Patent Abstract:
In various aspects, the processes disclosed herein may include the steps of inducing an electric field about a non-conductive substrate, and depositing functionalized nanoparticles upon the non-conductive substrate by contacting a nanoparticle dispersion with the non-conductive substrate, the nanoparticle dispersion comprising functionalized nanoparticles having an electrical charge, the electric field drawing the functionalized nanoparticles to the non-conductive substrate. In various aspects, the related composition of matter disclosed herein comprise functionalized nanoparticles bonded to a surface of a non-conductive fiber, the surface of the non-conductive fiber comprising a sizing adhered to the surface of the non-conductive fiber. This Abstract is presented to meet requirements of 37 C.F.R. §1.72(b) only. This Abstract is not intended to identify key elements of the processes, and related apparatus and compositions of matter disclosed herein or to delineate the scope thereof.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application is a divisional of prior U.S. patent application Ser. No. 14/606,292 filed 27 Jan. 2015 that, in turn, claims priority and benefits of U.S. Provisional Patent Application 61/932,465 filed 28 Jan. 2014 and U.S. Provisional Patent Application 61/941,686 filed 19 Feb. 2014, all of which are hereby incorporated by reference in their entireties herein. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
       [0002]    This invention was made with government support awarded by the National Science Foundation under grant #1234830 and #1254540/ARL#W911NF-07-2-0026/W911NF-06-2-0011 and by DTFH61-13-H-00010 from the Federal Highway Administration. The government has certain rights in the invention. 
     
    
     BACKGROUND OF THE INVENTION 
     Field 
       [0003]    The present disclosure relates to the deposition of nanoparticles on substrates, and, more particularly, to the deposition of nanoparticles on electrically non-conductive substrates including the formation of bonds between the nanoparticles and substrates. 
       Background 
       [0004]    There has been broad scientific and technical interest in producing nanostructured composite material systems that exploit the unique properties of nanoparticles in engineering applications. The selective and intelligent integration of nanoparticles by hybridizing with various substrates enables the ability to form local multi-scale architectures for the tailoring of both mechanical and physical properties such as mechanical strength, electrical conductivity, or thermal conductivity of the nanoparticle-substrate combination. 
         [0005]    For example, the direct hybridization where nanoparticles fully penetrate the fiber bundles of a textile, the textile forming the substrate, may be utilized as conductors for integrating sensors into the textile. 
         [0006]    Advanced fiber-reinforced composites, such as carbon fiber reinforced polymer (CFRP) and glass fiber reinforced polymer (GFRP) composites may offer improved in-plane tensile properties for their equivalent weight in comparison with traditional metallic materials. However, Advanced fiber-reinforced composites may exhibit poor through-thickness strength and toughness properties. Previous efforts to improve the through-thickness properties of Advanced fiber-reinforced composites, for example, have examined the addition of nanoparticles such as carbon nanotubes to a substrate comprising carbon fibers. Carbon nanotubes offer high strength and stiffness on a sub-micron scale and, therefore are potential candidates to be used to modify the interstitial regions between the carbon fibers where the polymer matrix dominates the composite strength and toughness properties. 
         [0007]    Chemical vapor deposition processes have been used for incorporating carbon nanotubes into CFRP composites by growing CNTs directly upon the reinforcing fiber using chemical vapor deposition prior to resin infusion. The chemical vapor deposition process enables carbon nanotubes to be grown at high coverage, leading to high-effective volume fraction of the carbon nanotubes in the matrix. 
         [0008]    Chemical vapor deposition processes may cause a reduction in the strength of the carbon fibers as well as of various non-conductive fibers, and, therefore, compromise the tensile properties. For example, chemical vapor deposition may remove sizing(s) disposed about the surface of the fibers that prevent stress corrosion cracking of the fibers or that confer ultra violet light (UV light) protection to the fibers. Removal of the sizing(s) may accordingly degrade the mechanical and physical properties of the fibers, for example, due to increased stress corrosion cracking or degradation by UV light. While the chemical vapor deposition process may be scalable, the high temperatures that may be employed for chemical vapor deposition, for example, between 600° C. and 1,000° C., makes the chemical vapor deposition process energy intensive. The chemical vapor deposition process may also be less amenable to the control of carbon nanotubes purity and manipulation of surface chemistry and adhesion of the carbon nanotubes to the surface of the substrate. Furthermore, the high temperatures of the chemical vapor deposition process may make this process inapplicable to various electrically non-conductive substrates. 
         [0009]    Dispersion/infusion approaches have been used for incorporating carbon nanotubes into CFRP composites by inclusion of the CNT within the polymer matrix. CNT volume fraction may be limited to be generally less than 1% because processing high carbon nanotubes volumes in the polymer may be difficult due to factors such as viscosity increases, fabric filtering effects, and adequate dispersion. 
         [0010]    Accordingly, there is a need for improved processes as well as related apparatus and compositions of matter that incorporate nanoparticles with various substrates including electrically non-conductive substrates. 
       BRIEF SUMMARY OF THE INVENTION 
       [0011]    These and other needs and disadvantages may be overcome by the processes and related apparatus and compositions of matter disclosed herein. Additional improvements and advantages may be recognized by those of ordinary skill in the art upon study of the present disclosure. 
         [0012]    In various aspects, the processes disclosed herein may include the steps of inducing an electric field about a non-conductive substrate, and depositing functionalized nanoparticles upon the non-conductive substrate by contacting a nanoparticle dispersion with the non-conductive substrate, the nanoparticle dispersion comprising functionalized nanoparticles having an electrical charge, the electric field drawing the functionalized nanoparticles to the non-conductive substrate. 
         [0013]    In various aspects, the related composition of matter disclosed herein comprise functionalized nanoparticles bonded to a surface of a non-conductive fiber, the surface of the non-conductive fiber comprising a sizing adhered to the surface of the non-conductive fiber. 
