WO2015107515A1

WO2015107515A1 - Nanometric cushion for enhancing scratch and wear resistance of hard films

Info

Publication number: WO2015107515A1
Application number: PCT/IL2015/050034
Authority: WO
Inventors: Chaim Sukenik; Katya GOTLIB VAINSHTEIN; Olga GIRSHEVITZ; Sidney Cohen
Original assignee: Bar Ilan University; Yeda Research And Development Co. Ltd.
Priority date: 2014-01-15
Filing date: 2015-01-08
Publication date: 2015-07-23

Abstract

A methodology is provided for generating fabricating reduced friction and/or wear resistant surfaces. Compositions comprising a compliant layer and a hard film, e.g., PDMS and titania, respectively, are disclosed. Process of preparing such compositions and articles incorporating such compositions are also disclosed.

Description

NANOMETRIC CUSHION FOR ENHANCING SCRATCH AND WEAR

RESISTANCE OF HARD FILMS

FIELD OF INVENTION

The present invention, in some embodiments thereof, relates to material science and, more particularly, but not exclusively, to surfaces having enhanced scratch and wear resistance and reduced friction, processes of preparing same and uses thereof.

BACKGROUND OF THE INVENTION

Polymers are versatile materials within an extraordinary range of properties. In many tribological applications, they are often preferred relative to metal alternatives [Shalwan, A.; Yousif, B. F. Mater. Des. 2013, 48, 14-24]. However, their relatively low hardness values results in susceptibility to surface damage. Transparent polymers, for example, are widely used in ophthalmology and the automobile industry, but scratches degrade their optical and mechanical properties [Jacobson, S.; Hogmark, S. Wear 2009, 266, 370-378].

There are several ways to improve the scratch resistance of polymers. One is to decrease E/o_y, where E is Young's modulus and a_y the yield stress. Materials with a low E/o_y ratio are less easily scratched [Gauthier, C. et al., Tribology International 2006, 39, 88-98]. Another way is to increase the elastic relaxation in elastic-plastic strain by increasing the strain-hardening coefficient [Bucaille, J. L. et al., Wear 2006, 260, 803- 814]. Polymeric composites also give substantial improvement in the wear and friction behavior [Czichos, H et al., Wear 1995, 190, 155-161].

A third approach, which has the major advantage of not changing the bulk polymer properties, is to use inorganic coatings [Yaghoubi, H. et al., Surface & Coatings Technology 2010, 204, 1562-1568]. One such attempt to reduce sensitivity to scratching involves depositing an oxide coating on the polymer surface [De Sanctis, O. et al., A. Journal of Non-Crystalline Solids 1990, 121, 338-343]. This solution is challenging due to issues of adhesion between layers and because of the mismatch in elastic strain between the coating and the substrate. A second approach used polysiloxane and acrylic coatings. They have similar elastic strain as the substrate and do provide some scratch protection due to their hardness [Gauthier, C. et al., Tribology International 2006, 39, 88-98].

Lackner et al., report on the effect of hard-on-soft coatings wherein the soft component is only marginally softer and more compliant than the stiffer and harder film [Lackner, J .M.; Major, L.; Kot, M. Bull. Pol. Acad. Sci.: Tech. Sci. 2011, 59, 343-355]. The softer underlying substrate is proposed to promote sliding and energy dissipation during deformation of the hard film.

In their classic model of friction, Bowden and Tabor [Bowden, F. P.; Tabor, D. Proceedings of the Royal Society of London. Series A Mathematical and Physical Sciences 1939, 169, 391-413] divide the friction into two terms, a plowing term and an adhesion term. The latter is associated with friction arising from the energy required to break the adhesive bonds, and the former from the displacement of plastically-deformed material when a harder surface pushes into and "plows" through the softer one. Plowing leads to release of wear particles due to abrasion of engineering surfaces, which themselves contribute significantly to friction [Komvopoulos, K. et al., J. Tribol. 1987, 109, 223-231].

The adhesion term arises from growth of junctions forming between asperities on the opposing surfaces, which is influenced by local stress. For hard surfaces, where asperities can reach high stress before breaking or plastically deforming, both of these terms may come into play. Simplistically, one may expect that by providing a cushioning affect, to reduce local stress, both junction growth and plowing could be reduced. Hard on soft/flexible structures also result in a larger threshold for plasticity [Tsui, T. Y.et al., Mater. Res. Soc. Symp. Proc. 1995, 383, 447-452].

Friction has both theoretical and practical interest in materials science in general, and polymer science in particular, with applications ranging from the tire industry [Heinrich, G.; Klueppel, M. Wear 2008, 265, 1052-1060], to medical catheters [Brostow, W.; et al., J. Mater. Educ. 2003, 25, 119-132]. Many techniques have been applied to study scratch resistance and friction [Rudermann, Y. et al., Tribol. Int. 2011, 44, 585-591, Sander, T.; et al., S. Surf. Coat. Technol. 2011, 206, 1873-1878]. Atomic force microscopy (AFM) allows extending such studies to the nanoscale while providing high-resolution imaging of the damage caused by wear or scratching [Martinez-Martinez, D. et al., Surf. Sci. 2009, 603, 973- 979]. The quantitative mechanical measurements require calibration both of the normal and lateral forces. For scratch resistance, only the normal force calibration is necessary. According to the ASTM Standard G171 (03) - Standard Test Method for Scratch Hardness of Materials Using a Diamond Stylus

[http://www.astm.Org/DATABASE.CART/HISTORICAL/G 171 -0.3htm. ] , scratch hardness varies inversely as scratch width at a given load.

U.S. Patent 8,066,676 discloses a guidewire lumen for a catheter which includes a tubular member, with at least a portion of the tubular member being formed of a compound comprising a polymer and particles or fibers, and, the particles or fibers can reduce a friction coefficient of the portion of the tubular member.

U.S. Patent 8,389, 129 discloses an article system having low-friction surface coatings, by depositing individual particles of a composite of metal powder of molybdenum and molybdenum disulfide sub-particles that are fused together.

SUMMARY OF THE INVENTION

In a search for novel methodologies for fabricating wear resistant surfaces, the present inventors have surprisingly uncovered a process for generating surfaces which exhibit exceptional properties, particularly, but not exclusively, having desired wear resistance and low friction.

According to one aspect, the present invention provides a process for manufacturing an article having a reduced friction and/or wear resistant surface, the process comprising the sequential steps of:

a) coating at least a portion of a substrate of an article with a compliant layer, the compliant layer having a thickness that ranges of at least 100 nm; and b) depositing on at least a portion of a surface of the compliant layer a uniform hard film, the uniform hard film comprising at least one material selected from the group consisting of: metal, metal oxide, a ceramic composition, hard polymers, diamond, and diamond-like materials, thereby manufacturing an article having a reduced friction and/or wear resistant surface.

In some embodiments, the uniform hard film is characterized by a thickness that ranges from 5 nm to 300 nm. In some embodiments, the uniform hard film is characterized by less than 30 % variation in thickness.

In some embodiments, the compliant layer is an elastomeric polymer selected from the group consisting of: polydimethylsiloxane (PDMS), polybutadiene, kapton, silicone rubber, and any copolymer thereof. In some embodiments, the elastomeric polymer is PDMS.

In some embodiments, the substrate is one or more materials selected from the group consisting of: polyethylene, silicon, kapton, PDMS and polycarbonate (PC), wherein the substrate is other than the compliant layer.

According to some embodiments, the process further comprises prior to step (b) a step of activating a surface of the elastomeric polymer to oxidize at least portion thereof. In some embodiments, activating is performed by air plasma for a time period that ranges from about 1 min to about 30 min.

According to some embodiments, step (b) is performed by depositing a solution of a precursor of the hard material on the elastomeric polymer for a period that ranges from 30 min to about 5 hours. In some embodiments, the solution is a solution of a precursor of titania. In some embodiments, the solution is a solution of a precursor of Sn0₂.

According to some embodiments, the process comprises a step of aging of the solution from which the surface film is deposited, the aging being performed for a time period that ranges from 2 hours to about 20 hours, or 3 hours to 18 hours prior to step (b).

According to another aspect, there is provided a composition comprising a compliant layer and a uniform hard film, said hard film is deposited on at least a portion of a surface of the compliant layer, the compliant layer being characterized by a thickness of at least 100 nm, and is characterized by Young's modulus of less than about 500 MPa, the hard film is characterized by a thickness that ranges from about 5 nm to about 300 nm, and comprises at least one material selected from the group consisting of: metal, metal oxide, a ceramic composition, hard polymers, diamond, and diamond-like materials. According to some embodiments, the film comprises Ti0₂. According to some embodiments, the film comprises Sn0₂. According to some embodiments, the compliant layer is or comprises an elastomeric polymer being one or more polymers selected from the group consisting of: polydimethylsiloxane (PDMS), polybutadiene, silicone rubber, silicone composite, kapton, polycarbonate, and any copolymer thereof. In some embodiments, the elastomeric polymer is PDMS. In some embodiments, the PDMS is at least partially hydroxylated. In some embodiments, the film is characterized by less than 30% variation in thickness.

According to another aspect, there is provided an article comprising a substrate and a dual layer deposited thereupon, the dual layer comprises a compliant layer and a uniform hard film, wherein:

(a) the compliant layer is deposited on at least a portion of a surface of said substrate, is characterized by a thickness of at least 100 nm, and is characterized by Young's modulus that is less than about 500 MPa, and

(b) the film is deposited on at least a portion of a surface of said compliant layer, the film comprising at least one material selected from the group consisting of: metal, metal oxide, a ceramic composition, hard polymers, diamond, and diamond-like materials, and wherein said film is characterized by a thickness that ranges from about 5 nm to about 300 nm.

