Atty. Dkt. No.05400-0074-PCT SPECTRUM-SELECTIVE TEXTILE FOR RADIATIVE COOLING IN URBAN AREAS CROSS-REFERENCE TO RELATED APPLICATIONS [0001] The present application claims priority to U.S. provisional patent application number 63/574,394 that was filed April 4, 2024, the entire contents of which are incorporated herein by reference. BACKGROUND [0002] The urban heat island effect has emerged as a significant concern impacting the thermal homeostasis of the human body, exacerbating the effects of global warming. This phenomenon leads to a range of heat-related illnesses, including cardiovascular mortality, respiratory illnesses, neurological disorders, and injuries. One main cause of the urban heat island effect is that urban infrastructures, such as buildings and ground, absorb a greater amount of solar radiation and re-emit to the ambiance as compared to natural landscapes like grasses, forests, and water bodies. It not only amplifies heat waves that result in higher morbidity and mortality risk, but also has significant implications for energy consumption, air quality, and urban ecosystems. Currently, more than half of the world’s population resides in cities. With increasing urbanization in all countries, a greater proportion of people worldwide will be exposed to the urban heat island effect, with increased risks from heat extremes in urban areas in the near future. Therefore, taking proactive measures to stay healthy against the urban heat island effect is crucial for contemporary society. [0003] Radiative cooling textile that emits thermal radiation to the outer space and rejects the solar radiation is a promising approach to maintaining personal health and thermal comfort against global warming. While previous research showed pioneeringly outstanding passive daytime radiative cooling performance under the clear sky, (W. Xie et al., Advanced Functional Materials 33, 2305734 (2023); P. Liu et al., ACS Applied Electronic Materials 5, 5755-5776 (2023); M. Li, Z. Yan, D. Fan, ACS Applied Materials & Interfaces 15, 17848- 17857 (2023); S. Wang et al., Small, (2023).) the realistic heat gain from the heated ground and urban structures was not taken into account. Specifically, the radiative cooling textiles were often designed as broadband emitters in the entire mid-infrared (MIR) region and assumed to have an unobstructed view of the sky. Thereafter, their cooling performance, including cooling power and temperature reduction, is normally compared horizontally. This
Atty. Dkt. No.05400-0074-PCT assumption neglects the fact that around 97% of textiles from a fully clothed standing person are typically used vertically. (C. D. Fryar et al., Anthropometric reference data for children and adults: United States, 2015-2018. (2021); E. Gazzuolo, et al., Applied Ergonomics 23, 161-171 (1992).) Only a small amount of cloth area (< 3%), such as hat, shoulder, and shoe coverings, is horizontally oriented, as shown in the inlet image in FIGS.1A-1B. Therefore, in a realistic scenario, 50% of the field of view of the apparel is subtended by the ground (FIG. 1A), and this proportion goes even higher in an urban scenario with buildings and other infrastructures (FIG.1B). These human-made structures, when exposed to intense solar radiation, can reach high temperatures exceeding 70 ℃ and emit significant amounts of heat. For example, the thermographs in FIG.1C represent a landscape in Apache Junction, Arizona, showing that urban terrestrial objects are much hotter than human skin, thereby working as heat sources for the human body. According to Kirchhoff’s law, emissivity equals absorptivity at thermodynamic equilibrium. In other words, the cooling performance of a broadband emitter textile is greatly compromised by the incoming thermal radiation from the surroundings. SUMMARY [0004] Layered textiles and articles made from the layered textiles are provided. Methods of making the layered textiles are also provided. The textiles have thermal and radiation emissivity and reflectivity properties that render them well-suited for use as cooling textiles in urban environments. Articles that can formed from or incorporate the textiles include articles of clothing and articles of interior or exterior building décor, such as window coverings. [0005] One example of a layered textile includes: a fabric having a broadband emission for thermal radiation; nanostructures on a surface of the fabric, wherein the nanostructures reflect thermal radiation having wavelengths in the range from 13 µm to 20 µm; and a layer of non-woven polymer fibers on the nanostructures, such that the nanostructures are disposed between the fabric and the layer of non-woven polymer fibers. The non-woven polymer fibers have selective emissivity for thermal radiation in a wavelength range from 8 µm to 13 µm and reflect radiation across the solar spectrum. [0006] One example of a method of forming a layered textile includes the steps of: forming a layer of non-woven polymer fibers, wherein the non-woven polymer fibers have selective emissivity for thermal radiation in a wavelength range from 8 µm to 13 µm and
Atty. Dkt. No.05400-0074-PCT reflect radiation across the solar spectrum; applying nanostructures to a surface of the layer of non-woven polymer fibers, wherein the nanostructures reflect thermal radiation having wavelengths in the range from 13 µm to 20 µm; and applying a fabric having a broadband emission for thermal radiation over the nanostructures on the layer of non-woven polymer fibers, such that the nanostructures are disposed between the non-woven polymer fibers and the fabric. BRIEF DESCRIPTION OF THE DRAWINGS [0007] Illustrative embodiments of the invention will hereafter be described with reference to the accompanying drawings. [0008] FIGS.1A-1F. Concept and advantages of spectrally selective textile for vertically oriented fabrics for radiative cooling. Schematic of wearable fabrics in an (FIG.1A) open scenario and (FIG.1B) urban scenario. (FIG.1C(i)-(ii)) Optical and infrared images of characteristic urban scenarios in Apache Junction, Arizona, showing that terrestrial objects work as heat source for the human body. The images were taken at (FIG.1C (i)) 14:13 pm MST, May 29th, 2023, 33.41° N, 111.60° W (Elevation: 480 m), and (FIG.1C (ii)) 12:35 pm MST, May 29th, 2023, 33.44° N, 111.48° W (Elevation: 635 m). (FIG.1D) The radiated power from a perfect broadband or spectrum selective textile emitter at human skin temperature ^^skin = 34°^^, and hemispherical irradiances from the terrestrial features at effective radiative temperature ^^terr = 50 °^^. The selective textile reflected the thermal radiation from the terrestrial features through the non-Atmospheric Transmission Window (ATW) wavelength region, while the broadband emitter tended to absorb that thermal radiation. (FIG.1E) Calculated cooling power for broadband and selective vertical-oriented textile in the function of solar intensity in an open scenario, such as Levant, Kansas. Solar intensity of March 19th and June 1st, 2021 were picked for better clarity. (FIG.1F) Calculated cooling power in an urban scenario, such as Chicago downtown, Illinois. Assume a view factor of 0.17 was subtended by the buildings, so the view factor of the vertical-oriented fabric to the sky was 0.33. (Note that in the context of cooling power, a positive value indicates that the sample was being cooled.) [0009] FIG.2. Theoretical ground temperature as the function of solar intensity. [0010] FIG.3. Two cases of emissivity spectra for textiles: ideally selective and broadband.
