG. 1, the exhaled humidified gas is returned from the patient interface 115 through the expiratory tube 117 to the ventilator / blower 105. As described above with respect to the inspiratory tube 103, the expiratory tube 117 can have a temperature probe and / or a heating filament and can be incorporated into the expiratory tube to reduce the chance of condensation occurring. Further, the expiratory tube 117 is not required to return the exhaled gas to the ventilator / blower 105. Alternatively, the exhaled humidified gas can be passed directly to the ambient environment or to other accessories, such as an air scrubber / filter (not shown). In some embodiments, the expiratory tube is completely omitted.

[0040] As described above, the inspiratory tube 103, expiratory tube 117, humidification chamber 129, and / or patient interface 115 of the exemplary medical circuit may include a microstructure. Descriptions of these components follow. Although the present invention is not limited by these embodiments, it is contemplated that the disclosed microstructure can be incorporated into various medical components that contact and / or transport humidified gas, such as humidified air.

[0041] Medical tube with microstructure Figure 2 shows a perspective view of a tube 201 suitable for use in a medical circuit according to at least one embodiment. As shown in Figure 2, the tube 201 can be formed into a waveform, which conveniently enhances the flexibility of the tube. However, in some embodiments, the tube 201 can have a relatively smooth and non-wavy wall.

[0042] In some embodiments, the tube 201 can be used to transport gas to and / or from an infant or neonatal patient. In some embodiments, the tube 201 can be used to transport gas to and / or from a standard patient, such as an older child and an adult. Some exemplary dimensions of the "infant" and "standard" medical tubes described herein, as well as some preferred ranges for these dimensions, are described in co-owned U.S. Provisional Patent Application No. 61 / 492,970, filed on June 3, 2011, and co-owned U.S. Provisional Patent Application No. 61 / 610,109, filed on March 13, 2012, and co-owned International Publication No. 2011 / 077250A1 pamphlet, the entire contents of each of which are incorporated herein by reference. Exemplary lengths of the infant and standard tubes can be 1 - 2 m (or about 1 - 2 m).

[0043] In at least one embodiment, tube 201 is formed from an extrudate that includes one or more polymers. Preferably, the polymer is selected such that the resulting tube 201 is generally flexible. Preferred polymers include linear low density polyethylene (LLDPE), low density polyethylene (LDPE), polypropylene (PP), polyolefin plastomer (POP), ethylene vinyl acetate (EVA), flexible polyvinyl chloride (PVC), or blends of two or more of these materials. The one or more polymers comprise at least 98.4 (or about 98.4), 98.5 (or about 98.5), 98.6 (or about 98.6), 98.7 (or about 98.7), 98.8 (or about 98.8), 98.9 (or about 98.9), 99.0 (or about 99.0), 99.1 (or about 99.1), 99.2 (or about 99.2), 99.3 (or about 99.3), 99.4 (or about 99.4), 99.5 (or about 99.5), 99.6 (or about 99.6), 99.7 (or about 99.7), 99.8 (or about 99.8), or 99.9 (or about 99.9) weight percent (wt.%) of the total extrudate. In certain embodiments, the extrudate comprises 99.488 (or about 99.488) wt.% or about 99.49 (or about 99.49) wt.% of LLDPE. In some embodiments, tube 201 is formed from a foamed polymer as described in International Publication No. WO 2001 / 077250A1 by the same applicant, which is incorporated by reference in its entirety.

[0044] In some embodiments, the microstructure can be formed of a soft metal material such as aluminum foil, brass, and copper. In some such embodiments, the selected material can have a high surface energy. In some embodiments, the substrate material can be coated and can include an additive that enhances the surface energy of the substrate material. In some embodiments, using only the metal without forming a microstructure can be advantageous simply because the surface energy is high. However, the microstructure can be formed of metal, for example, by first forming a soft metal into a film or thin film and subsequently embossing the material to form the microstructure. Thereafter, the embossed material can be used to form any number of suitable components in the humidification device of the present disclosure. For example, at least the interior of the tube 201 can be formed of a metal that may or may not be embossed to form a microstructure. And in some embodiments, the embossed metal film can form a surface on any number of structures (walls, towers, fins, bases, etc.) within the humidification chamber.

[0045] In some embodiments, the tube 201 can include one or more conductive filaments. In some embodiments, the tube 201 can include two or four conductive filaments, and a plurality of pairs of conductive filaments can form a connection loop at one or both ends of the tube 201. One or more filaments can be wound spirally around the outside of the tube 201, for example, and disposed outside the tube 201, or wound spirally around the lumen wall thereof, for example, and disposed on the inner wall of the tube 201. The filaments are described in detail below.

[0046] It has been found that, due to the interaction between a liquid and a surface comprising a dedicated microstructure, the liquid can be spread on the surface and inside or on the microstructure. This interaction has further been found to increase the gas-liquid interface region and reduce the thickness of the liquid layer on top of the surface. The combination of the increased surface area and the reduced thickness enhances liquid evaporation compared to the same amount of liquid on a flat surface. As will be explained below, the combination of the increased surface area, the reduced thickness, and heating further enhances liquid evaporation. As a result, in various embodiments, the inner wall of the tube 201 comprises a microstructure 301 as shown in FIG. 3A (not to scale). A first enlarged view of a portion of the microstructure 301 is shown in FIG. 3B. FIG. 3B shows the microstructure 301 enlarged more than in FIG. 3A. In FIGS. 3A and 3B, the microstructure 301 is arranged axially along the tube 201 (i.e., the microstructure extends in a direction perpendicular to the longitudinal or vertical length of the tube 201).

[0047] Polymers generally have a low surface energy and poor wettability. To improve the water spreading ability of the microstructure 301 on the polymer tube 201, it may be convenient to treat one or more polymers with one or more materials that increase the surface energy. Particularly desirable additive materials can be surfactants, such as cationic surfactants. Suitable surface modifiers include glycerol monostearate (GMS), ethoxylated amine, alkanesulphonate sodium salt, and lauric acid diethanolamide, and additives containing these substances. MLDNA-418, supplied by Clariant (New Zealand) Ltd. under the product name "418 LD Masterbatch Antistatic", is a masterbatch of a surface modifier with 5 (±0.25)% glycerol monostearate (CAS No. 123-94-4) as the active ingredient. Preferably, the surface modifier comprises at least about 0.05 (or about 0.05), 0.1 (or about 0.1), 0.15 (or about 0.15), 0.2 (or about 0.2), 0.25 (or about 0.25), 0.3 (or about 0.3), 0.35 (or about 0.35), 0.4 (or about 0.4), 0.45 (or about 0.45), 0.5 (or about 0.5), 1.1 (or about 1.1), 1.2 (or about 1.2), 1.3 (or about 1.3), 1.4 (or about 1.4), or 1.5 (or about 1.5) wt.% of the total extrudate. For example, in at least one embodiment, the tube extrudate comprises 0.25 wt.% (or about 0.25 wt.%) of the surface modifier. As another example, in at least one embodiment, the tube extrudate comprises 0.5 wt.% (or about 0.5 wt.%) of the surface modifier.

