WET SONICATION SYSTEM AND METHOD FOR SONICATING A FABRIC

CROSS REFERENCE TO RELATED APPLICATIONS

[001] This application claims the benefit of priority under 35 U.S.C. § 119(e) of U.S. Provisional Patent Application No. 63/348,109, filed on June 02, 2022. The content of the above application is incorporated by reference as if fully set forth herein in its entirety.

FIELD OF THE INVENTION

[002] The present invention relates generally to sonication systems. More specifically, the present invention relates to wet sonication systems and a method for sonicating a fabric.

BACKGROUND OF THE INVENTION

[003] Ultrasonic waves have been implemented for impregnating fabrics with nanoparticles (such as metal nanoparticles). In general, current methods are based on ultrasonic irradiation of fabrics immersed within an ultrasonic bath containing a nanoparticle suspension. The ultrasonic treatment results in fabrics characterized by deeper embedment of the nanoparticles and consequently by improved wash resistance, compared to conventional coating methods.

[004] However, the penetration depth of the nanoparticles into and between the fibers of the fabric in the current industrial ultrasonication treatment is insufficient, thus affecting the yield of the ultrasonication sonication treatment and as a consequence reducing costefficiency of the entire process. Furthermore, the penetration depth may have an impact on the ability of the nanoparticles to remain embedded inside the fabric upon multiple washing cycles.

[005] Accordingly, there is a need for new systems and ultrasonication methods having an improved ability to impregnate particles into fibrous substrates.

SUMMARY OF THE INVENTION

[006] Some aspects of the invention may be directed to wet sonication system comprising: a pre-wetting bath; a sonication unit comprising: at least one first sonotrode; a sonication bath; and at least one of: at least one second sonotrode; and at least one reflector. The system may further include a delivery system configured to continuously deliver a fabric into the pre- wetting bath, and continuously deliver the fabric from the pre- wetting bath to the sonication bath such that a predetermined distance is formed between the fabric and the first sonotrode.

[007] In some embodiments, the pre-wetting bath and the sonication bath are the same baths. In some embodiments, the at least the sonication bath comprises an aqueous solution comprising nanoparticle dispersion. In some embodiments, the predetermined distance is 5- 25 mm.

[008] In some embodiments, the reflector is located at a distance of 20-40 mm from the first sonotrode and wherein the delivery system directs the fabric between the reflector and the at least one sonotrode. In some embodiments, the second sonotrode is located at a distance of 50-70 mm from the first sonotrode and wherein the delivery system directs the fabric between the first and second sonotrodes.

[009] In some embodiments, at least, one first sonotrode is configured to provide between 30 to 150 W per 100 cm ² . In some embodiments, at least, one first sonotrode is configured to vibrate at a frequency of: between 20 to 40 Khz, preferentially 25 Khz.

[0010] Some additional aspects of the invention are directed to a method for sonicating a fabric, comprising: a. prewetting the fabric with a first aqueous composition; and b. sonicating the fabric with a second aqueous composition comprising a nanoparticle dispersion.

[0011] In some embodiments, the sonicating is conducted by continuously delivering the fabric between a first sonotrode and at least one of: a second sonotrode; and a reflector.

[0012] In some embodiments, during the sonication, the first sonotrode to provides to the fabric between 30 to 150 W per 100 cm ² . In some embodiments, the first aqueous composition is similar to the second aqueous composition. In some embodiments, continuously delivering the fabric is at a distance of 5-25 mm from the first sonotrode.

[0013] In some embodiments, the reflector is located at a distance of 20-40 mm from the first sonotrode. In some embodiments, the second sonotrode is located at a distance of 50- 70 mm from the first sonotrode.

[0014] Some additional aspects of the invention may be directed to another wet sonication system comprising: a sonication bath comprising an aqueous solution comprising nanoparticle dispersion and at least one of: a wetting agent and a wicking agent; a first sonotrode; and at least one of: a second sonotrode; and a reflector. In some embodiments, the system may include a delivery system configured to continuously deliver a fabric into the sonication bath such that a predetermined distance is formed between the fabric and the first sonotrode.

[0015] In some embodiments, the predetermined distance is 5-25 mm. In some embodiments, the reflector is located at a distance of 20-40 mm from the first sonotrode and wherein the delivery system directs the fabric between the reflector and the at least one sonotrode. In some embodiments, the second sonotrode is located at a distance of 50-70 mm from the first sonotrode and wherein the delivery system directs the fabric between the first and second sono trades .