According to some embodiments, the film comprises Ti0₂. In some embodiments, the film comprises Sn0₂. In some embodiments, the compliant layer is an elastomeric polymer being one or more polymers selected from the group consisting of: polydimethylsiloxane (PDMS), polybutadiene, silicone rubber, and any copolymer thereof. In some embodiments, the elastomeric polymer is PDMS. In some embodiments, the PDMS is at least partially hydroxylated. According to some embodiments, the substrate is one or more materials selected from the group consisting of: polyethylene, silicon, kapton, PDMS and polycarbonate (PC). In one embodiment, the substrate is other than the compliant layer.

According to some embodiments, the compliant layer of the composition and/or the article of the invention is characterized as having Young's modulus of less than 500 MPa or from 10 MPa to 50 MPa.

According to additional embodiments, the composition and/or the article are identified as having reduced friction capabilities. According to some embodiments, the composition and/or the article are characterized by a reduced friction coefficient relative to a solid body, the reduced friction coefficient being at least 30% lower than a friction coefficient of a control material relative to said solid body.

According to some embodiments, the composition and/or the article are characterized by AFM with diamond-coated AFM tip of radius of approximately 150 nm, as capable to withstand scratch by loads of up to about 20 μΝ.

According to some embodiments, the composition and/or the article are characterized by low optical absorption and high transparency in the visible light range.

According to some embodiments, the composition and/or the article are identified as having wear resistance capabilities. According to some embodiments, the composition and/or the article are characterized by reduced wear volume of at least 30 % lower than a wear volume of a control material.

According to some embodiments of the invention, the article is selected from the group consisting of: an electronic device, an optical device, a medical device and a mechanical device. In some embodiments, the electronic device is selected from the group consisting of: hard disk, an electronic circuit component, LED, touch screen and a large area display array. In some embodiments, the optical device is selected from the group consisting of lens, eye glasses, and microscope. In some embodiments, the medical device is an orthopedic implant. In some embodiments, the mechanical device is selected from the group consisting of cylinder liner, cylinders, gear, switch, including devices fabricated by MEMS or NEMS techniques or by 3-D printing. BRIEF DESCRIPTION OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description together with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIG. 1 presents schematic illustration of an exemplary scratch-resistance system according to some embodiments of the present invention.

FIGs. 2A-C presents SEM images of titania coating on: Si (FIG. 2A; bar is 2 μιη), kapton (FIG. 2B; bar is 1 μιη), and on PDMS (FIG. 2C; bar isl μιη), AFM based roughness factor (denoted as Rq), and RBS based thickness.

FIGs. 3A-B present SEM images of titania coating on PC (FIG. 3A), and on PC coated with PDMS (FIG. 3B).

FIGs. 4A-B present SEM images of Sn0₂ thin film on PC (FIG. 4A), and on PC coated with PDMS (FIG. 4B)

FIG. 5 presents AFM images of titania on: Si (panel I and II), kapton (panel III and IV), and PDMS (panel V and VI) before (panels I, III, and V), and after (panels II, IV, and VI) scratching, with the loads for the 3 scratch lines being: a) 15 μΝ, b) 20 μΝ, c) 25 μΝ.

FIG. 6 presents bar graphs showing wear volumes (in μπι ) resulting from different loads (10 μΝ, 15 μΝ, 20 μΝ, and 25μΝ) for the titania coatings on Si, and on kapton

FIGs. 7A-C present AFM images showing the scratch profile of: uncoated PC (FIG. 7A), 40 nm titania coating on PC (FIG. 7B) and 40 nm titania film deposited on activated PDMS underlayer on PC( FIG. 7C). FIGs. 8A-B present AFM image of PC coated with Ti0₂ after scratching (FIG. 8A) and graphs showing the cross-sections of the scratches at three different velocities and constant load of ΙΟμΝ (FIG. 8B), demonstrating the dependence of scratch resistance on sliding speed.

FIG. 9 presents AFM images showing results of scratch tests of Sn0₂ thin film on: PC (FIG. 9A), and on PC coated with PDMS (FIG. 9B). Arrows indicate relative load forces.

FIG. 10 presents graphs showing applied load vs friction force curves for four dual layers indicated therein, and μ for each curve evaluated by Lateral Force Microscopy.

FIGs.llA-B present curve graphs of UV-Vis spectra, transmission (FIG. 11A), and absorption (FIG. 11B), for polycarbonate (PC) with and without coating of titania, showing no evident absorption in the visible region (FIG. 11 A).

DETAILED DESCRIPTION OF THE INVENTION

The present invention, in some embodiments thereof, relates to material science and, more particularly, but not exclusively, to surfaces having enhanced scratch and wear resistance and released friction, processes of preparing same and uses thereof.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details set forth in the following description or exemplified by the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

As discussed herein above, currently known methodologies of preparing polymeric surfaces characterized by scratch protection is a difficult task, often requiring specialized equipment and coating conditions to produce robust coatings that are suitable for a wide variety substrate sizes and shapes.

While conceiving the present invention, the present inventors have considered employing a production route of two-layer coating to alter the stiffness property of a substrate and to enhance its scratch and wear resistance, The present inventors have devised and successfully prepared and practiced novel structures, which are based on the use of a compliant, flexible underlayer to control the scratch resistance of hard surfaces such as, without being limited thereto, metal oxides, for example, titania. The present inventors have demonstrated that such structures exhibit an improved degree of scratch resistance.

As demonstrated in the Examples section that follows, oxide overlayer, e.g., titania on a compliant, flexible underlayer on variable substrates (e.g., kapton, polycarbonate, and PDMS etc.) resulted in improved scratch resistance of the oxide surfaces. As exemplified in Figure 5, the deposited dual-layer composition exhibits highly improved scratch resistance.

As further demonstrated in the Examples section that follows, measurements have showed a substantial decrease in the friction coefficient, compared to non-treated substrates. By "non-treated substrates" it is meant to refer to uncoated substrates or substrates that are directly coated with the hard film without the compliant underlayer thereon.

As further demonstrated in the Examples section that follows, when PDMS is applied as an intermediate layer between a harder substrate and titania, marked improvement in the scratch and wear resistance is achieved.

As used herein and in the art, the expressions "scratch resistance", "anti- scratch", "abrasion resistance", and any grammatical derivative thereof, which are used hereinthroughout interchangeably, refer to a physical property that promotes resistance to scratching, and is associated with surface hardness. The scratch resistance property is reflected in the ability of a material to resist displacement upon exposure to relative motion against hard particles or protuberances. Displacement can be observed visually or by methods known in the art, including, without limitation, AFM, as described herein throughout, as a removal of the coating material thereby exposing the underlying surface.

The term "wear" refers to diminishment or decay through use. As known in the art, wear is erosion or sideways displacement of material from its "derivative" and original position on a solid surface performed by the action of another surface. Wear is related to interactions between surfaces and more specifically the removal and deformation of material on a surface as a result of mechanical action of the opposite surface. Wear can also be defined as a process where interaction between two surfaces or bounding faces of solids within the working environment results in dimensional loss of one solid, with or without any actual decoupling and loss of material. Aspects of the working environment which affect wear include loads and features such as unidirectional sliding, reciprocating, rolling, and impact loads, speed, temperature, but also different types of counter-bodies such as solid, liquid or gas and type of contact ranging between single phase or multiphase, in which the last multiphase may combine liquid with solid particles and gas bubbles.

The term "scratch" or any grammatical derivative thereof, refers to a physical deformation by the mechanical or chemical abrasion generated.

Wear resistance is a property correlated to scratch resistance and can be determined through a variety of tests known in the art.

Compositions:

In some embodiments, for any of the aspects described herein, there is provided a composition, the composition comprising one or more compliant layers and one or more hard films, the compliant layers being characterized by a thickness of at least 100 nm. In accordance with the present invention, the hard film remains adherent to the compliant layer even under stress.

In some embodiments, the film is deposited on at least portion of a surface of the compliant layer. In some embodiments, the film comprises, without limitation, at least one material selected from the group consisting of: metal, metal oxide, mica, a ceramic composition, and hard carbon-based materials.

As described hereinthroughout, in exemplary embodiments, the metal oxides are selected from, without being limited thereto, Ti0₂, and Sn0₂. By "hard carbon-based materials" it is meant to refer to materials having a network of carbon, with, or without hydrogen atoms, such as, without limitation, diamond and diamond-like materials.

In some embodiments of the invention relating to any one of the aforementioned compositions, or articles as described herein below, the film is characterized by a thickness that ranges from about 10 nm to about 300 nm. In additional embodiments of the invention relating to any one of the aforementioned compositions, or articles as described herein below, the film is characterized by a thickness that ranges from about 30 nm to about 300 nm. In some embodiments, the thickness of the film is from about 30 nm to about 250 nm. In some embodiments, the thickness of the film is e.g., about 10 nm, about 20 nm, , about 30 nm, about 40 nm, about 50 nm, about 60 nm, about 70 nm, about 80 nm, about 90 nm, about 100 nm, about 110 nm, about 120 nm, about 130 nm, about 140 nm, about 150 nm, about 160 nm, about 170 nm, about 180 nm, about 190 nm, about 200 nm, about 210 nm, about 220 nm, about 230 nm, about 240 nm, about 250 nm, about 260 nm, about 270 nm, about 280 nm, about 290 nm, about 300 nm, including any value between.

In some embodiments, the thickness of the film, is e.g., at least 30 nm, at least 40 nm, at least 50 nm, at least 60 nm, at least 70 nm, at least 80 nm, at least 90 nm, at least 100 nm, at least 110 nm, at least 120 nm, at least 130 nm, at least 140 nm, at least 150 nm, at least 160 nm, at least 170 nm, at least 180 nm, at least 190 nm, at least 200 nm, at least 210 nm, at least 220 nm, at least 230 nm, at least 240 nm, at least 250 nm, at least 260 nm, at least 270 nm, at least 280 nm, at least 290 nm, at least 300 nm, including any value therebetween.

