METHOD FOR MANUFACTURING A PART OR A SUPPORTED MICROSTRUCTURE BY LASER EXPOSURE OF A METAL OXALATE LAYER

Abstract

The invention relates to a process for the manufacture of a metal, ceramic or composite part or of a supported metal, ceramic or composite microstructure by laser irradiation starting from metal oxalates, and also to the part and the microstructure obtained by said process, and to their uses.

Claims

1. Process for the manufacture of a metal, ceramic or metal-ceramic composite part or of a supported metal, ceramic or metal-ceramic composite microstructure, wherein said process comprises at least the following stages: i) the deposition of a suspension or of a powder of at least one metal oxalate, optionally as a mixture with one or more compounds resulting from the partial decomposition of said metal oxalate, on at least a portion of a surface of a solid substrate, in order to form a layer of said metal oxalate optionally as a mixture with said compound or compounds, it being understood that: the metal oxalate corresponds to the following formula (I):
M.sub.2(C.sub.2O.sub.4).sub.v.nH.sub.2O(I) in which: M is a metal cation in the +v oxidation state or a mixture of metal cations with a +v mean oxidation state, v is an integer such that 1v4, n is such that n0, and the metal oxalate of the suspension or of the powder is in the form of particles and/or of agglomerates of particles, with a mean size ranging from 10 nm to 100 m, ii) the local heating of at least one zone of the layer of stage i), using a laser beam operating at a wavelength ranging from 150 nm to 2000 nm, at a power density sufficient to irreversibly transform the layer of the locally heated zone into a metal, ceramic or metal-ceramic composite layer exhibiting a pattern corresponding to the heated zone, iii) optionally removing the non-heated zones of the layer, and iv) optionally the repetition, one or more times, of the sequence of stages i) to ii) or i) to iii), so as to form one or more new metal, ceramic or metal-ceramic composite layer(s) on at least a portion of a free surface of the solid substrate and/or on at least a portion of the preceding metal, ceramic or metal-ceramic composite layer.

2. Process according to claim 1, wherein the metal cation M of the metal oxalate of formula (I) is chosen from Ag.sup.+, Li.sup.+, Cu.sup.2+, Fe.sup.2+, Ni.sup.2+, Mn.sup.2+, Co.sup.2+, Zn.sup.2+, Mg.sup.2+, Sr.sup.2+, Ba.sup.2+, Sn.sup.2+, Ca.sup.2+, Cd.sup.2+, Fe.sup.3+, Cr.sup.3+, Bi.sup.3+, Ce.sup.3+, Al.sup.3+, Sb.sup.3+, Ga.sup.3+, In.sup.3+, Y.sup.3+, La.sup.3+, Am.sup.3+, Zr.sup.4+, Hf.sup.4+ and U.sup.4+.

3. Process according to claim 1, wherein the solid substrate is made of glass, of metal, of glass-ceramic, of ceramic, of plastic or of any material which is resistant and/or inert with regard to the heating of stage ii) brought about by the laser beam.

4. Process according to claim 1, wherein the layer formed in stage i) exhibits a thickness ranging from 1 to 700 m.

5. Process according to claim, wherein said metal oxalate of formula (I), and optionally the compound or compounds originating from the partial decomposition of said metal oxalate of formula (I).

6. Process according to claim 1, wherein said metal oxalate of formula (I), represent(s) at least 80% by weight, with respect to the total weight of the layer.

7. (canceled)

8. Process according to claim 1, wherein the suspension is a suspension of a metal oxalate of formula (I), optionally as a mixture with one or more compounds resulting from the partial decomposition of said metal oxalate of formula (I), in a solvent chosen from polyols, simple alcohols, tetrahydrofuran, dodecane, water and a mixture of at least two of the abovementioned solvents, if they are miscible.

9. Process according to claim 1, wherein stage i) is carried out by depositing the suspension of the metal oxalate of formula (I), optionally as a mixture with one or more compounds originating from the partial decomposition of said metal oxalate of formula (I), on at least a portion of a surface of the solid substrate and by then drying said suspension.