[0016] Some additional aspects of the invention are directed to a method of sonicating a fabric, comprising: a. continuously delivering the fabric onto a sonication bath; b. sonicating the fabric with an aqueous solution comprising a nanoparticle dispersion and at least one of: a wetting agent and a wicking agent.

[0017] In some embodiments, the sonicating is conducted by continuously delivering the fabric between a first sonotrode and at least one of: a second sonotrode; and a reflector.

BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings in which:

[0019] Figs. 1A, IB, and 1C are illustrations of wet sonication systems according to some embodiments of the invention;

[0020] Fig. 2 is a flowchart of a method of sonicating a fabric according to some embodiments of the invention;

[0021] Fig. 3 is a flowchart of another method of sonicating a fabric according to some embodiments of the invention.

[0022] It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements.

DETAILED DESCRIPTION

[0023] One skilled in the art will realize the invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The foregoing embodiments are therefore to be considered in all respects illustrative rather than limiting of the invention described herein. Scope of the invention is thus indicated by the appended claims, rather than by the foregoing description, and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

[0024] In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be understood by those skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, and components have not been described in detail so as not to obscure the present invention. Some features or elements described with respect to one embodiment may be combined with features or elements described with respect to other embodiments. For the sake of clarity, discussion of same or similar features or elements may not be repeated.

[0025] Some aspects of the present invention are directed to a system and method for conducting wet sonication of fabrics in order to improve the fabrics antibacterial resistance after multiple washing cycles. During the sonication process antibacterial nanoparticles such as zinc oxide are embedded into the fabric.

[0026] As used herein the term “sonotrode” refers to an ultrasonic (US) unit comprising at least one US transducer configured to vibrate at least one contact surface of the sonotrode. The sonotrode may have any geomaterial shape, for example, a box, a cylinder, and the like. The sonotrode may be powered by electrical power provided to the at least one US transducer.

[0027] A ‘fabric’ according to embodiments of the present invention, may include any fibrous substrate, either woven or non-woven made from fibers, yams, filaments, threads, etc. The fabric may include natural fibers (e.g., cotton, wool, etc.), synthetic fibers (e.g., polyester, polyethylene, etc.) or any combination thereof. [0028] Reference is now made to Figs. 1A, IB, and 1C which are illustrations of wet sonication systems accoridng to some embodiments of the invention. A wet sonication system 100 may include a sonication unit 20 that may include at least one first sonotrode 22 and a sonication bath 21. In some embodiments, sonication unit 20 may further include at least one of: at least one second sonotrode 24 (illustrated in Figs 1A and IB) and optionally at least one reflector 26 (illustrated in Fig. 1C). In some embodiments, the sonication unit 20 is devoid of a reflector. In some embodiments, the wet sonication systems comprises a plurality of sonotrodes. In some embodiments, the sonotrodes are located within the sonication bath 21. In some embodiments, the sonotrodes are fully or partially immersed within the aqueous composition.

[0029] In some embodiments, the system comprises a plurality of sonotrodes, wherein the plurality of sonotrodes (e.g. the first sonotrode 22 and the second sonotrode 24) are located at opposed sides of the fabric, as illustrated in Figs 1A and IB.

[0030] In some embodiments, sonication bath 21 is configured to hold a liquid volume. In some embodiments, the liquid volume is sufficient for sonicating the fabric. In some embodiments, the dimensions of the sonication bath 2 land or the pre-wetting bath (length, width, height dimensions) and/or the volume thereof are sufficient for immersing at least a portion of the fabric within the liquid volume included within the sonication bath 21.

[0031] In some embodiments, sonication bath 21 may include an aqueous composition comprising a nanoparticles. In some embodiments, the aqueous composition may include a dispersion of nanoparticles. In some embodiments, the aqueous composition may include the nanoparticle dispersion and at least one of: a wetting agent and a wicking agent.

