HYDROPHOBIC/OLEOPHOBIC FABRICS WITH DIRECTIONAL LIQUID TRANSPORT PROPERTY

Abstract

Described are fabrics and articles of manufacture. Also described are methods of making the fabrics. A fabric may exhibit directional liquid transport. The fabrics have a plurality of domains. A domain may connect a first side of the fabric and a second side of the fabric that is opposite the first side. The plurality of domains may have a gradient in concentration of hydrophobic and/or oleophobic groups. The fabrics may include nanoparticles. The fabrics may be made by exposing selected areas of a superhydrophobic and/or oleophobic fabric to an oxygen or air plasma.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application No. 62/750,062, filed on Oct. 24, 2018, the disclosure of which is hereby incorporated by reference.

BACKGROUND OF THE DISCLOSURE

Clothing provides a microclimate between the body and the external environment, and acts as a barrier for heat and vapor transfer in between. There are various functional requirements for textile or fibrous systems for different clothing applications. In particular, the huge demand of sportswear and sports equipment has raised up development of new technologies with better functional properties. Generally, the sportswear clothing system has specific features that can be modulated using the properties of the constituent materials (fiber, yarn and fabric), of which, thermal comfort including moisture and liquid transport properties is a critical requirement. For instance, in sweating conditions under active sports, the fibrous system next to the skin should not absorb sweat (water), instead, it has to transport sweat (water) through the fabric promptly to avoid the discomfort of the fabric sticking to the skin. On the other hand, it is desirable to have the side of the fabric exposed to the external environment to be omni-repellent so as to protect rain, stains and liquid pathogen. Therefore, there is a high demand to design fabric materials that have directional water transport (also referred as “one-way” water transport) property, i.e. directionally transport water from the skin to the environment, but minimize the transport in the reverse direction (from the environment to the skin).

Recently, two major strategies have been reported to endow the fibrous materials with directional liquid transport properties. One is to create lyophilicity (e.g. hydrophilicity or oleophilicity) gradient through the fabric thickness, another one is to assemble two layers of materials with different lyophilicity as an asymmetric construct. In both cases, liquid tends to transport from lyophobic (e.g. hydrophobic or oleophobic) side to lyophobilic (e.g. hydrophilic or oleophilic) side of the fibrous materials, but is blocked in the reverse direction. For instance, for the first case, Wang et al., Kong et al. and Zhou et al. separately applied photo-sensitive superhydrophobic coating on cotton or polyester fabrics followed by UV illumination on one-side to induce hydrophilicity gradient to enable directional water transport abilities through the fabric thickness. Zhang et al. prepared hydrophilic-to-hydrophobic gradient dynamers via phase separation and used them as asymmetric membranes for directional water transport. For the second case, Wu et al. and Wang et al. used electrospinning to form hydrophobic/hydrophilic and oleophobic/oleophilic dual-layer nanofibrous membrane with directional water and oil transport properties, respectively. Tian et al. used vapor diffusion method to deposit fluoroalkyl silane on one side of cotton fabric to form hydrophilic/hydrophobic Janus-type membrane with directional water droplet gating behavior. Sun et al. used three-step plasma polymerization to create asymmetric wettability on bifacial fabrics to develop directional water transport ability. Zeng et al., Liu et al. and Wang et al. similarly electrosprayed a thin layer of hydrophobic coating on a hydrophilic fabric to endow the directional water transport ability. Yang et al. and Si et al. similarly treated hydrophobic membranes by floating one side on the hydrophilic solution to form Janus membranes with directional water penetration ability.

Although, in these current designs, liquid (e.g. water) is able to directionally transport from the hydrophobic side to the hydrophilic side of the fabrics or membranes, but not vice versa, liquid tends to spread and be absorbed on the hydrophilic side. Consequently, the directional water transport will stop when the hydrophilic side is fully saturated and the saturation of water on the hydrophilic side may also increase discomfort due to increased weight. In addition, the hydrophilic external side of the fabric make it non-preventive to external water, stain or liquid pathogen. A desirable situation for a smart sportswear is to mimic the behavior of human skin. Human skin is a desirable directional liquid transport material as it excretes liquid sweat and protect the body from external liquid contaminants. In a desirable “skin-like” directional liquid transport fabric, water (e.g., sweat) can not only transport from the water-source, e.g., skin side, to the environment side and keep the skin side dry, it can also transport through to the external side for evaporation, which results in cooling, and any extra sweat will be rolled off from the external side of the fabric; meanwhile, water (e.g., rain, liquid stain, or pathogen) will not transport from the external side to the skin side, neither will it be absorbed on the outer layer facing the environment.

Based on the foregoing, there exists an ongoing and unmet need for fabrics having desirable directional liquid transport and/or water repellent properties.

SUMMARY OF THE DISCLOSURE

The present disclosure provides fabrics. The present disclosure also provides methods of making fabrics and uses thereof.

In this disclosure, a directional water transportable hydrophobic fabric by, for example, a selective plasma treatment via patterned mask to create gradient wettability channels through the fabric thickness. The gradient wettability was confirmed by chemical analysis, where hydrophobic chains were found etched away by plasma selective treatment. The directional water transport property was confirmed via various measurements, such as, for example, contact angle test, water dripping test, shower test as well as water flux test, where water was found to be directionally transported from a hydrophobic surface to a less hydrophobic surface or a hydrophilic surface through the spot channels across the fabric thickness, while non-treated surfaces on both sides remained hydrophobic. The technology can be readily extended for other membranes as well as directional flow of other types of liquid, such as oils.

In an aspect, the present disclosure provides fabrics. The fabrics comprise a plurality of domains (e.g., channels, pores, and the like), connecting (e.g., in fluid communication with) a first side of the fabric (e.g., superhydrophobic fabric, oleophobic fabric, and the like) and a second side of the fabric (e.g., superhydrophobic fabric, oleophobic fabric, and the like) opposite the first side.

In an aspect, the present disclosure provides methods of making fabrics. The fabrics may be fabrics of the present disclosure. In various examples, a fabric (e.g., a fabric of the present disclosure) is made by a method of the present disclosure. In various examples, the methods use selective formation (e.g., using masking and selective treatment) of a fabric to form domains exhibiting directional liquid (e.g., water and/or oil) transport. Non-limiting examples of methods of making fabrics are described herein.

In an aspect, the present disclosure provides uses of fabrics. Non-limiting examples of uses of fabrics of the present disclosure are described herein.

BRIEF DESCRIPTION OF THE FIGURES

For a fuller understanding of the nature and objects of the disclosure, reference should be made to the following detailed description taken in conjunction with the accompanying figures.

FIG. 1 shows a design of a hydrophobic fabric with gradient wettability channels through the fabric thickness to enable directional water transport property.

FIG. 2 shows water droplet images taken from contact angle measurement on horizontally laid superhydrophobic finished cotton fabric after plasma selective treatment under 300 W for 3 min. ((a1), (b1)) Typical droplet motion on (a1) exposed top spot and (b1) unexposed back spot areas of the fabric for 3 s, respectively. ((a2), (b2)) Typical droplet images on both spot and non-spot areas of the (a2) top side and (b2) back side of the fabric, respectively.

FIG. 3 shows still frames taken from videos when water was dripped on the inclinedly laid (an angle of 45°) plasma selectively treated (300 W, 3 min) superhydrophobic finished cotton fabric, on (a1) exposed top spots (time interval, 0.25 s) and (b1) unexposed back spots (time interval, 1.00 s), respectively. Spots on the fabrics indicate the exposed top spots. Arrows in the last images indicate final water adhesion only on exposed top spots.

FIG. 4 shows a schematic design and fabrication process of a “skin-like” hydrophobic fabric with both directional water transport and water repellent properties. (A) Schematic demonstration of the dual properties of the “skin-like” fabric. (B) A combination of superhydrophobic finishing via perfluorosilane-coated titanium dioxide (TiO₂) nanoparticles and selective plasma treatment via a patterned mask to create gradient wettability spot channels through the fabric thickness to endow the dual properties.

