Device having a switchable wet-dry lubricating coating

Abstract

A lubricating coating including at least one polymer A, a cross-linker and at least one lubricating agent, and wherein a portion of the at least two reactive groups of the cross-linker are covalently linked to the polymer A to form a three-dimensional network in which the lubricant is incorporated, and wherein at the same time another portion of the reactive groups of the cross-linker are covalently linked to the surface of the device or to the optional adhesion layer on the surface of the device.

Claims

1. A device comprising a lubricating coating directly on its surface for use in wet and dry conditions, wherein the lubricating coating comprises i. at least one polymer A selected from the group consisting of polyvinylpyrrolidone (PVP), linear or branched polyethyleneglycol (PEG), dextran, polyalkyloxazolines (PAOXA), poly(2-methyl-2-oxazoline) (PMOXA), poly(ethyl-oxazoline) (PEOXA), hyaluronic acid, polyvinylalcohol (PVA), poly(2-hydroxyethyl methacrylate) (pHEMA), poly(1-vinylpyrrolidone-co-styrene), poly(1-vinylpyrrolidone)-graft-(1-triacontene), poly(1-vinylpyrrolidone-co-vinyl acetate), poly(ethylene-co-vinyl alcohol), poly(ethylene-co-vinyl-pyrrolidone), poly(maleic acid), poly(ethylene-co-maleic acid), polyacrylic acid, poly(acrylamide), poly[N-(2-hydroxypropyl) methacrylamide] (PHPMA), poly(N-isopropylacrylamide) (PNIPAM), poly[(organo)phosphazenes], chitosan and its derivatives, xantham gum, starch, pectin, algin, agarose, cellulose and its derivatives or a mixture thereof, ii. at least one cross-linker comprising a core and at least two reactive groups, wherein: the core is selected from the group consisting of polyallylamine (PAAm), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), polyethyleneimine (PEI), polylysine (PLL), polyacrylic acid (PAA), polyvinylalcohol (PVA), polyaspartic acid, dextran, chitin, chitosan, agarose, albumin, fibronectin, fibrinogen, keratin, collagen, lysozyme and multivalent molecules having less than 20 carbon atoms, the reactive groups are each independently selected from the group consisting of ##STR00007##  and mixtures thereof, wherein: R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are, independently from one another, H, F or Cl; R.sub.5 and R.sub.5′ is independently methyl, ethyl, propyl, isopropyl or dimethylamine and n is 0 to 4, and R.sub.6 and R.sub.6′ is independently methyl, ethyl, propyl, isopropyl or dimethylamine and m is 0 to 4, and the core is linked to the reactive group by a linker group B selected from the group consisting of a secondary or tertiary amine, an ether, a thioether, a carboxylic acid ester, an amide and a thioester, and iii. at least one lubricant which is a synthetic oil or at least one member selected from the group consisting of an edible oil, a fat from plants, a fat from animals, a lipid and a hyaloronate, wherein: a portion of the at least two reactive groups of the cross-linker are covalently linked to the polymer A to form a three-dimensional network in which the lubricant is incorporated, and at the same time another portion of the reactive groups of the cross-linker are covalently linked to the surface of the device.

2. The device according to claim 1 wherein the core of the at least one cross-linker is polyallylamine (PAAm), polyvinylpyrrolidone (PVP) or polyethyleneimine (PEI).

3. The device according to claim 1, wherein the core of the at least one cross-linker is a multivalent molecule having less than 20 carbon atoms.

4. The device according to claim 1, wherein the device is a medical device.

5. The device according to claim 1, wherein the coating comprises at least two different cross-linkers.

6. The device according to claim 1, wherein the cross-linker is selected from the group consisting of polyethyleneimine-grafted-perfluorophenylazide (PEI-g-PFPA), tris(2-PFPA-aminoethyl)amine and 2,2′-(ethylenedioxy)bis(ethylamine-PFPA).

7. The device according to claim 1, wherein the three-dimensional network further comprises a fluorescent marker.

8. The device according to claim 1, wherein the coating is free from UV-radical initiators.

9. A method for producing a device according to claim 1, by a. preparing a coating formulation comprising the at least one polymer A, the at least one cross-linker and at least one solvent, b. applying the coating on the surface of the device, c. forming a three-dimensional network and simultaneously linking the network to the surface of the device by radiation or/and by heat, wherein the lubricant which is a synthetic oil or at least one member selected from the group consisting of an edible oil, a fat from plants, a fat from animals, a lipid and a hyaloronate is added to the coating formulation or after the formation of the three-dimensional network.