Atty. Dkt. No.05400-0074-PCT [0011] FIGS.4A-4K. MIR spectral selectivity and solar reflectivity of polymethylpentene (PMP) fabric. (FIG.4A) Molecular structure of PMP. (FIG.4B) Transmittance spectrum of PMP in the infrared (IR) wavelength range. Most of the chemical bonds vibrational modes resonated within the ATW range, showing useful spectrum selectivity. Some typical polymer chemical bonds were outside of the ATW range and thus were desirably excluded for a selective emitter, such as amide (-CONH-), ester (-COO-), and nitrile (-CN), as labelled in the figure. (FIG.4C) Real (n) and imaginary (κ) parts of the refractive indices of PMP extracted by fitting the transmittance spectra and spectroscopic ellipsometry data. (FIG.4D) Both experimental and theoretical results (calculated based on effective medium theory) show the emissivity of PMP predominantly overlapped with the ATW. (FIG.4E) The emissivity selective ratio and theoretical cooling power for PMP, common polymer films, and textile materials. PMP showed the highest selective ratio and cooling power. The cooling power was calculated considering the heat gain from the ground and building (T = 323.15 K) and the heat loss to outer space (T = 3 K). The material temperature was set as skin temperature (307.15 K) and the ambient temperature was set as 303.15K. (FIG.4F) Nano-CT and (FIG.4G) SEM image showing the irregular morphology of the PMP fibers prepared by electrospinning. (FIG.4H) Theoretical scattering efficiency of PMP fiber in the wavelength range of 8-13 μm at two different incident directions, each obtained by averaging different polarizations. (FIG.4I) Theoretical scattering efficiency of PMP fibers in the UV-VIS-NIR wavelength, obtained by averaging different incidental directions and polarizations. (FIG.4J) UV-VIS-NIR reflectivity of PMP fabric in different thicknesses. (FIG.4K) MIR emissivity of PMP fabric in different thicknesses. An optimized thickness of 292 μm was selected for spectrum-selective fabric for outdoor radiative cooling textile. [0012] FIGS.5A-5B. The effect of polymer concentration on the morphology of PMP fibers. (FIG.5A) Width and (FIG.5B) thickness distribution of fiber prepared using 1.5 wt.% polymer solution. [0013] FIGS.6A-6I. Structure and wearable properties of spectral selective hierarchical fabric (SSHF). (FIG.6A) Structure of the multilevel SSHF composed of PMP fabric, AgNW, and wool fabric layer. (FIG.6B) Radiative heat transfer network of SSHF in outdoor environments. Note the convective and conductive heat transfer are not shown for simplicity. (FIG.6C) MIR emissivity of SSHF (measured from top and bottom surface), PMP, and AgNW. SSHF shows a selective emissivity on the outward-facing side and a broadband emissivity on the inward-facing side. AgNW has a broadband high MIR high reflectivity,
Atty. Dkt. No.05400-0074-PCT preventing the transmission through PMP fabric in the wavelength range of 13-20 μm. (FIG. 6D (i)-(ii)) Schematic showing the impact of wool fabric on absorbing thermal radiation emitted from the human skin. (FIG.6D (i)) Without the wool fabric, AgNW reflects the thermal radiation from the human skin within the air gap. (FIG.6D (ii)) With the wool fabric that has a high broadband emissivity, SSHF absorbs the heat radiated from the skin and subsequently conducts the heat to the surface PMP layer for selective emission. (FIG.6E) Water vapor transmission analysis showing the SSHF has air permeability. (FIG.6F) High breaking strength of SSHF that is comparable to the wool fabric. (FIG.6G) Excellent stability of SSHF under 1000 times stretching and releasing cycles with a strain of 2%. (FIG.6H) Hydrophobic performance of SSHF with a contact angle of ~ 135°, exhibiting a self-cleaning capability to maintain the spectral selectivity. (FIG.6I) MIR emissivity of SSHF before and after machine washing 8 times. [0014] FIGS.7A-7C. Radiative heat transfer network comparison of (FIG.7A) broadband emitter, (FIG.7B) broadband transparent emitter, and (FIG.7C) semi-transparent selective emitter. [0015] FIGS.8A-8G. Outdoor thermal measurements of SSHF and various common textile samples. (FIGS.8A-8B) Overall and cross-sectional schematic of the vertical measurement apparatus. (FIG.8C) Near all-day continuous measurement of the subambient radiative cooling performance on May 28th, 2023. Inset is the schematic showing the measurement setup tilted 15° from the horizon. (FIG.8D) Temperature of different vertical oriented samples measured on May 27th, 2023. (FIG.8E) Temperature comparison of vertical placed SSHF and broadband emitter at nighttime on Dec 18th, 2023. (FIG.8F) Temperature of different vertical oriented samples with metabolic heat simulation on May 8th, 2023. (FIG. 8G) Temperature tracking of the skin wearing SSHF and commercialized cotton fabric on the arms, measured on Dec 19th, 2023. [0016] FIGS.9A-9B. UV-VIS-NIR reflectivity and MIR emissivity of reference broadband sample, which is composed of polydimethylsiloxane (PDMS), Al2O3 (200 nm), and TiO2 (500 nm). [0017] FIGS.10A-10G. Cooling power comparison of SSHF, broadband, and ideal selective emitter at different urban scenarios. (FIG.10A) Schematic of the view angles of building, β and φ, in urban scenario. (FIG.10B) Calculation results demonstrate that the view factor from vertical-oriented textile to the territorial features increases from 0.5 to 1, while
Atty. Dkt. No.05400-0074-PCT that to the sky decreases from 0.5 to 0 when the angle of building view β is changed from 0° to 90°. (FIG.10C) Calculation results of cooling power for SSHF, broadband, and ideal selective emitter as a function of β and ^^. (d-g) Calculated cooling power at different urban scenarios with β and ^^ of (FIG. 10D) ^^ ൌ 0,^^ ൌ 0°, (FIG. 10E) ^^ ൌ 20,^^ ൌ 30°, (FIG. 10F) ^^ ൌ 45,^^ ൌ 60°, and (FIG. 10G) ^^ ൌ 80,^^ ൌ 80°. [0018] FIG.11. Temperature of different vertical oriented samples with a β = 20 ° with an artificial wall measured on May 27th, 2023. [0019] FIGS.12A-12C. Schematic of vertical-oriented textile for radiative cooling in urban scenario. (FIG.12A) Components of view factor for the fabric surface. (FIG.12B) Sideview schematic of the angle of building view (β) between the horizon and the line connecting the textile center point and building vertex. (FIG.12C) Top view schematic showing the angle φ between bottom center and bottom side of the building. [0020] FIGS.13A-13B. The effect of TBAB concentration and electric filed strength on the morphology of PMP fibers. (FIG.13A) The average fiber width as a function of TBAB concentration. The fiber dimension reduced with the addition of TBAB concentration. (FIG. 13B) The average fiber width as a function of electric field strength. The fiber dimension decreased with the enhancement of electric field strength. [0021] FIGS.14A-14C. Outdoor thermal measurements on May 4th, 2023, at Chicago, Illinois. (FIG.14A) Temperature of SSHF sample and ambient, as well as solar intensity at daytime. (FIG.14B) Schematic showing the two thermistors measuring sample center and edge. (FIG.14C) SSHF nighttime subambient temperature tracking. [0022] FIGS.15A-15B. Daytime outdoor thermal measurements without PE covering the setup. (FIG.15A) Temperature comparison of SSHF with silk, and a broadband emitter (PDMS/Al2O3/TiO2). (FIG.15B) Meteorological data including relative humidity, horizontal and vertical solar intensity. The vertical solar intensity was measured in the direction of S171°E, consistent with the sample measurement direction. [0023] FIGS.16A-16B. Nighttime outdoor thermal measurements without PE covering the setup on Dec.18th, 2023, at Apache Junction, Arizona (33.44° N, 111.48°W, Elevation: 637 m). (FIG.16A) Temperature comparison of SSHF with silk, and a broadband emitter (PDMS/Al2O3/TiO2). (FIG.16B) Meteorological data.
Atty. Dkt. No.05400-0074-PCT [0024] FIGS.17A-17B. Outdoor cooling power measurements on Dec.21th, 2023, at Apache Junction, Arizona (33.44° N, 111.48°W, Elevation: 637 m). (FIG.17A) Cooling power comparison between SSHF and broadband emitter. (FIG.17B) Ambient temperature and relative humidity. [0025] FIGS.18A-18E. The effect of humidity on radiative cooling performance of SSHF considering the distance between human body and building wall. (FIG.18A) Atmosphere transmission with 10 m at three relative humidity conditions. (FIG.18B) Atmospheric transmission window to the outer space at three relative humidity conditions. (FIGS.18C-18E) Cooling power comparison between SSHF, ideal selective emitter, and broadband emitter at an urban scenario of β=45° and φ=60° under different relative humidity of 10%, 30%, and 70%. DETAILED DESCRIPTION [0026] Spectrally selective textiles for radiative cooling are provided. Also provided are methods for making the textiles and articles of clothing and home décor articles comprising the textiles. The spectrally selective textiles have an asymmetrical design characterized by a high and selective outward-facing emissivity and a broadband inward-facing emissivity that efficiently emits heat from a wearer of the textile, or from a building interior to the outer environment, while suppressing the radiative heat gain. More specifically, the textiles selectivity emit thermal radiation in the wavelength range from about 8 µm to about 13 µm, while suppressing parasitic heat from the natural environment and from made-made objects, such as buildings. As such, the textiles are well suited for use in articles of clothing in urban settings. [0027] The textiles are based on a photonic design for human body cooling that meets stringent material requirements for wearability, breathability, and flexibility, and takes into account the intricacies of human body-textile microclimates. Articles of clothing that can be fabricated from or incorporate the spectrally selective textiles include, but are limited to, shirts, sweaters, pants, shorts, shawls, wraps, jackets, hats, and shoes. The textiles also find uses in cooling building interiors, particularly in urban areas. The textiles can be formed into or incorporated into home décor articles that are exposed to thermal radiation from the outdoor environment. Such home décor articles include window or doorway coverings, such as curtains, drapes, and blinds.