FIG. 5 shows wetting behavior, microstructure, and chemical analysis of the superhydrophobic finished fabric after selective plasma treatment. (A) Contact angles of the spot and non-spot areas of both top and back sides of the superhydrophobic finished fabric after plasma treatment for 0 to 5 min; insets are droplet images when dripped on the back spot areas. (B) Contact angle of a two-layer fabric assembly to prove the wettability gradient. (C) SEM morphologies of pristine cotton fabric, superhydrophobic finished fabric, and exposed top spot areas of the superhydrophobic finished fabric after selective plasma treatment for 3 and 5 min. (D) Table of atomic contents of C, O, Ti, Si and F on different fabric surfaces from X-ray photoelectron spectroscopy (XPS) results.

FIG. 6 shows directional water transport properties and water repellency of the superhydrophobic finished fabric after selective plasma treatment. (A) Still frames taken from videos when water was dripped onto an inclinedly laid (45°) plasma selectively treated superhydrophobic finished fabric on exposed top spot and unexposed back spot areas under a flow rate of 10 μL/min. (B, C) Breakthrough pressures of both top and back sides of the fabrics with (B) different sizes (diameters) of spot areas under a flow rate of 0.4 mL/min and (C) different flow rates through a spot diameter of 1 mm, respectively.

FIG. 7 shows a mechanism of directional water transport. (A) Illustration of directional water transport through the spot channel between elliptical yarns with gradient wettability. (B) Illustration of an axisymmetric water fluid front between elliptical yarns. Here, a and b are the semi-principal axes in x- and y-directions, respectively, c is the half distance between yarns, θ is the contact angle, co is the eccentric anomaly, a is the expansion/contraction angle, and β is the direction angle. (C) Dependence of direction angle on the eccentric anomaly of the elliptical yarns in different flow directions. (D) Dependence of capillary pressure on the eccentric anomaly of the elliptical yarns in different flow directions. (E) Mechanical analysis of the water drop hung under the porous spot of the horizontally placed fibrous layer with increasing water supply. (F) Relationship between the size of the porous spot and the volume of the dripped water drop. (G) Mechanical analysis of the water drop attached on the porous spot of the inclined fibrous layer at an incline angle of λ.

FIG. 8 shows water droplet images (from contact angle test) on pristine cotton fabric, and both spot areas and non-spot areas from both top and back sides of the superhydrophobic finished fabric before and after selective plasma treatment for 1 to 5 min.

FIG. 9 shows water droplet images taken from contact angle measurement on a horizontally laid superhydrophobic finished fabric after plasma selective treatment (300 W, 3 min). (A, B) Typical droplet motion on (A) exposed top spot and (B) unexposed back spot areas of the fabric for 3 s, respectively. (C, D) Typical droplet images on both spot and non-spot areas of the (C) top side and (D) back side of the fabric, respectively.

FIG. 10 shows wetting durability of the superhydrophobic finished fabric after selective plasma treatment. (A) Contact angles of the spot and non-spot areas of both top and back sides of the superhydrophobic finished fabric after plasma treatment for 0 to 5 min after 7 days; insets are droplet images when dripped on the back spot areas. (B) Water transport time from the back spot area to the top spot area in both Day 0 (as-prepared) and Day 7. (C) Overview images of multiple water droplets on either side of the superhydrophobic finished fabric after selective plasma treatment (300 W, 3 min), at Day 0 and Day 7. Arrows indicate the spot channels marked in black dots on the fabrics. Insets in as-prepared samples are side views of the fabrics and droplets.

FIG. 11 shows SEM morphologies of exposed top spot areas and unexposed back spot areas of the of the superhydrophobic finished fabric after selective plasma treatment for 1 to 10 min. Images in Line 2 and 4 are high magnifications of Line 1 and 3, respectively.

FIG. 12 shows SEM morphologies of unexposed top and back non-spot of the superhydrophobic finished fabric after selective plasma treatment for 1 to 10 min. Images in Line 2 and 4 are high magnifications of Line 1 and 3, respectively.

FIG. 13 shows thermogravimetric analysis (TGA) spectra of pristine cotton fabric, superhydrophobic finished fabric before and after plasma treatment (300 W, 3 min).

FIG. 14 shows (A) experimental set-up for measuring breakthrough pressure of the fabrics. (B) Water droplet diameters transported through different sizes (diameters) of spot areas under a flow rate of 0.4 mL/min.

FIG. 15 shows (A) a water shower test to measure the water transport through the different sides of the plasma selectively treated superhydrophobic finished fabric. Water (B) did not and (C) did transport (arrow) through the fabric at 10 s when (B) the top side and (C) back side of the fabric were up contacting the shower, respectively.

FIG. 16 shows SEM morphologies of (A) cross-section of the superhydrophobic finished cotton fabric, showing the semi-axes a and b of the yarn are approximately 80 μm and 50 μm, respectively, and (B) low magnification of images in FIG. 5C, showing a half distance c approximately 50 μm and a big pore with greater c (arrow) between yarns of the superhydrophobic finished fabric.

FIG. 17 shows dependence of direction angle on eccentric anomaly of the elliptical yarns in different flow directions. The semi-major axis and semi-minor axis vary at different values of the maximum contact angles on one side of the porous spot.

FIG. 18 shows dependence of capillary pressure on eccentric anomaly of the elliptical yarns: (A) at different semi-principal axes in different flow directions. The semi-principal axes and the half-distance between yarns vary in three groups as follows: a=80 μm, b=50 μm, c=50 μm; a=80 μm, b=50 μm, c=100 μm; and a=160 μm, b=100 μm, c=100 μm. (B) at different shapes of elliptical yarns in different flow directions. The semi-principal axes and vary in three groups as follows: a=40 μm, b=50 μm; a=80 μm, b=50 μm; and a=160 μm, b=50 μm. (C) at different maximum contact angles in different flow directions. The contact angles vary in three groups as follows: θ₀=109°; θ₀=130°; and θ₀=150°.

DETAILED DESCRIPTION OF THE DISCLOSURE

Although claimed subject matter will be described in terms of certain embodiments and examples, other embodiments and examples, including embodiments and examples that do not provide all of the benefits and features set forth herein, are also within the scope of this disclosure. Various structural, logical, and process step changes may be made without departing from the scope of the disclosure.

Ranges of values are disclosed herein. The ranges set out a lower limit value and an upper limit value. Unless otherwise stated, the ranges include the lower limit value, the upper limit value, and all values between the lower limit value and the upper limit value, including, but not limited to, all values to the magnitude of the smallest value (either the lower limit value or the upper limit value).

The present disclosure provides fabrics. The present disclosure also provides methods of making fabrics and uses thereof.

In this disclosure, a directional water transportable hydrophobic fabric by, for example, a selective plasma treatment via patterned mask to create gradient wettability channels through the fabric thickness. The gradient wettability was confirmed by chemical analysis, where hydrophobic chains were found etched away by plasma selective treatment. The directional water transport property was confirmed via various measurements, such as, for example, contact angle test, water dripping test, shower test as well as water flux test, where water was found to be directionally transported from a hydrophobic surface to a less hydrophobic surface or a hydrophilic surface through the spot channels across the fabric thickness, while non-treated surfaces on both sides remained hydrophobic. The technology can be readily extended for other membranes as well as directional flow of other types of liquid, such as oils.

In an aspect, the present disclosure provides fabrics. The fabrics comprise a plurality of domains (e.g., channels, pores, and the like), connecting (e.g., in fluid communication with) a first side of the fabric (e.g., superhydrophobic fabric, oleophobic fabric, and the like) and a second side of the fabric (e.g., superhydrophobic fabric, oleophobic fabric, and the like) opposite the first side.

In various examples, the fabric (e.g., superhydrophobic fabric, oleophobic fabric, and the like) comprises a plurality of hydrophilic and/or oleophilic domains, which may be non-randomly distributed (e.g., distributed in a non-random pattern). The fabrics may exhibit directional liquid transport. In various examples, a fabric disclosed herein exhibits a gradient property, such as, for example, the directional liquid (such as, for example, water, sweat, oil, such as, for example, oily compounds or mixtures of such compounds, and the like, and combinations thereof) transport for the inner layer and water repellent properties for the outer layer. Non-limiting examples of fabrics are described herein.