10. The method according to claim 9, wherein the coating formulation comprises the lubricant.

11. The method according to claim 9, wherein the coating is applied by jetting, spraying, dip-coating, printing, painting or filling and emptying.

12. A method comprising operating the device according to claim 1 in dry and in wet conditions.

13. A device comprising a lubricating coating directly on its surface for use in dry conditions, wherein the lubricating coating comprises i. at least one polymer A selected from the group consisting of polyvinylpyrrolidone (PVP), linear or branched polyethyleneglycol (PEG), dextran, polyalkyloxazolines (PAOXA), poly(2-methyl-2-oxazoline) (PMOXA), poly(ethyl-oxazoline) (PEOXA), hyaluronic acid, polyvinylalcohol (PVA), poly(2-hydroxyethyl methacrylate) (pHEMA), poly(1-vinylpyrrolidone-co-styrene), poly(1-vinylpyrrolidone)-graft-(1-triacontene), poly(1-vinylpyrrolidone-co-vinyl acetate), poly(ethylene-co-vinyl alcohol), poly(ethylene-co-vinyl-pyrrolidone), poly(maleic acid), poly(ethylene-co-maleic acid), polyacrylic acid, poly(acrylamide), poly[N-(2-hydroxypropyl) methacrylamide] (PHPMA), poly(N-isopropylacrylamide) (PNIPAM), poly[(organo)phosphazenes], chitosan and its derivatives, xantham gum, starch, pectin, algin, agarose, cellulose and its derivatives or a mixture thereof, ii. at least one cross-linker comprising a core and at least two reactive groups, wherein: the core is selected from the group consisting of polyallylamine (PAAm), polyethylene glycol (PEG), polyvinylpyrrolidone (PVP), polyethyleneimine (PEI), polylysine (PLL), polyacrylic acid (PAA), polyvinylalcohol (PVA), polyaspartic acid, dextran, chitin, chitosan, agarose, albumin, fibronectin, fibrinogen, keratin, collagen, lysozyme and multivalent molecules having less than 20 carbon atoms, the reactive groups are each independently selected from the group consisting of ##STR00008##  and mixtures thereof, wherein: R.sub.1, R.sub.2, R.sub.3 and R.sub.4 are, independently from one another, H, F or Cl; R.sub.5 and R.sub.5′ is independently methyl, ethyl, propyl, isopropyl or dimethylamine and n is 0 to 4, and R.sub.6 and R.sub.6′ is independently methyl, ethyl, propyl, isopropyl or dimethylamine and m is 0 to 4, and the core is linked to the reactive group by a linker group B selected from the group consisting of a secondary or tertiary amine, an ether, a thioether, a carboxylic acid ester, an amide and a thioester, and iii. at least one lubricant which is a synthetic oil or at least one member selected from the group consisting of an edible oil, a fat from plants, a fat from animals, a lipid and a hyaloronate, wherein: a portion of the at least two reactive groups of the cross-linker are covalently linked to the polymer A to form a three-dimensional network in which the lubricant is incorporated, and at the same time another portion of the reactive groups of the cross-linker are covalently linked to the surface of the device.

14. A method comprising operating the device according to claim 13 in dry conditions.

15. The device according to claim 1, wherein the lubricant is the edible oil.

16. The device according to claim 1, wherein the lubricant is the fat from plants.

17. The device according to claim 1, wherein the lubricant is the fat from animals.

18. The device according to claim 1, wherein the lubricant is the lipid.

19. The device according to claim 1, wherein the lubricant is the hyaloronate.

20. The device according to claim 1, wherein the cellulose derivatives comprise at least one selected from the group consisting of cellulose esters, cellulose ethers, hydroxypropylmethyl cellulose (HPMC), and hydroxyethyl cellulose (HEC).

21. The device according to claim 13, wherein the cellulose derivatives comprise at least one selected from the group consisting of cellulose esters, cellulose ethers, hydroxypropylmethyl cellulose (HPMC), and hydroxyethyl cellulose (HEC).

