Process for preparing an organic film at the surface of a solid support by transfer or by spraying

Abstract

A method is provided for preparing an organic film on the surface of a solid support including the steps of (a) applying, to the surface, by transfer or by spraying, a solution containing at least one cleavable aryl salt; and (b) subjecting the solution to a UV or visible irradiation, such that irradiation radical entities are formed from the cleavable aryl salt and an organic film is grafted. Further provided is a kit of elements for the implementation of such a method.

Claims

1. A method for preparing an organic film on the surface of a solid support by radical chemical grafting, comprising: a) applying onto said surface, by transfer or by spraying, a solution containing at least one salt of aryl diazonium, a photosensitizing agent, and a sacrificial electron donor, wherein applying by transfer consists of applying or depositing a layer of the solution not exceeding 5 mm thick onto the surface and applying by spraying consists of applying or depositing drops of the solution onto the surface wherein the volume of the drops is between 1 pl and 400 L and b) subjecting said solution to a UV or visible irradiation, by means of which radical entities are formed from the salt of aryl diazonium and an organic film in the form of (co)polymers is grafted to the surface; wherein at least one monomer unit of the (co)polymers constituting the grafted organic film is derived from the salt of aryl diazonium, and wherein said method is performed under ambient air.

2. The method according to claim 1, wherein said application by transfer requires a pen, a paintbrush, a roller, a marker, a pad or a micro-pad.

3. The method according to claim 1, wherein said application by spraying requires an electrostatic spray, a centrifugal spray, an atomiser, a mist-maker, an airbrush and/or a device of the inkjet type.

4. The method according to claim 1, wherein said step (a) is accomplished before said step (b).

5. The method according to claim 1, wherein said steps (a) and (b) are implemented simultaneously.

6. The method according to claim 1, wherein said solution also contains at least one monomer which can be polymerised by radical means, and which is distinct from said salt of aryl diazonium.

7. The method according to claim 6, wherein said solution also contains at least one element selected from the group consisting of a thickening agent, a gelling agent, a surfactant and a cross-linking agent.

8. A method to produce at least one track in which a liquid of interest may flow over a solid support, comprising preparing an organic film which is wettable by said liquid of interest on the surface of said solid support according to a method as defined in claim 6.

9. The method according to claim 1, wherein said solution also contains at least one element selected from the group consisting of a thickening agent, a gelling agent, a surfactant and a cross-linking agent.

10. The method according to claim 1, wherein said steps (a) and (b) are repeated at least two, three, four or five times, enabling a multi-layer structure to be obtained.

11. The method according to claim 1, wherein, prior to application, by transfer or by spraying, of the solution onto the surface of the solid support, the surface is subjected to an oxidising (pre-)treatment.

12. The method according to claim 1, wherein said steps (a) and (b) are followed by a step comprising applying, on the organic film obtained, by transfer or spraying, a suspension of nano-objects.

13. The method according to claim 12, wherein said suspension of nano-objects is a suspension of nanoparticles.

14. The method according to claim 1, wherein said steps (a) and (b) are followed by a step of metallisation.

15. A method to produce at least one track in which a liquid of interest may flow over a solid support, comprising preparing an organic film which is wettable by said liquid of interest on the surface of said solid support according to a method as defined in claim 1.

Description

BRIEF DESCRIPTION OF THE ILLUSTRATIONS

(1) FIG. 1 presents the spectra obtained by Fourier transform infrared spectroscopy (FTIR) of 2 gold plates on which has been sprayed, under ambient air or under nitrogen, a reaction solution containing a salt of aryl diazonium [nitrobenzene diazonium tetrafluoroborate (NBDT)], a monomer which can be polymerised by radical means [HydroxyEthylMethAcrylate (HEMA)] and a chemical initiator (ascorbic acid).

(2) FIG. 2 presents the infrared spectrum of a gold plate on which has been printed by inkjet a reaction solution containing a salt of aryl diazonium [4-nitrobenzene diazonium (NBD)], a monomer which can be polymerised by radical means [Acrylic Acid (AA)] and a complex pair favouring electron transfer made of Ruthenium/Sacrificial Donor, where the radical chemical grafting is initiated by a UV irradiation.