In an example, a fabric of the present disclosure provides 1) a continuous hydrophobic nature, which may result from gradient wettability domains (which may be referred to as channels), and/or 2) an overall superhydrophobic surface.

In various examples, the hydrophilic domains account for 0.1-75 mol % or wt % (e.g., 0.5-50 mol % or wt %) of the surface area of the fabric, including all 0.1% values and ranges therebetween.

The plurality of domains may have a variety of shapes. The shapes may be cross-sectional shapes. Examples of shapes include, but are not limited to, round shape, rectangular, oval, kidney shaped, triangular, star shaped, and the like, and combinations thereof.

Each of the plurality of domains has a size. In various examples, each of the plurality of domains has a size (e.g., one or more dimension(s)) of, individually, 100 microns to 5 mm, including all integer micron values and ranges therebetween. In various examples, each of the plurality of domains has a size (e.g., one or more dimension) of, individually, 500 microns to 3 mm. Each domain may be the same size, each domain may have a different size, or at least one of the domains of the plurality of the domains has a size that is different from at least one other domain of the plurality of domains.

A fabric of the present disclosure may comprise or be a fabric, which may be a hydrophobic fabric, comprising or made of natural fibers (e.g., cotton, flax, jute, wool, silk, linen, and the like), or synthetic fibers (e.g., polyester, nylon, polyolefin, acrylic, acetate, polyurethane, and the like), or semi-synthetic fibers (e.g. rayon, viscose, and the like), or a combination thereof. These fabrics may have a structure, including, but not limited to, a knitted fabric, a woven fabric, a non-woven fabric, and the like.

A fabric of the present disclosure may be characterized by a gradient in hydrophilicity (e.g., from hydrophobic character to hydrophilic character) and/or oleophobicity (e.g., from oleophobic character to oleophilic character) of (e.g., within) the plurality of domains along a direction from the first side (e.g., an interior side) to the second side (e.g., an exterior side) of the fabric (e.g., a superhydrophobic fabric, oleophobic fabric, and the like).

The gradient in hydrophilicity (e.g., from hydrophobic character to hydrophilic character) and/or oleophilicity (e.g., from oleophobic character to oleophilic character) results from a gradient in concentration of hydrophobic and/or oleophobic groups (e.g., fluoroalkyl groups, such as, for example, perfluoroalkyl groups, and the like; alkyl groups, such as, for example, propyl groups, and the like; silsesquioxane groups, such as, for example, polyoctahedral silsesquioxanes (POSS), and the like; and siloxane groups, such as, for example, polydimethylsiloxane (PDMS), and the like)) and, optionally, a plurality of nanoparticles and/or disposed on one or more (e.g., both) fabric surface(s) (e.g., the first side and/or second side of a fabric) and/or through at least a portion or all of a thickness of the fabric (e.g., to one or more fiber of the fabric). In various examples, the hydrophobic and/or oleophobic groups account for 1-10, 1-25, 1-50, 1-75, or 1-100 (e.g., 10-50, 10-75, or 10-100) mol % or wt % (based on the total weight of the fabric), including all 0.1 mol % or wt % values and ranges therebetween, of the fabric and/or the nanoparticles account for 1-50 (e.g., 1-20) wt % (based on the total weight of the fabric), including all 0.1 wt % values and ranges therebetween, of the fabric. In various other examples, the hydrophobic and/or oleophobic groups account for 1-100 (e.g., 10-100) wt % (where the weight percentage is the relative weight of hydrophobic and/or oleophobic groups to the weight of the fabric, for example, the weight of hydrophobic and/or oleophobic groups divided by the weight of the fabric multiplied by 100), including all 0.1 wt % values and ranges therebetween, of the fabric and/or the nanoparticles account for 1-50 (e.g., 1-20) wt % (based on the total weight of the fabric), including all 0.1 wt % values and ranges therebetween, of the fabric.

A plurality of nanoparticles (or at least a portion of the nanoparticles) may have a plurality of superhydrophobic groups (e.g., fluoroalkyl groups, such as, for example, perfluoroalkyl groups, and the like) covalently bound to a surface of the nanoparticles. The nanoparticles may be superhydrophobically-modified nanoparticles. Non-limiting examples of superhydrophobically-modified nanoparticles include fluorosilane-modified nanoparticles (such as, for example, fluorosilane-modified titania nanoparticles).

In various examples, hydrophobic and/or oleophobic groups (e.g., fluoroalkyl groups such as, for example, perfluoroalkyl groups) are connected to the fabric surface (e.g., to one or more fiber of the fabric) via one or more covalent bonds (e.g., —O—Si(—R)—O— moieties, where R is a hydrophobic group or an oleophobic group). The hydrophobic and/or oleophobic groups may be formed from (e.g., result from reaction of) one or more compound(s) and/or polymer(s), which may be inorganic polymers or organic polymers, comprising hydrophobic and/or oleophobic groups. In various examples, hydrophobic and/or oleophobic groups are formed from/using polyolefins, such as, for example, polypropylene, and the like, waxes, such as, for example, paraffin wax, and the like. In various examples, fluoroalkyl groups are formed from (e.g., result from reaction of) precursor compounds, such as, for example, ¹H,¹H,²H,²H-perfluorooctyltriethoxysilane (PFOTES), ¹H,¹H,²H,²H-perfluorodecyltrichlorosilane (PFTDS), ¹H,¹H-perfluorooctylamine (PFOTA), perfluorooctylated quaternary ammonium silane coupling agent (PFSC), ¹H,¹H,²H,²H-perfluorooctyltrichlorosilane (PFOTS), poly(tetrafluoroethylene) (PTFE), ¹H,¹H,²H,²H-perfluorodecyltrichlorosilane (PFODS), ¹H,¹H,²H-perfluoro-1-dodecene (PFDDE), (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane (FDTS), perfluoroalkyl methacrylic copolymer (PMC), and the like, and combinations thereof. The fluoroalkyl groups (e.g., perfluorinated alkyl groups) may be connected to the surface via one or more covalent bonds.

In various examples, the plurality of nanoparticles are chosen from titania nanoparticles, silica nanoparticles, zinc oxide nanoparticles, carbon nanoparticles (which may be carbon nanotubes), and the like, and combinations thereof. The nanoparticles may have a size (e.g., longest dimension) of 1 nm to 1 micron (e.g., 5 nm to 1 micron), including all integer nm values and ranges therebetween.

In an aspect, the present disclosure provides methods of making fabrics. The fabrics may be fabrics of the present disclosure. In various examples, a fabric (e.g., a fabric of the present disclosure) is made by a method of the present disclosure. In various examples, the methods use selective formation (e.g., using masking and selective treatment) of a fabric to form domains exhibiting directional liquid (e.g., water, sweat, oil, such as, for example, oily compounds or mixtures of such compounds, and the like, and combinations thereof) transport. Non-limiting examples of methods of making fabrics are described herein.

The fabrics, which may be hydrophobic fabrics, may be made of natural fibers (e.g., cotton, flax, jute, wool, silk, linen, and the like), synthetic fibers (e.g., polyester, nylon, viscose, polyolefin, acrylic, acetate, polyurethane, and the like), semi-synthetic fibers (e.g., rayon, viscose, and the like), or the like, or a combination thereof. In various examples, a fabric is chosen from cotton fabrics, polyester fabrics, nylon fabrics, viscose fabrics, polyurethane fabrics, and combinations thereof.