Description

(1) The accompanying drawings illustrate embodiments of the devices according to the present invention, explain some results together with the description and serve to explain the principles of the present disclosure.

(2) FIG. 1a and FIG. 1b show a schematic view of the present invention.

(3) FIG. 2a and FIG. 2b show a schematic view of another embodiment of the present invention

(4) FIG. 3 shows the coefficient of friction as a function of castor oil concentration in the coating formulation

(5) FIG. 4 shows the coefficient of friction as a function of wear cycles

(6) FIG. 5 shows the coefficient of friction as a function of coating thickness

(7) FIG. 6 shows the coefficient of friction as a function of percentage of PEG in water as viscosity modifier.

(8) FIG. 7 shows the coefficient of friction after 100 cycles as a function of solution viscosity

(9) FIG. 8 shows the coefficient of friction of coated and uncoated silicone-hydrogel lens.

(10) FIGS. 1a and 1b show a schematic view of the present invention. On the surface (5) of the device (10) is an optional adhesion layer (15). On said optional adhesion layer is a coating (20) which comprises at least a polymer A, at least one cross-linker and a lubricant (30). The polymer A and the cross-linker form a three-dimensional network (25) which is covalently attached to the optional adhesion layer (15) of the device or directly to the device surface. The lubricant (30) is incorporated in the three-dimensional network (25). In dry, ambient conditions the lubricant is incorporated in the three-dimensional network and forms under pressure a lubricating film on the surface of the coating (FIG. 1a). In wet condition, that is in water, water from the outer environment migrates into the three-dimensional network and forms a hydrogel surface (35). Under pressure, the water migrates to the surface of the hydrogel and forms a thin film which is responsible for the lubricating effect. Due to the confinement of the water in the hydrogel (35) it is not directly mixed with the water of the outer environment (40) (FIG. 1b).

(11) FIGS. 2a and 2b show a schematic view of further embodiment of the present invention. On the surface (5) of the device (10) is an optional adhesion layer (15). On said optional adhesion layer is a coating (20) which comprises at least a polymer A, at least one cross-linker. The polymer A and the cross-linker form a three-dimensional network (25) which is covalently attached to the optional adhesion layer (15) of the device or directly to the device surface. In wet condition, that is in water (40) which additionally comprises the lubricant (30), water and the lubricant from the outer environment migrate into the three-dimensional network and form a lubricant-hydrogel surface (35). Under pressure, the water and the lubricant migrate to the surface of the hydrogel and form a thin film which is responsible for the lubricating effect (FIG. 2b). In dry, ambient conditions the lubricant stays incorporated in the three-dimensional network and forms under pressure a lubricating film on the surface of the coating (FIG. 2a).

EXAMPLES

Example 1: Preparation of a Polyethyleneimine-Grafted-Perfluorophenylazide (PEI-g-PFPA) Stock Solution for Use as a Macromolecular Cross-Linker

(12) ##STR00003##

(13) A solution of branched polyethyleneimine (PEI, for example Aldrich 408727 average Mw 25,000 g/mol) in ethanol with a concentration of 100 mg/mL is prepared. 16.3 mL of this solution are placed inside a brown glass bottle with a magnetic stir bar. 2.09 g of perfluorophenylazide-N-hydroxy-succinimide (PFPA-NHS) are dissolved in a second bottle in 283.7 mL of ethanol. This PFPA-NHS solution is slowly added to the vigorously stirred PEI solution and stirred for more than 5 h at room temperature to obtain a PEI-g-PFPA stock solution with a nominal grafting ratio of ethyleneimine monomers to PFPA of 6 and a concentration of mg/mL. The grafting ratio of this polymer can be adjusted by varying the ratio of PEI to PFPA to tune the distance between crosslinking positions. Grafting ratios between 4 and 100 can be easily prepared. Higher concentrations are possible by reducing the amount of solvent in the synthesis or by evaporation.