In exemplary embodiments, the film comprises Ti0₂, for which the thickness, is e.g., at least 30 nm, at least 40 nm, at least 50 nm, at least 60 nm, at least 70 nm, at least 80 nm, at least 80 nm, at least 90 nm, at least 100 nm, at least 110 nm, at least 120 nm, at least 130 nm, at least 140 nm, at least 150 nm, at least 160 nm, at least 170 nm, at least 180 nm, at least 190 nm, at least 200 nm, at least 210 nm, at least 220 nm, at least 230 nm, at least 240 nm, at least 250 nm, at least 260 nm, at least 270 nm, at least 280 nm, at least 290 nm, at least 300 nm, including any value therebetween.

As used herein and in the art, "ceramic" refers to a hard, often crystalline, substantially heat and corrosion resistant material which may be made by firing a non- metallic material, sometimes with a metallic material. A number of oxide, nitride, and carbide materials considered to be ceramic are well known in the art, including without limitation, aluminum oxides, silicon oxides, boron nitrides, silicon nitrides, and silicon carbides, tungsten carbides, etc.

Herein, in the context of a surface, the expression "deposited (or applied) on at least a portion of a surface thereof or "deposited (or applied) there upon", is also referred to herein, for simplicity, as a coated substrate, a coated surface, a coated sample, a substrate or surface having a film (or a layer) deposited thereupon, and various combinations of the above expressions, and all of these expressions are referred to herein interchangeably.

As used herein, the terms "layer" and "film" are intended to mean a uniform thickness of a material or formulation over a surface, partially or substantially or completely covering the surface, and may also referred to as "coating" "coating material", "coating film", or "coating layer". It should also be pointed out that the terms "layer" and "film" must be understood in the broad sense of the terms, that is to say, the layer/film may be continuous or discontinuous. For example, the layer (or the film) may comprise a single layer as well as multiple layers of the same functional material or the same material. Herein, by "the same functional material" it is meant to include multilayer of different hard materials. Exemplary multilayers of different hard materials include, but are not limited to, anti-reflective (AR) stack which are used in e.g., ophthalmic lenses.

By "multilayer" it is meant e.g., at least 2 layers, at least 3 layers, at least 4 layers, at least 5 layers, at least 6 layers, at least 7 layers, at least 8 layers, at least 9 layers, or at least 10 layers. As used herein "uniform thickness" is intended to mean a thickness that varies within a range of e.g., less than 30%, less than 20%, e.g., less than 10%, e.g., less than 5%, e.g., less than 1%. Similarly, a "soft layer", i.e. "compliant layer" may include multiple layers of different materials or multiple layers of the same material, or a single layer of a material.

The terms "layer" and "film" have essentially the same meaning, and herein, for clarity, and unless stated otherwise, the term "layer", (or "underlayer"' which is used hereinthroughout interchangeably) is used in the context of soft coating, and the term "film" (or "overlayer", which is used hereinthroughout interchangeably) is used in the context of hard coating. Hereinthroughout, the term "dual layer", unless stated otherwise, refers to the composition as disclosed herein, i.e. a hard film being uniformly adhered on the soft layer.

By "soft layer" or "soft coating", or "compliant layer" it is meant to refer to a layer characterized as having a soft property, as defined hereinbelow.

Herein, the terms "hardness" or "stiffness" or any grammatical derivative thereof, which are used herein interchangeably, refer to the rigidity of an object, i.e., the extent to which it resists deformation in response to an applied force. The term "flexibility" refers to the complementary concept, that is, the more flexible an object is, the less stiff it is.

Scratch resistance is therefore the measure of the sample resistance to fracture or permanent plastic deformation due to friction from a sharp object. When testing coatings, scratch resistance refers to the force necessary to cut through the film to the substrate. In another variation the hardness of a layer is determined by the resistance of a sample to material deformation due to a constant compression load from a sharp object.

As described herein above, the term "wear" refers to mechanical damage which is characterized by diminishment, decay, or destruction through use. In this respects, parameters that may be improved in order to obtain more sustainable restorations are gathered under the term "wear resistance" and include, but not limited to, abrasion resistance, scratch resistance, resistance to failure, flexural strength, surface hardness, and volumetric integrity of the material during compression.

The scratch and/or wear resistance of a material may be characterized by several methods known in the art. Herein, the terms "soft" and "compliant", or any grammatical derivative thereof, which are used herein interchangeably, are intended to refer to a property of resistance of a material to deformation under load and can be described in term of elasticity, e.g., Young's modulus, or in any sense in which it is normally used in the art. As used herein "compliant layer" or "soft layer" is characterized by a lower hardness than the coating thereupon. For example, and without limitation, it can be understood to mean a material having an elasticity modulus of less than 500 MPa.

In some embodiments of the present invention, the soft layer and the hard film are essentially separate layers. As used herein "separate layers" refers to two separate dimensional sections while maintaining their being integrally adhered to each other.

In the context of the present application, soft layers may include, but are not limited to, elastomeric polymers, and silicone composite (e.g., silicone-rubber or combination thereof). The soft layer may be natural, isolated and/or synthetically prepared.

As used herein and in the art, "elastomeric polymer", or "elastomer", refers to any polymer or combination of polymers consistent with the ASTM D1566 definition of "a material that is capable of recovering from large deformations."

Relevant elastomeric polymers in the context of the present disclosure include, but not limited to, polysiloxane e.g., polydimethylsiloxane (PDMS), polybutadiene, silicone rubber, kapton, polycarbonate polyurethane, epoxy, polyacrylate, polyethylene and any copolymer and/or derivative thereof. The term "copolymer" as used herein throughout means a polymer of two or more different monomers.

In some embodiments, the compliant (or soft) layer is characterized by Young's modulus having a value that is below 500 MPa. In some embodiments, the compliant layer is characterized by Young's modulus having a value that is below 400 MPa. In some embodiments, the compliant layer is characterized by Young's modulus having a value that is below 300 MPa. In some embodiments, the compliant layer is characterized by Young's modulus having a value that is below 200 MPa. In some embodiments, the compliant layer is characterized by Young's modulus having a value that is below 100 MPa. In some embodiments, the compliant layer is characterized by Young's modulus having a value that is below 10 MPa. In some embodiments, the compliant layer is characterized by Young's modulus having a value that ranges from about 1 MPa to about 500 MPa. In some embodiments, the Young's modulus is e.g., about 1 MPa, about 2 MPa, about 10 MPa, about 20 MPa, about 30 MPa, about 40 MPa, about 50 MPa, about 60 MPa, about 70 MPa, about 80 MPa, about 90 MPa, about 100 MPa, about 110 MPa, about 120 MPa, about 130 MPa, about 140 MPa, about 150 MPa, about 160 MPa, about 170 MPa, about 180 MPa, about 190 MPa, about 200 MPa, about 210 MPa, about 220 MPa, about 230 MPa, about 240 MPa, about 250 MPa, about 260 MPa, about 270 MPa, about 280 MPa, about 290 MPa, about 300 MPa, about 310 MPa, about 320 MPa, about 330 MPa, about 340 MPa, about 350 MPa, about 360 MPa, about 370 MPa, about 380 MPa, about 390 MPa, 400 MPa, about 410 MPa, about 420 MPa, about 430 MPa, about 440 MPa, about 450 MPa, about 460 MPa, about 470 MPa, about 480 MPa, about 490 MPa, about 500 MPa, including any value therebetween.

In some embodiments the compliant layer is characterized by higher compliance than the hard film. By "higher compliance" it is meant that the soft layer is characterized by Young's Modulus value of e.g., at least 0.5 fold, 1 fold, 2 folds, 3 folds, 4 folds, 5 folds, 6 folds, 7 folds, 8 folds, 9 folds, 10 fold, 11 folds, 12 folds, 13 folds, 14 folds, 15 folds, 16 folds, 17 folds, 18 folds, 19 folds, 20 folds, including any value therebetween, lower than the Young's Modulus value of the hard film.

As used hereinthroughout, the term "fold" means order of magnitude, and generally refers to a factor of ten. For example, a one digit number is one order of magnitude below a two digit number, two orders of magnitude below a three digit number, and so on.

As used herein and in the art, the term "Young's Modulus" refers to a quantification of the stiffness of a given material. Young's modulus, E, can be calculated by dividing the tensile stress by the tensile strain.

In exemplary embodiments, the elastomeric polymer is PDMS. In some embodiments the PDMS is at least partially activated. By "activated" it is that meant that at least a portion of e.g., about 1%, about 10%, about 30%, about 40%, about 40%, about 50%, about 60%, about 70%, about 80%, about 90%, and even 100%, including any value therebetween, of the PDMS is hydroxylated (i.e. forming a Si-OH bond) or converted into some oxidized silicon derivative, by any method known in the art, for example by plasma etching.

Typically, without being bound by any particular theory or mechanism, the soft layer should have sufficient thickness so as to mask the stiffness of a substrate on which the soft layer is coated thereupon.

In some embodiments, the soft layer is characterized by a thickness of at least e.g., 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, 650 nm, 660 nm, 670 nm, 680 nm, 690 nm, 700 nm, including any value there between. In exemplary embodiments, the soft layer is characterized by a thickness of about 700 nm.

Accordingly, in some embodiments, the thickness ratio of compliant (soft) layer: film is e.g., at least about e.g., 10: 1, 5: 1, 3:2, 1: 1, 1 :2, 1:3, including any value there between.

In some embodiment, the film (also referred herein to as "hard coating" or "stiff coating") is deposited on at least portion of a surface of the soft layer.

By "at least portion of a surface" as used herein throughout, it is meant e.g., at least 1 percent, at least 20 percent, at least 30 percent, at least 40 percent, at least 50 percent, at least 60 percent, at least 70 percent, at least 80 percent, at least 90 percent, and optionally all of the surface is coated, as feasible, including any value there between.