Atty. Dkt. No.05400-0074-PCT [0028] The textiles, which include multiple hierarchical layers having different cooling functions, are referred to herein as spectrally selective hierarchical fabrics (SSHFs). The hierarchical layers, which are based on multimodal heat transfer mechanisms, include: a fabric having broadband emission for thermal radiation; a layer of nanostructures overlying the fabric layer; and a layer of non-woven polymer fibers overlying the nanostructures, such that the nanostructures are disposed between the fabric and the non-woven polymer fibers. The nanostructures reflect thermal radiation having wavelengths in the range from about 13 µm to about 20 µm and the non-woven polymer fibers have selective emissivity for thermal radiation in a wavelength range from 8 µm to 13 µm and scatter radiation across the solar spectrum. (The wavelength range from 8 µm to 13 µm is referred to herein as the Atmospheric Transmission Window (ATW) range.) [0029] By “selective emissivity for thermal radiation in a wavelength range from 8 µm to 13 µm,” it is meant that the intensity of the emission of thermal radiation across this wavelength range is higher than the intensity of the emission outside of this wavelength range and, particularly, that the intensity of the emission of thermal radiation across this wavelength range is higher than the intensity emission in the wavelength range from 2 µm to 8 µm and from 12 µm to 30 µm. By way of illustration, a material having “selective emissivity for thermal radiation in a wavelength range from 8 µm to 13 µm,” desirably has an emissivity across this wavelength range that is close to unity (for example, 0.7 or higher, 0.8 or higher, including 0.9 or higher), while the emissivity outside of this wavelength range is close to 0 (for example, 0.3 or lower, 0.2 or lower, or 0.1 or lower), and, particularly, the emissivity in the wavelength range from 2.5 µm to 8 µm and from 13 µm to 30 µm is close to 0. The layer of non-woven polymer fibers need not have zero emissivity outside the ATW window. However, in some embodiments of the layer of non-woven polymer fibers, at least 75%, at least 80%, at least 90%, or at least 95% of the emissivity across the wavelength range from 2 m to 30 m lies within the ATW window. [0030] By “having broadband emission for thermal radiation” it is meant that the fabric has a non-zero emissivity across the wavelength range from 2.5 µm to 20 µm and is not characterized by selective emissivity for thermal radiation in a wavelength range from 8 µm to 13 µm. By way of illustration, a material having “broadband emission for thermal radiation” desirably has an emissivity close to unity (for example,0.7 or higher, 0.8 or higher, including 0.9 or higher) across the wavelength ranges from 2.5 µm to 20 µm and is not
Atty. Dkt. No.05400-0074-PCT characterized by selective emissivity for thermal radiation in the wavelength range from 8 µm to 13 µm. [0031] The combination of these different material layers produces an SSHF characterized by a high ATW spectral selective ratio, γ, and a high average ATW emissivity. By way of illustration, SSHFs having an ATW spectral selective ratio, γ, of at least 2.0 and/or an average ATW emissivity of at least 0.80 are provided, where ATW spectral selective ratio, γ, and average ATW emissivity are defined in the Example. The high emissivity in the ATW range allows the SSHFs to emit heat away from the wearer’s body or a building’s interior, and the high reflectivity (low absorptivity) in the non-ATW region minimizes the textile’s heat absorption from the wearer’s or the building’s surroundings, including the ground, buildings, bridges, walls, and other architectural structures. [0032] The layer of non-woven polymer fibers is designed to provide outward-facing emissivity in the ATW range. As such, this layer faces away from the wearer’s skin (or away from a building’s interior) and is separated from the wearer’s skin (or a building’s interior) by the nanostructure and fabric layers. (By “faces away from the wearer’s skin,” it is meant that, of the fabric layer, the layer of nanostructures, and the layer of non-woven polymer fibers, the layer of non-woven polymer fibers is furthest removed from the wearers skin. Similarly, by “faces away from the building’s interior,” it is meant that, of the fabric layer, the layer of nanostructures, and the layer of non-woven polymer fibers, the layer of non-woven polymer fibers is furthest removed from the interior or a building) The polymer fibers selectively emit thermal radiation in the wavelength range from 8 µm to 13 µm at the typical temperature of human skin (i.e., about 33 ºC to about 35 ºC), but desirably exhibit wideband scattering efficiency across most or all of the solar spectrum (i.e., the range of wavelengths of energy emitted by the sun). Thermal radiation having wavelengths outside of the ATW range, and particularly in the UV-VIS-NIR range (e.g., wavelengths in the range from 0.4 µm to 1.6 µm), is selectively reflected. Preferably, the polymer of the polymer fibers should have chemical bond vibrations only within ATW range (8-13 μm); however, polymers in which a substantial majority of the chemical bond vibrations are within this range (e.g., ≥ 90% of the chemical bond vibrations) may also be used. Illustrative examples of suitable polymers include polymethylpentene (PMP), polyethylene oxide, and polypropylene. [0033] The layer of polymer fibers is a porous non-woven layer, and the polymer fibers in the layer desirably have a wide diameter distribution that promotes the scattering of solar
Atty. Dkt. No.05400-0074-PCT radiation. By way of illustration, in some embodiments, the polymer fibers include or consist of fibers having diameters in the range from 100 nm to 5 µm. Electrospinning is an advantageous method of forming the layer of polymer fibers because electrospun fibers can be formed with a wide diameter distribution range due to the sequential volatilization of solvents during electrospinning, which enables a wideband scattering efficiency covering the entire solar spectrum. Moreover, electrospinning conditions, such as solution conductivity, surface tension, flow rate, electric field strength, and polymer concentration, can be controlled to optimize fiber dimensions to provide an optimized optical spectrum for selective radiative cooling, as illustrated in the Example. By way of illustration only, non-woven polymer fiber layers having a weight-averaged solar reflectivity (as described in the Example) of at least 90, at least 95%, or at least 97% in the UV-VIS-NIR region of the electromagnetic spectrum may be used. The thickness of the layer of non-woven polymer fibers can be adjusted to achieve a desired level of ATW emissivity and solar reflectivity. Suitable layer thickness include, but are not limited to, those in the range from 100 µm to 1000 µm, including those in the range from 200 µm to 500 µm. [0034] The nanostructures underlying the layer of non-woven polymer fibers are used to suppress outward-facing non-ATW emissivity. This layer provides a high reflectivity across the MIR region, thereby preventing infrared transmission from urban infrastructures to the human body. Thus, the nanostructures reflect radiation from, for example, the ground or buildings, in the wavelength range from 13 µm to 20 µm. This is significant because such radiation would otherwise pass through the layer of non-woven polymer fibers and result in a heat gain. In addition, the nanostructure should be thermally conductive to allow for body heat conduction from the fabric layer to the non-woven polymer fiber layer. [0035] The nanostructures may be metal nanostructures, such as silver (Ag) nanostructures and are typically elongated (i.e., having an aspect ratio of at least 2, including at least 5, and at least 10.) As used herein, the term nanostructure refers to structures having at least one dimension (length, width, height, and/or diameter) that is no greater than 1 µm, including structures having at least one dimension no greater than 500 nm and structures having at least one dimension no greater than 250 nm. Some nanostructures include two or three dimensions of no greater than 1 µm, 500 nm, or 250 nm. Nanostructures include nanowires, nanorods, nanoflakes, and other nanoparticles. The nanostructures may be coated with or encapsulated with a polymer coating to enhance their mechanical properties and durability.
Atty. Dkt. No.05400-0074-PCT [0036] The fabric underlying the nanostructures provides a base layer and acts as an inward-facing broadband emitter that absorbs the thermal radiation from the human skin through the textile-skin air gap and conducts the heat to the polymer fiber layer via the nanostructures. Because the polymer fibers have transparency outside of the ATW range, the fabric layer is used to minimize or prevent non-ATW radiation transmitted by the polymer fiber layer from reaching and being absorbed by a wearer’s skin. Additionally, without the fabric, the metabolic heat emitted by the human skin would be reflected by the nanostructure layer within the air gap between the human skin and the textile. [0037] The fabric may be comprised of a natural or synthetic material and may be woven or non-woven (e.g., felt). Examples of suitable fabric materials include wool, cotton, silk, polyethylene, polyester, polyimide, polyacrylonitrile, and polytetrafluoroethylene. [0038] The different layers in the textile can be formed separately and then combined in a layered textile, or the different layers may be formed in situ as a layered stack. Thus, one basic embodiment of a method of making a SSHF is to: form a layer of the non-woven polymer fibers; apply the nanostructures to a surface of the layer of non-woven polymer fibers by, for example, spin-coating a suspension of the nanostructures on the non-woven polymer layer; and apply the fabric to the nanostructures, such that the nanostructures are disposed between the non-woven polymer fibers and the fabric. The layers may be connected by, for example, stitching or an adhesive that does not compromise the function of the textile. [0039] In addition to spectrally selective radiative cooling, the SSHFs can be designed to provide a high water vapor transmission rate (WVTR) to promote cooling via perspiration, robust and durable mechanical strength, and high hydrophobicity (e.g., having a contact angle of at least 135°) to impart a self-cleaning property. EXAMPLE [0040] This Example illustrates an MIR spectrally selective hierarchical textile (SSHF) that has a high ATW spectral selective ratio, γ, of 2.23 and an average ATW emissivity of 0.85, providing a remarkable cooling effect in urban areas. The SSHF consists of a polymethylpentene (PMP) nano-micro hybrid fibrous layer, silver nanowires (AgNWs), and wool fabric. The surface PMP fibers have a wide diameter distribution range of 500-3000 nm owing to the sequential volatilization of solvents during electrospinning, which enables a wideband scattering efficiency covering the entire solar spectrum. PMP only has C-C (954- 1004 cm-1), -CH2 (1176-1241 cm-1), -CH (862-881 cm-1), and -CH3 (931 cm-1) bonds, so it is