Example 2: Preparation of a Polyethyleneimine-Grafted-Salicylic Acid (PEI-g-Salicylate) Stock Solution as Radical Quencher (Stabilizer) and Fluorescent Marker

(14) ##STR00004##

(15) A solution of branched polyethyleneimine (PEI, for example Aldrich 408727 average Mw 25,000 g/mol) in ethanol with a concentration of 100 mg/mL is prepared. 7.57 mL of this solution are placed inside a brown glass bottle with a magnetic stir bar. 0.413 g of salicylate-N-hydroxy-succinimide (salicylate-NHS) are dissolved in a second bottle in 92.4 mL of ethanol. This salicylate-NHS solution is slowly added to the vigorously stirred PEI solution and stirred for more than 5 h at room temperature to obtain a PEI-g-salicylate stock solution with a nominal grafting ratio of ethyleneimine monomers to salicylate of 10 and a concentration of 10 mg/mL. The grafting ratio of this polymer can be adjusted by varying the ratio of PEI to salicylic acid to tune the distance between fluorophore positions. Grafting ratios between 4 and 100 can be easily prepared. This polymer is fluorescent with an emission wavelength of 400 nm. Salicylic acid also has a high reaction rate with hydroxyl free radicals and acts therefore as stabilizer for the coating formulation.

Example 3: Preparation of a Tris(2-PFPA-Aminoethyl)Amine as Cross Linker

(16) ##STR00005##

(17) Tris(2-aminoethyl)amine is dissolved in dichloromethane and 3.1 eq of perfluorophenylazide-N-hydroxy-succinimide (PFPA-NHS) are added to this solution. The mixture is stirred for 24 h. The product precipitates as a white powder that is filtered, washed with a small amount of cold dichloromethane and dried.

Example 4: Preparation of a 2,2′-(ethylenedioxy)bis(ethylamine-PFPA) Solution as Small Uncharged Cross-Linker

(18) ##STR00006##

(19) 2.5 mL of 2,2′-(ethylenedioxy)bis(ethylamine) (10 mg/mL in ethanol, 0.171 mmol) and 113.8 mg perfluorophenylazide-N-hydroxy-succinimide (PFPA-NHS) are stirred overnight and diluted with 17.4 mL of ethanol to obtain a solution of 2,2′-(ethylenedioxy)bis(ethylamine-PFPA) which is used without further purification.

Example 5: Production of Coating Formulations Containing a Lubricant, PVP Matrix and PEI-g-PFPA as Cross-Linker

(20) A solution of high molecular weight polyvinylpyrrolidone (PVP K94, Aldrich 437190) in ethanol, ethylacetate (or any other solvent where PVP is soluble) is prepared. This solution can be mixed with different amounts of PEI-g-PFPA (10 mg/mL) (Example 1) as cross-linker, a lubricant containing solution and ethanol, ethylacetate (or any other solvent where PVP and the other components are soluble) to obtain coating formulations that have different viscosities depending on total concentration and lead to different crosslink densities and various amounts of confined lubricant after curing of the applied coating.

(21) The following lubricants were tested: Soy bean oil (Soy bean) silicone oil (Si 1000 cst) silicone oil (Si 10000 cst) silicone paste (Si HS—N) from momentive (Si HS—N) poly-alpha-olefin (PAO) Castor oil (CO)

(22) TABLE-US-00001 TABLE 1 Examples of solutions prepared as described in Example 5. Solu- TopCoat Solvent Ethanol tion OIL TopCoat Solvent Percentage (wt %) A SOY 25 mg/ml PVP, EA 62.5 BEAN PVP: OIL = 0.6, PVP: HVE = 5 B Si 1000 15 mg/ml PVP, EA 37.5 cst PVP: OIL = 0.6, PVP: HVE = 5 C Si 10000 12.5 mg/ml PVP, EA 31.25 cst PVP: OIL = 0.6, PVP: HVE = 5 D Si HS—N 9.375 mg/ml PVP, EA 23.4375 PVP: OIL = 0.6, PVP: HVE 5 E PAO 25 mg/ml PVP, EA 62.5 PVP: OIL = 0.6, PVP: HVE = 5 F CO 25 mg/ml PVP, Ethanol 100 PVP: OIL = 0.6, PVP: HVE = 5 (Abbreviations EA: ethylacetate; HVE: PEI-g-PFPA; PVP: polyvinylpyrrolidone)

Example 6: Coating of Injection Needles

(23) Stainless steel, hypodermic needles (G19, 1-½″) were cleaned by oxygen plasma and coated with HVE primer as applied by spray coating from a 1 mg/ml in ethanol solution to form an adhesion layer. Coating solutions as described in Example 5 A-F were applied by spray coating on top of the primer layer. Coatings were cured by exposure to deep UV radiation (3-4 mW/cm.sup.2 flux at 254 nm) for 15 min.