(3) FIG. 3 presents the spectroscopy spectrum of X photoelectrons of the plate treated in accordance with FIG. 2.

(4) FIG. 4 presents the spectra obtained by FTIR of 2 polyethylene terephtalate substrates. The first is a blank PET and the second is a substrate treated under ambient air, by a solution containing a salt of aryl diazonium [NBDT], a monomer which can be polymerised by radical means (AA), a thickening agent (polyacrylic acid), printed by inkjet and irradiated by a desk lamp, and then rinsed in water and dried under nitrogen.

(5) FIGS. 5A and 5B are photographs at different enlargements of a polyethylene terephtalate substrate treated as described for FIG. 4 and then immersed in a reducing solution (NaBH.sub.4 0.1M, NaOH 0.1M, 3 min, 50 C.) and finally a commercially available Electroless bath made of copper (M Copper 85) for 15 min, rinsed in water and dried under nitrogen.

(6) FIG. 6 shows photographs of a polyethylene terephtalate substrate treated by a solution containing a salt of aryl diazonium (NBDT), a monomer which can be polymerised by radical means (AA), a thickening agent (polyacrylic acid), a complex of Ruthenium/Sacrificial Donor (triethylamine) and a copper salt, CuSO.sub.4, 5H.sub.2O, printed by inkjet and irradiated by a desk lamp, and then immersed in a reducing solution (FIG. 6A) followed by a commercially available copper Electroless bath, and finally a Gold Electroless bath, rinsed in water and dried under nitrogen (FIG. 6B).

(7) FIG. 7 is a photograph of a Plexiglas plate measuring 106 cm treated by formulation N 2 as defined at point V below, and then passed under a trickle of water from the tap.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS

I. Preliminary Work Before the Method of the Invention

(8) I.1. Vaporised Solution.

(9) In a beaker fitted with a magnetic stirring bar, 30 ml of deionised water, 4.5 ml of HEMA (1.1M) and 0.225 g of nitrobenzene diazonium tetrafluoroborate (NBDT) (2.7 10.sup.2 M) were poured. Lastly, 0.3 ml of a 0.29 M, i.e. 2.5 10.sup.3 M, solution of recently prepared ascorbic acid is poured into the reaction medium.

(10) I.2. Method Implemented.

(11) This functionalisation solution is rapidly poured into the flask of the spray. The latter and a gold plate previously treated by UV-ozone are placed in a glovebox vented 3 times with nitrogen and inflated with nitrogen.

(12) The reaction solution, which is under pressure in the spray, is sprayed onto the plate held in an oblique position. The plate, with a fine continuous layer of liquid deposited on the gold surface, is left in a horizontal position in the glovebox for one hour.

(13) Another gold plate is subjected to the same treatment but outside the glove box.

(14) After one hour of reaction the plates are rinsed by water jets, ethanol and acetone, and are then subjected to ultrasound, in the DMF for 2 min, in water, and lastly acetone for 30 s. They are then dried by nitrogen drying before being analysed by FTIR. The FTIR spectra obtained in this manner are represented in FIG. 1.

(15) In ambient air the droplets are in contact with air. The oxygen of the air kills the radicals. Initiation reactions and above all propagation reactions are inhibited. Polymerisation does not occur. Only a few oligomers are synthesised.

II. Procedure for Grafting PAA by Means of Inkjet and UV/Visible Irradiation, Followed by Metallisation on Rigid Substrates of Technical Polymers

(16) II.1 Grafting of PAA.

(17) Firstly, in order to prevent any pollution or contamination by external agents, the substrates used (i.e. ABS, ABS-PC, polyamide (PA), vinyl polychloride (PVC)) are subjected to a rinsing, depending on their nature, in a solvent and/or industrial detergent (TFD4) for 10 min with ultrasound.

(18) This cleaning is completed by a prior oxidising (pre-)treatment by UV/Ozone (UV/O.sub.3) irradiation for 10 min which enables the organic pollutants to be eliminated. For many substrates this UV/Ozone irradiation also induces activation of the surface by oxidisation. This oxidisation leads to an increase of the polarity which causes an increase of the surface energy and therefore a reduction of the contact angle.