[0048] Other materials, such as other surfactants or other hydrophilizing agents, can also be used to enhance the water spreading ability of the tube 201 or other embodiments. For example, any suitable anionic, cationic or non-ionic surfactant or other hydrophilizing agent, or a combination of such surfactants or hydrophilizing agents can be used. Suitable hydrophilizing agents can be any one or more substances that can generally enhance the hydrophilicity of the composition. In some configurations, the surfactant or hydrophilizing agent can include ethoxylized fatty alcohol, such as those described in European Patent No. 0480238B1 (incorporated herein by reference in its entirety). In some configurations, the surfactant or hydrophilizing agent can include non-ionic surfactant substances, such as nonylphenol ethoxylate, polyethylene glycol mono-esters and di-esters, sorbitan esters, polyethylene glycol mono-ethers and di-ethers, and others as described in European Patent No. 0268347B1, or non-ionic perfluoralkylated surfactant substances as described in International Publication No. 87 / 03001 pamphlet. The entire contents of these documents are incorporated herein by reference. In some configurations, the surfactant or hydrophilizing agent can contain a silicon moiety. In some configurations, the surfactant or hydrophilizing agent can include a wetting agent, such as a hydrophilic silicone oil as described in the above-mentioned International Publication No. 87 / 03001 pamphlet and European Patent No. 0231420B1 (incorporated herein by reference in their entirety). In some configurations, the surfactant or hydrophilizing agent can include polyether carbosilane as described in International Publication No. 2007 / 001869 pamphlet (incorporated herein by reference in its entirety), particularly on pages 13 and 14. Other such suitable substances are described in U.S. Patent No. 5,750,589, U.S. Patent No. 4,657,959 and European Patent No. 0231420B1 as referred to in International Publication No. 2007 / 001869 pamphlet, and the entire contents of these are incorporated herein by reference.In one configuration, the surfactant or hydrophilizing agent can include an ethoxylated surfactant containing a siloxane solubilizing group as described in the above-mentioned U.S. Patent No. 4,657,949 and International Publication No. WO 2007 / 001869 pamphlet. Examples of such ethoxylated surfactants are the SILWET® line of surfactant copolymers available from Momentive Performance Materials, Inc. (Albany, New York, USA) (e.g., SILWET® L-77), and MASIL® SF19 available from Emerald Performance Materials, LLC (Cuyahoga Falls, Ohio, USA).

[0049] Other methods can also be used to increase surface energy. Suitable methods include physical, chemical, and radiation-based methods. Physical methods include, for example, physical adsorption and Langmuir-Blodgett films. Chemical methods include oxidation by strong acids, ozone treatment, chemisorption, and flame treatment. Radiation-based methods include plasma (glow discharge), corona discharge, photoactivation (UV), laser, ion beam, electron beam, and gamma ray irradiation.

[0050] By selecting a suitable surface modification method or surface modifier, it is possible to provide a tube wall having surface characteristics such that the contact angle is less than 50 (or about 50), 45 (or about 45), 40 (or about 40), 35 (or about 35), 30 (or about 30), 25 (or about 25), 20 (or about 20) degrees (°) as measurable by an angle measuring device such as a goniometer. For example, a tube wall having surface characteristics with a contact angle less than 35° (or about 35°) provides useful results. The contact angle is desirably less than π / 2 (or about π / 2). More desirably, the contact angle is 0° or about 0°.

[0051] Table 1 below shows the measured contact angles for various LLDPE samples, including samples treated with a surface modifier and samples treated with radiation. The measured contact angles were based on the static drop shape testing method conducted in accordance with ASTM standard D7334, 2008, "Standard Practice for Surface Wettability of Coatings, Substrates and Pigments by Advancing Contact Angle Measurement".

[0052]

Table 1

[0053] The sample with 5% MLDNA-418 surface modifier produced the smallest measured contact angle compared to the other surface modification methods tested.

[0054] As described above, in some embodiments, the additive material is added to the bulk polymer extrudate. It may be desirable to add the material to the polymer matrix such that the additive material replenishes the surface for the useful life of the tube. In some configurations, the material can be added as a surface treatment of the polymer, for example, by coating the surface of the polymer with the material. For example, for a microstructured surface, the additive material, such as a HYDRON anti-fog coating (MXL Industries (Lancaster, Pennsylvania)), an EXXENE anti-foaming coating such as HCAF-100 (Exxene Corporation (Corpus Christi, Texas)), and MAKROLON anti-fog (Bayer Corporation), can be brushed, sprayed, or otherwise coated to produce a thin (e.g., 1 μm or approximately 1 μm) coating of the additive material. The surface coating may be desirable because it is inexpensive and easy to manufacture.

[0055] In some configurations, a thin film of a hydrophilic material, such as a breathable polyurethane, such as ESTANE 58245 (Lubrizol Corporation (Wickliffe, Ohio)), a breathable polyester, such as ARNITEL VT3108 (DSM Engineering Plastics (Sittard, the Netherlands)), or a breathable polyamide, such as PEBAX (Arkema (Colombes, France)), can be cast as a surface modifier. These hydrophilic materials can absorb moisture and become very wettable. An exemplary method of implementing the hydrophilic thin film includes dissolving a breathable polymer in a solvent, casting the mixture, and then evaporating the solvent, thereby leaving a thin film of the breathable material on the microstructure. For example, ESTANE 58245 pellets can be dissolved in tetrahydrofuran (THF) of dimethylformamide (DMF) solvent and cast onto a microstructure machined from brass or aluminum using a micro-milling process. Typical dimensions of the thin film range from 1 to 10 μm (or about 1 to 10 μm). Preferably, the combination of the solvent, the breathable material, and the microstructure material is selected such that the shape and quality of the microstructure are not substantially affected, for example, by dissolving the microstructure using the solvent.

[0056] Some embodiments include the recognition that the vertically oriented configuration shown in FIGS. 3A and 3B advantageously improves humidification and condensate management. As shown in FIG. 1, tubes (e.g., 103 and 117) extend generally horizontally, but some portions, particularly near the ends of the tubes, extend vertically, and some portions may be inclined. Under the action of gravity, condensate tends to flow downward in the vertical and inclined portions of the tubes and accumulate at the lowest point of the generally horizontal tube. When the microstructure is perpendicular to the bottom of the generally horizontal tube, the microstructure moves the accumulated condensate vertically against gravity. This action increases the amount of condensate on the tube wall and, therefore, the surface area of the condensate exposed to the airflow. By exposing more surface area of the condensate to the airflow, the likelihood that the condensate will evaporate into the airflow increases. Therefore, the vertically oriented configuration reduces the condensate accumulating in the tubes and increases the likelihood that the air flowing through the tubes will maintain the desired level of humidity near saturation.