In some embodiments, the film may comprise, without limitation, one or more materials selected from the group consisting of: metal, metal oxide, a ceramic composition, metal nitride (e.g., as titanium nitride), carbide (e.g., tungsten carbide), diamond, diamond-like carbon, and hard polymers. The choice of a particular film may be tailored to suit various applications or devices as described herein below under "Articles".

In the context of the present invention, hard polymers are neither soft nor tacky at temperatures near 20 °C. Hard-polymers may also be copolymers that exhibit the desired physical characteristics described herein throughout.

Alternatively, or additionally, hard-polymer is characterized by high density (e.g., high density polyethylene; HDPE) and/or high molecular weight (e.g., ultra high molecular weight polyethylene; UHMWPE).

Mixtures of one or more homopolymers with one or more copolymers may also be used in embodiments of the present invention.

In some embodiments, the hard film is characterized by a Young's modulus that is at least, e.g., 10%, 20%, 30%, 40%, 50%, 100%, 150%, 200%, 300%, higher that the Young's modulus of the soft layer.

In some embodiments, the film may comprise, without limitation, one or more metal oxides, including, without being limited thereto, titania (Ti0₂), alumina (AI₂O₃), zirconia (Zr0₂), zinc oxide (ZnO), tin oxide (Sn0₂), molybdenum oxide (Mo0₂ or M0O₃) or any combination thereof.

In exemplary embodiments, the film comprises titania (also referred to herein as titanium dioxide (Ti0₂)). As used herein, the titanium dioxide may be in a form of rutile, anatase, brookite, and any combination thereof.

In additional exemplary embodiments, the film can be comprised of or include tin oxide (Sn0₂).

Articles:

According to an aspect of some embodiments of the present invention there is provided an article which comprises the composition as described herein. In some embodiments, the article is, or is incorporated into, a device.

According to an aspect of some embodiments of the present invention there is provided an article which comprises a substrate and a dual layer deposited thereupon, the dual layer comprising a soft layer as described or exemplified in any embodiment herein above under the "Compositions" section, and a film as described or exemplified herein above in any embodiment under the" Compositions" section. It is to be understood that in the context of the embodiments of this aspect of the invention the article may encompass not only other items which include, but are not limited to, compositions of matter, additives, structures such as multi-directional arrangements, and the like.

As exemplified in the "Example" section that follows quantitative wear tests for substrates such as silicon or kapton, following coating thereof with a soft, flexible underlayer such as PDMS which is subsequently capped by a hard layer, such as a titania layer, result in enhanced scratch/wear resistance.

In some embodiments, the soft layer is deposited on at least a portion of a surface of the substrate. The compliant (soft) layer is as described herein above under "Compositions". For example, as described in any embodiment for the composition herein above, in some embodiments, in some embodiments, the soft layer is characterized by a thickness of at least e.g., 100 nm, 110 nm, 120 nm, 130 nm, 140 nm, 150 nm, 160 nm, 170 nm, 180 nm, 190 nm, 200 nm, 210 nm, 220 nm, 230 nm, 240 nm, 250 nm, 260 nm, 270 nm, 280 nm, 290 nm, 300 nm, 310 nm, 320 nm, 330 nm, 340 nm, 350 nm, 360 nm, 370 nm, 380 nm, 390 nm, 400 nm, 410 nm, 420 nm, 430 nm, 440 nm, 450 nm, 460 nm, 470 nm, 480 nm, 490 nm, 500 nm, 510 nm, 520 nm, 530 nm, 540 nm, 550 nm, 560 nm, 570 nm, 580 nm, 590 nm, 600 nm, 610 nm, 620 nm, 630 nm, 640 nm, 650 nm, 660 nm, 670 nm, 680 nm, 690 nm, 700 nm, including any value there between.

In some embodiments, the film is deposited on at least a portion of a surface of the soft layer. The film is as described herein above under the "Compositions". In some embodiments, the film may comprise, without limitation, one or more metal oxides as described for the composition herein above. In exemplary embodiments, the film comprises titania, as described in any embodiment for the composition herein above. In additional exemplary embodiments, the film comprises tin oxide (Sn0₂), as described in any embodiment for the composition herein above. Substrate surfaces usable according to some embodiments of the present invention can therefore be hard or soft, organic or inorganic surfaces, including, but not limited to, glass surfaces; porcelain surfaces; ceramic surfaces; metal oxide, polymeric surfaces such as, for example, plastic surfaces, rubbery surfaces, and surfaces comprising or made of polymers such as polypropylene (PP), polycarbonate (PC), high-density polyethylene (HDPE), unplasticized polyvinyl chloride (PVC), and fluoropolymers including but not limited to polytetrafluoroethylene (PTFE, Teflon®); metallic surfaces (e.g., gold surfaces) or can comprise or be made of silicon, organosilicon, stainless steel, gold, mica, a polymers as described herein or include any combination of the above.

The substrate's surfaces as described herein can further be modified by various chemical and mechanical processes, including, for example, PVD, lithography plasma etching or by organic monolayer or multilayer thin films.

In exemplary embodiments, the substrate is one or more materials selected from the group consisting of: polysiloxane, polyurethane, epoxy, polyacrylate, polyethylene, silicon, kapton, PDMS, and polycarbonate (PC).

In some embodiments, the substrate comprises a composition similar to that of the soft layer. In some embodiments, the substrate is other than the compliant layer. By "other than" it is meant that at least a portion of the substrate e.g., 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90% or even the complete substrate is different from the soft layer. By "different" it is meant to include different composition, and/or polymer having different characteristics such as, without limitation, Young's modulus value, molecule weight, branching, added fillers and/or additives and the like.

In some embodiments, the substrate is characterized by a Young's modulus that is 0.5 fold, 1 fold, 2 folds, 3 folds, 4 folds, 5 folds, 6 folds, 7 folds, 8 folds, 9 folds, 10 fold, 11 folds, 12 folds, 13 folds, 14 folds, 15 folds, 16 folds, 17 folds, 18 folds, 19 folds, 20 folds, including any value therebetween, higher that the Young's modulus of the soft layer.

As described herein above, the Young's modulus can be referred to as a non- limiting parameter characterizing the compliant layer that dictates the cushion effect. For the various substrates that can be used in the context of the invention this parameter is about, e.g., 200 GPa, 180 GPa, 160 GPa, 140 GPa, 180 GPa, 160 GPa, 140 GPa, 120 GPa, 100 GPa, 80 GPa, 60 GPa, 40 GPa, 20 GPa, 10 GPa, 8 GPa, 6 GPa, 4 GPa, 2 GPa, 1 GPa. For example the Young's modulus of Si is 170 GPa, and for kapton of polycarbonate the Young's modulus is 2.5 GPa. These values are in sharp distinction to the Young's modulus of the compliant layers, as described hereinabove. For example, for PDMS which has undergone plasma activation the Young's modulus is about 20 MPa.

In some embodiments, the article or the composition, in any embodiments as disclosed herein is characterized by reduced friction coefficient relative to a solid body. The term "friction" refers to the force that resists relative motion between two bodies in contact. The term "friction coefficient" is known in the art and is defined as a ratio of the force of friction between two bodies and the force pressing them together and can refer to static or kinetic friction. The force pressing two bodies together is also referred to herein as a normal force. The friction coefficient μ is evaluated by the following equation:

where F_n is the normal force and Fi the corresponding lateral force.

As described hereinabove, friction can be divided into two terms, a plowing term and an adhesion term. The latter is associated with friction arising from the energy required to break the adhesive bonds, and the former from the displacement of plastically- deformed material when a harder surface pushes into and "plows" through the softer one. Plowing leads to release of wear particles due to abrasion of engineering surfaces, which contribute significantly to friction. Therefore the cushioning effect which increases the scratch and/or wear resistance, also reduces both junction growth and plowing and therefore the friction.

In some embodiments, the reduced friction coefficient is e.g., at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, or at least 50%, lower than a friction coefficient of a control material relative to said solid body, including any value there between. The term "control material" as used herein refers to a reference material being partially different from the dual layer of the article as disclosed herein. By "partially different" it is meant to refer to the dual layer as disclosed herein while being different thereof by at least one parameter of its substructure, including, without limitation, the thickness of the soft layer, the thickness of the film, and the composition of the soft layer.

The term "solid body" is meant to include any object with distinct surface shape.

As demonstrated in the Examples section that follows, the presence of a PDMS underlayer is seen to provide a significant reduction in friction coefficient, μ, relative to a titania layer alone. Furthermore, μ varies systematically with the thickness of the titania layer.

As known in the art, wear tests, can be expressed as loss of material during wear in terms of volume. As exemplified in the Example section that follows, the atomic force microscopy (AFM) may be used to characterize the hardness property of a layer.

In some embodiments, the article, or the composition in any embodiments as disclosed herein throughout, is characterized by as exhibiting reduced wear volume. In the context of friction and scratch tests, "by characterized" it is meant, to refer to characterization by any common tribological or nanotribological technique known in the art. Exemplary techniques include, but are not limited to, Bayer test (abrasion resistance), drop ball test (impact resistance)

In exemplary embodiments, the article is characterized by AFM for testing the scratch resistance and for the wear test. In some embodiments, the article is characterized by AFM as exhibiting reduced wear volume, the reduced wear volume being e.g., at least 5% lower, at least 10% lower, at least 15% lower, at least 20% lower, at least 25% lower, at least 30% lower, at least 35% lower, or at least 40% lower, than a wear volume of a control material, including any value therebetween.

As demonstrated in the Examples section that follows, titania films deposited directly on kapton and Si wafers were least resistant to scratching. It is clearly seen that titania on PDMS is more scratch resistant than on the other substrates. Furthermore, the volumes measured in the wear test show that titania on kapton performs better than the titania on the Si substrate (Fig. 6). These results demonstrate the beneficial influence of an underlying soft layer in improving the scratch resistance of hard films.