Atty. Dkt. No.05400-0074-PCT useful as a selective emitter with high absorption only in ATW range. The middle AgNW layer provides a high reflectivity in the whole MIR region, preventing infrared transmission from urban infrastructures to the human body. The bottom wool fabric is a broadband emitter, which absorbs the thermal radiation from the human skin through the textile-skin air gap, and further conducts the heat to the top PMP fabric via the AgNW layer. [0041] Significance of spectrally selective textile [0042] The ground and building temperatures were theoretically calculated by taking the most common infrastructure materials as an example, such as concrete and asphalt, as shown in Supplementary Text 1 and FIG.2. When the solar intensity reaches 300 W/m2 with ambient temperature of 303.15 K (30 ℃), which is common on a typical sunny day, the ground and building temperature can readily surpass the average temperature of human skin. Therefore, the effect of such infrastructure heat sources on the cooling performance of traditional broadband emissive textiles, such as cotton, silk, polyester fabrics, is significant. The reason is that the high broadband emissivity of these textiles will result in considerable heat gain from the environment based on Kirchhoff's radiation law. As illustrated in FIG.1D, although a broadband emitter (dashed line labeled “broadband emitter”) can result in heat loss through the ATW (8~13 μm) to the deep space, there is still remarkable heat gain from the surrounding ground and buildings within the wavelength of 2.5~8 μm and 13~20 μm. Note that the ATW wavelength range is simplified to 8~13 μm, since the spectral emissive power in 3-4 μm for human body radiation is much lower. Therefore, to minimize the heat gain from ambient while maintaining the heat emission to the deep space through ATW (dashed line labeled “selective emitter” in FIG.1D), the radiative cooler should selectively emit in ATW, and reflect in non-ATW wavelengths (FIG.3). The cooling power performance of a vertically placed broadband emitting textile and the MIR spectrally selective emitting textile were compared under different solar illumination conditions (Supplementary Text 2). Here, the broadband textile had an emissivity of unity in the whole MIR wavelength range (2.5-20 μm), while selective textile was assumed to be an ideal selective emitter that had emissivity of 1 in the ATW wavelength range and 0 in the non-ATW wavelength range. When the vertical textiles were exposed to an open scenario surrounded by asphalt ground, the broadband textile initially showed a higher cooling power than the selective emitter under low solar intensity illumination. However, when the solar intensity exceeded the cross point 520 W/m2 (where the cooling demand was reasonably higher), the selective emitter textile showed a higher cooling power due to its capability to selectively block the radiation emitted
Atty. Dkt. No.05400-0074-PCT by the hot ground (~49 ℃), as shown in FIG.1E and FIG.2. Take the weather data of Levant, Kansas (from National solar radiation database) as an example: at 9:00 am, Marth 19th, 2021, CST, broadband textile emitter showed a higher cooling potential than the selective one. However, at 10:30 am, the cooling power of selective textile in turn exceeded that of the broadband emitting textile. At 12:30 pm June 1st, 2021, the cooling power gap between the broadband and selective emitting cloth further increased to 44.1 W/m2. When vertical textiles are exposed to an urban scenario, where buildings are densely distributed, such as Chicago downtown, the heat gain phenomenon is even more pronounced, as shown in FIG.1F. For example, assuming the distance between the vertical textile and the brown dark brick building wall (with infinite width) is 2.7 times of the building height (such as on a street near three-floor construction, or in a vast football field near high-rise buildings, etc.), the cross-point cooling power point shifted to 437 W/m2 of the solar radiation intensity. Therefore, the cooling power difference between the broadband and selective emitting cloth reached 60.9 W/m2 at 12:30 pm, June 1st, 2021, CST. These calculations clearly show the importance and efficacy of selective textiles for wearable personal radiative cooling in the urban areas. [0043] MIR spectrum selectivity and UV-VIS reflectivity of PMP fabrics [0044] The preparation of a MIR spectrally selective textile uses a spinnable and robust polymer material with proper chemical bonding from meticulous molecular level design (FIG.4A). Desirably, such polymer should have chemical bond vibrations only within ATW range (8-13 μm). However, the majority of natural and synthetic textiles exhibit a significant amount of chemical bond vibrations outside of this range, such as -OH (3100-3600 cm-1) in cotton, -CONH- (1520-1720 cm-1) in silk and wool, C=O (1725-1780 cm-1) in polyester (PET) and polyimide (PI), -CN (2240 cm-1) in polyacrylonitrile, -CF2 (507-640 cm-1) in polytetrafluoroethylene (PTFE), as shown in FIG.4B and Table 1. Therefore, they normally show broadband emissivity. Polymethylpentene (PMP) with only C-C (stretching in 942- 1066 cm-1), -CH2 (twisting and wagging in 1168-1241 cm-1), -CH (bending dominate in 848- 871 cm-1) and -CH3 (rocking in 931 cm-1 and twisting in 1103 cm-1-1150 cm-1) is a good candidate for achieving the desired selective emissivity spectrum (FIGS.4A-4B). To further investigate the optical properties of PMP, complex refractive indices (both visible and MIR region) were derived from the optical data of spectroscopic ellipsometry and transmittance spectra. The detailed extraction process and results can be found in Supplementary Text 3. The fitted real (n) and imaginary (κ) parts of the refractive indices of PMP are shown in FIG.
Atty. Dkt. No.05400-0074-PCT 4C. Based on the intrinsic complex refractive index, the effective medium theory was employed to calculate the emissivity of PMP, which indeed showed a substantial overlap with ATW (FIG.4D). This was also verified experimentally with four PMP films in different thicknesses from 10 µm to 1 mm. [0045] Table 1. Examples of the typical adsorption peaks for common textile materials. The shown wavenumbers are located outside of the atmospheric transparent window (1250-769 cm-1). Materials Assignment Wavenumber (cm-1) Cotton O-H stretching 3391 Silk Amide vibration 1520,1650 Wool Amide vibration 1520,1650 Polyamide (PA) Amide vibration 1520,1650 Polyethylene terephthalate C=O vibration in ester 1725 (PET) Polyimide (PI) C=O stretching in imide 1779, 1726 Polyacrylonitrile (PAN) -CN vibration 2240 Polyethylene oxide (PEO) O-H stretching 3183-3617 Polytetrafluoroethylene (PTFE) CF2 rocking, wagging, and 507, 636 bending [0046] To quantitatively compare the emissivity of PMP and other commonly used polymer and textile materials, ATW spectral selective ratio, γ, was defined as the ratio of the average emissivity within ATW (8-13 μm) (“average ATW emissivity”) and the non-ATW emissivity (2.5-8 and 13-20 μm). 13μm 13μm ^ ^ ^ ^ ^ ^ d ^ ^ / ^ ^ d ^ ^ ^ ,
where ^^^^^^ is and their thicknesses were as follows: PEO – 88 µm; PP – 1300 µm; PE – 403 µm; PI – 160 µm; PA – 654 µm; wool fabric – 230 µm; PET fabric – 180 µm; cotton fabric – 256 µm; silk fabric – 178 µm. Among the ten polymer materials, PMP showed the highest selective ratio of 2.34 (FIG.4E), followed by polyethylene oxide (PEO) and polypropylene (PP). Natural textile materials, such as cotton, silk, wool, and synthetic textile PET all exhibited a ratio close to 1,
Atty. Dkt. No.05400-0074-PCT indicating their broadband emissive characteristics. Assuming these materials are vertically used and exposed to an urban scenario with a ground and building temperature of 323.15 K (50 °C), PMP yielded the highest cooling power of 52.9 W/m2. as shown in FIG.4E. Such a performance represents 81.9 % of the theoretical limit of an ideal selective fabric (64.6 W/m2). [0047] Scalable electrospinning technique was employed to fabricate PMP polymer into textiles. PMP polymer and tetrabutylammonium bromide (TBAB) was firstly dissolved in a mixed solution of dimethylformamide (DMF), cyclohexane, and acetone (Experimental section), and then extruded and stretched into uniform ribbon-shape nano-micro hybrid fibers under a strong electrical field. TBAB decreased the surface tension and improved the solution conductivity, thereby diminishing the Rayleigh instability during the unstable jet movement, facilitating uniform and bead-free PMP fiber formation. The X-ray nano-computed tomography (nano-CT) and scanning electron microscope (SEM) images in FIGS.4F and 4G show that PMP fabric has a porous structure, with irregular twists on single fiber, which is caused by the volatilization speed of different solvents. Fiber dimension plays a role in ensuring an ideal optical spectrum because a selective radiative cooling textile requires a high emissivity (low reflectivity) in the ATW range, and a high reflectivity in the UV-VIS-NIR range. Therefore, fiber morphology was engineered by manipulating the spinning conditions including solution conductivity, surface tension, flow rate, electric field strength, and polymer concentration (Supplementary Text 4). For instance, fiber dimension dramatically decreased with the concentration drop from 2.5 wt.% to 1 wt.%, as shown in FIG.4H. Specifically, when the concentration was 1.5 wt.%, the fiber had an average width of 720 nm and a thickness of 113 nm, based on the fiber size statistical distribution in FIGS.5A and 5B. This smaller cross-section area resulted in a significantly lower scattering efficiency at the atmospheric transmission window (8-13 um) compared to that of the fibers fabricated using 2 wt.% concentration, based on based on the COMSOL Multiphysics finite element modeling, as shown in FIG.4H. In addition, PMP fiber with this dimension had a high average scattering efficiency at the wavelength ~500 nm, near the peak wavelength value of the solar spectrum, as shown in FIG.4I. The randomly stacked and twisted multilayer nano-micro hierarchical fibers with broadly distributed fiber sizes resulted in strong sunlight scattering, and the whole fabric showed a white color (FIG.4J). The UV-VIS-NIR spectrum (FIG.4J) showed that the weight-averaged solar reflectivity reached 97% (with respect to AM1.5 spectrum) when the PMP fabric thickness was 292 μm. At this condition, the average
Atty. Dkt. No.05400-0074-PCT emissivity of PMP fabric in the ATW range was 85.3%, accompanied by a notably high selective ratio of 2.23, as shown in FIG.4K. [0048] Optical design rationale and SSHF wearable properties [0049] In addition to selective emissivity, other characteristics of heat exchange with the human body and textile wearability are also useful. For example, although PMP is selectively emissive in 8~13 μm, it is transparent rather than reflective in the non-ATW regime. In this case, the human skin (nearly perfect blackbody) beneath the textile would directly absorb the thermal radiation and compromise the entire selective emitter concept. Hence, the SSHF was engineered by integrating PMP fabric, AgNWs, and a wool fabric layer into a multilevel fabric, as shown in FIG.6A. The optical design rationale was to use PMP to achieve outward-facing emissivity in ATW, AgNWs to suppress the outward-facing non-ATW emissivity (which equals absorptivity), and wool fabric to ensure the inward-facing broadband emissivity (FIG.6B). It is worth mentioning that the inward-facing fabric is not limited to wool fabric. It can be replaced with fabrics featuring broadband emissivity, such as cotton, nylon, silk, etc. All these SSHFs have a high and selective outward-facing emissivity and a broadband inward-facing emissivity; therefore, they can work similarly as the radiative cooler SSHF-wool fabric. With the selective and asymmetrical designs, SSHF efficiently emitted heat to the outer space while largely suppressing the radiative heat gain and enhancing the human body heat loss, as shown in the radiative heat transfer network in FIG. 6B. Other textiles, such as broadband textile emitter, broadband transparent textile, and semi- transparent selective emitter were also analyzed using the similar heat transfer networks in FIGS.7A-7C and Supplementary Text 5. Among them, SSHF provided an optimal radiative heat transfer design pathway for human body radiative cooling in the scenarios with hot urban infrastructures. [0050] Experimentally, AgNW network was first deposited on the backside of PMP fabric by spray coating. To enhance the mechanical property and durability, AgNW was encapsulated with a thin layer of poly(ethylene-ran-butylene)-block-polystyrene (SEBS) (Experimental section). A SEM image showed the porosity of the AgNWs network remained substantial after the SEBS coating. The AgNWs aggregated into bundles and were encapsulated by SEBS, with the pores between different bundles remaining intact. Emissivity spectra of SSHF before and after SEBS coating showed no significant change. The AgNW layer provided MIR reflectivity against the building and ground thermal radiation, especially