Example 7: Friction Testing of Coated Injection Needles in Wet and Dry Conditions

(24) The frictional properties of the coated needles in Example 6 were tested by means of micro tribometry (BASALT MUST, Tetra) and penetration through a skin mimic polyurethane (PU) foil (DEKA PU 0.4 mm thick). For tribometry testing, the needles were mounted in a 3D printed sample holder and fixed with a luer lock. A cylindrical counter surface made from poly dimethyl siloxane (elastic modulus ˜2 MPa) was slid against the needle in a cross cylinder configuration at different normal loads between 400-1400 mN to extract the coefficient of friction (slope of frictional to normal forces). Additionally, to extract the wear resistance of the coating, the PDMS pin was slid back and forth over the needle at ˜1200 mN normal load for 50 cycles while recording the frictional force. The experiment was conducted in the following sequence: 1. Coefficient of friction determination in the dry state 2. Wear resistance in the dry state 3. Wear resistance in the dry state for 10-20 cycles after which phosphate buffered saline was added to the sample holder to record the transition in friction when going from dry to wet state. 4. Coefficient of friction determination in the wet state.

(25) Coefficient of friction wet and dry for the different coatings are measured. An uncoated needle was also measured, which had high friction and high adhesion to the counter surface. All coatings, except PAO, had reduced friction dry compared with the uncoated needle. All coatings had low CoF when immersed in PBS.

(26) The frictional properties were further evaluated by measuring the force necessary to penetrate, and maintain motion through, a PU DEKA foil. The needle was mounted on a fixed force gauge (PCE-LFG 20, PCE instruments), and the PU foil suspended on a linear motion drive moving at 1 mm/s. The force was recorded both during insertion and withdrawal of the needle. The penetration phase was conducted dry, and during the withdrawal, the needle was wetted. An uncoated needle was measured and compared to coated ones. All coatings reduced the friction force dry compared to the uncoated needle, and castor oil, soybean oil and PAO had low forces in the wetted stage.

Example 8 Determining the Lubricant Capacity of PVP/PEI-g-PFPA Coatings

(27) The solutions 1-6 (see Table 2) with increasing amounts of castor oil as lubricant content were prepared.

(28) TABLE-US-00002 TABLE 2 Examples of different coating formulations prepared as described in Example 5. conc. of conc. of conc. of PVP to castor oil solution PEI-g-PFPA PVP lubricant PEI-g-PFPA to PVP no. [mg/mL] [mg/mL] [mg/mL] m/m ratio ratio 1 0.5 25 0 50 0 2 0.5 25 12.5 50 0.5 3 0.5 25 25 50 1 4 0.5 25 50 50 2 5 0.5 25 75 50 3 6 0.5 25 100 50 4

(29) These solutions were spin-coated onto glass slides and cured for 2 min with UV-C (254 nm, 3.5 mW/cm.sup.2). A clean aluminium foil is placed on the coating and slowly peeled off. Coatings with a ratio of castor oil to PVP below 2 (solutions 1-4) did not leave visible oil traces on the foil, while coatings with higher castor oil content left oil residues on the aluminium foil (solutions 5-6). A coating which does not leave oil traces on touching surfaces is preferred.

Example 9: Single Use Razor-Blade Plastic Casing

(30) Razor blade casings were plasma cleaned for 2 min, and coated according to any of the three coating strategies outlined in Table 3. Primer solution I: 0.1 mg/ml PEI-g-PFPA in ethanol and II: 5 mg/ml PEI-g-PFPA in ethanol. After coating with primer solution II, the primer was cured for 4 min at 3.7 mW/cm.sup.2 UV flux at 254 nm. Topcoat was applied by spray coating. After drying, the coating was cured for 5 min at 3.7 mW/cm.sup.2 UV flux at 254 nm.