In some embodiments, the article or the composition as disclosed herein is characterized by AFM using a diamond-coated tip having curvature radius of e.g., approximately 150 nm capable to withstand scratch by loads of up to e.g., 1 μΝ, 2 μΝ, 3 μΝ, 4 μΝ, 5 μΝ, 6 μΝ, 7 μΝ, 8 μΝ, 9 μΝ, 10 μΝ, 11 μΝ, 12 μΝ, 13 μΝ, 14 μΝ, 15 μΝ, 16 μΝ, 17 μΝ, 18 μΝ, 19 μΝ, 20 μΝ, 21 μΝ, 22 μΝ, 23 μΝ, 24 μΝ, 25 μΝ, 26 μΝ, 27 μΝ, 28 μΝ, 29 μΝ, 30 μΝ, 31 μΝ, 32 μΝ, 33 μΝ, 34 μΝ, 35 μΝ, including any value therebetween. In exemplary embodiments, a titania film deposited on a PDMS layer is characterized by AFM as able to withstand scratch by loads of up to about 25 μΝ. In another exemplary embodiment, PC coated with titania can be scratched by a 10 μΝ load while PC coated with a dual layer of PDMS and titania is only scratched by a 20 μΝ load; i.e., the scratch resistance of PC/PDMS/Ti0₂ is twice as higher than that of Ti0₂ films on PC, and four times higher that of the PC substrates.

In some embodiments, the article, or the composition in any embodiments as disclosed herein, is characterized by low optic absorption in the visible light range. In some embodiments, the composition or the article is characterized by high transparency in the visible light range. In some embodiments, the article, or the composition in any embodiments as disclosed herein, is characterized by low optic absorption in the infrared (IR) range. Additionally, or alternatively, in some embodiments, the article is characterized by high transparency in the IR range. Additionally, or alternatively, in some embodiments, the article, or the composition in any embodiments as disclosed herein, is characterized by low optic absorption in the ultra-violet (UV) range. Additionally, or alternatively, in some embodiments, the article is characterized by high transparency in the UV range.

As used herein and in the art, the UV range refers to a range of from about 100 nm to about 380 nm, and the IR range refers to a range of from about 780 nm and less than about 500 μηι (including the near IR at between about 700 nm and about 1300 nm).

In some embodiments, the article is characterized by low optic absorption and by high transparency in the visible light range, as exemplified in Figures 11 which show UV-Vis spectra for PC with a dual coating of PDMS and titania.

As used herein and in the art, visible light range refers to a range of from about 380 nm to about 780 nm. Any article that may benefit from the wear resistance property and/or the low friction of the compositions or the articles described herein is contemplated.

The properties of the article can be tuned to meet the needs of a given application, for example, by modifying one or more parameters selected from, but not limited to, the composition of the film, the composition of the soft layer, the thickness of the film, the thickness of the soft layer, the thickness of the dual layer. In some embodiments of the present invention, the parameters are selected so as to improve one or more surface characteristics of the film layer, including, without limitation, wetting (hydrophobicity) properties and antistatic behavior. For example, Sn0₂ coatings exhibit good electrical and/or antistatic properties, therefore, using such an oxide may provide the desired combination of mechanical and antistatic properties.

Exemplary articles may include any article in tribological application that can benefits from the high compliance of the dual layer as described hereinabove.

Exemplary articles include, but are not limited to, implantable medical devices such as, but are not limited to, orthopedic implants, replacement joints, catheter access ports, screw plates, artificial spinal disc replacements, implantable cardiac monitors, implantable infusion pumps, implantable insulin pumps, stents, implantable neurostimulators, maxillofacial implants, dental implants, and the like.

Other exemplary articles include, but are not limited to, electronic devices such as, without being limited thereto, an energy harvesting device, for example, a microelectronic device, electronic circuit component, touch screen, large area display array, light-emitting diode (LED), a microelectromechanic device, including, without limitation, hard disk, a photovoltaic device and the like.

Other exemplary articles include, but are not limited to, optical devices such as, without being limited thereto, lenses, e.g., ophthalmic lenses, progressive lenses (multifocal), monofocal lenses, glass molds, eye glasses, cameras, binoculars, telescopes and the like.

Other exemplary articles include, but are not limited to, mechanical devices, such as, without being limited thereto, micromotors, gear trains, mechanical relays, and valves.

Process:

According to an aspect of some embodiments of the present invention there is provided a process of preparing any of the compositions or the articles described herein.

In some embodiments, there is provided a process for manufacturing an article having a wear resistant surface, the process comprising the sequential steps of:

a) coating at least a portion of a substrate with a soft layer. In some embodiments, the soft layer has a thickness of e.g. at least 50 nm, at least 70 nm, at least 100 nm including any value therebetween.

b) depositing on at least portion of a surface of said soft layer a film comprising at least one material selected from metal, metal oxide, a ceramic composition, and metal, metal oxide, metal nitride, carbide, a ceramic composition, hard polymers, diamond, and diamond-like materials.

In some embodiments, the film is characterized as described herein above under "The Composition of the Invention" for example, by a thickness of e.g., about 10 nm, about 20 nm, about 30 nm, about 40 nm, about 50 nm, 60 nm, about 70 nm, about 80 nm, about 90 nm, about 100 nm, about 110 nm, about 120 nm, about 130 nm, about 140 nm, about 150 nm, 160 nm, about 170 nm, about 180 nm, about 190 nm, about 200 nm, about 210 nm, about 220 nm, about 230 nm, about 240 nm, about 250 nm, 260 nm, about 270 nm, about 280 nm, about 290 nm, or about 300 nm, including any value therebetween, to thereby manufacturing an article having a wear resistant surface.

As used herein, the term "process" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the art. According to another aspect of some embodiments of the present invention there is provided a method of enhancing wear and/or reducing friction of an article, the method comprising depositing the dual-layer composition of the invention on a substrate of said article, such as described herein.

The soft layer may be of any composition and embodiments thereof as described and/or characterized hereinabove under the "Articles" and/or under "Compositions".

The film may be of any composition and embodiments thereof as described and/or characterized hereinabove under the "Articles" and/or under "Compositions".

The substrate may be of any composition and embodiments thereof as described and/or characterized hereinabove under the "Articles" and/or under "Compositions".

The coating of step (a) may be performed by any coating method or film deposition technique known in the art aimed at achieving the objectives of uniform coating, including, without limitation, chemical vapor deposition, plasma chemical vapor deposition, physical vapor deposition, thermal spray, plasma spray, solid state deposition process electroplating or electroless plating, and liquid phase processes such as, without limitation, spin-coating or dip coating.

In exemplary embodiments, the coating of step (a) is performed by a spin coating technique, as described in the Example section that follows. Spin coating is a commonly used technique for fabricating thin films.

In some embodiments, the soft layer is PDMS. The thickness of the PDMS layer may be controlled by diluting the PDMS with hexane prior to the spin coating. For example, thinner layers of PDMS may be obtained by diluting it with hexane in a ratio of e.g., 1: 10 (PDMS:hexane) prior to the spin coating. The hexane is evaporated during a subsequent curing process.

In some embodiments, the soft layer is at least partially activated prior to step (b) to provide a stronger adherence between a surface of the soft layer and a film deposited thereon.

By "activated" it is meant that at least a portion of a surface of the soft layer is oxidized. In some embodiments at least a portion of a surface of the soft layer is oxidized by exposing thereof to air plasma for e.g., about 1 min, about 5 min, about 15 min, about 20 min, about 25 min, about 30 min, including any value therebetween. In some embodiments the plasma intensity is 1W; or in some embodiments, 2W; or in some embodiments, 3W; or in some embodiments, 4W; or some embodiments, 5W; or in some embodiments, 6W; or in some embodiments, 7W; or in some embodiments, 8W; or some embodiments, 9W; or some embodiments, 10W; or some embodiments, 11W; or some embodiments, 12W; or some embodiments, 13W; or in some embodiments, 14W; or some embodiments, 15W; or some embodiments, 16W; or some embodiments, 17W; or in some embodiments, 18W; or in some embodiments, 19W; or in some embodiments, 20W; or some embodiments, 21W; or some embodiments, 22W; or some embodiments, 23W; or some embodiments, 24W; or some embodiments, 25W; or in some embodiments, 26W; or some embodiments, 27W; or some embodiments, 28W. or some embodiments, 29W; or some embodiments, 30W; or some embodiments, 40W; or in some embodiments, 50W; or some embodiments, 100W; or some embodiments, 500W, including any value therebetween. In exemplary embodiments, the plasma intensity is 18W.

In some embodiments, the activation is performed by other methods known in the art including, without limitation, flame, ozone, ultra violet ozone cleaning systems (UVOCS), or by etching with an oxidative solution, e.g., KMn0₄ solution.

In some embodiments, at least portion of a surface of the soft layer is hydroxylated by exposing thereof to an aqueous acid solution. Exemplary acid solutions include, but are not limited to, HC1, HN0₃, and H₂S0₄. In some embodiments, a solution of 20% H₂S0₄ in water is for e.g., about 1 min, about 5 min, about 15 min, about 20 min, about 25 min, about 30 min, including any value therebetween.

In some embodiments, the term "oxidized", or grammatical derivatives thereof, refers to a formation of hydroxylated group (e.g., Si-OH) on a surface of the soft layer.

In some embodiments, the term "oxidized", or grammatical derivatives thereof, refers to a formation of carboxylic group (e.g., PC-COOH) on a surface of the soft layer.

In some embodiments, the average thickness of the PDMS layer is as described herein above under "The composition of the Invention" and or under "Articles", as characterized based on e.g., cross-sectional FIB measurements, as described in the Example section that follows.

The depositing of step (b) may be performed by any coating method or film deposition technique known in the art aimed at achieving the objectives of uniform coating, including, without limitation, chemical vapor deposition, plasma chemical vapor deposition, physical vapor deposition, thermal spray, plasma spray, solid state deposition process electroplating or electroless plating technique, or liquid phase processes such as, without limitation, spin-coating or dip coating.