Atty. Dkt. No.05400-0074-PCT within the 13-20 μm wavelength range, which would otherwise pass through the PMP fabric and become a heat gain (FIG.6C). Then, a broadband emissive wool fabric was sewn to the bottom of AgNW/PMP fabric using ultra-high-molecular-weight polyethylene (UHMWPE) yarn. Without wool fabric, the metabolic heat emitted by the human skin would be reflected by the AgNW layer within the air gap between the human skin and the textile, blocking the heat exchange from the human body to the fabric, as illustrated in FIG.6D (i). On the contrary, SSHF with the bottom wool fabric absorbed the thermal radiation emitted from the skin and conducted to the surface PMP fabric through AgNW for selective thermal emission, improving the cooling capability (FIG.6D (ii)). [0051] The porous structure of SSHF provided decent breathability, as shown in FIG.6E. PMP fabric and SSHF have high water vapor transmission rates (WVTR) of 0.345 g/(cm2^day) and 0.271 g/(cm2^day), respectively, which serves as an efficient conduit for the natural diffusion and convection of water vapor, facilitating the cooling via perspiration. Cotton and wool fabrics demonstrated comparable WVTR to that of PMP fabric. In contrast, the PMP film exhibited no water vapor permeability. After 30 days, the water in the vial covered by the SSHF fabric completely evaporated, whereas the water in the vial covered by the PMP film remained, as shown in the inlet in FIG.6E. Furthermore, SSHF exhibited a robust and durable mechanical performance under the tensile test. As shown in FIG.6F, owing to the multiscale hierarchical structure, the strain-force curve showed two characteristic peaks during stretching, which belonged to the fracture of UHMWPE sewing yarn and wool fabric. Due to the isotropic characteristics of nonwoven PMP fabric and AgNW layer, no significant breaking peaks were observed. After 1000 times repeated stretching and releasing with 2% strain, SSHF continued to exhibit excellent mechanical performance (FIG.6G). Also, the UV-VIS-NIR reflectivity and MIR emissivity after 100 times bending and stretching showed no significant difference, demonstrating its long-term durability for wear. The hydrophobic property (contact angle 135°) of the top PMP fabric of SSHF imparted a self-cleaning property, which was caused by the rough surface from nano- micro hybrid fiber network (FIG.6H). The contact angle maintained a high value of 128° after 10 mins. This self-cleaning capability can preserve its spectral property over extended periods of use. SSHF also has excellent washability. It can preserve the MIR emissivity after 8 cycles of machine-washing tests with detergent, as shown in FIG.6I. Besides, SSHF showed an excellent sweat resistance and on-skin comfort, without inflammation detected after wearing 4 days. Emissivity did not change before and after the sweating. Additionally,
Atty. Dkt. No.05400-0074-PCT to measure the SSHF stability in air, accelerated durability characterization was conducted under the environmental condition of 85 °C and 90-100 RH% (Experimental section). The emissivity spectrum for SSHF with SEBS showed no significant change after 14 days, while the one without SEBS exhibited notable increase in the wavelength range of 13-20 µm, caused by the oxidation of AgNWs. SEBS encapsulation ensured SSHF with an excellent oxidation durability in air. SSHF also exhibited exceptional resistance to UV aging. Its multispectral property barely changed after direct exposure to a 350 W/m² UV lamp for one week, equivalent to approximately half year of direct sunlight exposure. These outstanding properties demonstrate the durability and longevity of SSHF, ensuring its excellent wearability over time. [0052] Outdoor thermal measurements [0053] The outdoor radiative cooling performance of SSHF was demonstrated by direct thermal measurements in Apache Junction, Arizona and Chicago, Illinois. To ensure a precise and uniform measurement, the textile temperature was continuously monitored in real-time using thermistors affixed to a copper plate. Polystyrene foam with size of 17’’ ´ 11’’ ´ 9’’ was used for thermal insulation. To minimize sunlight absorption, the entire device was shielded by aluminum foil and silver mylar, except for the sample area (FIGS.8A-8B and Supplementary Text 6). Temperatures for both vertically and horizontally oriented samples were measured. For the horizontal test, the apparatus was tilted 15° towards the west (FIG. 8C). Near 24-hour continuous measurement demonstrated that SSHF consistently exhibited a lower temperature than ambient temperature under clear sky conditions on May 28th, 2023, at Apache Junction. During the nighttime, the SSHF yielded a remarkable sub-ambient temperature drop of 12.6 ℃ on average. Even during daytime, when subjected to solar intensities of 1010 W/m², the SSHF managed to maintain a significant temperature drop of 6.2 ℃ (FIG.8C). This highlights the impressive cooling performance of the SSHF throughout both day and night conditions. [0054] Even in a situation with high relative humidity (RH%), such as ~70 RH% with total precipitable water of 22.8 mm (Supplementary Text 7), on May 4th in Chicago, the daytime sub-ambient temperature drop can still be ~2.5 ℃. The temperature difference between commercialized textile materials and SSHF when vertically placed towards S178°E were then compared. At 12:30 pm, SSHF, silk, cotton, and rubber temperatures were 40.4 ℃, 43.8 ℃, 44.1 ℃, and 44.6 ℃, respectively (FIG.8D). This pronounced cooling performance
Atty. Dkt. No.05400-0074-PCT of SSHF was attributed to its ability to simultaneously emit heat to the outer space while selectively blocking thermal radiation from the ground (> 60℃). The ground temperature was also calculated based on the heat transfer model and the monitored meteorological data (i.e., solar intensity, relative humidity, and ambient temperature) (Supplementary Text 1). Apparently, the ground was an intense heat source for vertically facing textiles, which makes selective spectrum engineering critical to achieve radiative cooling. To mitigate the influence of solar absorbance on the comparison of cooling performance, a reference sample with high solar reflectivity of 90% and broadband emissivity of 91% was prepared for outdoor daytime temperature comparison (FIGS.9A-9B). Both daytime and nighttime measurements were carried out with a simulated hot ground on Dec.18th-21st 2023, at Apache Junction, Arizona. At nighttime, SSHF showed 0.2 °C cooler than the broadband emitter (FIG.8F). In addition, it showed a 4.7 W/m2 higher cooling power than the broadband emitter (Supplementary Text 6). This can directly demonstrate the radiative cooling advantage of the selective emitter in the urban scenario with hot ground. During the daytime, SSHF exhibited 2.3°C and 8.9°C cooler than the broadband emitter and commercialized silk fabric, respectively, which benefited from both high solar reflectivity and MIR selective emissivity of SSHF. [0055] To further demonstrate the cooling effect of SSHF in a realistic wearing condition, a heater was used to simulate the metabolic heat of a human body by giving a consistent power of 115 W/m2. The temperatures for SSHF, silk, cotton, and rubber were 49.4, 51.6, 52.5, and 52.2 ℃, respectively at 4:30 pm (FIG.8F) while ground temperature was 56.6 ℃. This result again shows the superior cooling performance of SSHF compared to commercial fabrics. In addition, on-skin measurements were conducted by wearing the SSHF and cotton fabric on the two arms of a volunteer standing on the hot ground of around 44 ℃. The skin temperature was measured using the thermistors attached to the skin underneath the fabrics. As shown in FIG.8E, the SSHF was ~0.25°C cooler than the cotton fabric on average, further verifying the on-skin cooling effect of SSHF at urban scenarios. [0056] Radiative cooling textiles in urban areas are essential due to the increasing heat island effect. To extrapolate the cooling performance of SSHF in urban scenarios, a 3D theoretical model was built and the impact of the building view factors on the human body under different scenarios was calculated. The view angle β was defined as the angle between the horizon and the line connecting the textile and the top center point of the building, and ^^ as the angle between the bottom center and bottom side of the building (assuming the building is symmetric), as shown in FIG.10A. The view angle β is regarded to be consistent
Atty. Dkt. No.05400-0074-PCT along the vertical direction considering the height of the human body is small compared to that of the buildings in urban areas. Assuming the human is at the center of the building facade, the 3D view factor of the textile to the sky and terrestrial features (including ground and buildings) are shown in FIG.10B and Supplementary Text 2. In an open scenario (β = 0°, and ^^ = 0°), the view factor to the sky and terrestrial features are both 0.5. As β and ^^ increases, the view factor to the infrastructure objects becomes larger and reaches unity when β = 90° and ^^ = 90°. The cooling power of SSHF was theoretically compared with a broadband fabric under a solar intensity of 850 W/m2 (FIG.10C). SSHF consistently exhibited higher cooling power compared to the broadband textile. With β and ^^ increasing from 0° to 90°, the difference of cooling power between SSHF and broadband textile further increased from 4.7 W/m2 to 67.4 W/m2. [0057] The cooling effect was experimentally tested in outdoor measurements by using a wallpaper (with a height of 0.68 m) to simulate the scenario in urban areas. To simulate the scenario with β and ^^ equals to 20° and 60°, the distance between the textile and wall was set as 1.86 m. The temperatures for SSHF, silk, cotton, and rubber were 40.9 ℃, 42.5 ℃, 44.1℃, and 44.6℃, respectively, at 3:30 pm, May 28th, 2023 (FIG.11). This further demonstrates SSHF as a promising textile for outdoor personal thermoregulation in urban areas. [0058] A selective textile emitter with higher selective ratio and ATW emissivity will further promote the cooling performance. For example, in an open scenario, such as plain ground in Levant, Kansas, when the solar intensity is 1000 W/m2, the SSHF has the potential to yield an additional 16.1 W/m² of cooling power compared to a broadband emitter (FIG. 10D). Under the same illumination conditions with β = 20° and ^^ = 30° (e.g., on a street near a 3-floor building), β = 45° and ^^ = 60° (e.g., on a street near an 8-floor building), and β = 80° and ^^ = 80° (e.g. near high-rise buildings in a downtown city), SSHF outperformed broadband emitter with additional cooling power of 19.0 W/m2, 52.2 W/m2, 95 W/m2, respectively, which correspond to 33.8%, 65.4%, and 79.8% of that can be realized by an ideal selective emitter (FIGS.10E-10G). In other words, spectrum engineering to approach the ideal selectivity can boost the cooling performance, especially in scenarios with low β and ^^ (such as plain ground or suburb areas). Additionally, the coloration of such selective textiles can be accomplished by incorporating electrospinning solution with pigments featuring low absorption coefficients in the non-ATW range. This approach allows for various colors while maintaining their spectrum selectivity performance.