[0057] This configuration can be advantageous because it minimizes interference with the airflow within the lumen of the tube due to the absence of structures extending into the lumen. At least one embodiment includes the recognition that in order to enhance evaporation, it is not necessary or required for the microstructure to extend into or cover the lumen.

[0058] According to some embodiments, the microstructure can be oriented in the direction of the tube. For example, FIG. 19 shows an embodiment of a chamber 129 in which a tube 1901 incorporating a microstructure 1903 is attached at an inlet 701. The tube 1901 can be disposed at the inlet 701 of the evaporation chamber 129. A liquid, such as water, is introduced into the tube 1901 slightly above the inlet 701 and flows through and along the microstructure 1903 in the direction of the humidification chamber 129.

[0059] In one configuration, the liquid can be metered onto the inner surface of the tube 1901 and introduced in a controlled manner, and by using the microstructure and gravity, the liquid is spread circumferentially along the inner surface of the tube 1901. The introduction of the liquid can be controlled using any suitable flow restrictor. The rate of water flowing into the tube 1901 can be adjusted using a flow restrictor to maximize the interaction between the water and the microstructure 1903 of the tube 1901. For example, increasing the amount of water in the tube 1901 can increase the amount of evaporation that occurs. However, the microstructure 1903 can be most effective when not completely or not at all covered with water. It has been found that evaporation mainly occurs at the edges of the water, i.e., the water margins and along the surrounding structures, on rough surfaces. Therefore, it may be desirable to control the amount of water flowing through the tube 1901 to maximize the number of water margins for the water.

[0060] In one configuration, a liquid supply tube can extend between a flow restrictor and a collar. The collar includes microchannels on the outer surface of the sleeve, and the microchannels can communicate with the microchannels on the tube 1901. As such, the collar can be used to supply liquid to the tube 1901. Further, the collar can include an outer surface to which a gas supply conduit can be connected. Air flowing downward or through the tube 1901 towards the humidification chamber 129 begins to evaporate water from the inner surface of the tube 1901 and carry it away. Therefore, the air reaching the humidification chamber 129 already has at least some degree of water vapor.

[0061] In some embodiments (not shown), a heating jacket may also be incorporated into or surround at least a portion of the tube 1901. The heating jacket may further enhance the evaporation of water or liquid into the flowing gas. In some embodiments, instead of or in addition to having a heating jacket, the tube 1901 may have heaters printed on one or more portions of the tube 1901. In some embodiments, the tube 1901 may include structures such as thick film heating elements, etched foils, or wire elements for providing heating elements.

[0062] The tube 1901 with the microstructure 1903 can be formed in any suitable manner and using any suitable materials. In some embodiments, the tube 1901 can be formed of a corrugated sheet formed from a hydrophilic polymer. Once formed, the corrugated material can be wrapped to form the tube 1901 such that the microstructure 1903 extends along at least a portion of the length of the inner surface of the resulting structure. In some embodiments, the microstructure 1903 is a V-shaped trench. In some embodiments, the V-shaped trench includes valleys that are spaced approximately 30 μm apart from adjacent valleys when the sheet is laid flat. In some configurations, the sheet, and thus the resulting tube 1901, may be approximately 150 mm in length and may have a diameter of approximately 20 mm when folded to form the tube 1901.

[0063] Figure 4 shows a cross-section of an exemplary microstructure 301. In this exemplary embodiment, the microstructure 301 is a continuous microchannel having a wedge-like structure. A continuous microchannel can generally be defined as a continuous channel having dimensions of 1000 μm (or about 1000 μm) or less. In at least one embodiment, the microchannel has a depth d of 20 - 40 μm (or about 20 - 40 μm), a maximum width w of 20 μm (or about 20 μm), and an angle θ of 30 - 60° (or about 30 - 60°). In some embodiments, the surface of the tube has a microchannel-to-solid ratio of 1:1 (or about 1:1). The dimensions described above are not limiting, and additional suitable dimensions are described in detail below. Due to the difference in scale between these exemplary embodiments and the dimensions of the exemplary tubes described above, the microstructure surface can exist in and operate in an open system rather than a closed system such as a lab-on-a-chip.

[0064] Some embodiments include the recognition that the movement of liquid in the microchannel is based primarily on surface forces rather than inertial or gravitational forces. Some embodiments also recognize that surface forces generally act when the characteristic dimension of the microstructure is

Number

[0065] According to the above recognition, in order to promote wicking, it was determined that a structure with a high aspect ratio and / or high surface energy (low contact angle) is desirable. Surfactants such as those described above produce a contact angle close to 0°, so wicking can occur easily. Since the equilibrium contact angle on most polymer surfaces is greater than about 0.87 radians (about 50°), deeper channels can be formed to facilitate wetting.

[0066] Surface roughness or microstructure (e.g., regular microstructure) promotes the dispersion of droplets and, therefore, when the equilibrium contact angle is less than about 90°, can reduce the thickness / depth of the droplets, thereby increasing the liquid / vapor surface area. The surface roughness of the microchannel also plays a role in wicking. Microscopic structures, i.e., microstructures or nanostructures, of protrusions within the microchannel are thought to play a role in fixing the solid / liquid / vapor contact line, increasing the surface area, and / or serving as nucleation sites for condensation. FIG. 17 shows a microchannel viewed using an environmental control scanning electron microscope, similar to that shown in FIG. 18C. The roughness on the surface is clearly visible. In some configurations, when the contact angle is greater than about 90°, the surface roughness can have an adverse effect on spreading and evaporation. This is because the droplets do not spread much, thereby reducing the liquid / vapor surface area. At least for this reason, structures with an equilibrium contact angle of less than about 90° are generally preferred.

[0067] Many different shapes of the microstructure can achieve desirable results. For example, the profile of the continuous microchannel can be sinusoidal or sharp trenches. In some embodiments, the microchannel has an aspect ratio that increases with a distance, such as a chemical gradient or a physical gradient. In some embodiments, the depth gradient of the channel is used to control the movement of the liquid in a specific direction. It has been found that the liquid tends to move in the direction of the deeper channel. The gradient may be desirable provided that the hysteresis is slow, as the substrate can move the droplet towards the high-energy region to reduce the energy. The gradient can also accelerate or otherwise improve the wicking of the liquid. For example, in some embodiments, the depth gradient of the channel is used to move the liquid towards the region of the faster air flow, thereby increasing evaporation. In some embodiments, larger channels are used along the vertical walls of the structure to direct water from the bottom of the structure to the top of the corrugated structure, thereby bringing the water closer to the heating element for evaporation.