According to some embodiments of the present invention, the depositing step (b) is carried out by liquid phase deposition (LPD), atomic layer deposition (ALD) or vapor phase techniques.

Atomic layer deposition (ALD) of hard film, such as, without limitation, metal oxides (e.g., titania), on the soft layer according to this invention, typically involves four steps that, in some embodiments, are repeated in a cycle: 1) introducing the metal containing precursor (e.g., a titanium compound) and allowing it enough time to react with all available surface sites (e.g., 0.5 seconds); 2) evacuating the chamber to remove excess metal containing reagent (e.g. applying vacuum along with an argon purge); 3) introducing an oxygen source (e.g. water, oxygen) into the chamber and allowing it enough time to react with the new surface sites created by the treatment with the first reagent (e.g., 20 seconds); 4) evacuating the chamber to remove excess oxygen source reagent (e.g., vacuum along with an argon purge); then starting back at step one. The cycles may be repeated as a way of growing progressively thicker films, in one embodiment 50 cycles; or in another embodiment 100 cycles; or in another embodiment 200 cycles; or in another embodiment 500 cycles; or in another embodiment 1000 cycles; or in another embodiment 2000 cycles.

In some embodiments, the reagent used for coating in step (b) is a precursor solution selected from: (NH₂)₄TiF₆/H₃B0₃ or Ti(NMe₂)4/0₂ or Ti(NMe₂)₄/H₂0 (for Ti0₂); SnF₂/H₃B0₃ (for Sn0₂), A1(CH₃)₃/H₂0 or Al(CH₃)₃/0₂ (for A1₂0₃); and Zn(CH₂CH₃)2/H₂0, Zn(CH₂CH₃)₂/0₂ for ZnO.

In some embodiments, the precursor solution is aged for a time period of e.g., at least 30 min, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 18 hours, including any value therebetween. In exemplary embodiments, the precursor solution is aged for a time period of 6 hours. As used herein, the term "aged", or any grammatical derivative thereof, means stored for an indicated period of time. As exemplified in the Example section that follows the aged solution is further filtered.

Without being bound by any particular theory, it is assumed that the aging and/or the filtering give rise to the formation of thinner and/or smoother films as compared to film prepared with freshly prepared precursor solution.

In some embodiments, the coating step is carried out by liquid phase deposition (LPD). In some embodiments, the reagent used for coating in step (b) is (NH₄)TiF₆/H₃B0₃, for titania film. In some embodiments, the reagent used for coating in step (b) is SnF₂/H₃B0₃ for Sn0₂ film. In some embodiments, the reagent used for coating in step (b) is generated in situ. In some embodiments, H₂SnF₆ is synthesized in situ from SnF₂, HF and H₂0₂.

In some embodiments, the coating step is carried out by atomic layer deposition (ALD). In some embodiments, the reagent used for coating in step (b) is Ti(NMe₂)4/0₂. In some embodiments, the reagent used for coating in step (b) is Al(CH₃)₃/0₂.

In some embodiments, the deposition step (b) is carried out by liquid phase deposition, wherein at least a portion of a surface of the soft layer coating as obtained in step (a) is immersed into an aqueous solution containing (NH₄)TiF₆ and H₃B0₃ reagent for a sufficient period of time, which is in some embodiments, for 1 hour; or in some embodiments, for 2 hours; or in some embodiments, for 3 hours; or in some embodiments, for about 4 to 8 hours; or in some embodiments, for about 5 to 7 hours; or in some embodiments, for 6 hours; or in some embodiments, for 4 hours.

In exemplary embodiments, at least a portion of the surface of the soft layer coating (e.g., PDMS) as obtained in step (a) is immersed into an aqueous solution containing (NH₂)₂TiF₆ and H₃B0₃ reagent for four hours to thereby obtain a film having a thickness of about 40 nm.

It is noteworthy that the thickness of the film is proportionally to the period of time of the immersion. By "proportionally" it is meant within about ±30 percent.

In some embodiments, the deposition step (b) is carried out by atomic layer deposition, wherein at least a portion of a surface of the soft layer coating obtained in step (a) is introduced together with a metal oxide precursor, into a closed chamber where they react in a self-limiting fashion for a sufficient period of time, following by introduction of an oxygen source and allowing it to react with new surface sites created by the treatment with the metal oxide forming reagent for a sufficient period of time. This ALD coating step can be repeated as many times as needed in order to progressively grow thicker films, which in some embodiments is 1000 times; or in some embodiments, 500 times; or in some embodiments, 200 times; or in some embodiments, 100 times; or in some embodiments, 50 times; or in some embodiments, 20 times, including any value therebetween.

In some embodiments, the methods according to this invention may further comprise a drying step. In some embodiments, the methods according to this invention do not require a drying step.

In some embodiments, the methods as disclosed herein, further comprise a drying step. In another embodiment, the drying step is carried out in controlled conditions.

Drying in "controlled conditions" typically refers to setting the temperature and humidity to a specific value, following by slowly reducing the relative humidity, while leaving the temperature at the same value or reducing the temperature in a controlled fashion. In some embodiments, the temperature is set at 70°C, or in some embodiments at 80°C; or in some embodiments at 90°C; or in some embodiments at 100°C; or in some embodiments at 40°C; or in some embodiments at 60°C. In one embodiment, the relative humidity is varied from 70% to 20%; or in some embodiments, from 100% to 40%; or in some embodiments, from 65% to 20%; or in some embodiments, from 60% to 35%. In some embodiments, the temperature is set at 70°C and the relative humidity is varied from 70% to 20%. Drying time can be varied and the rate of change of the humidity can be varied. In some embodiments, drying under controlled conditions can take as long as about three days; or in some embodiments, about 2 days; or in some embodiments, about 1 day; or in some embodiments, about 18 hours; or in some embodiments, about 12 hours; or in some embodiments, about 6 hours; or in some embodiments, about 3 hours; or some embodiments, about 1 hour.

In some embodiments, the drying step is a quick drying that does not require controlled conditions. In some embodiments, the drying step is carried out under heat or vacuum, or any combination thereof. In some embodiments, the heating is carried out at a specific temperature range. In some embodiments, the temperature is in a range of 25°C to 70°C. In some embodiments, the temperature is in a range of 15°C to 100°C. In some embodiments, the temperature is in a range of 25°C to 120°C. In some embodiments, the temperature is room temperature. In some embodiments, the temperature is in a range of 25°C to 50°C. In some embodiments, the temperature is in a range of 40°C to 70°C. In some embodiments, the temperature is about 120°C; or about 100°C; or about 70°C; or about 50°C; or about 40°C; or about 25°C. In some embodiments, the relative humidity is in a range of 20-70%. In some embodiments, the relative humidity is in a range of 40-100%. In some embodiments, the relative humidity is in a range of 20-65%. In some embodiments, the relative humidity is in a range of 35- 60%. In some embodiments, the optional drying step in the method of the present invention is carried out at a temperature in the range of 25°C to 70°C and at a relative humidity in the range of 20-70%.

In some embodiments, the coated surfaces of the soft layer obtained in step (b) of the method as disclosed herein is optionally washed with water followed by washing with alcohol prior to the drying step.

Further embodiments of this aspect of the present embodiments are included herein above, under ""Compositions", and under the "Articles" form an integral part of the embodiments relating to the process.

As demonstrated in the "Examples" section that follows, the titania bonds to PDMS that had been suitably activated, typically by plasma treatment. The substrate chosen for demonstrating the benefits of such coating systems was polycarbonate (PC), due to its use in optical lenses, an application that could benefit from improved scratch/wear resistance

General:

It is expected that during the life of a patent maturing from this application many relevant compositions comprising a dual layer of compliant layer and a hard film as disclosed herein will be developed and the scope of the term "compositions comprising a compliant layer and a hard film" is intended to include all such new technologies a priori.

As used herein the term "about" refers to ± 20 %.

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to".

The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". Any particular embodiment of the invention may include a plurality of "optional" features unless such features conflict.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

As used herein the term "method" refers to manners, means, techniques and procedures for accomplishing a given task including, but not limited to, those manners, means, techniques and procedures either known to, or readily developed from known manners, means, techniques and procedures by practitioners of the chemical, pharmacological, biological, biochemical and medical arts..

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements. Various embodiments and aspects of the present invention as delineated herein above and as claimed in the claims section below find experimental support in the following examples.

EXAMPLES

Reference is now made to the following examples which, together with the above descriptions, illustrate the invention in a non-limiting fashion.

EXAMPLE 1

SAMPLE PREPARATION

Materials:

Silicon wafers (n-type); Kapon 50 NH sheets (DuPont); SYLGARD silicon elastomer 184; SYLGARD silicon elastomer 184 curing agent; polycarbonate PC3107 sheets (Palram); H₃B0₃; (NH₂)₂TiF₆;SnF₂; and H₃B0₃.

Sample Preparation (liquid phase deposition of metal oxide film):

In exemplary procedures, titania film coatings were prepared as follows:

1) silicon wafers which were cleaned successively by chloroform, acetone, and then ethanol, drying the surfaces in a dry nitrogen stream after each rinse.

2) 125 μιτι thick kapton. Prior to titania coating, the as-received sheets were cut into 1 cm x 1 cm squares, washed with double distillated water and ethanol, and dried under nitrogen.

3) PDMS: a mixture of SYLGARD silicon elastomer 184 and SYLGARD silicon elastomer 184 curing agent (ratio 10: 1 w:w) was spin-coated onto n-type silicon wafers after cleaning as above, using a Model KW-4A spin-coater (ChemSols Corp.).

4) 1 mm thick polycarbonate PC3107 sheets (Palram).