In various examples, a method of forming a fabric (e.g., superhydrophobic and/or oleophobic fabric, and the like) exhibiting directional liquid (e.g., water, sweat, oil, such as, for example, oily compounds or mixtures of such compounds, and the like, and combinations thereof) transport (e.g., a superhydrophobic and/or oleophobic fabric), the method comprising: exposing selected areas (e.g., selected areas of one side) of a superhydrophobic and/or oleophobic fabric to an oxygen or air plasma (e.g., using a mask), chemical etching (e.g. sodium hydroxide), or chemical deposition (e.g., fluorochemicals), such that one or more domains exhibiting a water (e.g., wettability), sweat, oil, such as, for example, oily compounds or mixtures of such compounds, and the like, and combinations thereof transport gradient from a first side of the fabric to the second side of the fabric opposite the first side of the fabric are formed, where the superhydrophobic and/or oleophobic fabric exhibiting directional liquid (e.g., water and/or oil) transport is formed. For example, the method is carried out at room temperature and ambient/unaltered atmospheric conditions.

In various examples, the exposing selected areas of the superhydrophobic and/or oleophobic fabric to a plasma (e.g. oxygen plasma, air plasma, and the like) or UV luminance, chemical etching (e.g. sodium hydroxide), chemical deposition (e.g., fluorochemicals) is carried out using a masking material (e.g., a paper tape mask, hot melt film mask, impermeable lining film, water-based adhesive or resist (e.g. glue) to form a mask film, and the like) having a plurality of apertures, the apertures corresponding to the selected areas (e.g., plurality of domains). For example, the plasma conditions are 50-500 W, including all integer W values and ranges therebetween, and/or treatment time of 30 s (s=second(s)) to 30 min (min=minute(s)) (e.g., 30 s to 10 min), including all integer second values and ranges therebetween (e.g., the plasma power is 100-300 W and treatment time is 1-15 min (e.g., 1-5 min) (shorter time may be desirable if the power is higher)).

In various examples, a superhydrophobic and/or oleophobic fabric is formed by: contacting a fabric (e.g., a hydrophilic and/or oleophilic fabric) with: i) one or more hydrophobic group precursor (e.g., fluoroalkyltrialkoxysilane(s)) and/or one or more oleophobic group precursor (e.g., fluoroalkyltrialkoxysilane(s)), ii) optionally, nanoparticles, ii) optionally, a solvent (e.g., ethanol, propanol, acetone, dimethyl formamide (DMF), and the like, and combinations thereof) to form a superhydrophobic and/or oleophobic fabric.

Fabrics prepared by a method of the present disclosure may have a hydrophobic and/or oleophobic coating (e.g., the fabric is subjected to a hydrophobic and/or oleophobic finishing process). A finishing process may comprise contacting the fabric with a plurality of nanoparticles and the like. For example, in the case of a hydrophilic and/or oleophilic fabric, subjecting the hydrophilic and/or oleophilic fabric to a process (e.g., a pre-finishing process) may provide a hydrophobic and/or oleophobic fabric. Examples of suitable processes for rendering a hydrophilic fabric hydrophobic are known in the art.

In various examples, the one or more hydrophobic group precursors and/or one or more oleophobic group precursors, optionally the plurality of nanoparticles, and optionally the solvent are present as a preformed mixture. For example, the one or more hydrophobic and/or oleophobic precursors comprise 1-100 (e.g., 10-100) mol % or wt % based on the total weight of the fabric, including all 0.1% values and ranges therebetween, and/or the plurality of nanoparticles comprise 1-50 (e.g., 1-20) wt % based on the total weight of the fabric, including all 0.1% values and ranges therebetween.

Various hydrophobic group precursors may be used in a method of the present disclosure. For example, fluoroalkyltrialkoxysilane groups are used. Non-limiting examples of fluoroalkyltrialkoxysilane groups include ¹H,¹H,²H,²H-perfluorooctyltriethoxysilane (PFOTES), ¹H,¹H,²H,²H-perfluorodecyltrichlorosilane (PFTDS), ¹H,¹H-perfluorooctylamine (PFOTA), perfluorooctylated quaternary ammonium silane coupling agent (PFSC), ¹H,¹H,²H,²H-perfluorooctyltrichlorosilane (PFOTS), poly(tetrafluoroethylene) (PTFE), ¹H,¹H,²H,²H-perfluorodecyltrichlorosilane (PFODS), ¹H,¹H,²H-perfluoro-1-dodecene (PFDDE), (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane (FDTS), perfluoroalkyl methacrylic copolymer (PMC), and the like, and combinations thereof.

Various nanoparticles may be used in a method of the present disclosure. Examples of nanoparticles include, but are not limited to, titania nanoparticles, silica nanoparticles, zinc oxide nanoparticles, carbon nanoparticles (which may be carbon nanotubes), and the like, and combinations thereof. The nanoparticles may have a size (e.g., longest dimension) of 1 nm to 1 micron (e.g., 5 nm to 1 micron), including all integer nm values and ranges therebetween.

In an aspect, the present disclosure provides uses of the fabrics. Non-limiting examples of uses of the fabrics of the present disclosure are described herein.

An article of manufacture may be an article of clothing. The article of clothing may be a breathable article of clothing. For example, the article of clothing is rainwear, outdoor clothing, sportswear, skiwear, hiking wear, underwear, or the like. The article of clothing may be a jacket, pants, or the like.

In various examples, articles of manufacture may comprise fabrics of the present disclosure. An article of manufacture may be a wearable article, such as, for example, an article of clothing (e.g., a waterproof or oil-proof article of clothing). In various examples, wearable articles include, but are not limited to, rainwear, outerwear, outdoor clothing, sportswear, skiwear, hiking wear, under garments (e.g., underwear, undershirt, and the like), socks, t-shirts, hats, gloves, mittens, jackets, coats, ponchos, or the like. The articles of manufacture may be an article of outdoor equipment article. In various examples, outdoor equipment article is a tent, an awning, a tarp, a sleeping bag, or the like.

The steps of the method described in the various embodiments and examples disclosed herein are sufficient to produce a fabric of the present disclosure. Thus, in an embodiment, a method consists essentially of a combination of the steps of the methods disclosed herein. In another embodiment, a method consists of such steps.

The following examples are presented to illustrate the present disclosure. The examples are not intended to be limiting in any matter.

Example 1

This example provides examples of fabrics of the present disclosure, characterization of same, methods of making same, and uses of same.

Asymmetric wettability channels were created on a hydrophobic fabric to enable directional water transport properties. A combination of superhydrophobic finishing via fluorosilane-coated titanium dioxide (TiO₂) nanoparticles and selective plasma treatment via patterned mask were used to create gradient wettability channels through the cotton fabric thickness (FIG. 1). While these channels are served for directional water transport, the untreated larger surface remained superhydrophobic, therefore still provide water-repellent properties and thermal comfort next to the environment and the skin, respectively, when the fabric is used as a textile material.

The water transport ability was confirmed via various measurements, such as contact angle test, water dripping test, shower test as well as water flux test. For instance, FIG. 2(a1), 2(b1) shows a series of typical images taken from contact angle video when 10 μL water droplet was placed on top and back spot areas of the plasma (300 W, 3 minutes (min)) selectively treated superhydrophobic finished cotton fabric, respectively. When water was dropped onto the top spot area, the droplet stayed on the surface steadily for 3 seconds (s) (FIG. 2(a1)) and longer time (not shown), with an average contact angle (CA) of 97°. However, when it was dropped on the back spot area, the droplet quickly transported through to the other side (top side) of the fabric (FIG. 2(b1)). This difference indicates the directional water transport ability of the plasma selectively treated fabric through the spot channels from back to top side.

While the phenomena of directional water transport looks similarly at the first glance as those reported in prior studies, our technology differs from them in two advantages, 1) the continuous hydrophobic nature on the top spot, and/or 2) an overall superhydrophobic surface on other non-spot areas. To be more specific, firstly, the as-showed top spot area (plasma treated under 300 W, for 3 min) has an average CA of 97° and did not change within 3 s and longer time (FIG. 2(a1)), while that of the fabrics in prior studies was zero within 3 s and quickly spread to surrounding areas. Secondly, the unexposed non-spot areas on both top and back sides of the as-prepared fabric were still superhydrophobic, shown as two still round droplets at both sides of the top and back spots (FIG. 2(a2), 2(b2)), with average CA over 140°, while the surface of the fabrics in prior studies had no selectivity in the hydrophilicity on the same side, i.e. the surface was either hydrophilic or hydrophobic.