(19) The diazonium salts are reduced by irradiation in the UV/Visible spectra for wavelengths notably of 350 to 550 nm.

(20) In addition, to favour the reduction, a ruthenium complex favouring electron transfer and a sacrificial electron donor are added to the reaction medium. The complete system thus contains a diazonium salt/acrylic acid/complex favouring electron transfer made of Ruthenium/Sacrificial Donor.

(21) Thus, 4-nitrobenzene diazonium (NBD; 1.1846 g, 5.Math.10.sup.2 M) was solubilised in a solution of Milli-Q water (100 ml). To this solution, 100 ml of a solution of tris-bipyridine ruthenium (II) chloride (Ru complex; 3.74.Math.10.sup.3 g, 5.Math.10.sup.5 M), 100 ml of AA and 100 ml of triethylamine (TEA, 5.Math.10.sup.2 M) as the sacrificial electron donor are added.

(22) The solution is then deposited directly on the substrate which has been pretreated by various methods. Advantageously this involves inkjet printing, or more simply printing by drop depositing.

(23) The substrate and drops are then irradiated by a UV/visible lamp for a duration of between several seconds to one hour, preferentially from 30 s to 10 min. The samples are then rinsed in succession for 10 min with ultrasound in Milli-Q water, in a 0.1M solution of sodium hydroxide and then once again in Milli-Q water before being dried.

(24) In order to check the grafting of PAA, tests on a gold plate were also undertaken with the same procedure. However, to check the effectiveness of the rinsing, and to ensure that the physisorbed material has been eliminated, the gold substrates were rinsed with additional solvents (Acetone, Ethanol, NaOH and DMF), with ultrasound for 10 min.

(25) The TEA (sacrificial donor)/Ru complex (facilitates the electron transfer) pair enables the reduction of aryl diazonium salt (NBD) to a phenyl radical under the irradiation to be heightened. Without the presence of this pair it is possible to form the film of PAA, but it is slower and metallisation is also possible.

(26) II.2. Characterisation of the deposits of PAA.

(27) This characterisation was undertaken by different methods.

(28) A. Measurement of Contact Angle.

(29) The contact angle was measured on a Dataphysics-OCA15 EC device, fitted with a CCD (Charge-Coupled Device) camera. After grafting of PAA the contact angle falls to around 60.

(30) The results are shown in the Table 1 below:

(31) TABLE-US-00001 TABLE 1 Average of measurements of contact angles for 4 different polymers (ABS, ABS-PC, PA, PVC and gold plate) when blank and after grafting of PAA ABS ABS/PC PA PVC Gold plate Blank 90 81.8 63.2 98 90 Grafting of PAA 65.8 66 63.4 67.2 56

(32) B. Infrared Characterisation.

(33) The infrared spectra were recorded on a Bruker Vertex 70 spectrometer fitted with a Pike-Miracle Attenuated Total Reflection (ATR) accessory. The detector is an MCT. The spectra were obtained after 256 scans with a resolution of 2 cm.sup.1.

(34) Grafting of PAA is confirmed by the analysis by IR spectrometry. Whatever the substrate, the specific bands at 17151732 cm.sup.1 (CO elongation of COOH acid) and 15751592 cm.sup. (CO elongation of the COO carboxylate form) are present (FIG. 2).

(35) C. XPS Characterisation.

(36) The XPS analyses were undertaken with a Kratos Axis Ultra DLD spectrometer, using the monochromatic Al Ka line at 1486.6 eV. The pass energy of the analyser was maintained constant at 20 eV for C.sub.1s, base-level analysis. The photoelectron collection angle is 90 relative to the plane of the sample, which provides for a sampling depth of the integrated probe at 15 nm in the case of a dense substrate.

(37) After grafting of PAA spectrum C.sub.1s is characteristic of the presence of PAA. Indeed, 2 peaks are observed at 289.76 and 285.74 eV, which correspond respectively to the COOH/COO.sup. and CH.sub.2/CH groups of polyacrylic acid (FIG. 3).

(38) II.3. Metallisation.

(39) A. Chelation of the Metal Ions.