[0032] In some embodiments, the nanoparticles are selected from metal nanoparticles, including any salt, any complex (inorganic or organometallic complex), any oxide, or any combination thereof. In some embodiments, the nanoparticles are metal oxide nanoparticles (such as titanium oxide, zirconium oxide, zinc oxide, copper oxide, aluminum oxide, etc.). In some embodiments, the nanoparticles are metalloid nanoparticles, including any salt, any complex (inorganic or organometallic complex), any oxide, or any combination thereof. In some embodiments, the nanoparticles are carbon nanoparticles (such as carbon black, graphene, CNT, fullerene, etc.). In some embodiments, the nanoparticles are ceramic nanoparticles. In some embodiments, the nanoparticles are metalloid oxide particles (such as silica particles). [0033] In some embodiments, the nanoparticles (e.g. metal particles) are characterized by an average dry particle size of between 1 and 2000 nm, between 1 and 5 nm, between 5 and 10 nm, between 10 and 20 nm, between 20 and 50 nm, between 50 and 100 nm, between 100 and 300 nm, between 300 and 500 nm, between 500 and 700 nm, between 700 and 1000 nm, between 1000 and 1500 nm, between 1500 and 2000 nm, including any range or value therebetween.

[0034] In some embodiments, sonotrodes 22 and 24 may be similar or different. In the nonlimiting example illustrated in Figs. 1A-1C sonotrodes 22 and 24 are rectangular plates. In some embodiments, sonotrodes 22 and 24 can provide between 30 to 150 W per 100 cm ² of a treated fabric 5. In some embodiments, at least, sonotrodes 22 and 24 are configured to vibrate at a frequency of: between 20 to 40 Khz, preferentially 25 Khz.

[0035] In some embodiments, reflector 26 includes any material (e.g., metal) that can reflect back US waves inside a sonication bath.

[0036] System 100 may further include a delivery system 30 configured to deliver fabric 5 to and from sonication bath 21. delivery system 30 may include a conveyor configured to continuously convey fabric 5, for example, using a plurality of rollers 35 configured to deliver fabric 5 inside sonication bath 21 such that a predetermined distance is formed between the fabric and first sonotrode 22, and/or between the fabric and any one of the plurality of sonotrodes. In some embodiments, the predetermined distance between the fabric and a sonotrode (e.g. first sonotrode 22, second sonotrode 24, or any of the sonotrodes in the system 100) is equivalent to a distance of between about 0.1 and about 1.0 times (such as 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1, 1.1, or between about 0.4 and about 0.6 times, between about 0.1 and about 0.6 times, between about 0.2 and about 1 times, between about 0.3 and about 0.8 times, between 0.3 and 0.7, between 0.4 and 0.8 times) of ultrasound wavelength emitted by the sonotrode, including any range between.

[0037] The ultrasound wavelength may be calculated from the corresponding ultrasound frequency emitted by the sonotrode, taking into account the velocity of sound in an aqueous solution. In some embodiments, the predetermined distance is 5-40 mm, between 5 and 35mm, between about 5 and about 40mm, between about 5 and about 30mm, for example, 5, 10 mm, 15 mm, 20 mm, 30mm, 40mm including any value in between.

[0038] In some embodiments, the first sonotrode 22 faces a first surface of said fabric, and the second sonotrode 24 faces a second surface of the fabric. In some embodiments, the delivery system 30 is configured to deliver fabric between the first sonotrode 22 and the second sonotrode 24. In some embodiments, the plurality of sonotrodes located at both sides of fabric delivered by the delivery system 30, induce uniform impregnation or embedding of the nanoparticles into the first surface and into the second surface of the fabric. In some embodiments, the delivery system 30, is configured to deliver fabric between the first sonotrode 22 and the second sonotrode 24 so that the predetermined distance is formed between the fabric and first sonotrode 22 and between the fabric and second sonotrode 24. In some embodiments, the first sonotrode 22 and the second sonotrode 24 are opposed to each other. In some embodiments, the first sonotrode 22 and the second sonotrode 24 are distant from each other along the propagation direction of the fabric.

[0039] Without being bound to any particular theory or mechanism it is postulated that the predetermined distance is essential for substantially increasing incorporation efficiency of the nanoparticles into the fabric and/or operability of the entire method of the invention. While it has been observed that the distance below 0.1 times of the ultrasound wavelength resulted in attraction of the baric to the sonotrode, thus hampering a continuous delivery of the fabric, while a distance above 1 time of the ultrasound wavelength significantly reduced incorporation efficiency of the process. Additionally, it has been observed that the distance between about 0.4 and about 0.6 times of the ultrasound wavelength is preferable in terms of incorporation efficiency and processability (e.g. unhampered and continuous delivery of the fabric by the delivery system).