Prior to titania coating, the as-received sheets were cut into 1 cm x 1 cm squares, washed with isopropanol, and dried under nitrogen. Further, before the titania coating, the surface was pretreated by exposing to an air plasma (Harrick, model PDC-3XG) at a pressure of 0.3 mm Hg and 18 W power for 20 min for Si, kapton and PC and 5 min for PDMS. Immediately after plasma activation, samples were immersed in a room temperature titania deposition solution (0.3 M H₃BO₃ and 0.1 M (NH₂)₂ iF₆ in water; Deki, S. et al., Materials Research Bulletin 1996, 31, 1399-1406) that was first aged for 6 hours and then filtered through a 0.45 μπι, 7 bar max filter (Schlecher & Schuele). The deposition was allowed to proceed for a specified time period. In exemplary procedure the immersing time is 4 hours. In additional exemplary procedure the deposition was allowed to proceed for less than 4 hours or more than 4 hour to thereby control the titania thickness, with the longer immersing time producing increased an titania thickness.

The aged/filtered solution gave thinner and smoother coatings as compared to coatings done with freshly prepared solutions. The Ti0₂-coated samples were rinsed in water and methanol before drying under conditions of controlled humidity (Razgon, A.; Sukenik, C. N. J. Mater. Res. 2005, 20, 2544-2552).The stability of the coating was confirmed by sonication in water for 10 min.

In additional exemplary procedures, coatings of Sn0₂ films were prepared using procedures similar to those described herein above for titania, with the use of 0.03M SnF₂/0.45M H₃BO₃ as the deposition solution. In exemplary procedures, 0.15 M HF and 0.06 M H₂0₂ were further added to the solution. In exemplary procedures, the immersing time used for achieving the desired oxide coating was 4 hours.

The samples as obtained by the exemplary procedures as described herein were further characterized as described under "Example 2" below.

EXAMPLE 2

SAMPLE CHARACTERIZATION

Methods

Scanning Electron Microscopy (SEM):

The surface morphology of the samples was assessed by SEM (Inspect, FEI), at an accelerating voltage of 5 kV or 30 kV with surface gold coatings of approximately 10 nm thickness.

Rutherford Backscattering Spectrometry (RBS): In exemplary procedures, the thicknesses of the Ti0₂ layers were measured by Rutherford Backscattering Spectrometry (RBS). This work was done using a 1.7 MV Pelletron accelerator (NEC, USA). All spectra were collected using a 2.023 MeV ¾⁺ ± IKev beam. The beam current was -13 nA, with a nominal beam diameter of 2 mm. An electron suppressor was used between the beam entrance and the sample holder, biased at -100V vs. ground. The data were collected by the fixed, (ULTRA™ Silicon-Charged Particle Detector, ORTEC) with detector scattering angle 169° (RBS Fixed detector - A, Cornell geometry), and solid angles of 2.7 str. An OEM window of 125 Ώ Βε plus 15 μηι Mylar filter was utilized. A normal incident beam was used in all measurements. All samples were mounted on the holder by double sided, self-adhesive carbon tape. Charging effect on the kapton was compensated by a thin Au coating (8 nm). NDFv9.4e software was used to fit the data (Barradas, N. P.; Jeynes, C. Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 2008, 266, 1875-18790).

Focused Ion Beam (FIB):

The PDMS thickness was obtained using a dual beam FIB (FEI, Helios 600), with electron and ion beam with up to 30kV each. The combination of two beams with different angles (52 degree between the beams) enables simultaneous work using both beams.

Atomic Force Microscopy (AFM):

All scanning probe microscopy was done using an ICON instrument (Bruker AXS SAS). The deflection sensitivity of each probe was measured by pressing the probe on a hard surface and spring constant was calibrated by the "Sader method" (Sader, J. E.; Chon, J. W. M.; P., M. Review of Scientific Instruments 1999, 70, 3967-3969).

Nanoscratching was done using a diamond coated tip (DDESP) (force constant of 20-80 N/m, Digital Instruments, Santa Barbara, CA) with the indenter at variable normal loads of 5 to 25 μΝ, a sliding speed of 0.3 μνα/s and a scratch length of about 1.5 μιτι. The same indenter was used to image the area after the nanomechanical tests. The modulus of the PDMS was measured using PeakForce QNM (Quantitative Nanomechanical property mapping), an extension of the Peak Force Tapping mode, using ScanAsyst-air probes (force constant of 0.4 N/m, Digital Instruments, Santa Barbara, CA). To quantify the mechanical properties of the sample, the tip radius was determined by measurements on a reference sample of known modulus

(http://www.veeco.com/pdfs/appnotes/quantitative-mechanical-property-mapping-at-the- nanoscale-with-peakforce-qnm-anl28-lores.pdf.).

Friction measurements:

The Dimension ICON SPM in the AFM is capable of measuring frictional forces on the surfaces of samples using lateral force microscopy (LFM). Frictional information was obtained via the torsional deflection of the cantilever with the scan direction running perpendicular to the major axis of the cantilever. Quantitative values of the frictional force were made as per reference (Varenberg, M.; Etsion, I.; Halperin, G. Rev. Sci. Instrum. 2003, 74, 3362-3367). A silicon nitride "A" shaped cantilever (normal spring constant 0.32 N/m) with a gold reflective coating was used for the LFM mode. Nanoscope analysis software was used for analyses of the data.

Nano-friction measurements were performed at loads that were sufficiently low such that no evidence of wear is observed. This was done so as to avoid plowing and debris eneration. The friction coefficient μ is evaluated by

where F_n is the normal force and Fi the corresponding lateral force. In these experiments, the normal contact force was varied in a controlled fashion by changing the feedback setpoint and recording corresponding changes in frictional (torsion) forces. Adhesion as determined from force-distance curves was negligible so the normal force is that applied, determined from setpoint and cantilever calibration. The normal forces in the friction measurements were 8 to 30 nN.

Optical measurements:

Scratch resistance of titania-coated polycarbonate substrates (with and without a PDMS inter-layer) was measured for its potential relevance to the lens industry. For maximal optical throughput, the thickness of the soft polymer (PDMS) must be minimized. Thinner layers of PDMS were obtained by diluting it with hexane in a ratio of 1: 10 followed by spincoating under standard conditions. The hexane evaporated during curing time (overnight). The transmittance of the coated and uncoated PC was measured using a Cary Model 100 spectrometer in double beam transmission mode. Spectra were run against a reference sample of PC. All samples were measured in the wavelength range of 200 - 800 nm.

Experimental Results

SEM and RBS measurements:

Figures 2A-C show SEM images of plasma treated Si wafers (Figures 2A), kapton (Figures 2B) and PDMS (Figures 2C) taken after deposition with a Ti0₂ film, demonstrating uniform Ti0₂ nanoscale film. RBS measurements demonstrated a Ti0₂ thicknesses of 43 nm (Figures 2A), 38 nm Figures 2B), and 40 nm (Figures 2C), respectively, for the various substrates.

Figures 3A-B show SEM micrographs of the titania films on PC without (Figure 3A) and with (Figure 3B) the intervening PDMS layer.

Figures 4A-B show SEM micrographs of the PC coated with Sn0₂ film (Fig. 4A), and PC coated with PDMS layer with Sn0₂ film deposited thereon (Fig. 4B) with an estimated Sn0₂ thickness of about 60 nm.

AFM measurements:

Figure 5 depicts AFM images of Ti0₂ films, on: Si, on kapton, and on PDMS, before and after scratching. The scratch rate was 0.3 μιη/sec and the load was varied from 10-25 μΝ. It can be seen that all films are disrupted at the maximum load of 25 μΝ. Titania films deposited directly on kapton and Si wafers were least resistant to scratching. It is clearly seen that titania on PDMS is more scratch resistant than on the other substrates.

Furthermore, as shown in Figure 6 the volumes measured in the wear test show that titania on kapton performs better than the titania on the Si substrate. These results suggest the beneficial influence of a softer substrate in improving the scratch resistance of the titania films, which can be referred to hereinthroughout as a "cushioning effect".

Figures 7A-C show the AFM images of the scratch tests on PC with and without the coatings. The load was varied from 5 to 25 μΝ and the scratch rate was 0.3 μιη/s. It can be seen that uncoated PC is readily scratched by a 5 μΝ load (Figure 7A). PC with titania can be scratched by a 10 μΝ load (Figure 7B) and PC with PDMS and titania (denoted herein throughout as: "PC/PDMS/Ti0₂") is only scratched by a 20 μΝ load (Figure 7C); i.e., the scratch resistance of PC/PDMS/Ti0₂ is as twice higher than that of Ti0₂ films on PC, and four times than that of the PC substrates.

It is noteworthy that the scratch profiles in the presence of the PDMS interlayer are qualitatively different than for the bare PC and for titania on PC: for the latter two, the profile is sharp, and defined by the shape of the tip. In the presence of PDMS, wear is inhibited at the lower loads but when a wear track appears at the higher loads it is significantly broader. For all scratch tracks except the 25 μΝ load on titania+ PDMS on PC the measured depth was less than the thickness of the titania coating. These results are qualitatively similar to those observed on kapton (as shown in Figure 5) which is in line with the similarity in Young's modulus of kapton and PC: 2.5 and 2.6 GPa, respectively.

The dependence of sliding velocity on scratch resistance was checked for Ti0₂ on PC samples over the range of 0.05 to 1 μιη/s, using a constant normal force of 10 μΝ, and as shown in Figures 8A-B, there is no dependence of the scratch depth on the scratch rate in the measured range.

Figures 9A-B present AFM based scratching qualitative results showing that the Sn0₂ on PC scratches film (as presented in Figure 4A) at 2X, 3X and 4X forces ("X" denotes a force unit and "2X, 3X and 4X" stand for: two times, three times, four times, respectively, of said force unit); Figure 9A). The Sn0₂ film on PC/PDMS bilayer (as presented in Figure 4B) scratches at 4X force (Figure 9B).

Friction measurements: Following both normal and lateral force calibration, absolute values for the friction coefficient were determined from slopes of lines as shown in Figure 10. The presence of a PDMS underlayer is seen to provide a significant reduction in friction coefficient relative to a titania film alone. As further demonstrated in Figure 10, μ varies systematically with the thickness of the titania film.