(31) The tactile feeling of Coating No. 3 when dry was smooth and lubricious without being oily or greasy. All coatings were lubricious when immersed in water.

(32) TABLE-US-00003 TABLE 3 Coating formulations and strategies for razor blade casings. Adhesion layer UV curing Lubrication coating after conc. of conc. of PVP to castor oil Coating Adhesion primer PEI-g-PFPA conc. of lubricant PEI-g-PFPA to PVP no. layer (Y/N) [mg/mL] PVP [mg/mL] [mg/mL] m/m ratio ratio 1 I N 1 10 0 10 0 2 II Y 1 10 0 10 0 3 I N 2 10 6 5 0.6

Example 10: Coating of Pen Needles by Dip-Coating

(33) Uncoated stainless steel pen needles (clickfine 31G× 5/16″, 0.25×8 mm) are used for the coating experiments. The needles are coated according the following procedure: 1.2 minutes' oxygen plasma 2. Dip in PEI-g-PFPA (0.1 mg/mL in ethanol) solution for 10 sec to form an adhesion promoting layer 3. Dip in coating formulation according Table 4 for 10 sec 4. Dry in air 5. UV-C illuminate for 2 minutes in case of PVP coatings

(34) TABLE-US-00004 TABLE 4 Examples of coating formulations used for pen needle coatings. matrix Matrix to Coating crosslinking lubricant no. description Matrix chemistry lubricant ratio 1 PVP only PVP PEI-g-PFPA none — 2 HVE only none none none — 3 castor oil only none none castor oil — 4 PVP + 50% PVP PEI-g-PFPA castor oil 2:1 castor oil

Example 11: Injection Force Measurements of Coated Pen Needles

(35) Injection force was measured by injection of the needle into a 0.40 mm PU test foil while measuring the force with a Zwick Z2.5 force gauge. The results for the different coated needles are listed in Table 5 and compared to a standard siliconized Clickfine reference. Only for the coating where the matrix is combined with the lubricant castor oil (5) low values as for a siliconized reference needle can be obtained for dry friction. PVP only or PHEMA only as well as cross-linker only or castor oil only leads to higher friction values. PVP containing castor oil based coatings resist gamma sterilisation.

(36) TABLE-US-00005 TABLE 5 Maximal injection force (Fmax) and average friction force (Fmid) for different coated clickfine pen needles. Coating Fmax Injection Fmid Friction no. Coating (N) (N) — Clickfine (Reference 0.52 ± 0.08 0.27 ± 0.07 siliconized) 1 PVP only 1.55 ± 0.13 1.39 ± 0.10 2 PHEMA only 1.48 ± 0.10 1.25 ± 0.05 3 HVE only 1.02 ± 0.06  0.59 ± 0.071 4 Castor oil only 0.85 ± 0.03 0.24 ± 0.04 5 PVP + 50% castor oil, 0.68 ± 0.06 0.22 ± 0.03 HVE 5 PVP + 50% castor oil, 0.77 ± 0.06 0.19 ± 0.04 HVE - gamma sterilized

Example 12: Influence of Composition on CoF (Ratio PVP:PEI-g-PFPA:Castor Oil) and Wear

(37) To optimize the coating properties in terms of slipperiness (both wet and dry) and the dry appearance (not oily) several coating formulations were prepared as shown in Table 6. Polyester cover slips (Thermanox) were plasma cleaned for 2 min, and spray coated with coating formulations shown in Table 6. Coatings were cured under UV for 2 min at 3-4 mW/cm.sup.2 UV flux at 254 nm. The appearance of the coatings was tested by placing a piece of aluminum foil on the sample, which was firstly pressed down with a pressure of approximately 26 MPa and then removed from the disk surface. The oiliness was qualitatively judged by ranking the amount of oil transferred from the coating to the foil. Coatings started to become oily above a Castor oil to PVP ratio of 0.6.

(38) The frictional properties were evaluated in three different positions on each sample, first in the dry state, and in phosphate buffered saline. The coefficient of friction was calculated from a normal force ramp between 400-1200 mN against a PDMS pin with radius 2.5 mm. The results are shown in FIG. 3. The CoF when dry was very high with <3 mg/ml CO, and decreased until 10 mg/ml, after which the CoF was steadily below 0.04.