[0040] In some embodiments, the system or the method of the invention is characterized by an incorporation efficiency ranging between 10 and 80%, between 10 and 80%, between 20 and 80%, between 20 and 50%, between 40 and 80%, between 30 and 80%, between 50 and 80%, between 50 and 90%, including any range between. In some embodiments, the term “incorporation efficiency” refers to a weight portion of the nanoparticles embedded into the substrate, relative to the total amount (e.g. dry weight) of the nanoparticles within the sonication bath.

[0041] In some embodiments, reflector 26 is optionally located at the predetermined distance (e.g. a distance of 20-40 mm) from first sonotrode 22, and delivery system 30 directs fabric 5 between reflector 26 and sonotrode 22, as illustrated in Fig. IB. The inventors observed that the system may be operated without the reflector. It is postulated that the fabric reflects almost the entire ultrasound waves applied thereto. [0042] In some embodiments, second sonotrode 24 is located at the predetermined distance from the fabric, and delivery system 30 directs fabric 5 between first and second sonotrodes 22 and 24, as illustrated in Figs. 1A and 1C.

[0043] In some embodiments, delivery system 30 may further be configured to deliver fabric 5 into a prewashing step, that may be performed in sonication bath 21, as illustrated in Figs. IB and 1C or into the pre-wetting bath 10, illustrated in Fig. 1 A. In such case, system 100 may further include pre-wetting bath 10 and delivery system 30 may continuously deliver fabric 5 from the pre-wetting bath to the sonication bath 21.

[0044] In some embodiments, pre-wetting bath 10 is in operable communication with the sonication bath 21. In some embodiments, pre- wetting bath 10 is in fluid communication with the sonication bath 21.

[0045] In some embodiments, pre-wetting bath 10 is configured to hold a liquid volume. In some embodiments, the liquid volume is sufficient for sonicating the fabric. In some embodiments, the dimensions of pre-wetting bath 10 (length, width, height dimensions) and/or the volume thereof are sufficient for immersing at least a portion of the fabric within the liquid volume included within the pre-wetting bath 10. In some embodiments, prewetting bath 10 is adopted for immersion of the fabric.

[0046] In some embodiments, the aqueous composition in prewetting bath 21 may be the same or may be different form the aqueous composition in sonication bath 21. In some embodiments, the pre-wetting bath and the sonication bath are the same bath 21, as illustrated in Figs. IB and 1C. The pre-wetting step is required only when bath 21 is filled with a solution that does not include a wetting agent and/or a wicking agent. When bath 21 includes a wetting agent and/or a wicking agent, the prewetting step is redundant.

[0047] Reference is now made to Fig. 2 which is a method of sonicating a fabric accoridng to some embodiments of the invention. The method of Fig. 2 can be performed using system 100. In some embodiments, the method is for embedding a fabric with nanoparticles. In some embodiments, the method is for impregnating nanoparticles into the fabric. In some embodiments, the method is for embedding a baric with nanoparticles. In some embodiment, a fabric treated according to the method of the invention is characterized by (i) uniform distribution of the nanoparticles at the first surface and at the second surface of the fabric, and/or (ii) a loading of the nanoparticles of between 0.001 and 10%, between 0.01 and 1%, between 0.001 and 1%, between 0.1 and 1%, between 0.01 and 2%, between 0.01 and 5%, between 0.001 and 0.1%, between 1 and 5%, between 5 and 10%, including any range between.

[0048] The term “loading” refers to a w/w concentration of the nanoparticle within the fabric. A skilled artisan will appreciate that the loading may vary based on the predestined amount of the nanoparticles sufficient for modifying the surface of the fabric. In some embodiments, surface modification is sufficient for providing one or more predefined properties to the fabrics such as antimicrobial properties, bacteriostatic and/or bactericidal properties, water repellence, hydrophobicity, superhydrophobicity, oleophobicity, flame retardant properties, or any combination thereof.

[0049] In step 210, the method may include pre- wetting the fabric with a first aqueous composition. In some embodiments, pre-wetting is performed for a time sufficient for obtaining a wet fabric. In some embodiments, the moisture content of the wet fabric is at least 10%, at least 20%, at least 50%, between 10 and 300%, between 15 and 300%, between 20 and 300%, between 20 and 30%, between 25 and 300%, between 30 and 50%, between 50 and 100%, between 100 and 150%, between 150 and 200%, between 250 and 300%w/w, including any range between. In some embodiments, the moisture content of the wet fabric is greater than 100% w/w.