         [0014]    This summary is presented to provide a basic understanding of some aspects of the processes and related apparatus and compositions of matter disclosed herein as a prelude to the detailed description that follows below. Accordingly, this summary is not intended to identify key elements of the processes and related apparatus and compositions of matter disclosed herein or to delineate the scope thereof. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  illustrates by process flow chart an exemplary electrophoretic deposition (EPD) process for the deposition of functionalized nanoparticles upon non-conductive fibers; 
           [0016]      FIG. 2  illustrates by process flow chart an exemplary process for forming an exemplary nanoparticle dispersion for use in the exemplary EPD process of  FIG. 1 ; 
           [0017]      FIG. 3  illustrates by schematic diagram an exemplary apparatus for implementing at least portions of the exemplary process for forming an exemplary nanoparticle dispersion of  FIG. 2 ; 
           [0018]      FIG. 4A  illustrates by perspective view an exemplary electrophoresis apparatus for performing the exemplary electrophoretic deposition (EPD) process of  FIG. 1 ; 
           [0019]      FIG. 4B  illustrates by side view portions of the exemplary electrophoresis apparatus of  FIG. 4A ; 
           [0020]      FIG. 4C  illustrates by perspective exploded view portions of the exemplary electrophoresis apparatus of  FIG. 4A ; 
           [0021]      FIG. 4D  illustrates by perspective exploded view portions of another exemplary implementation of an electrophoresis apparatus; 
           [0022]      FIG. 4E  illustrates by perspective view yet another exemplary implementation of an electrophoresis apparatus; 
           [0023]      FIG. 4F  illustrates by Cartesian plot an exemplary waveform having a net zero integral as may be generated in the exemplary implementation of an electrophoresis apparatus of  FIG. 4E ; 
           [0024]      FIG. 5A  illustrates by Cartesian plot exemplary results of exemplary Example 2; 
           [0025]      FIG. 5B  illustrates by Cartesian plot more exemplary results of exemplary Example 2; 
           [0026]      FIG. 6A  constitutes an SEM image of glass fiber coated with functionalized MWCNTs fabricated in exemplary Example 2; 
           [0027]      FIG. 6B  constitutes another SEM image of glass fiber coated with functionalized MWCNTs fabricated in exemplary Example 2; 
           [0028]      FIG. 6C  constitutes another SEM image of glass fiber coated with functionalized MWCNTs fabricated in exemplary Example 2; 
           [0029]      FIG. 6D  constitutes yet another SEM image of glass fiber coated with functionalized MWCNTs fabricated in exemplary Example 2; 
           [0030]      FIG. 7A  constitutes an SEM image of cross-sections of glass fibers coated with functionalized MWCNTs and then infused with resin as fabricated in exemplary Example 2; 
           [0031]      FIG. 7B  constitutes another SEM image of cross-sections of glass fibers coated with functionalized MWCNTs and then infused with resin as fabricated in exemplary Example 2; 
           [0032]      FIG. 7C  constitutes another SEM image of cross-sections of glass fibers coated with functionalized MWCNTs and then infused with resin as fabricated in exemplary Example 2; 
           [0033]      FIG. 7D  constitutes another SEM image of cross-sections of glass fibers coated with functionalized MWCNTs and then infused with resin as fabricated in exemplary Example 2; 
           [0034]      FIG. 8A  constitutes SEM images of the surfaces of glass fibers coated with functionalized MWCNTs as fabricated in exemplary Example 2 and showing porosity; 
           [0035]      FIG. 8B  constitutes SEM images of the surfaces of glass fibers coated with functionalized MWCNTs as fabricated in exemplary Example 2 and showing spalling; 
           [0036]      FIG. 9A  constitutes an optical micrograph of MWCNTs deposited upon glass fibers as fabricated in exemplary Example 4; 
           [0037]      FIG. 9B  illustrates schematically an exemplary distribution of MWCNTs deposited upon glass fibers as fabricated in exemplary Example 4; 
           [0038]      FIG. 10A  constitutes an optical micrograph of xGnP deposited upon glass fibers as fabricated in exemplary Example 4; 
           [0039]      FIG. 10B  illustrates schematically an exemplary distribution of xGnP deposited upon glass fibers as fabricated in exemplary Example 4; 
           [0040]      FIG. 11  illustrates by exploded perspective view various exemplary apparatus employed in conducting exemplary screen printing process of  FIG. 12A ; 
           [0041]      FIG. 12A  illustrates by process flow chart an exemplary screen printing process; 
           [0042]      FIG. 12B  illustrates by process flow chart details of an exemplary step of the exemplary screen printing process of  FIG. 12A ; 
           [0043]      FIG. 13  constitutes a photograph showing an exemplary pattern comprising nanoparticles printed onto an electrically non-conductive woven glass fabric; and, 
           [0044]      FIG. 14  illustrates by perspective view an exemplary application of nanoparticle printer ink onto a non-conductive substrate by an inkjet printer. 
       
    
    
       [0045]    The Figures are exemplary only, and the implementations illustrated therein are selected to facilitate explanation. The number, position, relationship, and dimensions of the elements shown in the Figures to form the various implementations described herein, as well as dimensions and dimensional proportions to conform to specific force, weight, strength, flow and similar requirements are explained herein or are understandable to a person of ordinary skill in the art upon study of this disclosure. Where used in the various Figures, the same numerals designate the same or similar elements. Furthermore, when the terms “top,” “bottom,” “right,” “left,” “forward,” “rear,” “first,” “second,” “inside,” “outside,” and similar terms are used, the terms should be understood in reference to the orientation of the implementations shown in the drawings and are utilized to facilitate description thereof. Use herein of relative terms such as generally, about, approximately, essentially, may be indicative of engineering, manufacturing, or scientific tolerances such as ±0.1%, ±1%, ±2.5%, ±5%, or other such tolerances, as would be recognized by those of ordinary skill in the art upon study of this disclosure. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0046]    In various aspects, processes for the deposition of nanoparticles upon electrically non-conductive substrates and related apparatus and compositions of matter are disclosed herein. The processes for the deposition of nanoparticles upon electrically non-conductive substrate include the steps of forming a nanoparticle dispersion comprising functionalized nanoparticles dispersed in solvent with the functionalized nanoparticles having a charge, generating an electric field about the non-conductive substrate, and attracting the functionalized nanoparticles to the substrate using the electric field to deposit the functionalized nanoparticles upon the substrate. 
         [0047]    The non-conductive substrate may be, for example, a non-conductive fiber, fabric formed of non-conductive fiber(s) including micron-sized non-conductive fibers, fabric, cloth, textile, powder including other discretized materials, in various aspects. The non-conductive substrate may be, for example, a non-woven, woven, knitted, or braided textile assembly of the non-conductive fiber(s). Non-conductive substrate, in various aspects, includes non-conductive fibers and non-conductive fibrous-like structures including their various forms: fiber bundles, fibers and bundles formed in 2-D or 3-D arrangements using textile techniques (such as braiding, weaving, knitting, stitching, etc.), non-woven fabric, and fiber-like structures such as open cell foams. Fibers can be continuous or discontinuous or a combination thereof. 
         [0048]    The non-conductive substrate is porous, and a fluid may pass through the non-conductive substrate, in various aspects. The non-conductive substrate, in various aspects, is electrically non-conductive (i.e. an electrical insulator). The non-conductive substrate may be composed of, for example, glass, aromatic polyamide (aramid), or polyethylene terephthalate (polyester), other polymers, or other generally electrically non-conductive materials. 
         [0049]    The solvent may be, for example, water, alcohol, or other suitable solvent. The charge of the functionalized nanoparticle may be either positive or negative. 
         [0050]    Nanoparticle, as used herein, includes, for example, carbon nanotubes, graphene, expanded graphite nanoparticle (xGnP), graphite, carbon black, copper, silver, other metals, and other materials, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. A nanoparticle may behave as a unit with respect to transport and with respect to various physical properties. A nanoparticle may be sized, for example, in the range of from about 1×10 −9  m to about 1×10 −7  m. The nanoparticles are functionalized, in various aspects. 