(40) Chelation of the Cu.sup.2+ ions is undertaken by immersion for 10 min of the substrate in a copper/ammonia solution ([Cu.sup.2+]=0.1M/[NH.sub.3]=0.6 M) in water. This chelation is followed by a 0.1 M NaOH rinsing for 1 min to eliminate the physisorbed CuSO.sub.4.

(41) B. Reduction of the Metal Ions.

(42) The Cu.sup.2+ ions are reduced by immersion for 10 min of the substrate in a reducing solution of sodium borohydride (NaBH.sub.4=0.1 M) in a solution of sodium hydroxide (0.1 M) at 70 C. This reduction is followed by a 0.1 M NaOH rinsing for 1 min to eliminate the physisorbed material (NaBH.sub.4, NaOH in particular).

(43) C. Electroless Bath.

(44) The growth of the metal layer is accomplished by immersing the substrate in an industrial copper-plating bath, called Electroless, manufactured by the company MacDermid (Reference: M Copper 85 MacDermid). As with all metallisation baths, it is a stable solution at ambient temperature which has a metal cation, in the form of CuSO.sub.4, a reducer (Formaldehyde), a complexing agent and a constant pH (pH=12) adjusted with sodium hydroxide.

(45) The ideal metallisation temperature is 48 C. Spontaneous metallisation may take place only at the surface of the previously deposited copper metal particles. The latter catalyse the dehydrogenation of the reducers and therefore their oxidisation. The reducers and the complexed copper salts are presumed to be adsorbed at the surface of the metal particles. The sphere of coordination of the copper salts is modified and the electrons of the reducer are sent to the copper ions to form the copper in the metal state. The process is then autocatalytic. Nonetheless, the mechanism of this reduction is still widely studied, and many mathematical models are still attempting to explain it.

(46) The immersion time in this bath determines the thickness of the metal layer deposited on the substrate. In the present case, a 15 min immersion is applied to obtain a 1 m layer. The samples are then rinsed in Milli-Q water, with ultrasound, for 10 min, before being dried.

(47) II.4. Test on the Metal Layer.

(48) The mechanical adherence between the metal layer and the substrate was studied by an adhesion test consisting in a quantitative scotch test inspired by standard ASTM D3359 scotch test (strip with transverse cut test). This widely used criterion provides a direct comparison of the adherence of the films obtained under different conditions on similar substrates, and is the test used by industrial companies.

(49) A. Principle.

(50) The adhesion test procedure is accomplished in 4 steps described below:

(51) Step 1: Use of a cutting instrument to establish the test area, namely 16 clearly distinct squares on the surface of the metallised sample.

(52) Step 2: Cleaning of the area of the 16 squares using a paintbrush in the cutting direction.

(53) Step 3: Deposition of a strip of adhesive normalised in the direction of the vertical or transverse cut.

(54) Step 4: After 5 min the adhesive is removed with an angle of 60; the fewer the number of squares torn away the greater the adhesion is.

(55) B. Result.

(56) By taking the example of the PVC grafted with PAA according to the procedure of point 11.1 and metallised according to the procedure of point 11.3, it is observed that no square is torn away after the adhesion test.

III. Procedure for Grafting PAA by Means of Inkjet and UV/Visible Irradiation, Followed by Metallisation on Flexible Substrates of Polyethylene Terephtalate

(57) III.1. Grafting of PAA.

(58) Firstly, in order to prevent any pollution or contamination by external agents, the substrates are subjected to rinsing in industrial detergent (TFD4) for 10 min with ultrasound.

(59) The reduction of the diazonium salts is initially accomplished by irradiation in the visible spectrum through use of a 75 W desk lamp. In a second stage the irradiation is also a source of heat, and probably contributes to the acceleration of the polymerisation of the acrylic acid.

(60) To improve the wettability of the solution sprayed by inkjet onto the substrate, a thickening agent is added to the reaction medium. This is a polymer of polyacrylic acid (PAA, 30,000 g/mol).

(61) Lastly, in preparation for the metallisation, a copper salt is added to this solution. The chelation of the copper ions is thus accomplished at the same time as the grafting of PAA. The reaction solution therefore contains a diazonium salt/acrylic acid/PAA thickening agent/CuSO.sub.4.