[0068] Furthermore, the microstructure does not need to be continuous. Individual microstructures help disperse the liquid, thereby accelerating evaporation. It has been found that in a rough surface, most evaporation occurs around the transition region between the solid structure and the liquid (i.e., the edge of the liquid, i.e., the interface). As a result, increasing the roughness of the entire structure increases the transition region and enhances evaporation. For example, the surface can include individual features such as cylindrical, pyramidal, or cubic posts or pillars. The microstructure can also include a hierarchy of the above-described features. In some embodiments, the individual features are uniform or partially uniform. In some embodiments, the individual features are randomly distributed on the surface. For example, some embodiments use crystals with irregular shapes that spread over or adhere to the surface. In some embodiments, a rough (i.e., non-smooth) surface can advantageously enhance evaporation.

[0069] Figures 20 and 21 show embodiments that enhance the evaporation of a liquid using a rough or textured surface. FIG. 20 shows that a dispensing mechanism 2003 can apply a liquid to a rough surface 2001 at a distance D from the surface 2001, and the dispensing mechanism dispenses a small amount of liquid. In some configurations, droplets are dispensed one at a time. In some configurations, the droplets can bounce upon contact to produce smaller droplets.

[0070] Each droplet contacts the rough or textured surface 2001 and spreads quickly over the surface 2001, thereby promoting the evaporation of the liquid into the gas flowing over the upper side of the surface 2001. In some embodiments, the surface 2001 is heated to further promote the evaporation of the liquid into the gas passing over the upper side of the surface. The embodiment of FIG. 20 is shown with only a single liquid dispenser 2003 or dropper, but some embodiments, as shown in FIG. 21, may include two or more liquid dispensers 2003. The plurality of liquid dispensers 2101 can be arranged at various locations above the surface 2001 to increase the coverage rate of the liquid on the surface 2001. In some embodiments (not shown), a surface including a plurality of holes serves the function of the liquid dispenser 2101. A liquid such as water can flow over its surface. The liquid then drips or falls downward through a plurality of holes in the surface to the rough or textured surface 2001 below. Gas flows between the two surfaces (i.e., the first surface and the rough or textured surface 2001) to evaporate the liquid as it falls and can then disperse around the microstructure of the rough or textured surface 2101. FIG. 21 further shows that in some embodiments, a gas flow, such as air to be humidified, can be sent or shaped to form a relatively flat flow covering the rough surface 2001. Such a configuration can further interact the gas with the rough surface 2001.

[0071] Figure 22 shows one type of rough surface that includes a plurality of ridges 2201 with different heights and widths. A rough surface with a higher height-to-width ratio (e.g., a steeper slope) is thought to spread the liquid and enhance evaporation. In some configurations, having a steeper slope is thought to increase the number of contact lines. In some embodiments, an increase in the number of contact lines between the liquid and the rough surface is thought to enhance evaporation. In some embodiments, the presence of higher ridges 2201 increases the number of contact lines between the liquid and the rough surface, thereby enhancing evaporation compared to a surface with lower ridges 2203. In some embodiments, the use of heat that can be applied to the rough surface can accelerate the evaporation rate, particularly at the contact lines. In some embodiments, the use of a surface with an integral microstructure, i.e., a microstructure integrally connected to the underlying surface, can enable better heat transfer when heating the underlying surface. Such a configuration can enhance the ability of heat to assist in the evaporation of the liquid.

[0072] The above description regarding FIGS. 20 - 22 pertains to rough or textured surfaces, but a microstructured surface with a regular pattern can achieve similar results. Similar to droplets on a rough surface, droplets on a surface with a microstructure disperse and evaporate into the passing gas more rapidly than on a smooth surface without a microstructure or surface irregularities. In some embodiments, the microstructure is uniform. In some embodiments, the microstructure is sized and arranged according to a pattern, even if not all microstructures are the same.

[0073] When the above-mentioned wicking criteria are met, water wicks into microchannels and / or micropillars according to a certain type of dynamics called Lucas - Washburn dynamics. The wicking or suction length (L) is proportional to the square root of time (t), as long as the cross-section is uniform, regardless of the shape or aspect ratio of the channel.

Number

[0074] Some embodiments include the recognition that low contact angle, high aspect ratio, high surface tension, and low viscosity can improve wicking. Since the wicking length is proportional to the square root of time, the wicking speed is inversely proportional to the wicking length and inversely proportional to the square root of time. In other words, wicking slows down in speed as distance and time elapse.

[0075] Figures 18A - 18L show images of continuous and individual microstructures. The substrate material in Figure 18A is polyethylene terephthalate (PET). The substrate materials in the other drawings are acrylic. The V-shaped grooves in Figure 18A were cut using a double-edged razor. The other microstructures were fabricated using a 3D printer (ProJet HD3000). In some embodiments, the microstructures, or the surfaces incorporating the microstructures, can be manufactured by direct injection molding or thermal embossing. Although not shown in these drawings, it is also possible to machine the microstructures using a CNC machine equipped with a micro end mill, such as those sold by Performance Micro Tool (Janesville, Wisconsin). Figures 18B and 18C show rectangular grooves. Figure 18D shows a front view of a rectangular microchannel array having a gradient in topography, specifically, a front view of the long end of the microchannel. Figure 18E shows a front view of the short end of the microchannel of Figure 18D. Figure 18F shows a side view of the rectangular microchannel array of Figure 18D. As described herein, with a gradient in topography, the dynamics of wicking (specifically, the velocity-time relationship) can be modified by having microstructures that vary depth with distance. This topography may desirably affect the way in which liquid evaporates and condenses on the surface. Such variable depth configurations can be achieved by embossing, machining, or casting. Figure 18G shows a droplet on a rectangular groove not treated with a surfactant. Figure 18H shows the spreading of a droplet on a rectangular groove treated with a surfactant. Figures 18I and 18J show top-down views of a surface with pillars at different magnifications. Figure 18K shows a side view of the surface with pillars. Figure 18L shows another embodiment of a microstructure defining a surface shape that is the reverse of the shape of the microstructure in Figure 18A. The microstructure in Figure 18L includes alternating high and low ridges, each separated from the other by a small channel, i.e., a first microchannel. Preferably, the high ridges are substantially higher than the low ridges and are at least 2 - 3 times the height of the low ridges.In the illustrated arrangement, the low ridges are substantially wider than the high ridges, for example, about 3 to 5 times wider. The small channels can be of any suitable size, such as approximately the width of the high ridges. Further, the high ridges define a large channel, i.e., a second microchannel, therebetween, and can communicate with or be adjacent to the small channels. The depth of the large channel is deeper than the depth of the small channels and can be 2 to 3 times or more deeper. The small channels have a substantially triangular cross-sectional shape, while the large channels can have a cross-sectional shape similar to a frustum of a pyramid. The low ridges preferably define a much larger area than the high ridges, so the upper surface of the low ridges can be regarded as the outer surface of the material or substrate, the small channels are recessed from the outer surface, and the high ridges protrude from the outer surface.