         [0051]    The functionalized nanoparticles may be formed, for example, by bonding polyethyleneimine (PEI) to oxidized carbon atoms upon surfaces of nanoparticles comprised of carbon, with the oxidized carbon atoms formed by ozonolysis of the nanoparticles. The nanoparticles may be deposited upon the substrate in various patterns, and the patterns may, for example, form electrical circuits for applications such as flexible electronics, solar cells, sensors, strain gauges, or electroluminescent displays. The nanoparticles may be bonded to the substrate by a covalent bond, and the functional group that functionalizes the nanoparticles may be selected to bond to the substrate in order to bond the nanoparticles to the substrate. 
         [0052]    The electrophoretic deposition, screen-printing, and inkjet printing processes disclosed herein may be carried out generally at ambient (room) temperature and may be generally energy efficient, in contrast to vapor deposition processes. In various aspects, the temperature at which the electrophoretic deposition, screen-printing, and inkjet printing processes disclosed herein are carried out may range from about 5° C. to about 50° C. The electrophoretic deposition, screen-printing, or inkjet printing processes disclosed herein may be industrially scalable. 
         [0053]    Because the electrophoretic deposition, screen printing, and inkjet printing processes may be carried out generally at ambient temperatures, the electrophoretic deposition, screen printing, and inkjet printing processes may not remove sizing(s), if any, adhering to the surface of the electrically non-conductive substrate. For example, when the substrate comprises glass fibers, sizing(s) adhering to the surface of the glass fibers may comprise silanes such as γ-glycidoxypropyltrimethoxy silane (GPS) or other silicon based compounds that adhere to glass. Sizing(s) may comprise various surfactants that, for example, control wetting of the substrate, in various implementations. The sizing(s) may increase the tensile strength of non-conductive fibers that comprise the non-conductive substrate, for example, by preventing stress corrosion cracking of the non-conductive fibers. The sizing(s) may protect non-conductive fibers that comprise the non-conductive substrate from degradation by UV light when the non-conductive fibers comprise, for example, aromatic polyamide, cotton, wool, or polyethylene terephthalate. Sizing may include various dyes. Sizing may include other material(s) and may convey various beneficial properties to the various non-conductive substrates, as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. The sizing(s) may be disposed between the surface of non-conductive fibers forming a non-conductive substrate and functionalized nanoparticles deposited upon the non-conductive fiber to retain, for example, the resistance to stress corrosion cracking of the non-conductive fiber imparted to the non-conductive fiber by the sizing agent, in various aspects. 
         [0054]    In various aspects, functionalized nanoparticles in a nanoparticle dispersion are deposited upon the non-conductive substrate. The process of forming the functionalized nanoparticle dispersion may include ozonolysis in alternating combination with high-energy circulative sonication of a solution of nanoparticles to oxidize the nanoparticles and to break up agglomerations of nanoparticles, respectively. Following the steps of ozonolysis in combination with sonication, the process may include the step functionalizing the nanoparticles by attaching functional groups to the surface of the nanoparticles in order to form a functionalized nanoparticle dispersion that is stable. In various aspects, the nanoparticle dispersion is water-based, although other solvents may be used in lieu of water or in combination with water. The addition of functional groups onto the surface of the nanoparticles may be crucial for forming the stable functionalized nanoparticle dispersion by altering the zeta potential of the nanoparticles. The addition of functional groups onto the surface of the nanoparticles may enhance bonding between the nanoparticles and non-conductive fibers to which the nanoparticles are to be bonded, in various aspects. The step of adding functional groups onto the surface of the nanoparticles may include adding a polyelectrolyte to the ozonated and sonicated solution of nanoparticles and then further sonicating the polyelectrolyte—nanoparticle mixture thereby bonding the polyelectrolyte as the functional group to the surface of the nanoparticle. 
         [0055]    In various aspects, a variety of additives may be combined with the functionalized nanoparticle dispersion following formation of the functionalized nanoparticle dispersion, for example, to modify the surface tension in order to enable wetting of a surface of the non-conductive substrate by the functionalized nanoparticle dispersion. Various additives may be combined with the functionalized nanoparticle dispersion to alter the viscosity of the functionalized nanoparticle dispersion. 
         [0056]    Although the Examples included in this disclosure are generally for carbon nanotubes and graphene nanoplatelets, the techniques for integration may be amenable to a wide range of nanostructures. Similarly, although the Examples herein are generally for glass fiber, the electrophoretic deposition, screen printing, and inkjet printing processes have been successfully applied to aromatic polyamide (aramid), polyethylene terephthalate (polyester), cotton, wool, and to various other non-conductive fibers. 
         [0057]      FIG. 1  illustrates an exemplary electrophoretic deposition (EPD) process  100  for the deposition of functionalized nanoparticles upon a non-conductive substrate. EPD process  100  is entered at step  101 . At step  103 , a nanoparticle dispersion, such as nanoparticle dispersion  128 , is formed. The nanoparticle dispersion  128  may be formed by process  200 , which is illustrated in  FIG. 2 . The nanoparticle dispersion  128  comprises functionalized nanoparticles dispersed in a solvent such as water. 
         [0058]    At step  105 , the functionalized nanoparticles are deposited upon a non-conductive substrate. The non-conductive substrate is biased against an electrode, and positioned between the electrode and the opposing electrode. The nanoparticle dispersion is interposed between the electrode and an opposing electrode, and the nanoparticle dispersion is in contact with the non-conductive substrate. A voltage potential is applied between the electrode and the opposing electrode to generate an electrical field about the non-conductive substrate to attract the charged functionalized nanoparticles toward the non-conductive substrate in order to deposit the functionalized nanoparticles upon the non-conductive substrate. The applied field may be constant or time varying. In other implementations, the electrical field may be generated by imparting a static electric charge to the non-conductive substrate, and the nanoparticle dispersion may be introduced to the non-conductive substrate as an aerosol with the functionalized nanoparticles attracted by the static electric charge of the non-conductive substrate. In still other implementations, the nanoparticle dispersion may be dispersed as an aerosol between the electrodes instead of as a liquid. 
         [0059]    At step  111 , the non-conductive substrate is withdrawn from contact with the nanoparticle dispersion and the non-conductive substrate is allowed to dry. 
         [0060]    At step  117 , the non-conductive substrate is infused with a polymer when manufacturing a hybrid composite. Exemplary EPD process  100  terminates at step  121   
         [0061]      FIG. 2  illustrates an exemplary process  200  for forming exemplary nanoparticle dispersion  128 . Step  103  of EPD process  100 , which is illustrated in  FIG. 1 , may be implemented according to process  200 , which is illustrated in  FIG. 2 . Process flows in  FIG. 2  are indicated by arrows and material inputs and material outputs are indicated by the double arrows. 
         [0062]    As illustrated in  FIG. 2 , process  200  is entered at step  203 , and process  200  advances from step  203  to step  210 . At step  210 , nanoparticles  106  are combined with water  104  as solvent to form a nanoparticle-water mixture. Other solvents may be used in other implementations. The water may be ultra-pure, deionized, and so forth. The nanoparticle-water mixture formed at step  210  is then ozonated by the addition of O 3  to the water-nanoparticle mixture at step  215 . Ozonation may create various oxidized sites on the surface of the nanoparticle to which the functionalizing material  108  may then bond to functionalize the nanoparticle. The functional group, in various implementations, includes the oxidized carbon bonded to the functionalizing material  108 . 