(62) 4-nitrobenzene diazonium (NBD; 0.205 g) was solubilised in a solution containing 2 mL of an aqueous acidic solution (0.5 M H.sub.2SO.sub.4), 2 mL of acrylic acid, 130 mg of thickening agent (PAA) and 240 mg of copper salt (CuSO.sub.4, 5H.sub.2O).

(63) The solution is then deposited directly on the substrate by printing by inkjet, through the use of a commercially available printer, EPSON Stylus Photo P50.

(64) The substrate+inkjet deposit is then irradiated by a 75 W desk lamp for a period of 10 min.

(65) The grafting of PAA is confirmed by the analysis by IR spectrometry (FIG. 4).

(66) III.2. Reduction of the Metal Ions.

(67) The Cu.sup.2+ ions are reduced by immersion for 3 min of the substrate in a reducing solution of sodium borohydride (NaBH.sub.4=0.1 M) in a solution of sodium hydroxide (0.1 M) at 50 C. This reduction is followed by a 0.1 M NaOH rinsing for 1 min to eliminate the physisorbed material (NaBH.sub.4, NaOH in particular).

(68) III.3. Electroless Bath.

(69) The growth of the metal layer is accomplished by immersing the substrate in an industrial copper-plating bath, called Electroless, manufactured by the company MacDermid (Ref: M Copper 85 MacDermid). As with all metallisation baths, it is a stable solution at ambient temperature which has a metal cation, in the form of CuSO.sub.4, a reducer (Formaldehyde), a complexing agent and a constant pH (pH=12) adjusted with sodium hydroxide.

(70) The ideal metallisation temperature is 48 C. Spontaneous metallisation may take place only at the surface of the previously deposited copper metal particles. These catalyse the dehydrogenation of the reducers and therefore their oxidisation. The reducers and the complexed copper salts are presumed to be adsorbed at the surface of the metal particles. The sphere of coordination of the copper salts is modified and the electrons of the reducer are sent to the copper ions to form the copper in the metal state. The process is then autocatalytic. Nonetheless, the mechanism of this reduction is still widely studied, and many mathematical models are still attempting to explain it.

(71) The immersion time in this bath determines the thickness of the metal layer deposited on the substrate. In the present case, a 15 min immersion is applied to obtain a 1 m layer. The samples are then rinsed in Milli-Q water, with ultrasound, for 10 min, before being dried.

(72) Photographs of a substrate of polyethylene terephtalate treated in accordance with the procedures of points III.1, III.2 and III.3 are shown in FIGS. 5A and 5B.

(73) III.4. Result of Scotch Test for Adhesion of the Metal Layer.

(74) By carrying out the scotch test inspired by previously described standard ASTM D3359, it is observed that no square is torn away after the adhesion test.

IV. Another Procedure for Grafting PAA by Means of Inkjet and UV/Visible Irradiation, Followed by Metallisation on Flexible Substrates of Polyethylene Terephtalate

(75) IV.1. Grafting of PAA.

(76) Firstly, in order to prevent any pollution or contamination by external agents, the substrates are subjected to rinsing in industrial detergent (TFD4) for 10 min with ultrasound.

(77) The reduction of the diazonium salts is initially accomplished by irradiation in the visible spectrum through use of a 75 W desk lamp. In a second stage the irradiation is also a source of heat, and probably contributes to the acceleration of the polymerisation of the acrylic acid.

(78) In addition, to favour the reduction, a ruthenium complex favouring electron transfer and a sacrificial electron donor are added to the reaction medium.

(79) Secondly, to improve the wettability of the solution sprayed by inkjet on to the substrate, a thickening agent is added to the reaction medium. In this case this is a polymer of polyacrylic acid (30,000 g/mol).

(80) Lastly, in preparation for the metallisation, a copper salt is added to this solution. The chelation of the copper ions is thus accomplished at the same time as the grafting of PAA.

(81) The complete system thus contains a diazonium salt/acrylic acid/complex favouring electron transfer made of Ruthenium/Sacrificial Donor/PAA thickening agent/CuSO.sub.4.