[0076] The microstructure 301 can extend along the entire length of the tube 201 or along a portion of the length of the tube 201, such as a central portion where condensate may be collected. Alternatively, the microstructure 301 can extend along the tube 201 at regular or irregular intervals and be separated by portions without microstructure. The above drawings show the microstructure 301 surrounding the inner circumference of the tube 201. However, the microstructure 301 does not need to surround the entire inner circumference in all embodiments. For example, the microstructure 301 can be arranged around half or a quarter of the circumference.

[0077] It has been found that when a drop of liquid spreads many times its radius and heat is supplied to a substrate below the liquid, very efficient evaporation of the liquid can be achieved. As a result, in some embodiments, one or more of the filaments described above may include heating filaments. The heating filaments may be embedded in or inserted into the wall of the tube 201. For example, one or more filaments may be wound in a spiral around the lumen of the tube in the wall of the tube 201. One or more filaments may be disposed within the tube 201, for example, in a wound configuration as described in U.S. Patent No. 6,078,730 to Huddard et al., which is hereby incorporated by reference in its entirety. The arrangement of the heating filaments is not limited to one of the configurations described above. Further, the heating filaments may be arranged in a combination of the configurations described above.

[0078] In some embodiments, the tube 201 includes an inner component that includes a microstructure. An exemplary inner component 501 is shown in FIG. 5. An enlarged view of the inner component 501 is shown in FIG. 5B. The exemplary inner component 501 is a serrated strip. The serrations of the inner component 510 may complement the waveform (not shown) of the tube such that the tube is sized and configured to hold the inner component 501 in place overall. In FIG. 5B, the microstructure 301 extends vertically to cover both axial surfaces of the inner component 501 along the longitudinal or vertical length of the inner component 501. Alternatively, the microstructure 301 may cover one axial surface. In some configurations, the microstructure 301 may extend along a portion of the longitudinal length or at regular or irregular intervals along the longitudinal length. The inner component 501 may include two or more serrated strips. For example, the inner component may include two serrated strips and resemble a plus sign having serrations along its longitudinal length. These embodiments are not limiting. A number of strips may be incorporated. However, it may be advantageous to have fewer strips to improve the flow of air through the lumen of the tube and / or increase the flexibility of the tube.

[0079] It may be advantageous to include the inner component 501. This is because the inner component 501 allows the microstructures 301 to extend to the lumen of the tube and reach the center of the lumen of the tube 201. As shown in FIG. 6, the air flow velocity increases from the wall of the tube towards the center of the lumen (center line) of the tube and reaches a maximum at the center line. Therefore, the water generated from the microstructures 301 in FIGS. 5A and 5B is exposed to the warm and high-speed air flow. By exposing the condensate to the higher-speed air flow near the center of the tube, the possibility of the condensate evaporating into the air flow is increased.

[0080] Alternative configurations are possible for the inner component 501. For example, the inner component 501 can be wound inside the tube 201. This configuration may be desirable as it allows the microstructures to extend a certain distance to the lumen of the tube 201, thereby exposing them to a higher-speed air flow than the wall of the tube 201. In at least one embodiment, the inner component 501 is wound such that at least a portion of the inner component 501 crosses the center of the lumen of the tube.

[0081] As described above, it has been found that adding heat to the microstructured surface can dramatically increase the evaporation rate. As a result, the inner component 501 of any of the above embodiments incorporates a heating filament, thereby improving the heating of the air flow along the tube and thus increasing the possibility that the condensate in the microchannels evaporates into the air flow. Incorporating one or more heating filaments into the inner component 501 also reduces the possibility of condensate forming within the warm inner component. Evaporation has been found to be greatest in the contact area where the solid surface, the droplet, and the evaporated vapor come into contact. This is due to being close to the heated surface. The closer to the solid, the more the mass transfer. As a result, some embodiments include the recognition that it may be desirable to have a large number of narrow channels. For example, a surface with 10 channels of 100 μm can achieve a higher evaporation rate than a surface with 5 channels of 200 μm.

[0082] It should be noted that the above-described configuration of the microstructure can be advantageously used to transport liquids without using one or more pumps. Further, some embodiments include the recognition that since the movement of the liquid is driven by capillary action, the microstructure surface does not require a pump to direct the liquid.

[0083] Method for manufacturing a tube As described above, the tube can be made from one or more extruded polymer components. The properties of the extrudate (including the composition, surface modifiers, methods for enhancing surface energy) have been described above.

[0084] A first manufacturing method will be described with reference to FIG. 14. This method includes extruding an elongated conduit having a longitudinal axis, a lumen extending along the longitudinal axis, and a wall surrounding the lumen. The microstructure can be pressed or otherwise formed on the conduit during extrusion. The microstructure can also be formed on the conduit by molding, printing, cutting, thermoforming, or other methods after extrusion. As shown in FIGS. 4, 8D, and 9D, it has been observed that by using a sharp object to cut microchannels into the surface, a raised edge can be created around the upper part of the microchannels. As a result, in some methods, it may be desirable to polish or abrade the surface after the formation of the microchannels to enhance surface uniformity. This method can also include corrugating the elongated conduit, such as by using a corrugator die. More specifically, the process includes mixing or providing a masterbatch of the extrudate material (i.e., the extrusion material), feeding the masterbatch to an extrusion die head, extruding the above-described extrudate, and (optionally) feeding the elongated conduit to a corrugator using an endless chain of die blocks to form a corrugated tube.

[0085] Figure 14 generally shows a configuration provided with a supply hopper 1401. The supply hopper receives raw materials or materials (such as masterbatch and other materials) that are sent in the direction A towards the die head 1407 through a screw feeder 1403 driven by a motor 1405. A molten tube 1409 is extruded from the die head 1411. Conductive filaments can optionally be co-extruded onto or within the molten tube 1409.

[0086] Extruders such as a Welex extruder with a screw of 30 - 40 mm in diameter and generally an annular die head of 12 - 16 mm with a gap of 0.5 - 1.0 mm have been found to be suitable for quickly producing low-cost tubes. Similar extruders are provided by American Kuhne (Germany), AXON AB Plastics Machinery (Sweden), AMUT (Italy), and Battenfeld (Germany and China). Collators such as those manufactured and supplied by Unicor® (Hassfurt, Germany) have been found to be suitable for the corrugation step. Similar machines are provided by OLMAS (Carate Brianza, Italy), Qingdao HUASU Machinery Fabricate Co., Ltd (Qingdao Jiaozhou City, P.R. China), or Top Industry (Chengdu) Co., Ltd. (Chengdu, P.R. China).