         [0063]    The nanoparticle-water mixture is sonicated at step  217  with the ozonation and the sonication occurring alternately as the nanoparticle-water mixture flows between an ozonation reservoir  425  and a sonicator cell  420  (see  FIG. 3 ). As illustrated in  FIG. 2 , step  215  and step  217  are repeated in alternation with one another until the ozonation of step  215  in combination with the sonication of step  217  is sufficient to oxidize surfaces of the nanoparticles and to separate the nanoparticles, respectively. 
         [0064]    After sufficient ozonation and sonication at steps  215 ,  217 , process  200  then advances from steps  215 ,  217  to step  220 . At step  220 , the functionalizing material  108  is added to the nanoparticle-water mixture to functionalize the nanoparticles by bonding to the nanoparticles. The water-nanoparticle mixture with the functionalizing material  108  is then sonicated at step  225  to facilitate functionalizing the nanoparticles by the functionalizing material  108 . Following sonication, the functionalized nanoparticle dispersion  128  is output from step  225 . Process  200  terminates at step  231 . 
         [0065]    The functionalizing material  108  may comprise a polyelectrolyte such as polyethyleneimine (PEI). Various molecular weights of PEI may be used, in various implementations. Some implementations may omit functionalizing material  108  and steps  220 ,  225 . In such implementations, the functional groups are the oxidized sites such as oxidized carbon atoms on the surface of the nanoparticles. Nanoparticles comprised of carbon have a negative charge following ozonation at step  215 . 
       Example 1 
       [0066]    The nanoparticles, in exemplary Example 1, comprise multi-walled carbon nanotubes (MWCNT) (CM-95, Hanwha Nanotech, Korea) functionalized according to process  200  to produce a functionalized nanoparticle dispersion, such as functionalized nanoparticle dispersion  128  (see  FIG. 2 ). Steps  210 ,  215 ,  220 ,  225  of process  200 , in Example 1, were implemented, at least in part, using apparatus  400 , which is illustrated in  FIG. 3 . Exemplary material flows through apparatus  400  are indicated by the arrows in  FIG. 3 . 
         [0067]    As illustrated in  FIG. 3 , oxygen with a flow rate of 500 mL/min flows from reservoir  440  through moisture trap  435 , and, then the oxygen flows from moisture trap  435  to ozone generator  430  (1000BT-12 from Taoture International). Moisture trap  435  removes water (moisture) from the oxygen prior to introduction of the oxygen into ozone generator  430 . Ozone generator  430  produces ozone from the oxygen. 
         [0068]    Ozone from ozone generator  430  flows from ozone generator  430  into ozonation reservoir  425  where the ozone contacts the MWCNT-water mixture in order to ozonate the MWCNT-water mixer per step  215  of process  200 . Ozonation reservoir  425 , in this implementation, is maintained at 5° C. by immersion of ozonation reservoir  425  in temperature control bath  426 . Ozone concentration reached 20 mg/L after 2 h of operation as determined by iodometric titration. 
         [0069]    As illustrated in  FIG. 3 , the MWCNT-water mixture was sonicated in sonicator cell  420  per step  217  of process  200 . Sonication of the MWCNT-water mixture in sonicator cell  420  used a 12.7 mm diameter horn operating at 60 W (Sonicator 3000 from Misonix, USA). Sonicator cell  420 , in this implementation, was maintained at 5° C. by immersion in temperature control bath  421 . Water is circulated between temperature control bath  421  and temperature control bath  426 , in this implementation. 
         [0070]    In this exemplary implementation of steps  215 ,  217  of process  200 , the MWCNT-water mixture was ozonated and sonicated for 16 h. A peristaltic pump  410  (Model MU-D01 from Major Science, USA) recirculated the MWCNT-water mixture between ozonation reservoir  425  and sonicator cell  420  (800B Flocell, Qsonica), as illustrated in  FIG. 2 . Accordingly, steps  215 ,  217  of process  200  were applied to the MWCNT-water mixture as the MWCNT-water mixture recirculated between ozonation reservoir  425  and sonicator cell  420  in a continuous flow process, so that the MWCNT-water mixture was continuously ozonated and sonicated, respectively. 
         [0071]    After 16 hours of sonication, the few agglomerates observed were all submicron in size. Ozonolysis oxidized carbon atoms generally on the surface of the MWCNT, and the oxidized carbons may form, for example, carboxyl groups, hydroxyl groups, or carbonyl groups. Following ozonolysis, the MWCNTs, in this implementation, are functionalized by the oxidized carbons on the surface and have a negative surface charge. 
         [0072]    The functionalizing material  108  introduced into the now sonicated and ozonated MWCT-water mixture at step  220  of process  200  as implemented in Example 1 was polyethylene-imine (PEI) (H(NHCH 2 CH 2 ) 58 NH 2 ; Mw 25,000; Sigma-Aldrich, USA). Other molecular weights of PEI may be used in other implementations. The PEI was at equal concentration to the MWCNT, in this Example. The PEI-MWCNT-water mixture was sonicated for 4h in the Example 1 implementation of step  225  of process  200  to functionalize the MWCNT by bonding the PEI to the MWCNT in order to form the functionalized nanoparticle dispersion, such as functionalized nanoparticle dispersion  128 . The PEI may bond to the oxidized carbons on the surface of the MWCNT, and the PEI may be bonded to the MWCNT by a covalent bond. The pH of the PEI-MWCNT-water was adjusted with glacial-acetic add (Sigma-Aldrich) to a pH around 6 during step  225 . The resultant nanoparticle dispersion was then output from apparatus  400 . 
         [0073]    The functionalization of the MWCNTs enables a surface charge to develop, and the PEI functionalized MWCNTs have a positive surface charge. The surface charge, which may be described in terms of zeta-potential, may be dependent on the solution pH and may repulse adjacent MWCNTs to aid dispersion and mobility under applied electric fields. PEI has a high-natural pH in aqueous solution, but with addition of a mild acid, the amine groups protonate and a +50 mV zeta-potential may be established below a pH of 8, enabling cathodic deposition of the PEI functionalized MWCNTs. The resultant functionalized nanoparticle dispersion of Example 1 has been stable for at least a year. 
         [0074]    In electrophoretic deposition (EPD), an electric field is induced about a non-conductive substrate. Then, the functionalized nanoparticle, which has a surface charge, is accelerated in the electric field toward the non-conductive substrate for deposition on the non-conductive substrate. As illustrated in  FIG. 4A , functionalized nanoparticles  461  may be deposited upon non-conductive substrate  476  that comprises fabric  480  formed of non-conductive fibers  482  by, at least in part, electrophoresis of a functionalized nanoparticle dispersion, such as functionalized nanoparticle dispersion  128 . Non-conductive substrate  476 , fabric  480 , and non-conductive fibers  482  are electrically non-conductive, in this implementation. 