These two advantages of our technology were further validated by another water transport test, where the fabrics were placed inclinedly with an angle of 45°, and water was dripped from either top or back spot areas of the fabric. FIGS. 2(a1)-2(b2) shows a series of photos taken from videos during these experiments. When water was dripped from top side of the fabric, it tended to roll off from the fabric very quickly (FIG. 3(a)); no transport was observed during this process. On the reserve direction, water tended to transport to the top side when being supplied from the back spot areas, and roll off again after accumulating to a large droplet (FIG. 3b)). For both cases, most of water has rolled off from the top side of the fabric, with only slightly adhesion on the spot area (arrow of last images in FIGS. 3(a), 3(b)). While the directional water transport property was further proved in this test, the roll-off ability of water droplets indicates the water repellency of the fabric, which is clearly due to the superhydrophobicity of the non-spot areas of the both surfaces.

The design of selective hydrophilicity gradient across the fabric thickness enabled directional water transport occurs only in the spot channel areas, while the hydrophobic nature of the other larger areas will provide the water repellency for the fabric and thereafter thermal comfort for the clothing application. The technology is applicable for all kinds of fabrics. For hydrophilic fabrics, as in the example of cotton fabric, one needs to first make it hydrophobic, such as pre-finishing, and then make the hydrophilic gradient channels; for hydrophobic fabrics, this pretreatment is not necessary. A desirable percentage of the hydrophilic areas on the external side provides directional water transport, i.e. if the percentage is too small, it will not transport water effectively and reduce the water evaporation area for evaporative cooling, while too large, the water droplets will not fall off. Either the hydrophobic pre-finishing or plasma selective treatment is simple, cost-effective and efficient, therefore will be very feasible for the commercial applications.

This technology can be used to provide a directional water transportable hydrophobic fabric. It has a high significance to the apparel industry to provide the clothing systems, particularly sportswear, with both directional water property and water repellency, therefore would bring a huge value for the industry players and market end-users. The technology can also be leveraged into other fabric or membrane applications, such as water-treatment films, fuel cells in energy industries, and wound dress, hygiene clothes in health-care industries.

Example 2

The following example provides examples of fabrics of the present disclosure, characterization of same, methods of making same, and uses of same.

Personal moisture management fabrics that facilitate sweat transport away from the skin is highly desirable for wearer's comfort and performance. Demonstrated herein, for the first time, is a “skin-like” directional liquid transport fabric which enables continuous one-way liquid flow through spatially distributed channels acting like “sweating glands,” yet repels external liquid contaminants. The water transmission rate was up to 15 times greater than that of best commercial breathable fabrics. This exceptional property is achieved by creating gradient wettability channels across a predominantly superhydrophobic substrate. The flow directionality is explained by the Gibbs pinning criterion. In additional to functional clothing, this concept can be extended to develop materials for oil-water separation, wound dressing, geotechnical engineering, flexible microfluidics and fuel cell membranes.

A fabric acts like a skin in directionally excreting water droplets and expelling external liquid contaminants, with the water transmission rate being 15 times greater than that of best commercial breathable fabrics.

Described in this example is a conceptually novel design strategy that biomimetically mimics the behavior human skin. Human skin is a desirable directional liquid flow material as it excretes liquid sweat and protect the body from external liquid contaminants (FIG. 4A). Herein, for the first time, a “skin-like” directional liquid transport fabric was developed, which allows continuous one-way water flow and repels external liquid. This is achieved by endowing gradient wettability in distributed porous channels on a predominantly hydrophobic fabric. We used a hydrophilic cotton fabric as a starting material, and pre-treated it with 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane (PFOTES)-coated titanium dioxide (TiO₂) nanoparticles to impart superhydrophobic finishing. Selective plasma treatment via a patterned mask was then applied to create the gradient wettability porous channels across this hydrophobic fabric (FIG. 4B), acting as localized sweat glands. While these channels serve for one-way liquid flow, the predominantly superhydrophobic nature of the fabric makes it expel the transported liquid or external liquid from the surface. This “skin-like” fabric has great potentials to various applications such as functional clothing, oil-water separation, wound dressing, geotechnical engineering, flexible microfluidics, fuel cell membranes, etc.

Firstly, the wetting behavior of the fabrics was checked before and after superhydrophobic finishing and successive selective plasma treatment. As shown in FIG. 5A, the superhydrophobic finished fabric showed a contact angle (CA) of 152°, while that of the pristine cotton fabric is 0° (superhydrophilic, FIG. 8). The increased hydrophobicity was caused by the surface nanostructures of the perfluorosilane-coated titanium dioxide nanoparticles. When the fabric was treated by the plasma etcher, the contact angles have a significant difference between exposed spot and unexposed non-spot areas. The CAs of the non-spot areas on both top and back sides of the fabrics only decreased slightly and still stayed at high values. This should be due to a complete coverage of the tape mask which prevents the 02 plasma going inside the fabrics and therefore less chance to endow hydrophilicity. On the contrary, the CAs of the exposed spot areas on both top and back sides of the fabrics decreased dramatically with the increase of plasma treatment time. For instance, 1 min treatment brought the CA of the spot areas on the top side of the fabric down to 135°, which further decreased to 114° after 2 min, 97° after 3 min, and 44° after 5 min, respectively. The CA change of the spot areas on the back side of the fabrics was interesting, which dropped down to 141° after 1 min, but was no longer measurable (N/A, noted as 0°) after 2 min or longer. This is because the water droplets transported quickly from the back spot areas to the top spot areas (FIG. 5A, inset images, and FIG. 8), therefore a zero CA values were recorded. A series of dynamic CA images can be found in FIG. 9 when 10 μL water droplet was placed on either side of the plasma (300 W, 3 min) treated superhydrophobic finished fabric. When water was dripped onto the plasma-exposed top spot area, the droplet stayed on the surface steadily for 3 s and longer time (not shown), with an average CA of 97° (FIG. 9A); however, when it was dripped on the reverse side (unexposed back spot area), the droplet quickly transported through to the other side (top side) of the fabric (FIG. 9B); for other non-spot areas on both sides, the round water droplets kept still there (FIGS. 9C and 9D). A dynamic process of directional water transport can further be viewed where a 20 μL water is manually dripped from the pipette onto top and back spot areas of the fabric, respectively.

An initial guess for the reason of the water transport was that either differentiated wettability or wettability gradient occurred along the vertical direction of the spot areas through the fabric thickness. To verify the cause, the “real” CAs of the spot areas on the back side of the fabrics need to be “measured”. To do this, two layers of the superhydrophobic finished fabric were assembled, then covered the top and back sides of the assembly with the patterned tape mask (FIG. 5B, inset image), and treated it with plasma. The CAs of the spot area were measured on the top side of the second layer and used it as the “real” CAs of the spot area on the back side of the first layer, with the assumption that they should be similar as the two layers are closely stuck. FIG. 5B shows that CAs decrease gradually along with the plasma prolongation, but they are far over “zero”, e.g., 109° for the sample after 3 min plasma treatment. This means the plasma penetrates into the spot channels, and decreases the hydrophobicity to different degrees, therefore a wettability gradient should be formed through the fabric thickness. Notice, for the samples with less than 3 min treatment, both top and back spots are still hydrophobic (CA over 90°), whereas the sample with 5 min treatment turns to be hydrophilic on both sides through the spot (also see FIG. 8). This may explain the hanging round droplet appearances for the transported water droplets on the opposite (top) side for the 2 and 3 min samples, and a spreading shape for the 5 min sample, respectively (FIG. 5A, inset images, and FIG. 8). The contact angles of the plasma treated fabrics were also measured after 7 days' aging at room temperature (FIG. 10A), and they showed the similar trends as those at Day 0 (FIG. 5A), indicating the samples were stable. In addition, the water transport time from the back spots to the top spots decreased with the plasma treatment prolongation, e.g. ˜5 s for the as-prepared 2 min plasma treated fabric, about and below 1 s for the 3 and 5 min samples, respectively; and the 7 days' samples only slightly increased the transport time at each corresponding condition (FIG. 10B). Overview images of multiple water droplets on either side of the treated fabric at Day 0 and Day 7 can be found in FIG. 10C.