10. Process according to claim 1, wherein stage i) is carried out by directly depositing the powder of the metal oxalate of formula (I), optionally as a mixture with one or more compounds originating from the partial decomposition of said metal oxalate of formula (I), on at least a portion of a surface of the solid substrate.

11. Process according to claim 1, wherein stage ii) is carried out at a power density ranging from 0.110.sup.6 to 1010.sup.6 W/cm.sup.2.

12. Process according to claim 1, wherein stage ii) is carried out with a laser beam exhibiting a diameter ranging from 1 to 70 m.

13. Process according to claim 1, wherein stage ii) is carried out several times before or after stage iii).

14. (canceled)

15. Process according to claim 1, wherein the metal, ceramic or metal-ceramic composite layer formed in stage ii) and the metal, ceramic or metal-ceramic composite layers formed in stage iv), if stage iv) exists, are not separated from the solid substrate and form a supported microstructure.

16. Process according to claim 15, wherein the solid substrate is a transparent substrate and the metal cation of the oxalate of formula (I) used in stage i) is a cation of a conductive metal.

17. Process according to claim 1, wherein said process comprises stage iv) and the metal, ceramic or metal-ceramic composite layers formed in stages ii) and iv) form a part which is separated from the solid substrate according to a stage v).

18-21. (canceled)

Description

EXAMPLES

[0161] Example 1: Manufacture of a Metal Microstructure Having Periodic Patterns According to the Process in Accordance with the Invention A silver oxalate corresponding to the formula Ag.sub.2C.sub.2O.sub.4 and in the form of a powder of acicular particles with a mean length of 5 m approximately and with a mean width of 1 m was prepared according to the procedure described in K. Kiryukhina et al., Scripta Materialia, 2013, 68, 623-626.

[0162] 1 g of this oxalate was mixed with 4 g of ethylene glycol in an agate mortar. The resulting mixture was subsequently placed in an ultrasonic bath in order to provide good dispersion of the particles in the ethylene glycol. The viscosity of the mixture was 32 cP approximately and was measured under the conditions as defined in the present invention.

[0163] 3 drops (approximately 1.5 ml in volume) of the suspension obtained above were deposited on a glass slide with dimensions of 3 cm2.5 cm as substrate, in order to produce a smear. The assembly was placed in a freeze-drying device sold under the trade name Alpha2-4 by the company Christ in order to make possible the evaporation of the ethylene glycol. The compartment of the freeze dryer including the sample was brought from atmospheric pressure down to 10.sup.3 mbar approximately in 3 hours approximately, in order to avoid the splitting of the deposit in the dry state. The temperature was 25 C. approximately throughout the operation. After bringing back to atmospheric pressure, the layer of silver oxalate deposited on the glass slide had a thickness of approximately 300 m.

[0164] The glass slide comprising the layer of silver oxalate was subsequently placed in a laser lithography device sold under the trade name Dilase 250 by the company Klo. Laser irradiation was carried out while adjusting the focus of a laser diode with a wavelength of 405 nm at the glass slide/layer of silver oxalate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 5 mm.Math.s.sup.1 approximately and the power density of the laser was 0.1610.sup.6 W/cm.sup.2 approximately.

[0165] The pattern to be irradiated was a grid of 200200 m.sup.2 and was preprogrammed on the lithography device.

[0166] Subsequently, the sample was placed in a 4 mol/l aqueous ammonia solution in order to dissolve the silver oxalate present in the zones which were not irradiated. All that remains on the glass slide is a grid of silver metal comprising silver wires with a width of 12 m approximately and with a thickness of 3 to 5 m approximately. This is because, during the laser irradiation stage, the silver oxalate has been reduced to silver metal in the irradiated zones. FIG. 1 shows an image of the supported microstructure obtained by the process of the invention, said microstructure being in the form of a grid of silver metal.

[0167] The microstructure obtained was transparent.