As demonstrated in Figure 10, for the thinnest titania coating, 8 nm, μ was 0.21, half that of a plain titania surface. Increasing the titania thickness resulted in a corresponding increase in μ: 0.31 for 17 nm titania and 0.38 for 36 nm titania.

Without being bound by any particular theory, the effect is not related to changes in surface roughness [Raman, V et al., Journal of Applied Physics 1991, 70, 1826-1836], as has been previously shown that roughness does not vary with thickness for these films [Gotlib-Vainshtein, K. et al., J. Phys. Chem. C,]. Nonetheless, local roughness can significantly affect the absolute values of friction coefficient measured in single and multiple asperity friction experiments [Bhushan, B. Micro/Nanotribology and Materials Characterizaiton Studies Using Scanning Probe Microscopy in Nanotribology and Nanomechanics An Introduction; Springer- Verlag Berlin Heidelberg 2005].

As used herein and in the art, the terms "surface roughness" or "roughness factor" which are used hereinthroughout interchangeably, refer to the relation between the actual surface area and the projected area.

Without being bound by any particular theory, many elastomers are known to exhibit high friction, due to the adhesion component of friction, which leads to extensive growth of the junctions between the interfaces under sliding. For instance, the frictional stress in rubber is almost entirely due to adhesive interactions which cause the rubber to fill in the cavities caused by roughness on the mating surfaces. However, the hard film coating, such as titania, prevents this adhesion from occurring. Without being bound by any particular theory, the higher yield stress and modulus of the titania relative to the PDMS underlayer mean that higher pressures are required to deform the asperities.

It is therefore assumed, without being bound by any particular theory, that the inclusion of a PDMS underlayer reduces friction relative to a simple titania film, without the PDMS underlayer, and this effect diminishes as the thickness of the titania increases, with the more flexible PDMS layer leading to significant lowering of local stiffness. These combined effects of hard film and compliant underlayer can be directly related to the ratio of hardness to elastic modulus. This quotient has proven to be an excellent indicator of wear resistance where larger values indicate better wear resistance. The yield pressure, which is proportional to:

R²[H³/E²],

where R is the contact radius, H is hardness and E is reduced modulus, has an even stronger dependence on the hardness to modulus ratio. This ratio is enhanced for the titania on PDMS film since the effective E is significantly reduced relative to pure titania, whereas H remains high as dictated by the properties of the titania film.

Without being bound by any particular theory, it is assumed that the negligible effect on H is due to the fact that the contact area of the indenter in the titania film itself at a given load is not increased here relative to that for pure titania). Without being bound by any particular theory, the reduced compliance arising from the presence of the PDMS substrate is thus assumed to be a key factor in wear reduction. Furthermore, the PDMS is below its glassy transition so there is little internal friction. Under this model, the polymer serves as a cushion, which reduces the local pressure at the contacting asperities of the titania, and thus reduces plowing and wear. As the titania layer thickness increases, the surface stiffness increases and the effect becomes less efficient.

Optical measurements:

The average thickness of the PDMS layer used for optical measurements was about 700 nm, based on cross-sectional FIB measurements. The Young's modulus of PDMS after hexane evaporation was measured with Peak-Force QNM^® and found to be the same as in samples with 10 μπι thickness (obtained with no dilution with hexane): about 1.5 MPa (before oxidative activation).

Figures 11A-B present the UV/V transmission (Fig. 11A) and absorption (Fig. 11B) spectra for coated and uncoated PC. The PC/PDMS/titania sample has high transmission throughout the visible spectrum, but has only negligible absorbance in the visible light, as required for e.g., satisfied lens quality.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.

Claims

WHAT IS CLAIMED IS:

1. A process for manufacturing an article having a reduced friction and/or wear resistant surface, the process comprising the sequential steps of:

a) coating at least a portion of a substrate of said article with a compliant layer, said compliant layer having a thickness of at least 100 nm; and

b) depositing on at least a portion of a surface of said compliant layer a uniform hard film, said uniform hard film comprises at least one material selected from the group consisting of: metal, metal oxide, a ceramic composition, hard polymers, diamond, and diamond-like materials;

thereby manufacturing an article having a reduced friction and/or wear resistant surface.

2. The process of claim 1, wherein said uniform hard film is characterized by a thickness that ranges from 5 nm to 300 nm.

3. The process of any one of claims 1 or 2, wherein said uniform hard film is characterized by less than 30 % variation in thickness.

4. The process of claim 1, wherein said compliant layer is an elastomeric polymer selected from the group consisting of: polydimethylsiloxane (PDMS), polybutadiene, kapton, silicone rubber, and any derivative or copolymer thereof.

5. The process of claim 4, wherein said elastomeric polymer is PDMS.

6. The process of claim 1, further comprising prior to step (b) a step of activating a surface of said compliant layer to oxidize at least a portion thereof.

7. The process claim 6, wherein said step of activating a surface of said compliant layer is performed by air plasma for a time period that ranges from about 1 min to about 30 min.

8. The process of claim 1, wherein step (b) is performed by depositing a solution of a precursor of said material on said compliant layer for a period that ranges from 30 min to about 5 hours.

9. The process of claim 8, further comprising a step of aging of said solution, said aging being performed for a time period that ranges from 2 hours to about 18 hours prior to step (b).

10. The process of any one of claims 8 and 9, wherein said solution is a solution of a precursor selected from tiatania and/or Sn0₂.

11. The process of any one of claims 1 to 10, wherein said substrate is one or more materials selected from the group consisting of: polyethylene, silicon, kapton, PDMS and polycarbonate (PC), wherein said substrate is other than said compliant layer.

12. A composition comprising a compliant layer and a uniform hard film deposited on at least a portion of a surface of said compliant layer, said compliant layer being characterized by a thickness of at least 100 nm and is characterized by Young's modulus value lower than 500 MPa, said uniform hard film is characterized by a thickness that ranges from about 5 nm to about 300 nm, and comprises at least one material selected from the group consisting of: metal, metal oxide, a ceramic composition, hard polymers, diamond, and diamond-like materials.

13. The composition of claim 12, wherein said uniform hard film is characterized by less than 30 % variation in thickness.

14. The composition of claim 12, wherein said uniform hard film comprises

Ti0₂.

15. The composition of claim 12, wherein said uniform hard film comprises

Sn0₂.

16. The composition of claim 12, wherein said compliant layer is an elastomeric polymer being one or more polymers selected from the group consisting of: polydimethylsiloxane (PDMS), polybutadiene, silicone rubber, silicon composition, kapton, polycarbonate, and any copolymer thereof.

17. The composition of claim 16, wherein said elastomeric polymer is PDMS.

18. The composition of claim 17, wherein said PDMS is at least partially hydroxylated.

19. An article comprising the composition of any one of claims 12-18.

20. An article comprising a substrate and a dual layer deposited thereupon, said dual layer comprises a compliant layer and a uniform hard film, wherein:

(a) said compliant layer is deposited on at least a portion of a surface of said substrate, is characterized by a thickness of at least 100 nm and is characterized by Young's modulus value that is lower than 500 MPa, and

(b) said uniform hard film is deposited on at least a portion of a surface of said compliant layer and comprises at least one material selected from the group consisting of: metal, metal oxide, a ceramic composition, hard polymers, diamond, and diamond-like materials, said film is characterized by a thickness that ranges from about 5 nm to about 300 nm.

21. The article of claim 20, wherein said film comprises Ti0₂.

22. The article of claim 20, wherein said film comprises Sn0₂.

23. The article of claim 20, wherein said compliant layer is an elastomeric polymer being one or more polymers selected from the group consisting of: polydimethylsiloxane (PDMS), polybutadiene, silicone rubber, and any copolymer thereof.

24. The article of claim 23, wherein said elastomeric polymer is PDMS.

25. The article of claim 20, wherein said substrate is one or more materials selected from the group consisting of: polyethylene, silicon, kapton, PDMS, polycarbonate (PC), wherein said substrate is other than said compliant layer.

26. The article of claim 25, wherein said PDMS is at least partially hydroxylated.

27. The article of any one of claim 18-26 or the composition of any one of claims 11 to 18, wherein said compliant layer is characterized as having Young's modulus that ranges from about 10 MPa to 50 MPa.

28. The article of any one of claim 18-26 or the composition of any one of claims 11 to 18, being characterized by reduced friction coefficient relative to a solid body, said reduced friction coefficient being at least 30% lower than a friction coefficient of a control material relative to said solid body.

29. The article of any one of claim 18-26 or the composition of any one of claims 11 to 18, being characterized by reduced wear volume of at least 30 % lower than a wear volume of a control material.

30. The article of any one of claim 18-26 or the composition of any one of claims 11 to 18, being characterized by atomic force microscopy (AFM) with diamond- coated AFM tip of radius of approximately 150 nm as capable to withstand scratch by loads of up to about 20 μΝ.

31. The article of any one of claim 18-26 or the composition of any one of claims 11 to 18, being characterized by low optical absorption and high transparency in the visible light range.

32. The article of any one of claim 18-26 or the composition of any one of claims 11 to 18, being identified as having wear resistance capabilities.

33. The article of any one of claims 18-32, selected from the group consisting of: an electronic device, an optical device, a medical device and a mechanical device.

34. The article according to claim 33, wherein the electronic device is selected from the group consisting of: hard disk, an electronic circuit component, LED, touch screen and a large area display array.

35. The article according to claim 33, wherein the optical device is selected from the group consisting of lens, eye glasses, and microscope.

36. The article according to claim 33, wherein the medical device is an orthopedic implant.

37. The article according to claim 33, wherein the mechanical device is selected from the group consisting of: cylinder liner, cylinders, gear, switch, including devices fabricated by Micro-Electro Mechanical Systems (MEMS) or Nano-Electro Mechanical Systems (NEMS) techniques and 3-D printing.