FIG. 5C shows the typical morphologies of the fabrics after different treatments. Compared with a smooth fiber structure on the pristine cotton fabric, the superhydrophobic finished fabric showed a rougher fiber surface because of the TiO₂ nanoparticles. The top spot area of fabrics treated by plasma less than 3 min still kept woven fibrous structure, but those treated more than 5 min generated fuzzy surfaces and broken fibers. The back spot areas have a similar morphology trend as the top area (FIG. 11), indicating plasma, besides the surface treatment on the top spot areas, can penetrate through the thickness via spot channels and damage the fibers in different extents. All the non-spot areas on both top and back sides did not change the initial fibrous morphologies (FIG. 12), because of a complete coverage by the tape mask. Combining the water transport screening by the contact angle test (FIG. 5A) and SEM morphologies (FIG. 5C), we chose the superhydrophobic fabric after selective plasma treatment under 300 W for 3 min for further studies.

XPS was then used to investigate the chemical elements of the fabrics before and after superhydrophobic finishing and plasma treatment (300 W, 3 min). As shown in the table of FIG. 5D, both the titanium (Ti) and fluorine (F) content increased after the TiO₂/PFOTES superhydrophobic finishing on the cotton fabric. After selective plasma treatment, the Ti content kept stable on both top and back spots, which coincides with the TGA data (FIG. 13) and identical rough morphology on the corresponding areas (FIG. 5C, FIGS. 11 and 12). However, there was a significant difference in F content, which decreased from 34.53% to 0.91% and 15.36% on the exposed top and unexposed back spot areas, respectively. This indicates the fluorine-based hydrophobic silane chains on the exposed top spot areas might be severely etched away by the plasma, and those underneath the spots were also damaged by the penetration of the plasma through the thickness via spot channels, but in a less severe extent. Similar observations were previously reported. The indication of plasma penetration coincides with the SEM trend (FIG. 5C) and contact angle trend either for the one layer (FIG. 5A) or two-layer structures (FIG. 5B), and should be the reason for the gradient wettability and thereafter the directional water transport ability within the spot channel area.

In order to confirm that the dual directional flow property and water repellency, the fabrics were placed at an incline angle of 45°, and water was dripped from either top or back spot areas of the fabric by a needle connecting with a continuous water source at a flow rate of 10 μL/min. FIG. 6B shows a series of photos captured during these experiments. When water was dripped from top side of the fabric, it firstly adhered to the spot area, e.g. first droplet at 5.0 s; during the continuous supply with water, the droplet grew and after the last droplet at 280.8 s, it was big enough (˜46 μL) to roll off from the fabric; through the entire process, no water transport was observed. On the reserve direction, when the first droplet contacted the back spot area, it spontaneously transported from the pin of the needle to the other side after 10.0 s; and after accumulating to a similar volume at 248.5 s, the large droplets roll off again from the top surface. From this test, the maximum flow rate of each channel was estimated to be 46/248.5=0.185 μL/s. In one of the test specimens, the spatial distance of the channels is 1 cm, so the maximum water transport rate is 0.185×0.001 g×3600/0.0001 m²/hr=6660 g/m²/hr, which far exceeds the maximum sweating rate of an average person under strenuous activity and is about 15 times greater than that of the best commercial Gore-Tex fabric.

The breakthrough pressures of the top and back sides of the designed fabric having one spot were also experimentally examined via a water flux test by placing a plastic hollow cylinder on either side to hold water (FIG. 14A). The fabrics with different spot sizes at a flow rate of 0.4 mL/min were examined, as shown in FIG. 6B. Apparently, there are significant difference of the breakthrough pressures for the top and back sides of the fabric. For the top sides, the pressures were higher and decreased with the increase of the spot sizes, i.e. the smallest spot size (diameter) of 0.5 mm generated a 4.7 cm H₂O pressure, the medium size of 1 mm reduced the pressure to 3.76 cm H₂O, and the biggest size of 3 mm further reduced to 1.8 cm H₂O. This is reasonable, as a bigger plasma-exposed area would enlarge the channels for the water to pass through, thereby lower breakthrough pressure. When the fabrics were placed inversely (back sides), the supplied water droplets can quickly transport through, resulting a very low breakthrough pressure, ˜0.2 cm H₂O. The fabric with a spot size of 1 mm was tested at different flow rates, and it was found the pressure increased with the increase of the water flow rates (FIG. 6C), which should be caused by the delay of liquid penetration considering the predominantly flow resistance of the fabrics. In addition, the droplet sizes of the water transported through the spots were recorded and found they increased with the spot enlargement (FIG. 14B).

The directional water transport ability was further proved via another test by showering either top or back side of the fabric capping over a glass vessel loaded with blue silica gel beads (FIG. 15A). After the vessel being showered under an eye wash shower for 10 s, the color of the inside beads did not change when top side of the fabric was capped upside (FIG. 15B), whereas it partially turned to pink when back side was capped upside (FIG. 15C), indicating a water transport through the fabric into the vessel.

Theoretical basis has been proposed to explain the design approach and understand the mechanisms of the directional water transport and the release of water drops from the fabric surface. The dependence of the flow directionality and the breakthrough pressure on the microstructure and wettability of the fibrous systems has also been analyzed.

Water transport by liquid drops is much faster than that by vapor evaporation, while one water drops contains millions of vapor molecules. The underlying principle of the fluid directionality in the porous spot with gradient wettability is illustrated in FIG. 7A. Here, the Gibbs pinning criterion, which has been successfully correlated to the flow directionality in the fibrous fluid diodes with varied geometry, is extended to describe the directional water transport inside the hollow channels between yarns with both gradient wettability and varied microstructure. Since the channel between the yarns varies in size along the flow direction, an expansion/contraction angle (α) is used to characterize the degree of the expansion or contraction of flow path (FIG. 7B). When the channel is uniform in size, a becomes zero. And a approaches 90° or −90°, respectively, at the bottom and the top of the fibrous material in the flow direction. More specifically, the contact line gets pinned with the breakthrough angle α+θ beyond 90° based on the Gibbs pinning condition. On the contrary, the advancement of the liquid continues when the air-liquid interface is concave and the dragging force exists towards the flow direction. As such, continuous advancement of the liquid water can be satisfied, when the direction angle as a function of contact angle θ and the expansion/contraction angle α is satisfied as follows,

$\begin{array}{cc}\beta =\alpha +\theta -\frac{\pi }{2}<0,& \left(1\right)\end{array}$

It can also be seen from FIG. 7B that liquid water will flow inversely if β>0, as the driving force on the basis of surface tension becomes opposite to the intended flow direction. Assume the yarns are elliptical, their surface can be described as the locus of all points that satisfy the equations, viz., x=a cos ω, and y=b sin ω, where x and y are the coordinates of any point on the ellipse, a and b are the semi-axes in the x- and y-directions, respectively, ω is the angle of eccentric anomaly, which ranges from π/2 to −π/2 radians in FIG. 7B. The value of a can be determined by the slope of the tangent line at (a cos ω, b sin ω) to the ellipse, viz., α=arctan

$\left(\frac{1}{k}\right),$

where

$k=-\frac{b}{a}\frac{\cos \omega }{\sin \omega }.$

It has been shown in FIG. 5B that the bottom surface (back side) of the porous spot becomes less hydrophobic with increasing time of plasma treatment. Here, a linear gradient of wettability is assumed from the hydrophilic (simplified as ‘I’) top spot surface with contact angle at 0° when ω=π/2 to the hydrophobic (simplified as ‘O’) bottom surface with contact angle at θ₀ when ω=−π/2, with

$\theta ={\theta }_{\mathrm{IO}}=-\frac{{\theta }_0}{2}\sin \omega +\frac{{\theta }_0}{2}.$