         [0075]    In the exemplary implementation of  FIG. 4A , electrophoresis apparatus  450  comprises source  457  in communication with electrode  454  having negative charge (cathode) and in communication with an opposing electrode  452  having positive charge (anode). Source  457 , in the illustrated implementation, is a constant source that applies a constant voltage potential between opposing electrode  452  and electrode  454 . 
         [0076]    Nanoparticle dispersion  128  including functionalized nanoparticles  461 , as illustrated in  FIG. 4A , is disposed between electrode  454  and opposing electrode  452 . In the implementation of  FIG. 4A , functionalized nanoparticles  461  have a positive surface charge as, for example, the PEI functionalized MWCNTs of Example 1. The functionalized nanoparticles  461  (positive charge), in this implementation, are repelled by the like charged opposing electrode  452  (positive charge), and the functionalized nanoparticles  461  are drawn to the oppositely charged electrode  454  (negative charge) by the electric field induced about non-conductive substrate  476  by electrodes  452 ,  454 . 
         [0077]    Non-conductive substrate  476  is biased against electrode  454  between electrode  454  and opposing electrode  452 , and non-conductive substrate  476  is in contact with nanoparticle dispersion  128 . Non-conductive substrate  476  is illustrated in  FIG. 4A  as partially covering electrode  454  for explanatory purposes. Electrode  454  induces a positive electric field around non-conductive substrate  476  to attract the functionalized nanoparticles  461  into contact with the non-conductive substrate  476  for deposition upon non-conductive substrate  476 . The porous nature of non-conductive substrate  476  may facilitate the induction of the electric field about non-conductive substrate  476  by electrodes  454  by allowing charge to pass through the pores of non-conductive substrate  476 . (Note that juxtaposing a non-porous non-conductive substrate between electrodes  452 ,  454  may form a capacitor.) 
         [0078]    The transport of functionalized nanoparticles, such as functionalized nanoparticles  461 , toward the electrode  454  and non-conductive substrate  476  may depend upon the mobility of the functionalized nanoparticles  461  that, in turn, may depend upon the size of the functionalized nanoparticles and the magnitude of the surface charge of the functionalized nanoparticles. 
         [0079]    The surface charge of the functionalized nanoparticles may be negative in other implementations, for example, MWCNT following ozonolysis. For example, in implementations with negatively charged functionalized nanoparticles, the functionalized nanoparticles are drawn to the positively charged anode  452 , and the non-conductive substrate, such as non-conductive substrate  476 , is disposed about opposing electrode  454  which then induces a positive electric field about non-conductive substrate  476 . 
         [0080]    As illustrated in  FIG. 4B , mask  486  overlays portions of the non-conductive substrate  476  in biased engagement with non-conductive substrate  476  during deposition to shield the portions of non-conductive substrate  476  engaged with mask  486  from deposition of functionalized nanoparticles  461 . The mask  486  physically blocks the deposition of functionalized nanoparticles  461  onto those portions of non-conductive substrate  476  overlain by mask  486 . 
         [0081]    Mask  486  may be variously shaped, for example, as illustrated in  FIG. 4C , to create a patterned deposited morphology of the functionalized nanoparticles  461  upon non-conductive substrate  476 . Mask  486  may define a non-deposited region  488  on non-conductive substrate  476  that conforms to the shape of the mask  486  within which the functionalized nanoparticles  461  are not deposited upon non-conductive substrate  476 . Deposited region  487  on non-conductive substrate  476  is that portion of non-conductive substrate  476  that is not covered by the mask  486  within which the functionalized nanoparticles  461  are deposited on the non-conductive substrate  476 , as illustrated in  FIG. 4C . Deposited region  487 , as illustrated, has pattern  489  that may, for example, define electrically conductive pathway(s) on non-conductive substrate  476 . Mask  486  may be either conductive or non-conductive, in various implementations. If mask  486  is formed of a non-conductive material, mask  486  decreases the electric field proximate those portions of non-conductive substrate  476  overlain by mask  486  during EPD. 
         [0082]    As illustrated in  FIG. 4D , electrode  458  of electrophoresis apparatus  490  is shaped to create a patterned deposited morphology of the functionalized nanoparticles  461  upon non-conductive substrate  467  having pattern  471 . Because intimate contact between electrode  458  and non-conductive substrate  467  may be required for deposition of functionalized nanoparticles  461  upon non-conductive substrate  467 , the functionalized nanoparticles  461  may be deposited in a pattern  463  upon non-conductive substrate  467  by correspondingly patterning electrode  458  that biases against non-conductive substrate  467  during the EPD process. Note that, in this  FIG. 4D  implementation, non-conductive substrate  467  is formed of non-conductive fibers, such as non-conductive fibers  482 . 
         [0083]    As illustrated in  FIG. 4D , functionalized nanoparticles, such as functionalized nanoparticles  461 , are deposited upon non-conductive substrate  467  by EPD in a deposited region  463  having pattern  471  corresponding to the shape of electrode  458 . The deposited region  463  may, for example, define pattern  471  of electrically conductive pathways  473  upon non-conductive substrate  467  with a desired configuration. Non-deposited regions  459  where functionalized nanoparticles are not deposited may be formed on portions of non-conductive substrate  467  not in biased engagement with electrode  458 , as illustrated in  FIG. 4D . 
         [0084]    Various combinations of masks, such as mask  486 , and electrodes, such as electrode  454 ,  458 , may be combined with one another to create various patterns and combinations of patterns, such as patterns  471 ,  489 , of deposited functionalized nanoparticles upon non-conductive substrate, such as non-conductive substrate  476 ,  467 . The patterns of functionalized nanoparticles so formed may be hierarchically structured, in various implementations. The nanoscale conductive network can be utilized, itself, as a sensor where the piezoresistive properties of the network can be exploited to sense deformation, temperature and other external stimuli. The hybridization enables the future integration of adaptive, sensory, active, or energy storage capabilities of nanostructures within non-conductive substrate such as textile materials. Other applications may include EMI shielding and heating of the non-conductive substrate through resistive energy dissipation. 
         [0085]    Process parameters that may affect the EPD process may include concentration of functionalized nanoparticles in the nanoparticle dispersion, surface charge of the functionalized nanoparticles, spacing between the electrodes, applied field strength, and deposition time. While electro-kinetic factors lead to the deposition of functionalized nanoparticles on non-conductive fibers and film formation on the non-conductive fibers, Brownian diffusion randomizes the particle distribution in solution. Brownian diffusion redistributes the functionalized nanoparticles into inter-fiber regions at longer deposition times. 
         [0086]    A constant source, such as source  457 , may cause electrolysis of water and the formation of hydrogen and oxygen bubbles that result in micro-scale porosity and spalling of the deposited functionalized nanoparticles. Furthermore, functionalized nanoparticles may precipitate from solution when a constant source is used due to the high pH gradients that develop near the electrode, such as electrode  454 , and cause solution instability. 