(39) Additionally, the Solution No. 4-6 were tested for wear resistance in the dry state. The PDMS pin was slid back and forth 50 times whilst continuously recording the friction force, see FIG. 4. With increasing amount of CO in the coating formulation, the wear resistance of the coating increases.

(40) TABLE-US-00006 TABLE 6 Prepared coating formulations. conc. of conc. of conc. of PVP to Castor oil Solution PEI-g-PFPA PVP lubricant PEI-g-PFPA to PVP no. [mg/mL] [mg/mL] [mg/mL] m/m ratio ratio 1 5 25 0 5 0 2 5 25 1.5 5 0.06 3 5 25 2 5 0.08 4 5 25 3 5 0.12 5 5 25 5 5 0.2 6 5 25 10 5 0.4 7 5 25 15 5 0.6 8 5 25 20 5 0.8

Example 13: Influence on Coating Thickness on Dry Lubricity

(41) To evaluate the influence of coating thickness on CoF, a series of solutions were prepared having the same ratios of matrix:cross-linker:lubricant, but at different absolute concentrations, see Table 7. The thickness for the coating No 2 was approximately 500 nm, and for coating No 3, 1500 nm. The CoF was evaluated dry against PDMS pin (R=2.5 mm) between 400-1200 mN, see FIG. 5. No influence on coating thickness down to at least 500 nm could be detected.

(42) TABLE-US-00007 TABLE 7 Prepared coating formulations. conc. of conc. of conc. of PVP to Castor oil Solution PEI-g-PFPA PVP lubricant PEI-g-PFPA to PVP no. [mg/mL] [mg/mL] [mg/mL] m/m ratio ratio 1 1 5 2 5 0.4 2 2 10 4 5 0.4 3 5 25 10 5 0.4 4 10 50 20 5 0.4

Example 14: Production of Coating Formulations with Different Ratios of Hydrophilic Polymer and Cross-Linker where Lubricant can be Added after Curing

(43) A solution of high molecular weight polyvinylpyrrolidone (PVP K94, Aldrich 437190) in ethanol with a concentration of 200 mg/mL is prepared. This solution can be mixed with different amounts of PEI-g-PFPA (10 mg/mL), PEI-g-salicylate (10 mg/mL) and ethanol to obtain coating formulations that have different viscosities depending on total concentration and lead to different crosslink densities and fluorescent properties after curing of the applied coating. Table 8 provides a few examples of solutions prepared this way.

(44) TABLE-US-00008 TABLE 8 Examples of different coating formulations in ethanol prepared as described in Example 14 without containing an additional lubricant conc. of PEI-g- PEI-g-PFPA conc. of salicylate solu- [mg/mL] conc. of PEI-g- PVP to to PEI-g- tion grafting PVP salicylate PEI-g-PFPA PFPA no. ratio = 6 [mg/mL] [mg/mL] m/m ratio m/m ratio 1 1 50 — 50 2 0.5 25 — 50 3 0.2 10 — 50 4 2.5 50 — 20 5 1.25 25 — 20 6 0.5 10 — 20 7 5 50 — 10 8 2.5 25 — 10 9 1 10 — 10 10 10 50 — 5 11 5 25 — 5 12 2 10 — 5 13 0.5 25 2.5 50 5 14 0.375 18.75 1.875 50 5 15 0.75 37.5 3.75 50 5 16 0.75 37.5 0 50 0 17 0.375 18.75 1.875 50 5 18 0 18.75 1.875 19 0.75 18.75 1.875 25 2.5 20 0.75* 18.75 1.875 25 2.5 21 0.25 12.5 1.25 50 5 22 0.2 10 1 50 5 23 0.125 6.25 0.625 50 5 *grafting ratio of PEI-g-PFPA is 12

Example 15 Tribological Performance of Coatings with Low Molecular Weight PEG in the Liquid as Viscosity Modifier in Harsh Contact Conditions (150 MPa Contact Pressure)

(45) Silicon wafers (2×1 cm) were sonicated (2×10 min Toluene, 2×10 min IPA), rinsed and dried with a stream of nitrogen. Subsequently samples were spray coated with solution 2 of Table 8. Dry film thickness of 80 and 200 nm were produced by application of different amounts of coating formulation.