(82) 4-nitrobenzene diazonium (NBD; 0.205 g) was solubilised in a solution containing 2 mL of a solution of tris-bipyridine ruthenium (II) chloride (Ru complex; 5.Math.10.sup.3 M), 2 ml of a solution of triethylamine (TEA, 5.Math.10.sup.2 M) as a sacrificial electron donor, 2 mL of an aqueous acidic solution (H.sub.2SO.sub.4 at 0.5 M), 2 mL of acrylic acid, 130 mg of thickening agent and 240 mg of a copper salt (CuSO.sub.4, 5H.sub.2O).

(83) The solution is then deposited directly on the substrate by printing by inkjet, through the use of a commercially available printer, EPSON Stylus Photo P50.

(84) The substrate+inkjet deposit is then irradiated by a desk lamp for a period of between 30 s and 10 min.

(85) IV.2. Reduction of the Metal Ions.

(86) The Cu.sup.2+ ions are reduced by immersion for 3 min of the substrate in a reducing solution of sodium borohydride (NaBH.sub.4=0.1 M) in a solution of sodium hydroxide (0.1 M) at 50 C. This reduction is followed by a 0.1 M NaOH rinsing for 1 min to eliminate the physisorbed material (NaBH.sub.4, NaOH in particular).

(87) IV.3. Electroless Bath.

(88) In order to obtain a gold coating, the growth of the metal layer is accomplished by means of immersion in two Electroless baths, firstly of copper and then of gold.

(89) Initially, the growth of the metal layer is accomplished by immersing the substrate in an industrial copper-plating bath, called Electroless, manufactured by the company MacDermid (Ref: M Copper 85 MacDermid). As with all metallisation baths, it is a stable solution at ambient temperature which has a metal cation, in the form of CuSO.sub.4, a reducer (Formaldehyde), a complexing agent and a constant pH (pH=12) adjusted with sodium hydroxide.

(90) The ideal metallisation temperature is 48 C. Spontaneous metallisation may take place only at the surface of the previously deposited copper metal particles. The latter catalyse the dehydrogenation of the reducers and therefore their oxidisation. The reducers and the complexed copper salts are presumed to be adsorbed at the surface of the metal particles. The sphere of coordination of the copper salts is modified and the electrons of the reducer are sent to the copper ions to form the copper in the metal state. The process is then autocatalytic. Nonetheless, the mechanism of this reduction is still widely studied, and many mathematical models are still attempting to explain it.

(91) The immersion time in this bath determines the thickness of the metal layer deposited on the substrate. In the present case, a 15 min immersion is applied to obtain a 1 m layer. The samples are then rinsed in Milli-Q water, with ultrasound, for 10 min, before being dried.

(92) In a second stage the growth of a gold layer on the copper-plated substrate is accomplished by immersion in a gold Electroless bath, based on the same principle as the copper Electroless bath. The Electroless bath is manufactured by the company Alfa AESAR, and contains 3.7 g/l of metallic cation. The deposition temperature must be between 60 and 70 C. and the deposition speed is approximately 1 m/h. In the present case, a 30 min immersion is applied to obtain a 0.5 m layer.

(93) FIG. 6 shows photographs of the polyethylene terephtalate treated in accordance with the procedure of point IV.1 (FIG. 6A) and treated in accordance with the procedures of points IV.1, IV.2 and IV.3 (FIG. 6B). In the latter case, the gold plating of the printed tracks is visible.

(94) IV.4. Result of Scotch Test for Adhesion of the Metal Layer.

(95) By carrying out the scotch test inspired by previously described standard ASTM D3359, it is observed that no square is torn away after the adhesion test.

V. Localised Treatment of Plexiglas Surfaces According to the Method of the Invention

(96) This localised treatment of Plexiglas surfaces is implemented by a method of the stencil type, in which areas are masked by a vinyl adhesive. This method enables a localised treatment to be applied reproducing the hollowed-out patterns of the applied stencil.

(97) V.1. Preparation of the Plexiglas Plates.

(98) The Plexiglas support is washed in soapy water, rinsed in water and then dried. It is then cleaned with acetone and then with alcohol, and dried in gaseous nitrogen.