[0087] During manufacturing, the molten tube 1409, after exiting the extruder die head 1411, passes between a series of rotating molds / blocks on a corrugator and is formed into a corrugated tube. The molten tube is formed by a vacuum applied to the outside of the tube via slots and channels passing through the blocks, and / or a pressure applied to the inside of the tube via an air channel passing through the center of the core pins of the extrusion die. When internal pressure is applied, a special-shaped long internal rod extending from the core pins of the die and conforming to the inside of the corrugation may be required to prevent the escape of longitudinal air pressure along the tube.

[0088] The tube may also include a flat cuff region for connection to an end connector fitting. Therefore, during manufacturing, the molded plastic end connector fitting can be permanently fixed and / or made airtight by friction fitting, adhesive bonding, overmolding, or by heat welding or ultrasonic welding.

[0089] Another preferred method of manufacturing a tube according to the embodiments described herein includes the formation of a spiral as shown in FIG. 15. Generally, this method includes extruding a tape, winding the extruded tape in a spiral around a mandrel, thereby forming an elongated conduit having a longitudinal axis, a lumen extending along the longitudinal axis, and a wall surrounding the lumen. This method also optionally includes corrugating the elongated conduit. The microstructure can be formed on the tape by pressing or other means during extrusion. The microstructure can be formed on the tape by molding, printing, cutting, thermoforming, or other means after extrusion. Further, the microstructure can also be formed on the assembled conduit by molding, printing, cutting, thermoforming, or other means. In some methods, it may be desirable to polish or abrade the surface after microchannel formation to enhance surface uniformity.

[0090] The extrusion process includes mixing or providing a masterbatch (i.e., the extrusion material) of the extruded material, feeding the masterbatch to an extruder die head, and extruding the extrudate into a tape.

[0091]

[0091] Subsequently, the extruded or pre-formed tape is wound helically. In some embodiments, reinforcing beads are placed over the winding of the tape. The beads can provide helical reinforcement against tube collapse and also provide a heat source, chemical, or mechanical adhesive for melting or joining the overlapping portions of the tape.

[0092]

[0092] FIG. 15 shows a molten extruded tube 1501 emerging from the die 1503 of an extruder before passing through a corrugator 1505. As it exits the corrugator 1505, a heater wire 1507 is wound around the outer surface of the formed tubular part.

[0093]

[0093]

[0094] One advantage of the manufacture of the preferred type of tube described above with reference to FIG. 15 is that some of the mold blocks B can include end cuff features formed simultaneously with the tubular part. By reducing the complexity of the process and eliminating a secondary manufacturing process, the manufacturing speed can be significantly increased. This method is an improvement over separate cuff forming processes, but a drawback of prior art flat cuffs is that the corrugator needs to slow down (the extruder remains at the same speed) in order to be able to increase the wall thickness of the tube in this area. The cuff thickness is increased to achieve additional hoop strength and sealing with a cuff adapter fitting. Further, the heat of the molten polymer in this thickened area is difficult to remove during the limited contact time with the corrugator block, and this can be an important factor limiting the maximum operating speed of the tube production line.

[0094] Humidification chamber with microstructure Referring now to FIG. 7, a humidification chamber 129 according to at least one embodiment is shown. The humidification chamber 129 generally includes an inlet 701 and an outlet 703. The chamber 129 is configured to be mounted on a heating plate (described above as element 131 in FIG. 1) such that the base 705 of the chamber contacts the heating plate 131. The base 705 preferably includes a metal with good thermal conductivity, such as aluminum and copper. The humidification chamber 129 is further configured to hold an amount of liquid, such as water. In use, the liquid contacts a substantial portion of the base 705. The heating plate 131 heats the base 705 of the chamber 129, thereby causing at least a portion of the liquid in the chamber 129 to evaporate. In use, gas flows into the chamber 129 via the inlet 701. The gas is humidified within the chamber 129 and exits the chamber 129 through the outlet 703.

[0095] FIG. 8A shows an exemplary configuration of the microstructure 801 of the humidification chamber 129. The characteristics of the microstructure 801 described in the previous section are incorporated by reference. As shown in this example, the microstructure 801 is disposed perpendicular to the perimeter of the humidification chamber 129. In other words, the microstructure is perpendicular (or substantially perpendicular) to the base 705 of the chamber 129. The microstructure in FIG. 8A is shown larger than its actual size for illustrative purposes. The vertical microstructure 801 transports water 130 above the side surface of the chamber 129, exposing a larger surface area of water 130 to the air flow within the chamber 129. In at least one embodiment, the microstructure extends from the base of the chamber to a distance of 100%, 99%, 95%, 95 - 99%, 90%, or 90 - 95% (or approximately those values) of the height of the chamber 129. The height of the chamber 129 can be 50 mm (or about 50 mm). In some configurations, one or more additives, such as SILWET surfactant (Momentive Performance Materials, Inc. (Albany, New York, USA)), are included in the water 130 to enhance the uptake by the microstructure.

[0096] In FIG. 8A, the microstructure 801 is disposed around the entire circumference of the chamber 129. However, it should be understood that in some embodiments, the microstructure 801 may not extend around the entire circumference. For example, the microstructure 801 may be disposed in a single portion of the chamber 129, or around the chamber 129, either randomly or at regular intervals.

[0097] FIG. 8B shows a first enlarged view of a portion of the microstructure of FIG. 8A. As shown in FIG. 8B, water moves upward through the vertical microstructure 801. Microscale water droplets within or on the microstructure 801 are exposed to the air flow within the chamber 129. FIG. 8C shows a second enlarged view of a portion of the microstructure of FIG. 8A. As shown in FIG. 8C, air flows through the chamber 129 and across the microstructure 801, evaporating at least a portion of the water droplets in the microstructure 801. The water evaporated from the microstructure 801 enters the air flow as vapor.

[0098] As shown in the foregoing figures, the microstructure 801 exposes a larger surface area of the water 130 in the chamber 129 to the air flow passing therethrough, thereby enhancing the efficiency of the chamber 129 as compared to a chamber without any microstructure.

[0099] FIG. 8D shows a cross-section of an exemplary microstructure 801. In this exemplary embodiment, the microstructure 801 is a wedge-shaped microchannel. The characteristics of the microstructure described above for the tube configuration can also be incorporated into the microstructure for the humidification chamber configuration.

[0100] FIG. 9A shows another exemplary configuration of the microstructure of the humidification chamber 129. As shown, the microstructure can be arranged vertically and horizontally within the humidification chamber 129. The vertically arranged microstructure is perpendicular (or substantially perpendicular) to the base 605 and is labeled 901, and the horizontally arranged microstructure is parallel (or substantially parallel) to the base 705 and is labeled 903. Again, the microstructure is shown larger than its actual size for illustrative purposes only. Generally, in the configuration of FIG. 9A, the vertically arranged microstructure 901 transports water 130 above the sides of the chamber 129. The horizontally arranged microstructure 903 spreads the microscale water droplets from the vertically arranged microstructure 901 around the top of the chamber 129, exposing a larger water surface area to the air flow compared to a chamber without any microstructure. Thereby, the microstructures 901 and 903 enhance the efficiency of the chamber.