Atty. Dkt. No.05400-0074-PCT [0059] Materials and Methods [0060] SSHF preparation [0061] PMP fabric was prepared using electrospinning. First, a mixture solution of cyclohexane, DMF, and acetone with a weight ratio of 80:10:10 was prepared. Then, 1~2.5 wt.% PMP with 0.1~10 mM TBAB was added to the solution and dissolved in 60 ℃ oil bath for 12 hours until a completely clear solution was obtained. Prepared PMP solution was electrospun under conditions with positive 8 kV voltage at a flow rate of 1 mL/hour. The fibers were collected on the alumina foil, which was connected to the ground. The distance between the feeding needle (21#) and the collecting electrode was kept at 15 cm. The prepared PMP fibers were dried under vacuum at 60 ℃ overnight to remove the residual solvent. Afterwards, PMP fabric was stabilized in a 170 ℃ oven for 2 hours. Further, AgNW (5 mg/mL in isopropyl alcohol, Sigma) with average length and diameter of 60 nm and 40 µm, were coated to the backside of PMP fabric using spray coating techniques. Afterwards, 1.5 mL 5 wt% SEBS in toluene was spray coated on 6*6 cm2 AgNW side. After the PMP/AgNW fabric dried in a fume hood, micropores with 50 μm diameter were punched on the AgNW/SEBS surface with density of 175 pores/cm2 to increase the air permeability. Then, a wool fabric (obtained from Ningxia Zhongyin Cashmere Industry Co., Ltd.) with a thickness of 150 μm was integrated to the bottom side of the PMP/AgNW layer by sewing with UHMWPE yarn via plain stitch method. The sides of the SSHF were further soldered to ensure a better connection. [0062] PMP refractive indices measurements [0063] To study the optical property of PMP, visible and infrared spectroscopic ellipsometry (SE) data were firstly collected by alpha-SE and IR-VASE Mark II (both from JA Woollam Co.). A 25-nm thick PMP on Si wafer (prepared by spin-coating) was used for visible light SE measurement at incident angles equal to 65°, 70°, and 75°. A 1200 nm-thick PMP on heavily B-doped Si wafer sample (prepared by hot-pressing) was used for IR-SE measurement at incidence angles equal to 35°,45°, 55°, 65°, and 75°. Further, IR transmission spectra of PMP films with thicknesses of 70, 113, and 247 μm (prepared by hot-pressing) were measured using transmission measurement mode on IR-VASE Mark II at normal incidence. [0064] Optical properties of PMP were obtained by model fitting of the SE data (in both visible and IR regions) and transmission spectra (IR). Model fitting and data analysis were
Atty. Dkt. No.05400-0074-PCT performed in WVASE software and CompleteEASE software (both from JA Woollam Co.) in the range of IR and visible light, respectively. In the visible region, PMP was treated as a transparent material and the optical dispersion was fitted by Cauchy model: ^ ^ ^^ ^^ ^^ ൌ ^^ ^ ^^ଶ where A = 1.507േ0.002 and B = 0.00207േ0.00025 ^^^^ଶ for PMP. [0065] For IR transmission and ellipsometry spectra, standard Lorentz oscillator model was used to identify and describe the IR absorption of the chemical bonding in PMP. Permittivity (^^ ) dispersion described by standard Lorentz oscillator model was given by: ^^ ^^ ൌ ^^ െ ^ ^ ^ ^^ଶ െ ^^ଶ ^ ^ ^^^^^^^ where ^^^ is the effective -2
is the amplitude (cm ), ^^^ is frequency (cm-1), and ^^^ is the plasma collision frequency (cm-1) of the ^^th oscillator. The resulting parameters of 30 Lorentz oscillators of PMP are determined from fitting both the transmission spectra and SE data. The IR optical properties of the optically thick, heavily doped Si substrate were calculated from standard Drude model fitting. Details can be found in Supplementary Text 3. [0066] PMP film optical property simulation [0067] The refractive indices of PMP film were used to simulate the thermal emissivity by employing the effective medium theory (Bruggeman-type) by MATLAB: ^^ ^^^^^ െ ^^^^^ ^ ^1 െ ^ ^^ୟ୧୰ െ ^^^^^ ^^ ^ 2^^ ^^ ^ 2^ ൌ 0 ^^^ ^^^ ^^^^ where f is the volume
the emissivity of PMP, air, and the whole film, respectively. [0068] PMP fiber optical property simulation [0069] To optimize the fiber dimension in optical design, the scattering efficiency of the PMP fiber with different sizes was calculated based on a finite element method using COMSOL Multiphysics. (R. Asapu et al., ACS applied materials & interfaces 9, 41577- 41585 (2017).) A two-dimensional model was built with a rectangular cross-section. The length of the short side was set as one seventh of the fiber width (L) based on experimental
Atty. Dkt. No.05400-0074-PCT statistical results. The scattering efficiencies were obtained by dividing the scattering cross- sections with L. [0070] Optical characterizations of SSHF [0071] FTIR spectra were characterized by iS50 (ThermoFisher Scientific) equipped with a diffuse gold integration sphere. The incidental angle was 12°. Standard gold reference was used when performing baseline measurement. UV-VIS-NIR spectra were measured at an incident angle of 8° using Shimadzu UV-3600 spectrophotometer equipped with a barium sulfate integration sphere (ISR-1503). A Spectralon (S207-21744-43) standard white plate was utilized for baseline measurements. [0072] Water vapor transmission rate characterization [0073] The water vapor transmission rate was measured based on ASTM E96 standard with modification.20 mL vials (ThermoFisher Scientific) were filled with 10 mL deionized water. The bottles were covered and sealed by textile or polymer samples using epoxy adhesive (Loctite). The exposed area of the sample was 9 cm in diameter. The sealed bottles were then placed in an environment at room temperature ~ 25 °C and relative humidity at 30 ±10%. The mass of the whole bottles was measured periodically to track any changes, with the reduction in mass attributed to water evaporation. The reduced mass was divided by the sample area to derive the water vapor transmission rate. [0074] Washing resistance of SSHF [0075] The washability test was conducted using a laundry machine (Comfee CLV09N1AMG) based on AATCC washing standard 135 with modification. Each laundry cycle lasted ~25 mins, including washing, rinsing, and final spin.20 g of detergent (Tide) and 20 L of water were used for the washing step. After washing, the SSHF sample was dried at room temperature before the test. [0076] Sweat resistance and accelerated air stability test of SSHF [0077] 5 mL artificial eccrine perspiration from Pickering Lab (1700-0020) was dropped on the artificial skin and covered by AgNW/SEBS. The whole sample was completely in contact with the sweat. The sample was rinsed with the mixture of ethanol and water (70/30 v/v) and dried at room temperature before the optical spectra characterization. Accelerated air stability test was conducted under 85 °C and 90-100 RH% environment. The samples were dried in a 60 °C convection oven before spectra measurements.