[0050] In some embodiments, pre-wetting step substantially reduces the air content within the second aqueous composition, thus improving sonication efficiency and/or embedding depth of the nanoparticles. In some embodiments, pre-wetting is performed for a time sufficient for substantially reducing air content of the fabric (e.g. by at least 50%, at least 70%, at least 90% or more, including any combination thereof), wherein reducing is relative to a dry non-pre wetted fabric. In some embodiments, time sufficient for pre- wetting step is determined by measuring the air content of the prewetting solution (i.e. the first aqueous composition). In some embodiments, time sufficient for pre- wetting step is determined visually, as the time point when no more air bubbles are visible in the prewetting solution.

[0051] In contrast, the term ’’dry fabric” refers to a substrate which has been stored at ambient conditions and has not been wetted by a liquid. In some embodiments, the moisture content of the dry fabric substantially originates from the moisture absorbed during the manufacturing process, and/or during storage. One skilled artisan will appreciate that a moisture content of dry fabrics may vary, depending on the physico-chemical characteristic of the fabric (e.g. chemical composition of the fibers) and/or on the storage conditions. Usually, a moisture content of the dry fabric is less than 10%w/w.

[0052] In some embodiments, the first aqueous composition is water or an aqueous solution. The pre-wetting may be carried out in prewetting bath 10 or in sonication bath 21, by delivering fabric 5 into the bath for a sufficient amount of time, so as to reduce the air content in fabric 5 (e.g. reduce by at least 50%, at least 80%, or more); and/or to prevent or reduce foaming in the sonication bath, and/or to enhance the overall wetting of the fibers in fabric 5 (e.g. to obtain a wet fabric, as disclosed above). It is postulated that pre-wetting substantially improves incorporation efficiency of the sonication and further improves washing resistance (i.e. substantial retention of the initial nanoparticles loading upon at least 30 washing cycles) of the fabric treated by the method of the invention.

[0053] In step 220, the method may include sonicating the wet fabric with a second aqueous composition, wherein the second aqueous composition comprises nanoparticles. In some embodiments, the second aqueous composition may include a dispersion of nanoparticles. In some embodiments, the second aqueous composition may include the nanoparticles dispersion and at least one of: a wetting agent and a wicking agent.

[0054] In some embodiments, the second aqueous composition is a nanoparticles dispersion, wherein a concentration of the nanoparticles within the second aqueous composition is between 0.1 and 5%w/w, between 0.1 and 3%w/w, between 0.5 and 5%w/w, between 0.5 and 3%w/w, between 0.5 and 2%w/w, between 1 and 5%w/w, between 0.5 and 5%w/w, including any range between.

[0055] In some embodiments, step 220 comprises sonicating the wet fabric in contact with the second aqueous composition. In some embodiments, the wet fabric in step 220 is at least partially immersed within the second aqueous composition. The sonication may be conducted using sonication unit 30 disclosed hereinabove. In some embodiments, the step 220 is conducted by continuously delivering fabric 5 between first sonotrode 22 and the second sonotrode 24 and optionally reflector 26, wherein delivering is at the predetermined distance, as disclosed above. In some embodiments, the step 220 comprises immersing at least a portion of the wet fabric into the sonication bath 21 comprising the second aqueous composition, and sonicating the immersed portion of the wet fabric.

[0056] In some embodiments, the step 220 is as described hereinabove, wherein immersion is conducted by continuously delivering wet fabric between first sonotrode 22 and the second sonotrode 24 using the delivery system 30. In some embodiments, the chemical composition of the first aqueous composition is identical to chemical composition of the second aqueous composition. In some embodiments, the step 220 is performed so as to impregnate at least a portion of the wet fabric with the nanoparticles. In some embodiments, the step 220 is performed to embed the nanoparticles into at least a portion of the wet fabric.

[0057] Reference is now made to Fig. 3 which is another method of sonicating a fabric according to some embodiments of the invention. The method of Fig. 3 can be performed using system 100. In the method of Fig. 3 the prewetting step is redundant as the aqueous composition in sonication bath 21 may include in addition to nanoparticles also: a sufficient amount of a wetting agent, and optionally an additive selected from a wicking agent and a binder.

[0058] In some embodiments, the method of Fig. 3 is devoid of pre-wetting step. Accordingly, in step 310 of the method may include continuously delivering the dry fabric onto a sonication bath, for example, using delivery system 30. In some embodiments, delivering of step 310 further comprises continuously delivering the fabric within the sonication bath at a predetermined distance between the fabric and at least one sonotrode.