In the opposite flow direction, the contact angles will be

${\theta }_{\mathrm{IO}}=\frac{{\theta }_0}{2}\sin \omega +\frac{{\theta }_0}{2}$

with contact angle at 0° when ω=−π/2 to the bottom surface with contact angle at θ₀ when ω=π/2. The maximum value of the contact angle on the face away from plasma exposure is obtained as θ₀=109° for the sample with 3-min treatment (FIG. 5B). The dependence of the diode effect on co that indicates the water advancement is shown in FIG. 7A, where the sign “block” indicates the flow ceases or retreats at the local area while the sign “pass” means that the flow can continue moving. It is found that the values of a and b in Eq. (1) are approximately 80 μm and 50 μm, and c is approximately 50 μm, respectively (FIG. 16). Note that the surface tension force is always aligned with the flow direction at β<0, when the water flows from the hydrophobic side to the hydrophilic side as seen in FIG. 7C. It can be readily understood that the effect of dramatic contraction leading to high α (negative) overcomes that of the fair hydrophobicity with θ_OI>90° at the beginning stage and in the rest of flow process, while the condition of β<0 is always satisfied with the reduction of θ_OI. In the adverse flow direction, the condition of β<0 is also secured at the beginning with α<0 and θ_IO˜0. However, β eventually becomes positive and the surface tension force is opposite to the main flow direction, with continuously increasing a (positive) and θ_IO during the progress of water movement. As such, the asymmetric flow behaviors from different flow directions result from the changes of the geometrical structures and gradient wettability of the fibrous systems, as revealed by the theoretical model of Eq. (1) and experimental findings in FIG. 6. The dependence of direction angle on eccentric anomaly of the elliptical yarns in different flow directions has been further studied in FIG. 17, when the semi-major axis and semi-minor axis vary at different values of the maximum contact angles of one surface of the porous spot (i.e., θ₀=109° and θ₀=170°). It is interesting to note that both flows can be hindered from two different directions for θ₀=170° when b=80 μm and α=50 μm, because the contact angle of the yarn surface is always high in a wide area, where the expansion/contraction angles keep close to zero.

The detachment of water drops is essential to the continual directional water transport process. In this work, patterned hydrophilic porous spots are distributed on the predominantly superhydrophobic surface for easy water removal. The size and wettability of the spots are related to the breakthrough pressure and detachment of water drops. It is noted that the capillary pressure varies at different positions of fluid fronts, and the maximum value of capillary pressure that blocks the water transport will be equal to the breakthrough pressure when the gravitation force is negligible. The capillary pressure within the channel between yarns is determined by the Young-Laplace equation,

$\begin{array}{cc}p=\frac{\gamma \sin \left(\alpha +\theta -\frac{\pi }{2}\right)}{L}& \left(2\right)\end{array}$

where L=a+c−a cos ω is the half distance of the width of the fluid front and c is the half distance between yarns. It is clear that the capillary pressure is all negative in the OL flow direction in FIG. 7D (and FIG. 18A), so the breakthrough pressure will be equal to zero consistently with the advance of the liquid water. From the opposite flow direction, a positive capillary pressure is found with the maximum value at 800 Pa (8.16 cm water head). This capillary pressure is greater than the 3.76 cm water head shown in FIG. 6B, possibly because some porous spots contain larger channels with greater c (see arrow in FIG. 16B), leading to the reduction in capillary pressure. With increasing a while keeping b and c as constants, FIG. 18B reveals that a flatter shape of elliptical yarn can yield a lower breakthrough pressure. Besides, more hydrophobic porous spots with higher θ₀ leads to an increase in breakthrough pressures, as seen in FIG. 18C.

With increasing water supply, the volume of water drops increases until they fall off from the porous spot with the gravitational force overcoming the surface tension. The contacting circle interface line among the air, the water drop and the fabric cannot enlarge due to the repellence of the surrounding hydrophobic regions (FIG. 7E). Thus the corresponding surface tension drag is equal to F_a=2πrσ sin θ, where r is the radius of the hydrophilic porous spot and θ<90°. Then the drag will be balanced with the critical gravitational force of the growing water drop, which has a weight of G=μg(4πR³/3). Thus the scaling law is accounting for the relationship between r and R based on F_a=G, viz.,

r˜R³  (3)

which holds until the detachment of the water drops. Eq. (3) has been well verified by the experimental results of detachment of water drops at different sizes of porous spots (FIG. 7F, also see FIG. 14B).

When the fibrous layer is placed at an incline angle at λ=45°, the surface tension drag is generated by the hydrophilic and hydrophobic areas, F_a=πγR_f(cos θ_r−cos θ_a), where θ_a and θ_r are the advancing and receding contact angle, respectively (FIG. 7G). The hydrophilic force in the upper area of the porous spot holds the water drop and the hydrophobic force in the lower region repels and impedes the water drop from rolling off. The gravitation force of the water drop is scaling to mg sin λ, which will be equal to the capillary forces at the detachment condition, viz.,

mgsin λ˜πγR_f(cos θ_r−cos θ_a)  (4)

where the mass of water drop scales with the cubic drop radius R_f, viz., m˜R_f³. Analogous to the phenomenon described in Eq. (3), the increase in m is much faster than that of R_f in Eq. (4), which explains the detachment of growing water eventually drops. The directional water transport will stop if the Laplace pressure of the supplied water drop is equal to the hydrostatic pressure of the water column or water drop generated in the other side of the fabric. However, this condition cannot be met in reality as the water drop will fall off when growing slightly big.

In summary, described herein is a novel “skin-like” fabric with both directional water transport and water repellency. Distributed porous spot channels with gradient wettability across the thickness of hydrophobic fabrics via a combination of superhydrophobic finishing and selective plasma treatment were created. While these channels serve for directional liquid transport, the predominantly untreated surface area remained superhydrophobic, therefore repels external liquid contaminants. The mechanism of directional flow is explained by the Gibbs pinning criterion. The technology might be applicable for all kinds of fabrics. Either the hydrophobic pre-finishing or selective plasma treatment is simple and efficient, therefore will be very feasible for the commercial applications. The proposed fibrous materials can have a direct application in developing smart and high performance clothing, especially for sportswear. It has a high significance to the apparel industry, for bringing both directional water transport property and water repellency, therefore would bring a huge value for the industry players and market end-users. The technology can also be leveraged into other fabric or membrane applications, such as liquid separation and purification, fuel cells, wound dressing, and flexible microfluidic devices.

Materials and Methods. Superhydrophobic finishing of cotton fabrics. The fabrics used for the experiment were woven cotton fabrics. They were treated via conventional desizing, scouring, and bleaching process prior to the use.

The superhydrophobic coating was prepared using the following protocol. 2.0 g 1H, 1H, 2H, 2H-Perfluorooctyltriethoxysilane (C₁₄H₁₉F₁₃O₃Si, 97%, Oakwood) (noted as PFOTES) was dissolved in 198 g ethanol via vigorous mixing for 2 hours. The solution was subsequently mixed with 10 g Degussa P25 titanium dioxide nanoparticles (TiO₂, Rutile: Anatase/85:15, 99.9%, 20 nm; Degussa) to form a suspension. The cotton fabrics with designed sizes were immersed in the coating suspension for 5 min, and dried in air for 10 min before testing.

Selective plasma treatment of the finished fabrics. One side of the superhydrophobic finished cotton fabric (notated as top side) was tightly covered by a layer of paper tape mask with laser-cut hole patterns (diameter varies from 0.5 to 3 mm, with a typical one of 1 mm, the intervals between holes is 10 mm), another side (notated as back side) was covered by the same tape mask without the hole patterns (FIG. 3B). The masked fabric was placed into an oxygen gas plasma etcher (PE100RIE, Plasma Etch Inc.) and treated under 02 flow rate of 50 cc/min and power of 300 W, for a certain time. Because of the patterned mask, only the hole spot area of the top side of the fabric was expected to be exposed to the plasma. After plasma treatment, the tape mask was peeled off from both sides of the fabric.