         [0087]    Accordingly, in electrophoresis apparatus  510 , voltage source  507  is configured as a time varying source, as illustrated in  FIG. 4E . In the exemplary implementation of  FIG. 4E , electrophoresis apparatus  510  comprises source  507  in communication with electrodes  501 ,  509 . As illustrated, nanoparticle dispersion  128  with functionalized nanoparticles  161  lies between electrodes  501 ,  509 . 
         [0088]    In the implementation of  FIG. 4E , voltage source  507  is configured to generate a waveform having a net zero integral. For example, the exemplary waveform generated by source  507  is that of a simple triangular asymmetric wave where the integral over a single period is zero as illustrated in  FIG. 4F . Other waveforms having a net zero integral may be used in other implementations. The net zero integral suppresses the electrolysis of water, thereby eliminating the spalling and micro-porosity that may occur with a DC source. Furthermore, the suppression of electrolysis may reduce or eliminate the pH gradient and may enable deeper and more efficient penetration of the functionalized nanoparticles into fiber bundles of fibers, such as fibers  482 . In addition, the alternating mobility of the functionalized nanoparticles may further enhance penetration of the functionalized nanoparticles into fiber bundles. 
         [0089]    At high electric fields the velocity of the functionalized nanoparticle  461  being deposited is a non-linear function of the electric field expressed by: 
         [0000]        V   eph =μ 1   E+μ   2   E   3   (1)
 
         [0000]    where V eph  is the velocity of the functionalized nanoparticle  461 , E is the voltage potential, and μ 1  and μ 2  are the linear electrophoretic mobility and non-linear electrophoretic mobility, respectively. Because of the non-linearity of Eq. 1, the functionalized nanoparticle  461  moves a greater distance during the high amplitude segment of the waveform of  FIG. 4F  than during the low amplitude segment of the waveform of  FIG. 4F . Accordingly, the positively charged functionalized nanoparticle  461  will be drawn to the one of electrodes  501 ,  509  that is negatively charged during the high amplitude segment of the wave form of  FIG. 4F  in preference to the other of electrodes  501 ,  509  that is negatively charged during the low amplitude segment of the waveform of  FIG. 4F . Other waveforms having a net zero or net non-zero integral may be used in other implementations. 
       Example 2 
       [0090]    Functionalized nanoparticles in various nanoparticle dispersions were deposited by EPD process under differing conditions upon a non-conductive fabric formed of E glass fibers (non-conductive) and upon a conductive fabric formed of carbon fibers (conductive) in Example 2 for purposes of comparison. The functionalized nanoparticles were MWCNT functionalized with PEI as in Example 1. 
         [0091]    Sizing, such as GPS, if any, were not removed from the glass fiber during deposition of functionalized nanoparticles upon the glass fiber by the EPD process. The EPD process, in this Example, was carried out generally at ambient (room) temperature. Because EPD is carried out generally at ambient temperature, the EPD process does not remove sizing, if any, from the surface of other non-conductive fibers, in other implementations. 
         [0092]    The glass fiber deposition mass for the nanoparticle dispersion at field strengths between 12.5 and 64 V/cm is shown in the  FIG. 5A . In the initial linear deposition stage, it was possible to estimate the deposition rate as a function of field strength, which is shown in  FIG. 5B . The deposition rate for glass fibers is compared to that measured for carbon fibers in  FIG. 5B . As can be seen from  FIG. 5B , the deposition rate upon glass fibers at the same field strength is about the same as the deposition rate upon carbon fibers where the concentration of the nanoparticle dispersion for carbon fibers was only half the concentration of the nanoparticle dispersion for glass fibers. On the basis of the linear dependence of deposition rate with dispersion concentration, the deposition rate on glass is around half that observed on carbon fibers. The reduced rate may be expected as the film deposition process on glass fiber (non-conductive) would differ when compared to the film deposition process on carbon fiber (conductive). 
         [0093]      FIGS. 6A-6D  shows MWCNTs deposited on the E-glass fiber from the nanoparticle dispersion at 25 V/cm for 15 min. The film appears to be compact with the MWCNTs embedded in the PEI polymer. The outer surface of the fabric ( FIG. 6A, 6B ) shows a uniform film around 2 μm thick. Deeper into the fabric tow ( FIG. 6C, 6D ) the film appears as uniform and between 50 and 200 nm. Process parameters may be optimized to control the thickness. 
         [0094]    The following mechanism of MWCNT deposition upon the fabric is hypothesized. The MWCNTs precipitate out of solution onto the electrode and onto the surface of the fabric that is biased against the electrode. The portions of the fabric onto which the MWCNTs are deposited then become incorporated into the electrode. This initiation of precipitation of the MWCNTs at the electrode and fabric in biased contact with the electrode may explain why intimate contact is required between non-conductive substrates and the electrode. As portions of the fabric become incorporated into the electrode, the precipitation of the MWCNTs occurs at the boundary between the portion of the fabric incorporated into the electrode and remaining portions of the fabric. Accordingly, precipitation of the MWCNTS progresses from the surface of the fabric that is biased against the electrode outwardly into pores in the fabric to form the film upon fibers within the pores. As the MWCNTs build up upon the fibers, the MWCNTs, which are conductive, may bridge between fibers within the pores to extend the electrode into the fabric. The build-up of MWCNTs in the pores continues progressively from the surface of the fabric biased against the electrode outwardly through the fabric until the build-up of MWCNTs reaches the opposite surface of the fabric. When the build-up of MWCNTs reaches the opposite surface of the fabric, the fabric is incorporated into the electrode, and MWCNTs are deposited upon the opposite surface of the electrode by attraction to the opposite surface and precipitation upon the opposite surface. Accordingly, the deposition of MWCNTs upon the opposite surface and throughout the fabric may occur by precipitation, not by sedimentation. 
         [0095]    Continuing the hypothetical discussion of deposition of MWCNTs, the precipitation of the PEI functionalized MWCNTs or other functionalized nanoparticles may occur by de protonation of, for example, the PEI functional group at the electrode. Electrolysis of the water may enhance de protonation and, thus, the precipitation of the MWCNTs. Accordingly, regulation of electrolysis may control the precipitation of the MWCNTs. The porosity of the combination substrate-MWCNTs may be controlled by controlling the precipitation of MWCNTs along with selecting the size of the nanoparticles (MWCNTs). It may be advantageous to use a time varying source with a non-zero integral (bias), in some implementations, to regulate electrolysis in order to control precipitation. This concludes this particular hypothetical discussion. 
         [0096]    It was also noted during the experiments that the MWCNTs became strongly attached to the conductive electrode. Abrasion using sandpaper was required to remove the MWCNTs from the electrode, which was made of stainless steel. 