[0059] In step 320, the method may include sonicating the fabric with an aqueous composition (e.g., a nanoparticle dispersion) comprising a concentration of the nanoparticles within the aqueous composition is between 0.1 and 5%w/w, between 0.1 and 3%w/w, between 0.5 and 5%w/w, between 0.5 and 3%w/w, between 0.5 and 2%w/w, between 1 and 5%w/w, between 0.5 and 5%w/w, including any range between; and further comprising a concentration of the wetting agent of between 0.1 and 20%w/w, . In some embodiments, the aqueous composition further comprises a wicking agent, and/or a binder (e.g. acrylic type binder such as acrylic emulsion, styrene-acrylic copolymers, vinyl acetate acrylic copolymers, carboxylated acrylic polymers; and/or polyurethane based binder, such as: polyester based polyurethane, polyether based polyurethanes, aliphatic and aromatic polyurethanes, carboxylate or sulfonate based polyurethanes) .

[0060] In some embodiments, the wetting agent comprises any one of: non-ionic surfactant (e.g. ethoxylated alcohols, alkylphenol ethoxylates, and ethoxylated fatty acids); anionic surfactant (e.g. alkyl sulfates, alkylbenzenesulfonate, sulfonated fatty acid); cationic surfactant (e.g. quaternary ammonium salts such as alkyltrimethylammonium chloride), amphoteric surfactant (e.g. betaines and sulfobetaine), and silicon based surfactant. [0061] In some embodiments, the sonication is conducted by continuously delivering fabric 5 between first sonotrode 22 and the second sonotrode 24.

Experimental results

[0062] The following are results of sonication experiments conducted using wet sonication system 100.

Preseting

[0063] The influence of the prewetting step of the durability and washability of cotton fabric was tested and compared to cotton fabric sonicated without a prewetting step.

[0064] The fabric was immersed first in a prewetting bath filled with water or zinc oxide dispersion followed by an immersion into the actual sonication bath. The prewetting bath may help remove the air contained in the dry fabric and therefore allows a more efficient embedding of nanoparticles in the fabric during the immersion in the sonication bath as the bubbles created by the cavitation process will burst freely on contact with the fabric and not interfere with air bubbles. This process of dual immersion can be done without exposure to air in between baths or with brief exposure to air. In practice and in an industrial process, the fabric will run at the desired speed into the first tank for achieving the prewetting stage followed immediately by the sonication tank in which sonication power is applied.

[0065] A control fabric that was only sonicated with zinc oxide composition without prewetting retained a significant amount of zinc oxide particles for not more than 20 washings cycles. In contrast, the same fabric treated according to the method of the invention (including pre-wetting) and further sonicated within zinc oxide composition (same as in control) , showed an extended wash resistance and sustained zinc oxide values even after 40 washes. The amount of remaining zinc oxide after 30 washes was an order of magnitude higher after the prewetting treatments, as compared to the control (without pre-wetting). Similar results were achieved when using two sonotrodes positioned at the opposed sides of the fabric.

[0066] The experiments further confirmed the criticality of distance between the fabric and the sonotrode, showing that the nanoparticles impregnation was only effective at the predetermined distance in a range between 0.1 and 1 ultrasound wavelength, preferably in a range between 0.4 - 0.6 times of the ultrasound wavelength emitted by the sonotrode. Using wetting agents and/or wicking agents

[0067] Wetting agents, especially of the type that affect the dynamic surface tension such as Metolat 364 from Munzing can effectively improve wash resistance under sonication conditions even without prewetting. Metolat 364 was used at a concentration of 0.2% in the sonication bath together with 1 % of zinc oxide.

[0068] The inventors successfully implemented numerous wetting agents in a sonication bath (without prewetting) so as to obtain fabrics impregnated with ZnO nanoparticles. Fabrics sonicated in an aqueous composition that includes both 1 wt. % of zinc oxide and 0.2 wt.% Metolat 364 substantially retained zinc oxide impregnated in the fabric after at least 40 washing cycles.

[0069] While certain features of the invention have been illustrated and described herein, many modifications, substitutions, changes, and equivalents may occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.

[0070] Various embodiments have been presented. Each of these embodiments may of course include features from other embodiments presented, and embodiments not specifically described may include various features described herein.