Atty. Dkt. No.05400-0074-PCT [0078] UV-aging test of SSHF [0079] UV-aging test was conducted using a UV lamp with a flux of 350 W/m2. The sample was put beneath the UV lamp at a 10 cm distance. Considering that UV light constitutes approximately 4% of the total solar radiation, the UV intensity in summer can be estimated to be around 40 W/m2, assuming a solar intensity of 1000 W/m2. As a result, exposure to a UV lamp for 24 hours is equivalent to direct sunlight exposure for approximately 26.25 days, based on the assumption of an 8-hour daytime period. In total, SSHF was exposed to the UV lamp for one week, corresponding to an exposure to sunlight for approximately 184 days. Periodic measurements of UV-VIS-NIR and FTIR spectra were conducted throughout the experiment. [0080] Outdoor thermal measurement [0081] The setup for outdoor thermal measurement is shown in FIGS.8A-8B. A sample of 9´9 cm was cut and put in the side center of the thermal insulating Polystyrene foam (size 17’’ ´ 11’’ ´ 9’’). The entire foam (except for sample area) was covered by alumina foil and silver mylar. For vertical measurement, four legs with a height of 5 cm were attached to the bottom of the apparatus to prevent the conduction from the ground. Wallpaper with a height of 0.68 m was used to simulate a wall. For horizontal measurement, the setup was placed 1.2 m above the ground and tilted 15° horizontally to the west. The temperature was measured by thermistors (MP-3189, TE technology), which were attached in the middle of a copper plate under the sample. To simulate the metabolic heat from the human body, a heating power of 115 W/m2 was applied by a DC power supply (Rigol, DP821A). For the outdoor experiments on Dec.18th-21st 2023, given that ambient temperature and solar intensity are relatively low compared to the targeted application scenario in summer, an electrical heating blanket (in black color) and heating patch (in white color) were used to simulate a hot ground. Cooling power was measured using a Peltier temperature control feedback system, as reported in previous research works. (S. Liu et al., Nano Letters 23, 7767-7774 (2023); X. Li et al., Nature communications 11, 6101 (2020).) [0082] Outdoor thermal simulation [0083] Heat Transfer in Solids, Surface-to-Surface Radiation, and Heat Transfer with Surface-to-Surface Radiation Multiphysics Coupling were used to simulate the urban scenario. The Stationary Solver was used to calculate the temperature profile and the heat flux at the thermal equilibrium state. The temperature of the deep space was set to 3K and
Atty. Dkt. No.05400-0074-PCT had a unit MIR emissivity. The materials of buildings and ground were set as concrete and asphalt, with their materials properties being input. The skin temperature was set as 34 °C. The solar reflectivity of selective and broadband textiles was set as 97%. The emissivity for broadband textile was 95%, but the selective textile was 2-8 µm: 38.2% 8-13 µm: 85.3%, and 13-20 µm: 37.7%. [0084] Other characterizations [0085] The SEM images of the PMP fabric were taken by a high-resolution field emission scanning electron microscope (Carl Zeiss Merlin). The 3D X-ray Computed Tomography images were taken using Rigaku Nano 3Dx. The infrared images were recorded using an IR camera (FLIR E54). The transmission spectrum of PMP film in FIG.4B was measured using the Shimadzu IRTracer-100 Fourier transform infrared spectrophotometer with GladiATR (diamond prism) single bounce attenuated total reflection (ATR) mode. The contact angle was measured using DSA100 Drop Shape Analyzer. Mechanical test was performed using Zwick-Roell zwickiLine Z0.5 materials testing instrument with sample size 20 mm ´ 5 mm, preload 0.01N, stretching speed 10 mm/min. For the cyclic mechanical test, the stretching speed was set as 1 mm/s. [0086] Supplementary Text 1 [0087] Calculation of the temperature of territorial features [0088] Consider a ground whose temperature is ^^^^^௨^ௗ, and spectral emissivity is ^^^^௨^ௗ^^^^ ൌ 0.9. It is subject to solar irradiance, inward atmospheric thermal radiation (corresponding to ambient air temperature ^^^^^), radiation emittance to outer space through the atmospheric window, and conductive and convective heat transfer. Assuming the ground is at a thermal equilibrium state, the theoretical ground temperature can be calculated by solving the following equation: ^^^^^௨^ௗ_^^^௧^^^^^^௨^ௗ^ െ ^^^௧^^^^^^^^ െ ^^^௨^ െ ^^^^^ௗା^^^௩ ൌ 0 (1) [0089]
the angular integral over a hemisphere: ^^ ൌ ^ ଶగ గ⁄ ଶ ^ ^ ^ ^ ^ ^ ^^^^൫^^,^^^^^௨^ௗ൯^^^^௨^ௗ^^^,^^^sin^^ cos ^^ ^^^^^^^^^^^^ (2)
Atty. Dkt. No.05400-0074-PCT [0090] Here ^^ ^^^ ^ ଶ^^మ ^ ^^ ,^^ ൌ ఒఱ ^^^⁄ ^ഊೖಳ^^ ି^ is the spectral radiance of a blackbody at temperature T, where h is Planck’s constant, ^^^ is the Boltzmann constant, c is the speed of light and λ is the wavelength. ^^ is the surface area. [0091] ^^^௧^ is the adsorbed power owing to incident atmospheric thermal radiation: ^^^௧^ ൌ ^ ଶగ గ⁄ ଶ ^ ^ ^ ^ ^ ^ ^^^^^^^,^^^௧^^^^௧^^^^^^^^^௨^ௗ^^^,^^^sin^^ cos ^^ ^^^^^^^^^^^^ (3)
atmosphere, which is calculated by ^^௧^^^^^ ൌ 1 െ ^^^^^^, where ^^^^^^ is the atmospheric transmission. Here, ^^^^^^ is calculated using MODTRAN software, with Mid-Latitude Summer model. The total precipitation water (TPW) is calculated using: (Y. Fang et al, Joule 5, 752-754 (2021).) 3800 ^^^^^^ ൬ 17.625^^^^^ ^ ^^ ^ ^^^^^^ ൌ 2.15^^^ ^^^ ^ 243.04 െ 0.82 where RH is the
Pa. Unless specified, the TPW is assumed to be 7 mm in this Example. [0092] ^^^௨^ is the incident solar power: ^^^௨^ ൌ ^1 െ ^^^^^^^௨^ௗ^ ∙ ^^^^^^^ (4) [0093] ^^^^^^^ is solar irradiance. For most common ground or building materials, concrete and asphalt, solar reflectivity (SR) is assumed to be 0.35 and 0.15, respectively. [0094] ^^^^^ௗା^^^௩ is the power lost owing to convection and conduction: ^^^^^ௗା^^^௩൫^^^^^௨^ௗ,^^^^^൯ ൌ ℎ^൫^^^^^ െ ^^^^^௨^ௗ൯ (5) where ℎ is a
conduction and convection. Here, the ℎ^ is assumed to be 12 W/ (m2.K). [0095] Supplementary Text 2 [0096] Calculation of the cooling power for vertical textiles [0097] Consider a textile that has a fixed temperature near skin ^^௧^௫ ൌ 34 ℃, and spectral emissivity is ^௧^௫ ^^^^, when the textile is vertically exposed to an urban environment, it is subject to solar irradiance, atmospheric thermal radiation (corresponding to ambient air temperature ^^^^^) and territorial thermal radiation, including that from ground and buildings,
Atty. Dkt. No.05400-0074-PCT as shown in FIG.12A. Assuming the buildings have the same temperature as the ground and are labelled as ^^௧^^^ (both of them are assumed to be made of concrete), the net cooling power ^^^^^^ of such a radiative cooling textile is given by: ^^^^^^ ൌ ^^^^^௧^^^௧^௫^ െ ^^^^௬^^^௧^^^^^^^^ െ ^^^^^௨^ௗ^^^^^௨^ௗ^^^௧^^^^ െ ^^^௨^^ௗ^^^^^^௨^^ௗ^^^^^^௧^^^^ െ ^^^௨^ െ ^^^^^ௗା^^^௩ (6) [0098] ^^^௨^^ௗ^^^, ^^^^^௨^ௗ, ^^^^௬, are view factors, calculated based on the fraction of radiation leaving from the textile surface that is intercepted by the building, ground, and sky, respectively (FIG.12A and 12B). The view factor calculations for 3D geometries reported by Incropera et al. were referred to ( F. P. Incropera, et al., Fundamentals of heat and mass transfer, 6th ed., (Wiley New York, 2006), vol.6.) ଶఝ ఉ ^^^௨^^ௗ^^^ ൌ గ ^^ sin^^ cos ^^ ^^^^ (7)
(8) ^^^^௬ ൌ 1 െ ^^^௨^^ௗ^^^ െ ^^^^^௨^ௗ (9) where β is the angle between the horizontal line and the line connecting the textile and the building viewing vertex. ^^ is the angle between the bottom center and edge of the building (assuming the building is symmetric; FIG.12C). Since buildings are normally much higher than the human body, β is assumed to be consistent along the human body vertical direction. When calculating the cooling power for different materials in FIG.4D, β is assumed to be 45°, and ^^ is assumed to be 60°. [0099] ^^௧^௫ is the power radiated out by the textile: ^^௧^௫ ൌ ^ ଶగ గ⁄ ଶ ^ ^ ^ ^ ^ ^ ^^^^^^^,^^௧^௫^^௧^௫^^^^sin^^ cos ^^ ^^^^^^^^^^^^ (10) [00100]
ground and adsorbed by the textile: ^^^^^௨^ௗ ൌ ^ ଶగ ^ ^ గ⁄ ଶ ^ ^ ^ ^ ^^^^^^^,^^௧^^^^^௧^௫^^^^^^^^௨^ௗ^^^^sin^^ cos ^^ ^^^^^^^^^^^^ (11)
Assuming the distance between the building and the human body is 20 m, it can be calculated as follows: ^^^௨^^ௗ^^^ ൌ ^ ଶగ గ⁄ ଶ ^ ^ ^ ^ ^ ^ ^^^^^^^,^^௧^^^^^௧^௫^^^^^^^௧^ିଶ^^^^^^^^௨^^ௗ^^^^^^^sin^^ cos^^ ^^^^^^^^^^^^ (12)
Atty. Dkt. No.05400-0074-PCT where t^௧^ିଶ^^^^^^ is the atmospheric transmission with distance of 20 m. It was calculated using MODTRAN GUI by setting the sensor altitude to 200 m (near elevation of Chicago) and modeling a 90 deg path zenith with a 20 m path length. [00102] ^^^௨^ is the vertical incident solar power: ^^^௨^ ൌ ^^ ^ ^ ^ ^௧^௫^^^^^^^ெ^.ହ^^^^ ^^^^ (13) where ^^^ெ^.ହ ^ ^^ ^