         [0097]    Polished cross-sections of the polymer-infused glass-fibers with MWCNTs deposited were also examined to determine porosity and MWCNT distribution throughout the laminate, as shown in  FIGS. 7A-7D . The film that builds up on the outer fibers appears to be well infused ( FIG. 7A ) and there are few voids, even when observed at high magnification ( FIG. 7B ), indicating the resin diffuses through the coating and produces a good-quality, low-void laminate. Further into the interior of the fabric, the coating thickness decreases and a thin MWCNT coating is observed around individual fibers together with a network that spans between adjacent fibers ( FIGS. 7C, 7D ). The Figures show examples of microscale porosity ( FIG. 8A ) and spalling ( FIG. 8B ) of the deposited MWCNTs. The microscale porosity and spalling may be the result of the use of a constant voltage source and attendant electrolysis of water. 
         [0098]    Functionalized nanoparticles may be deposited in various patterns onto fabrics formed of non-conductive fibers by a screen-printing process, such exemplary screen-printing process  700  (see  FIG. 12A ), using screen ink, such as screen ink  640  (see Example 3 and  FIG. 11 ). The screen ink may also serve as a sizing for the non-conductive substrate. Sizing on the non-conductive fibers of the non-conductive substrate are not removed by the screen-printing process, in various implementations. Additional processing constraints that may be inherent to the screen-printing may require modification of surface tension and viscosity of the nanoparticle dispersion to obtain an ink with desirable rheological properties. 
         [0099]    As illustrated in  FIG. 12A , screen-printing process  700  is initiated at step  701 . At step  707 , the screen ink is formed. At step  711 , the stencil is made. Then, at step  717 , the screen ink is applied to the non-conductive substrate using the stencil in ways as would be readily recognized by those of ordinary skill in the art upon study of this disclosure. The non-conductive substrate may have a static electric charge to attract the functionalized nanoparticles. Process  700  terminates at step  721 . 
       Example 3 
       [0100]    Screen ink  640 , in this Example, was formed by, first, adding a coalescing agent (PVP K-90, Ashland Inc.) to ultra-pure water to form a mixture. Then, a polymeric ink binder (Polyox WSR N-60k, Dow) was added to the mixture. The coalescing agent ensures an even dispersion of the polymeric ink binder, which promotes adhesion of the deposition to the glass fibers of a glass fiber fabric. Non-conductive substrate  630  to which the screen ink  640  was applied, in this Example, was a fabric formed of unidirectional E-glass fibers that are electrically non-conductive, so that the substrate was electrically non-conductive. The binder is required to increase the screen ink&#39;s surface energy, because the surface energy of the ultrapure water ( 72  dynes/cm 2 ) exceeds the surface energy of the glass fibers ( 46  dynes/cm 2 ) causing poor wetting of the glass fibers. The viscosity of the mixture may then be adjusted with hydroxyethyl cellulose water-soluble polymer (Cellosize QP 52000, Dow) to thicken and impart a thixotropic behavior to the mixture. A thixotropic fluid is a form of pseudo-plasticity where the apparent viscosity of the thixotropic fluid decreases over time or ‘thins out’ during application of a constant shear rate to the thixotropic fluid. Shear thinning may be an essential property for printing clear patterns with consistent thicknesses and substrate penetration. All aforementioned rheological additives—coalescing agent, polymeric ink binder, hydroxyethyl cellulose water-soluble polymer—are added to the mixture at 1 weight % of the ultra-pure water in the order of presentation to form the precursor solution. 
         [0101]    Nanoparticles are then added to the precursor solution to form the screen ink. The nanoparticles comprise chemical vapor deposition grown multi-walled carbon nanotubes (MWCNT) from Hanwha Nanotech (CM-95, &gt;95% graphitic carbon, Korea) and exfoliated graphite nanoplatelets (xGnP). The nanoparticles are processed to reduce the agglomerated nanomaterials to the desired morphology. First, the MWCNT are added to the precursor solution and the precursor solution containing the MWCNT is then processed by calendaring. Calendering untangles the several micron-long MWCNT that is agglomerated into intertwined bundles while maintaining the desirable aspect ratio, thus enabling electrical percolation at lower concentrations. There exists a non-linear relationship between the extent of carbon nanotube processing and electrical resistivity where smaller gap settings in the calendering mill create local maximum and minimum resistivity values indicating a transition from agglomerated particulate versus disentangled carbon nanotube dispersion. 
         [0102]    Second, after calendering the MWCNTs, the as-received powdered xGnP nanomaterial is added to the precursor solution and then processed by a shear mixing approach using a three-roll calendering mill. The larger size of the xGnP in comparison to the MWCNT requires processing in the calendering mill at larger gap settings than the WMCNT to achieve an electrically conductive solution but requires less processing than carbon nanotubes, which require processing at finer gap settings. Shearing of the xGnP turbostatic carbon planes into the idealized few layer graphene increases the effectiveness of its nanocomposites. 
         [0103]    The precursor solution with the added MWCNT and xGnP nanoparticles and following the calendering of both the MWCNT and xGnP nanoparticles constitutes the screen ink  640  (see  FIG. 11 ). The MWCNT and xGnP nanoparticles, for example, provide the necessary electrical conductivity to form sensor networks in the non-conductive substrate for damage sensing or strain sensing. 
       Example 4 
       [0104]    Screen ink  640  formed according to Example 3 including the MWCNT and xGnP nanoparticles dispersed therein was deposited onto unidirectional E-glass substrate  630  in the desired pattern through use of an adapted screen printing process, as per step  717  of process  700 . 
         [0105]    The stencil was made, per step  711  of process  700 , according to process  750  illustrated in  FIG. 12B . Process  750  is initiated at step  751 , and mesh fabric  611  is stretched at step  757 . In this implementation of process  750 , a 120-count mesh fabric  611  was stretched by application of a force of 18 N to 22 N, as illustrated in  FIG. 11 . The mesh fabric  611 , per step  761  of process  750 , was coated with a UV-sensitive emulsion  613  (illustrated in  FIG. 11  as partially covering mesh fabric  611  for explanatory purposes). Then, per step  767  of process  750 , a transparency sheet  617  with a high opacity image  619  was used to shield regions of the mesh fabric  611  to prevent cure of the shielded regions thereby forming uncured regions  625  that conform to the high opacity image  619  (also see  FIG. 11 ). Other regions of the mesh fabric  611  were left exposed to allow curing of the exposed regions thereby forming cured regions  623 , as illustrated in  FIG. 11 . A UV light was applied to the mesh fabric causing curing of the exposed regions to form the cured regions  623  while the shielded regions remained uncured to form uncured regions  625 , per step  771  of process  750 . The uncured regions  625  conform to nanoparticle pathways  635  to be formed in the substrate  630 , as illustrated in  FIG. 11 . 
         [0106]    Following curing by application of the UV light, the mesh fabric  611  was rinsed with water to expose the mesh of the uncured regions  625  and to remove uncured UT  7  sensitive emulsion  613 , as per step  775  of process  750 . The mesh of the mesh fabric  611  was blocked by the cured UV-sensitive emulsion  613  in cured regions  623 . The mesh fabric  611  with uncured regions  625  having exposed mesh and cured regions  623  having a blocked mesh forms stencil  628 . 