(46) The covalent attachment and cross-linking was triggered by activating the PFPA by UV irradiation (2 min, lambda=254 nm, 800 μW/cm2). The coated samples were rinsed with pure water thereafter to remove potentially unbound species.

(47) Coated samples were evaluated with respect to coefficient of friction during tribological testing. Ratio of water and PEG (400 g/mol) confined in the coating was varied between 0 and 100%, with 0 being pure water and 100% being pure PEG (FIG. 6).

(48) Specifically, the time-scales associated with the onset of wear are controlled by the design of the coating in terms of poroviscoelastic properties (mesh size, permeability, modulus, viscosity, thickness) with respect to the final contact conditions it is exposed to. FIG. 7 shows how adjusting the viscosity of the solution allows one to adapt the squeeze-out time of the coating to match the migration time of the tribological contact.

Example 16 Application of an Optional Adhesion Layer on a Single Use Polypropylene Intraocular Lens Delivery Device for Cataract Surgery (PP IOL Device)

(49) Samples are treated with oxygen plasma for 8 minutes and dipped in a solution of PEI-g-PFPA in ethanol with a concentration of 0.5 mg/mL for 3 minutes. The samples are dried by spinning in a centrifuge and stored in the dark until further coating.

Example 17 Application of Coating Formulation Inside a PP IOL Device

(50) Devices, with or without optional adhesion layer, are coated by filling and emptying with solution 14 of Table 8 leaving behind a thin film of the coating formulation inside the device that its air dried. Alternatively, the coating can be applied by jetting, spraying, dip-coating printing or painting.

Example 18 Curing of Applied Coatings Inside a PP IOL Device

(51) Devices are placed in a UV-C chamber at an intensity of 6 mW/cm.sup.2 for 2-12 minutes. Optionally, in case the material is stable, samples can be cured thermally at a temperature above 120° C. for 1 hour or 160° C. for 5 minutes.

(52) Samples can be optionally washed by immersion in water to remove non-bound parts of the coating. Increasing the UV illumination time reduces the loss of unbound polymer after rinsing. Also, particles generated during injection of the intraocular lens are reduced.

Example 19 Testing Injection Force of Coated PP IOL Device

(53) Implant lenses were placed together with a drop of water containing a lubricant (sodium hyaluronate) into the channel of the device and then injected through the device, while recording the injection force. A significant reduction of the maximum force needed compared to uncoated devices is measured when coating formulation 14 of Table 8 is used. CoF slightly increases with increasing illumination time (10 versus 3 minutes). Without PEI-g-PFPA (solution 18 of Table 8), the coating does not adhere to the surface and injection force is as high as for the uncoated sample. Reducing the coating thickness reduces the lubricity (solution 23 versus solution 14 of Table 8).

Example 20 Coating of Soft Contact Lenses

(54) Silicone-hydrogel contact lenses were rinsed in ultra-pure water, and mounted on a rounded sample holder with the same internal diameter as the lens. The lens was dried with a stream of N.sub.2 gas. An adhesion primer of PEI-g-PFPA was sprayed over the entire lens surface from a 0.1 mg/ml dilution in ethanol. A coating formulation having 10 mg/ml PVP, and 1 mg/ml of cross-linker described in solution 9 of Table 8 in ethanol was applied by spray coating over the entire lens surface. After drying, the coating was cured for 2 min at 3-4 mW/cm.sup.2 UV flux at 254 nm. Lenses were immersed in phosphate buffered saline over night at 4° C. Friction testing of coated and uncoated lenses were performed using a a simulated tear solution described in Sterner, O.; Aeschlimann, R.; Zürcher, S.; Lorenz, K. O.; Kakkassery, J.; Spencer, N. D.; Tosatti, S. G. P. Friction Measurements on Contact Lenses in a Physiologically Relevant Environment: Effect of Testing Conditions on FrictionFriction Measurements on Contact Lenses. Investigative Ophthalmology & Visual Science 2016, 57 (13), 5383-5392. This solution is containing different lipids and mucin as in natural tears and acts as a viscosity modifier and lubricant.

(55) CoF values for coated and uncoated lenses are shown in FIG. 8. The coated lens had a 10 times reduction in CoF compared with the uncoated lens.