to the solar absorptivity of the textile α௧^௫^^^^. Since the textiles are vertically oriented, a coefficient ^^ ൌ 0.4 was introduced to convert the global horizontal solar irradiance to the vertical solar intensity. (E. L. Maxwell, et al., "Measuring and modeling solar irradiance on vertical surfaces," (Solar Energy Research Inst.(SERI), Golden, CO (United States), 1986); D. H. Li, et al., Renewable energy 25, 591-606 (2002). [00103] Supplementary Text 3 [00104] IR optical property calculation of the thick, heavily doped Si substrate [00105] The IR optical properties of the optically thick, heavily doped Si substrate were calculated from standard Drude model fitting. The permittivity dispersion of heavily B-doped Si is modelled and given by ^^ ^^ ൌ ^^^ െ ^^ଶ ^ ^^^^^^ where ^^^ is the effective
and A= ℏ ఌబఘ, in which ℏ is the Planck constant, ^^^ the vacuum permittivity, and ^^ the resistivity. For heavily B- doped Si wafer, ^^ =10. 14 -1 ^ 832, ^^=0.0014817 Ω ⋅ ^^^^ , and ^^=1.2499ൈ10 cm . [00106] Supplementary Text 4 [00107] PMP nano-micro hierarchical fiber morphology engineering [00108] Fiber dimension and spinning uniformity were controlled by the spinning conditions, including solution conductivity and surface tension, flow rate, electric field strength, and polymer concentration. In particular, tetrabutylammonium bromide (TBAB) was added to the electrospinning solution. First, TBAB had excellent solubility in the pristine electrospinning solvents, i.e., cyclohexane and acetone. Second, it increased the conductivity and decreased the surface tension, thereby diminishing the Rayleigh instability. Third, TBAB could be washed away easily by ethanol and water after the fibers were formed. PMP fibers
Atty. Dkt. No.05400-0074-PCT have a very uniform structure without noticeable beads. With the increase of TBAB concentration from 0.37 mM to 10 mM, the fiber width reduced from 2.33 µm to 1.54 µm (FIG.13A).1 mM was chosen as the concentration for further study because it can achieve ideal fiber dimensions and is easy for TBAB salt removal. Next, the effect of electric field strength on the fiber morphology was studied. As shown in FIG.13B, with electric field strength enhanced from 0.54 kV/cm to 0.94 kV/cm, the fiber dimension decreased from 2.74 µm to 1.96 µm. Therefore, 0.94 kV/cm was used for further study. In addition, the fiber dimension was further decreased by adjusting the polymer concentrations. With the addition of TBAB, the lowest concentration for bead-free and continuous electrospinning could be lowered to 1 wt.%. The fiber dimension dramatically decreased with the concentration drop from 2.5 wt.% to 1 wt.%, as shown in FIGS.5A-5B. The randomly stacked fibers maintained a ribbon structure with irregular twists, forming a multi-layered nano-micro hierarchical fiber network with broadly distributed fiber sizes. [00109] Supplementary Text 5 [00110] Radiative heat transfer network comparison of other reported textiles and SSHF [00111] FIGS.7A-7C shows the radiative heat transfer network comparison of three reported textile types, i.e., broadband emitter, broadband transparent emitter, and semi- transparent selective emitter, as well as SSHF in this work. Note that all these four types of textiles can achieve a low emissivity (high reflectance) in the UV-VIS-NIR range (0.28-2.5 μm), and therefore can block the solar light. [00112] A broadband textile emitter (FIG.7A) had a high emissivity in the whole MIR wavelength range (2.5-20 μm). Although a broadband emitter can emit thermal radiation to the deep space through the ATW (8~13 μm), there was remarkable heat gain from the surrounding ground and buildings within the wavelength of 2.5-8 μm and 13-20 μm. [00113] For a broadband transparent textile (FIG.7B) that has a low emissivity in the UV- VIS-NIR range (0.28-2.5 μm) and high transparency in the MIR wavelength range (2.5-20 μm), while human body thermal radiation can pass through the textile and radiate to the deep space, the heat radiation emitted from hot ground or buildings (2.5-8 μm and 13-20 μm) can pass through the textile and be absorbed by human skin. [00114] For a semi-transparent selective emitter (FIG.7C) with a high emissivity in 8-13 μm and a high transmittance in other ranges (2.5-8 μm, and 13-20 μm), the textile can benefit
Atty. Dkt. No.05400-0074-PCT from the thermal radiation to the deep space (8-13 μm). However, heat radiation from the hot ground and buildings can still pass through the textiles (2.5-8 μm, and 13-20 μm) and get absorbed by the human body, similar to the behavior of broadband transparent textiles. [00115] In this Example, SSHF can not only efficiently emit heat to the deep universe through ATW (8-13 μm), but also largely suppress the radiative heat gain from hot ground and buildings (2.5-8 μm and 13-20 μm) by the unique structure design, as shown in FIG.6A. Note that SSHF without AgNW and wool fabric layer (only PMP) will be a semi-transparent selective emitter, allowing thermal radiation from hot ground and buildings to pass through the textile and be absorbed by the human body. [00116] Supplementary Text 6 [00117] Outdoor thermal measurements [00118] The temperature measurement setup is shown in FIGS.8A-8B and FIG 14B. The temperature with and without PE covering the setup were measured. FIGS.8C, 8D, and 8F; FIGS.14A and 14C; and FIG.11 are the data measuring with PE covering the setup to cut down the convection heat loss/gain. To better simulate the real scenario, FIGS.8E and 8G, FIGS.15A-15B, and FIGS.16A-16B were measured without PE film. [00119] Further, to verify the effectiveness of radiative cooling of SSHF, the temperature underneath the sample edge was measured. In the setup, aluminum foil and silver mylar were used to shield the polystyrene foam to minimize the sunlight absorption, and SSHF sample edge was directly contacted with it. As shown in FIGS.14A and 14C, the sample center temperature was cooler than that on the edge, which effectively shows that the sample was cooler than the aluminum foil and silver mylar. [00120] Further, to quantitively minimize the effect of convective heat loss from the ambience, a Peltier temperature control feedback system was used to characterize the cooling power of the selective and the broadband emitter in a simulated urban scenario. The heat flux was real-time measured while the PID control program was used to minimize the temperature difference between the sample and the ambience, as reported in previous research works. (S. Liu et al., Nano Letters 23, 7767-7774 (2023); X. Li et al., Nature communications 11, 6101 (2020).) The cooling power characterization was done at nighttime to exclude the effect from solar radiation. An artificial ground with an average temperature of ~30 ºC was generated to simulate the urban scenario at daytime. The characterizations were conducted on Dec.21st, 2023, at Apache Junction, Arizona (33.44° N, 111.48°W, Elevation: 637 m). SSHF and
Atty. Dkt. No.05400-0074-PCT broadband emitter (PDMS/Al2O3/TiO2) showed an average cooling power of 13.5 W/m2 and 8.8 W/m2, respectively (FIGS.17A-17B), which further shows the advantage of selective emitter at simulated urban scenario. [00121] Supplementary Text 7 [00122] The impact of humidity on cooling effect of SSHF [00123] To consider the impact of air thermal radiation adsorption on the cooling performance of selective emitters, the atmospheric transmission between the building wall and the human body was calculated using MODTRAN software. The distance between the building wall and the human body was set as 10 m. The relative humidity was 10%, 30%, and 70%, which refers to dry, moderate, humid environment. The atmospheric transmission window is shown in FIGS.18A-18B. FIGS.18C-18E show the calculated cooling power of SSHF, ideal selective emitter, and broadband emitter at an urban scenario of β = 45° and φ = 60° under different relative humidity of 10%, 30%, and 70%. β is the angle between the horizon and the line connecting the textile and the top center point of the building, and φ is the angle between the bottom center and bottom side of the building. The far buildings may indeed have less thermal radiation emitted to the human body because of air absorption, especially in a humid environment. However, the solar intensity at the crosspoint where the selective emitter suppressed the broadband emitter shifted to a lower value when the humidity increased from 10% to 70%. This is because the high humidity restricted the radiation to the deep space for the emitters, which is more profound for broadband emitters. Therefore, selective emitters also play an important role in radiative cooling in urban scenarios, even in humid conditions. [00124] The word "illustrative" is used herein to mean serving as an example, instance, or illustration. Any aspect or design described herein as "illustrative" is not necessarily to be construed as preferred or advantageous over other aspects or designs. Further, for the purposes of this disclosure and unless otherwise specified, "a" or "an" means "one or more.” [00125] The foregoing description of illustrative embodiments of the invention has been presented for purposes of illustration and of description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and as practical applications of the invention to enable one skilled in the art to
Atty. Dkt. No.05400-0074-PCT utilize the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.