[0101] FIG. 9B shows a first enlarged view of a portion of the microstructure of FIG. 9A. As shown in FIG. 9B, water moves upward through the vertically arranged microstructure 901. When the microscale water droplets reach the top of their respective vertically arranged microstructures 901, the water droplets move along their corresponding horizontally arranged microstructure 903 (or a group of microstructures). FIG. 9C shows a second enlarged view of a portion of the microstructure of FIG. 9A. As shown in FIG. 9C, air flows through the chamber 129 and across the microstructures 901 and 903, evaporating at least a portion of the water droplets within the microstructures 901 and 903. The water evaporated from the microstructures 901 and 903 enters the air flow as vapor. In an alternative configuration (not shown), the chamber 129 can be configured to allow water to flow downward below the microstructure by gravity rather than against gravity. Additionally, the combination of channels and pins can direct the flow in any desired manner.

[0102] The vertical microstructure 901 can be made similar to that shown above in FIG. 8D and elsewhere in this disclosure, and the above description of its shape and characteristics is incorporated herein by reference. FIG. 9D shows a cross-section of an exemplary horizontal microstructure 903.

[0103] The shapes and configurations of the vertically arranged microstructures 901 and the horizontally arranged microstructures 903 in FIGS. 9A to 9D are shown only for illustration purposes. The present invention is not limited to the disclosed embodiments.

[0104] For the reasons described above with respect to the embodiments of the tube, it may be desirable to use microstructures in combination with a surface having a desired surface energy in order to improve the wettability and water spreading ability of the surface. Metals and glass are known to have relatively high surface energies and good wettability. As a result, the inner surface of the chamber 129 may include metal or glass. Metals such as aluminum and copper may be desirable because these materials also readily conduct heat, thereby increasing the evaporation rate within the chamber. Glass may be desirable because of its light transmissibility, allowing the user to visually inspect the liquid level within the chamber. Plastic is a particularly desirable material for the chamber 129 because of its low cost and ease of manufacture. However, as described above, the surface energy of plastic is relatively low. As a result, it may be desirable to treat the plastic with an additive to increase the surface energy. In at least one configuration, the wall of the chamber 129 includes poly(methyl methacrylate) plastic with an inner wall coated with a conductive metal layer, such as gold. In another configuration, the inner surface of the wall of the chamber 129 includes a ceramic material, a sintered material such as garnet, or TiO2.

[0105] As described above, it has been found that additional heat applied to the microstructure surface dramatically increases the evaporation rate. As a result, the chamber 129 incorporates a heating filament in the wall, thereby improving the heating of the wall and thus increasing the likelihood that the liquid within or on the microstructure will evaporate. In at least one configuration, a heating shroud is disposed around the chamber 129 to enhance heat transfer to the chamber 129. Further, an insulating jacket is disposed around the chamber 129 to avoid heat loss and increase the heat retention within the chamber 129.

[0106] FIG. 23 shows an embodiment of a humidification chamber 2301 that includes a number of stacks 2303 having a microstructure 2305 on at least a portion of the surface. As shown, the stacks 2303 can be arranged as a number of fins or walls; however, other configurations can include towers, columns, or combinations of fins, towers, and columns. As shown, the stacks 2303 can be arranged as fins oriented in the direction of the air flow through the humidification chamber 2301. However, other configurations can also be used to extend into the flow through the chamber 2301 and provide a more robust mixing and greater interaction with the microstructure 2305, and thus, induce evaporation. Further, in some embodiments, different stacks can have different heights to create an irregular flow pattern or turbulence in the gas passing through the humidification chamber 2301.

[0107] In the illustrated embodiment, the humidification chamber 2301 can be heated. In some embodiments, one or more of the plurality of stacks 2303 can include a thermally conductive material, such as metal, to further enhance evaporation. In some embodiments, all of the exposed surfaces of each stack 2303 can incorporate the microstructure 2305, which takes water 2307 from the bottom of the chamber 2301 and draws it upward into portions of the chamber 2301 with more air flow or less air moisture, and thus, causes the water to evaporate more. The chamber 2301 is shown as a square box; however, other shapes, such as rectangular, cylindrical, spherical, domed, etc., can be used.

[0108] The microstructures can be incorporated into any number of structures within the humidification system. One such structure is the base or bottom of the humidification chamber itself. In some embodiments, the use of microstructures or textured surface features at the bottom of the humidification chamber can create a large surface area to disperse the fluid and enhance evaporation. In some embodiments, the use of microstructures functions to reduce the depth of the liquid, thereby enhancing evaporation. In some embodiments, the microstructures can be configured in a pattern, such as a linear or straight pattern or a circular pattern. In some embodiments, a linear or straight pattern can spread the surface area better than a circular pattern. In some embodiments, there is no pattern and the surface can include irregular protrusions or surface irregularities.

[0109] Patient interface with microstructures Management of condensate is an important issue in the design of patient interfaces. As a result, some embodiments include the recognition that microstructures can be incorporated into patient interfaces, including but not limited to masks (such as tracheal masks, face masks, and nasal masks), cannulas, and nasal pillows.

[0110] FIG. 10A shows a perspective front view of an exemplary interface 115. The interface 115 can be used in the field of respiratory therapy. The interface 115 has particular utility in the form of positive pressure respiratory therapy. For example, the interface 115 can be used to administer continuous positive airway pressure (``CPAP'') therapy. Additionally, the interface 115 can be used with variable positive airway pressure (``VPAP'') therapy and bilevel set positive airway pressure (``BiPAP'') therapy. The interface 115 can be used with any suitable CPAP system.

[0111] Interface 115 may include any suitable mask configuration. For example, some features, aspects, and advantages of the present invention may find utility with a nasal mask, a full-face mask, an oro-nasal mask, or any other positive pressure mask. The illustrated interface is a full-face mask 1001. Mask 1001 generally includes a mask assembly 1003 and a connection port assembly 1005. Mask assembly 1003 generally includes a mask seal 1007 that contacts the user's face during use.

[0112] FIG. 10B shows the configuration of mask 1001 of FIG. 10A incorporating one or more conductive filaments 1009. As shown in FIG. 10B, the conductive filaments 1009 can be arranged in an overall serpentine pattern. However, various configurations are possible, such as a grid-like configuration, a coil, or a ring.