(99) The vinyl mask is bonded to the cleaned surface and the hollowed-out portions of the mask are cleaned with a solution of paratoluene sulfonic acid (0.9 g for 30 ml of water). The hollowed-out portions are then rinsed in water, dried under gaseous nitrogen and ready to be coated by one of the following formulations.

(100) V.2. Tested Formulations.

(101) Three different formulations were tested.

(102) A. 1.sup.st Example of Formulation:

(103) 200 mg of 4-nitrophenyl diazonium tetrafluoroborate are added to an aqueous solution of tris-bipyridine ruthenium (II) chloride hexahydrate (4 ml, 5.Math.10.sup.4 M) and triethylamine (2 ml, 0.1 M). Acrylic acid (2 ml) and acrylic acid-maleic acid copolymer in the form of a sodium salt (200 mg, average mass M=50,000 g.Math.mol.sup.1) are then added to the previous solution.

(104) This formulation is prepared immediately before use to take account of its lack of stability.

(105) B. 2.sup.nd Example of Formulation:

(106) 100 mg of 4-nitrophenyl diazonium tetrafluoroborate are dissolved in 2 ml of deionised water and 1 ml of pure acrylic acid and the solution is thoroughly stirred until complete dissolution. 1 ml of trielyamine (0.1 M) is then added to this solution. After thorough stirring, 50% of glycerol is poured in the 4 ml of the previous solution. The solution is thoroughly stirred and 50 it of a solution of tris-bipyridine ruthenium (II) chloride hexahydrate (5.Math.10.sup.4 M) are added to obtain the final ready-to-use solution.

(107) This formulation is stable for at least one day when stored in darkness.

(108) C. 3.sup.rd Example of Formulation:

(109) 100 mg of 4-nitrophenyl diazonium tetrafluoroborate are dissolved in 2 ml of deionised water and 1 ml of pure acrylic acid and the solution is thoroughly stirred until complete dissolution. 100 mg of acrylic acid-maleic acid copolymer in the form of a sodium salt (average mass M=50,000 g.Math.mol.sup.1) dissolved in 1 ml of trielyamine (0.1 M) are added to this solution. The solution is thoroughly stirred and 50 l of a solution of tris-bipyridine ruthenium (II) chloride hexahydrate (5.Math.10.sup.4 M) are added to obtain the final ready-to-use solution.

(110) This formulation is stable for at least one day when stored in darkness.

(111) V.3. Irradiation of the Mask.

(112) The hollowed-out portions of the vinyl mask are coated with one of the three previous formulations and covered with a transparent flexible or rigid material (glass, PET sheet, etc.) in order to spread the solution satisfactorily over the mask or over the surface if there is no mask.

(113) Irradiation is undertaken using a halogen desk lamp (OSRAM, 100 W) irradiating in the visible spectrum, and lasts preferentially for 25 min. A minimum time of 15 min is recommended.

(114) The transparent flexible or rigid material is then removed and the Plexiglas plate is rinsed in water and dried in gaseous nitrogen. The vinyl mask is detached and the Plexiglas plate is rinsed in water and in alcohol, and dried under gaseous nitrogen. The design of the mask is obtained by the small flow of water over the Plexiglas plate (FIG. 7).

(115) During the procedure the formation of bubbles under the glass slide is a sign of the mechanism of cleavage of the diazonium salt. Partial masking of the light by an aluminium sheet inhibits the formation of these bubbles during the experiment.

(116) Such a method may be used to modify locally the hydrophilicity/hydrophobicity of the substrate to produce tracks which a hydrophilic/hydrophobic liquid may follow as it flows, thereby preventing complete wetting of the substrate.

REFERENCES

(117) [1] Palacin et al., Molecule-to-metal bonds: Electrografting polymers on conducting surfaces. Chem. Phys. Chem., 2004. 5(10): 1469-1481. [2] International patent WO 2008/078052 in the name of CEA published on Jul. 3, 2008. [3] International patent WO 2005/033378 in the name of CEA published on Apr. 14, 2005. [4] International patent WO 2006/097611 in the name of CEA published on Sep. 21, 2006.