Characterization

Contact Angle Measurement:

Contact angles (CA) of the fabrics were measured via the sessile drop method using a Movie Contact Angle (VCA) System (AST Products, Billerica, Mass.) equipped with the software (VCA Optima XE). The fabrics were cut into strips, and hung in the air by fixing two ends using a thick (˜8 mm) epoxy putty tape on a glass slide. A 10 μL water droplet was placed on the fabric surface to check either its contact angle or the transport properties. At least five parallel measurements from both spot and non-spot areas on both sides of the fabrics were conducted on each specimen, and the results of either contact angles or transport time were averaged for each fabric sample.

Morphology Analysis:

Scanning electron microscopy (SEM, Tescan Mira3 FESEM) was used to study the microstructure of the cotton fabric before and after superhydrophobic and plasma selective treatments. The samples were coated with a thin layer of gold palladium before observation.

Chemical Analysis:

The surface chemical information of the cotton fabrics before and after superhydrophobic finishing and plasma treatment were analyzed using X-ray photoelectron spectroscopy (XPS) (SSX-100, Surface Science Instruments) with operating pressure of ˜2×10⁻⁹ Torr. Monochromatic Al Kα x rays (1486.6 eV) with 1 mm diameter beam size was used. Photoelectrons were collected at a 55° emission angle. Electron kinetic energy was determined by a hemispherical analyzer using a pass energy of 150 V for wide/survey scans ranging from 0 to 1100 eV. A flood gun was used for charge neutralization of all the samples. The data analysis was performed on CasaXPS software.

Thermal Analysis:

A thermogravimetric analyzer (TGA 500, TA Instruments) was used to determine the amount of TiO₂ nanoparticles deposited on the treated fabric. 5-10 mg of each sample was placed in an alumina ceramics crucible and thermally heated from 30 to 990° C. in a nitrogen gas medium with a heating rate of 10° C./min. The weight percentage of TiO₂ nanoparticles was estimated by calculating the difference between the remaining weight of pristine cotton fabric and TiO₂/PFOTES-coated fabric.

Water Dripping Test:

Water droplets of ˜20 μL per droplet were dripped onto either top or back sides of the horizontally laid superhydrophobic finished fabrics after selective plasma treatment. Continuous water droplet supplied from a syringe pump (SK-500 III, Shenzhen Shenke Medical, China) with a flow rate of 10 μL/min was dripped by a needle on either top or back sides of the 45° inclinedly laid fabrics.

Water Flux Test:

A home-made device was set-up to measure the breakthrough pressure of the fabrics (FIG. 14A). The device includes a water source from a syringe pump, a hollow syringe cylinder with the bottom end attached with the testing fabric and an underneath glass bottle collector. During the test, the fluid rate was set as 0.05, 0.09, 0.4 and 0.95 mL/min, respectively. The breakthrough pressure was recorded as the minimum pressure under which the water starts to pass through the fabric.

Water shower test: The water transport properties were further measured by a water shower test. A testing fabric was capped over on a 20 mL glass vessel loaded with ˜1 g blue silica gel beads. The vessel was then showered by an eye shower for 10 s, and the color of inside silica gel beads was checked to find whether there was water transported through the fabric. Both top and back sides of the fabrics were tested to check the transport difference.

Although the present disclosure has been described with respect to one or more particular embodiments and/or examples, it will be understood that other embodiments and/or examples of the present disclosure may be made without departing from the scope of the present disclosure.

Claims

1. A fabric exhibiting directional liquid transport comprising a plurality of domains, each of the domains connecting a first side of the fabric and a second side of the fabric opposite the first side,

wherein each of the domains has a gradient in concentration of hydrophobic and/or oleophobic groups and, optionally, a plurality of nanoparticles disposed on a fabric surface.

2. The fabric of claim 1, wherein the plurality of domains comprise 0.1-75 wt % of the surface area of the fabric and the hydrophobic and/or oleophobic groups comprise 1-75 wt % of the fabric.

3. The fabric of claim 1, wherein each of the domains is characterized by a gradient in hydrophilicity and/or oleophobicity along a direction from the first side of the fabric to the second side of the fabric.

4. The fabric of claim 1, wherein the hydrophobic and/or oleophobic groups are fluoroalkyl groups, alkyl groups, silsesquioxane groups, siloxane groups, or a combination thereof, and the hydrophobic and/or oleophobic groups are covalently bound to a surface of one or more nanoparticles of the plurality of nanoparticles.

5. The fabric of claim 1, wherein the hydrophobic and/or oleophobic groups are connected to the fabric surface via one or more covalent bonds.

6. The fabric of claim 1, wherein the plurality of nanoparticles are chosen from titania nanoparticles, silica nanoparticles, zinc oxide nanoparticles, carbon nanoparticles, and combinations thereof.

7. The fabric of claim 1, wherein the individual domains of the plurality of domains have a round shape, rectangular shape, oval shape, kidney shape, triangular shape, star shape, or a combination thereof.

8. The fabric of claim 1, wherein each of the domains has a size of 100 microns to 5 mm, wherein each of the domains has the same size or each of the domains has a different size.

9. The fabric of claim 1, wherein the fabric comprises natural fibers, synthetic fibers, semi-synthetic fibers, or a combination thereof.

10. The fabric of claim 1, wherein the fabric is a knitted fabric, a woven fabric, a non-woven fabric, or a combination thereof.

11. An article of manufacture comprising one or more fabric of claim 1.

12. The article of manufacture of claim 11, wherein the article of manufacture is a wearable article or an outdoor article.

13. The article of manufacture of claim 12, wherein the wearable article is chosen from rainwear, outerwear, outdoor clothing, sportswear, skiwear, hiking wear, under garments, socks, t-shirts, hats, gloves, mittens, jackets, coats, and ponchos.

14. The article of manufacture of claim 12, wherein the outdoor article is chosen from tents, awnings, tarps, and sleeping bags.

15. A method of forming a fabric exhibiting directional liquid transport, comprising: wherein a superhydrophobic and/or oleophobic fabric exhibiting directional liquid transport is formed.

exposing selected areas of a superhydrophobic and/or oleophobic fabric to an oxygen or air plasma, such that one or more domains exhibiting a water and/or oil transport gradient from a first side of the fabric to a second side of the fabric opposite the first side of the fabric are formed,

16. The method of claim 15, wherein the fabric has a hydrophobic and/or oleophobic coating.

17. The method of claim 15, wherein the superhydrophobic and/or oleophobic fabric is formed by: wherein the superhydrophobic and/or oleophobic fabric is formed.

contacting a fabric or a portion thereof with: one or more hydrophobic group precursors and/or one or more oleophobic group precursors, optionally, a plurality of nanoparticles, and optionally, a solvent

18. The method of claim 17, wherein the one or more hydrophobic group precursors and/or one or more oleophobic group precursors, optionally the plurality of nanoparticles, and optionally the solvent are present as a preformed mixture.

19. The method of claim 17, wherein the hydrophobic group precursors and/or oleophobic group precursors are 1-100 wt % of the fabric.

20. The method of claim 17, wherein the hydrophobic group precursor is chosen from fluoroalkyltrialkoxysilanes, silsesquioxanes, polydimethylsiloxanes (PDMSs), polyolefins, waxes, and combinations thereof.

21. The method of claim 20, wherein the fluoroalkyltrialkoxysilane is chosen from 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFOTES), 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFTDS), 1H,1H-perfluorooctylamine (PFOTA), perfluorooctylated quaternary ammonium silane coupling agent (PFSC), 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS), poly(tetrafluoroethylene) (PTFE), 1H,1H,2H,2H-perfluorodecyltrichlorosilane (PFODS), 1H,1H,2H-perfluoro-1-dodecene (PFDDE), (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trichlorosilane (FDTS), perfluoroalkyl methacrylic copolymer (PMC), and combinations thereof.

22. The method of claim 17, wherein the plurality of nanoparticles are chosen from titania nanoparticles, silica nanoparticles, zinc oxide nanoparticles, carbon nanoparticles, and combinations thereof.

23. The method of claim 15, wherein the exposing selected areas of the superhydrophobic and/or oleophobic fabric to an oxygen or air plasma is performed utilizing a masking material having a plurality of apertures, wherein the apertures correspond to the selected areas.