         [0107]    In applying the screen ink  640  to substrate  630  as per step  717  of process  700 , the stencil  628  was set above the substrate  630  in the 0° fiber direction. The screen ink  640  is then directed through the mesh of the un-cured regions  625  by hand using a blade at a consistent speed and pressure by in both forward and backwards directions twice to ensure a high-quality print. After screen printing according to process  700 , the substrate  630  was heated at 60° C. for four hours in a vented convention oven to expel the aqueous base of the screen ink leaving the nanoparticle adhered to the substrate  640 . The nanoparticles form pathways  635  upon the substrate  630  in conformance to the uncured regions  625  with exposed mesh of the stencil  628 . The substrate  630  may then be infused with resin. Silver paint may be applied to the pathways at selected locations to provide electrical contact with the pathways. 
         [0108]    Observation of the optical micrographs in  FIG. 9A  and  FIG. 10A  may elucidate the difference in damage sensing versus strain sensing between the MWCNT nanoparticles  661  and the xGnP nanoparticles  663 . As indicated by  FIG. 9A , the MWCNT nanoparticles  661  appear to be dispersed across the fiber lamina and penetrates within the fiber bundles to form an electrically conductive, non-invasive in situ network throughout the substrate  630 . The MWCNT nanoparticles  661  may preferentially form conductive pathways along the fiber direction. 
         [0109]    The xGnP nanoparticles  663 , as indicated in  FIG. 10A , do not penetrate the fiber bundles, in this Example, so that the xGnP nanoparticles  663  create an electrically conductive network adhered atop the substrate  630  with minimal penetration and with reduced sensitivity compared to the carbon nanotube sensor. 
         [0110]    Illustrations of the microstructure are included to aid in the visualization of the deposited MWCNT nanoparticle  661  sensor network and xGnP nanoparticle  663  sensor network in  FIG. 9B  and  FIG. 10B . Lower xGnP nanoparticle sense baseline resistance values may be the result of a higher concentration of conductive nanomaterial being confined to a limited space on top of the substrate  630 . 
         [0111]    Hierarchically structured patterns of nanoparticles may be deposited onto fabrics formed of non-conductive fibers by an ink jet printing process using an ink jet printer with nanoparticle printer ink. While the electrophoretic and screen hybridization approaches may require specific geometries or screens, respectively, to form patterns, inkjet printing may be used to form patterns of nanoparticles on a variety of substrates including non-conductive substrates form of non-conductive fibers. The nanoparticles in the patterns formed by inkjet printing may include carbon nanotube, graphene, or combinations of carbon nanotube and graphene. The patterns may form electrical circuits for applications such as flexible electronics, solar cells, sensors, strain gauges, and electroluminescent displays. 
         [0112]    A nanoparticle dispersion with carbon nanotubes as the nanoparticle may be specifically formulated to have low viscosity. After oxidation of the nanoparticles, the nanoparticles may be functionalized by the attachment of chemical groups to the surface of the nanoparticle to improve the adhesion between the nanoparticle and the fiber surface of the non-conductive fibers forming the fabric upon which the nanoparticles are deposited. After a stable nanoparticle dispersion is obtained, a variety of additives may be added to the nanoparticle dispersion to enable wetting of the fabric surface or to modify the viscosity of the nanoparticle dispersion. The resultant nanoparticle dispersion may form the nanoparticle printer ink. The nanoparticle printer ink may be applied to the fabric, which is the substrate in this implementation, by use of the inkjet printer. 
         [0113]    Use of inkjet printing to apply the nanoparticle printer ink to fabric, which is the non-conductive substrate in this implementation, may enables higher resolution patterning of the patterns of nanoparticles in comparison with either EPD or the screen printing process. Inkjet printing of patterns with nanoparticle printer ink may offer more flexibility in the design of the electrically conductive networks than either EPD or the screen printing processes. In various implementations, inkjet printing of patterns of nanoparticle printer ink may be industrially scalable. 
         [0114]    As illustrated in  FIG. 14 , the nanoparticle printer ink  811  may form an aerosol as the nanoparticle printer ink  811  is dispensed from the inkjet printer  805  onto the non-conductive substrate  820 , and the non-conductive substrate  820  may have a static electric charge to attract the functionalized nanoparticles in the aerosolized nanoparticle printer ink  811  to the non-conductive substrate  820 . Nanoparticle printer ink  811  forms pathway  825  on non-conductive substrate  820 , as illustrated in  FIG. 14 . Aerosol may include a single droplet or single particle in gas including air. 
         [0115]      FIG. 13  illustrates a pattern comprising nanoparticles printed onto an electrically non-conductive woven glass fabric in a rectangular pattern by an inkjet printer. The pattern appears as the darker lines in the photograph. The functionalized nanoparticle dispersion  128  of Example 1 was used at the nanoparticle printer ink in the implementation of  FIG. 13 . Key processing parameters may include the droplet size, solution concentration, and motion of the inkjet head. Different processing conditions result in varying nanotube morphologies on the fabric. Control of the process enables tailoring of the percolating structure to achieve desired electrical properties. 
         [0116]    In various implementations, the processes disclosed herein may include the steps of forming screen ink comprising a nanoparticle dispersion, making a stencil, the stencil allowing the selective passage of the screen ink through the stencil to form pathways in the substrate, and forming pathways of nanoparticles in the fabric by applying the screen ink to the fabric with the stencil interposed between the screen ink and the fabric. 
         [0117]    In various implementations, the processes disclosed herein may include the steps of formulating nanoparticle printer ink comprising a nanoparticle dispersion, and depositing hierarchically structured patterns of functionalized nanoparticles upon a fabric by inkjet printing of the nanoparticle printer ink onto the fabric using an inkjet printer. 
         [0118]    In various implementations, the processes disclosed herein may form related composition of matter, comprising functionalized nanoparticles bonded to a surface of a non-conductive fiber, the surface of the non-conductive fiber comprising a sizing adhered to the surface of the non-conductive fiber. The composition of matter may further comprise an electric field disposed about the non-conductive fiber. In the composition of matter, the functionalized nanoparticles bonded to the surface of the non-conductive fiber forming a uniform coating upon the non-conductive fiber. The functionalized nanoparticles in the various compositions of matter may include nanoparticles functionalized with polyethyleneimine (PEI) bonded to oxidized carbon atoms on surfaces of the nanoparticles, the nanoparticles selected from a group consisting essentially of carbon nanotubes and graphene. The functionalized nanoparticles in the various compositions of matter may include nanoparticles functionalized with oxidized carbon atoms on surfaces of the nanoparticles, the nanoparticles selected from a group consisting essentially of carbon nanotubes and graphene, and the oxidized carbon atoms formed by ozonolysis of the nanoparticles. 
         [0119]    The foregoing discussion along with the Figures discloses and describes various exemplary implementations. These implementations are not meant to limit the scope of coverage, but, instead, to assist in understanding the context of the language used in this specification and in the claims. Upon study of this disclosure and the exemplary implementations herein, one of ordinary skill in the art may readily recognize that various changes, modifications and variations can be made thereto without departing from the spirit and scope of the inventions as defined in the following claims.

Technology Classification (CPC): 2