[0113] One or more conductive filaments 1009 can be attached to the outer surface of the wall of mask 1001 (i.e., the surface of mask 1001 configured to face the ambient air during use). One or more conductive filaments 1009 can also be attached to the inner surface of the wall of mask 1001 (i.e., the surface of mask 1001 configured to face the patient during use). One or more conductive filaments 1009 can also be embedded in or otherwise incorporated into the wall of mask 1001. The last configuration may be desirable as it may prevent the patient from touching the conductive filaments 1009. Combinations of the above-described configurations can also be incorporated into mask 1001. Further, the wall of mask 1001 itself, or at least a portion of the wall of mask 1001, can be conductive. For example, mask 1001 can include a conductive polymer or a conductive metal.

[0114] Figure 11A is a rear elevation view of the mask 1001 of FIG. 10. Figure 11A generally shows an exemplary configuration of the microstructure 1101 on the inner surface of the mask. The characteristics of the microstructure 1101 described in the previous section are incorporated by reference. The exemplary mask 1001 has a vertical axis LA and a horizontal axis TA. The mask 1001 includes a first portion 1103 on one side of the vertical axis LA and a second portion 1105 on the other side of the vertical axis LA. Generally, the microstructure 1101 extends along the lower side of the mask 1001 parallel to the horizontal axis TA. The microstructures 1101 on both sides of the vertical axis LA form a mirror image pattern. The microstructure 1101 is not to scale and is shown for illustrative purposes only.

[0115] Figure 11B shows a first enlarged view of a portion of the microstructure 1101 of FIG. 11A. Figure 11C shows a cross-section of the exemplary microstructure 1101. In this exemplary embodiment, the microstructure is a microchannel. The microstructures are the same as those described above, and the descriptions of their shapes and characteristics are incorporated herein by reference.

[0116] As described below, some embodiments include the recognition that condensate management can be improved by preventing or reducing the formation of macroscale water droplets (i.e., water droplets having a diameter greater than 1000 μm (or about 1000 μm)) by incorporating microstructures into the patient interface. Figure 12A shows a schematic diagram of water droplet formation on the surface of an interface that does not incorporate microstructures. In contrast, Figure 12B shows a schematic diagram of water spreading on the surface of an interface that incorporates microstructures. In both figures, the outer surface of the interface (i.e., the surface of the interface configured to face the ambient air during use) is labeled 1201, and the inner surface of the interface (i.e., the surface of the interface configured to face the patient) is labeled 1203.

[0117] The patient interface experiences very high humidity conditions. As shown in boxes 1205 and 1207, water droplets can easily form on the inner surface of the patient interface when the inner surface 1203 of the interface is smooth (or relatively smooth). As shown in box 1209, during use, these water droplets flow downward into the lower region of the patient interface and either accumulate together or drip onto the patient's face. As shown in boxes 1211 - 1213, the incorporation of a microstructure into the inner surface 1203 of the patient interface can improve this problem. As shown in boxes 1211 and 1213, the microstructure spreads the condensate along the length of the microstructure (or at least a portion of the length), thereby preventing the condensate from forming droplets. As shown in box 1215, since the condensate spreads along the microstructure over a large surface area, the condensate can evaporate more easily. This spreading effect also reduces the likelihood of the condensate accumulating in the lower region or dripping onto the patient's face. In some embodiments, the incorporation of the microstructure into the inner surface 1203 redirects the condensate from the patient interface to an absorption layer (not shown), such as a sponge or a breathable membrane.

[0118] Figure 11D shows a rear elevation view of the mask 1001 of FIG. 10A. Figure 11D schematically shows the spread of condensate along the microstructure 1101 on the inner surface of the mask.

[0119] In at least some configurations, one or more conductive filaments 1009 (FIG. 10B) include one or more heating filaments configured to heat the walls of the mask 1001. When one or more conductive filaments 1009 include at least one heating filament, the heating filament is connected to a power supply and can therefore apply heat to the body of the mask 1001. As shown in FIG. 13, additional heating accelerates the evaporation of the condensate spread over the microstructure.

[0120] The foregoing description of the invention includes its preferred forms. Modifications may be made without departing from the scope of the invention. Many changes in structure, and widely differing embodiments and applications of the invention are proposed to those skilled in the art related to the invention without departing from the scope of the invention as defined in the appended claims. The disclosure and description herein are for illustrative purposes only and are not intended to be limiting in any way.

Claims

1. A humidification chamber for use in respiratory therapy, comprising: a gas inlet; a gas outlet through which gas flows along a gas flow path from the gas inlet to the gas outlet; a surface along the gas flow path, at least a part of the surface having a microstructure; at least one liquid dispenser configured to supply liquid droplets to the surface having the microstructure; wherein: the microstructure comprises a plurality of microchannels extending along at least a part of the surface; the plurality of microchannels are configured and arranged to spread the droplets along at least a part of the length of the microchannels by wicking to promote evaporation of the liquid droplets adhering to the surface, and the depth and width of the plurality of microchannels are in the range of 1 to 1000 μm. A humidification chamber.

2. The humidification chamber according to claim 1, wherein the surface is heated or configured to communicate with a heat source.

3. The humidification chamber according to claim 1 or 2, wherein the gas flow path is shaped to form a substantially flat gas flow on the surface.

4. The humidification chamber according to any one of claims 1 to 3, wherein the plurality of microchannels are integral with the surface.

5. The humidification chamber according to any one of claims 1 to 4, wherein the plurality of microchannels are sized and arranged according to a regular pattern.

6. The humidification chamber according to any one of claims 1 to 5, wherein the plurality of microchannels have an aspect ratio that increases with distance, and the aspect ratio is the ratio of the height to the width of the microchannels.

7. The humidification chamber according to any one of claims 1 to 6, wherein the surface having the microstructure is formed by the surface of a metal film.

8. The humidification chamber according to any one of claims 1 to 6, wherein the surface having the microstructure includes a substrate having an equilibrium contact angle of less than about π / 2 radians.

9. The humidification chamber according to any one of claims 1 to 8, wherein the microchannels exhibit at least one of a sine wave shape, a V shape, a sharp trench, a square shape, or a wedge shape in a cross section perpendicular to the longitudinal direction of the microchannels.

10. The humidification chamber according to any one of claims 1 to 9, wherein the surface provided with the microstructure is a generally horizontal and planar surface provided with a microstructure and configured to disperse the liquid placed thereon.

11. The humidification chamber according to any one of claims 1 to 10, wherein the liquid dispenser includes at least one dropper configured to supply the liquid drop by drop onto the surface provided with the microstructure.

12. The humidification chamber according to any one of claims 1 to 11, wherein the liquid dispenser includes a substantially flat plate disposed at a distance above the surface provided with the microstructure, the plate having a plurality of holes through which the liquid can fall onto the surface provided with the microstructure below.

13. The humidification chamber according to any one of claims 1 to 12, wherein the liquid dispenser is configured to be spaced apart from the surface provided with the microstructure.

14. The humidification chamber according to any one of claims 1 to 13, wherein the liquid is water.

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