Example 2: Manufacture of a Metal Microstructure Having Periodic Patterns According to the Process in Accordance with the Invention

[0168] The microstructure obtained according to Example 1 was heated up to a temperature of 300 C. approximately at a heating rate of 150 C./h approximately using a furnace having heating elements. The microstructure was maintained at 300 C. for 1 h and was then cooled down to ambient temperature at a cooling rate of 150 C./h approximately. This additional stage made possible the sintering of the silver wires as obtained in Example 1. A grid of silver metal comprising silver wires with a width of 10 m approximately and with a thickness of 5 m approximately was thus obtained.

[0169] The microstructure obtained remained transparent.

Example 3: Manufacture of a Metal Microstructure Having a Linear Pattern According to the Process in Accordance with the Invention

[0170] A microstructure was prepared under the same conditions as those described in Example 1, except as regards the rate of displacement of the sample, which was 1 mm/s instead of 5 mm/s, and the pattern to be irradiated, which was a line with a length of 15 mm instead of a grid of 200200 pmt.

[0171] Furthermore, ten successive passes were carried out according to said pattern without stage iii) (i.e., without removal of the layer in the unheated zones).

[0172] A line of silver metal with a width of 15 m approximately and with a thickness of approximately 5 m was thus obtained.

[0173] The electrical conductivity of this line was determined by the two-point method using a multimeter of the Keithley trademark, and was 7.510.sup.5 S.Math.m.sup.1 approximately.

[0174] Thus, the process of the invention makes it possible to confer an electrical conductivity on a glass substrate while retaining its optical transparency.

Example 4: Manufacture of a Metal Microstructure Having a Linear Pattern According to the Process in Accordance with the Invention

[0175] A copper oxalate corresponding to the formula CuC.sub.2O.sub.4.0.5H.sub.2O and in the form of a powder of grains with a length of 40 nm approximately and with a diameter of 25 nm approximately was prepared according to the procedure described in V. Baco-Carles et al., ISRN Nanotechnology, 2011, Article ID 729594, doi:10.5402/2011/729594, 7 pages).

[0176] 1 g of this oxalate was mixed with 4 g of water in an agate mortar. The resulting mixture was subsequently placed in an ultrasonic bath in order to provide good dispersion of the particles in the water. The resulting suspension was deposited on a silicon substrate in the form of a film using an item of coating equipment sold under the spin coater trade name by the company Suss and operating at a rotational speed of 3000 rev/min approximately. The thickness of the film obtained was 1 m approximately. The items of coating equipment (sometimes denoted spinners) are very common items of equipment sold by different companies.

[0177] The substrate comprising the layer of copper oxalate was subsequently placed in the laser lithography device as described in Example 1. Laser irradiation was carried out while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/layer of copper oxalate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 0.5 mm.Math.s.sup.1 approximately and the power density of the laser was 0.1610.sup.6 W/cm.sup.2 approximately.

[0178] The pattern to be irradiated was lines with a length of 5 mm and was preprogrammed on the lithography device.

[0179] After the irradiation stage, lines of copper metal partially oxidized at the surface with a width of 10 to 12 m approximately were formed on the substrate. This is because, during the laser irradiation stage, the copper oxalate was reduced to copper metal partially oxidized at the surface in contact with the air in the irradiated zones. FIG. 2 shows an image of the supported microstructure obtained by the process of the invention, said microstructure being in the form of lines of copper metal partially oxidized at the surface.

Example 5: Manufacture of a Metal Microstructure Having a Linear Pattern According to the Process in Accordance with the Invention

[0180] A copper oxalate in the form of a powder composed of isotropic particles with a mean diameter of 3 m approximately was prepared by modifying the precipitation conditions described in V. Baco-Carles et al., ISRN Nanotechnology, 2011, Article ID 729594, doi:10.5402/2011/729594, 7 pages, and in Tailhades, Thesis, 1988, Universit Paul Sabatier. An aqueous solution of copper nitrate Cu(NO.sub.3).sub.2.2.5H.sub.2O (98.5%, Alfa Aesar) with a concentration of 2M was then precipitated with an aqueous solution of ammonium oxalate (NH.sub.4).sub.2C.sub.2O.sub.4.H.sub.2O (98% Laurylab) with a concentration of 0.4M.

[0181] 1 g of this oxalate was mixed with 4 g of ethylene glycol in an agate mortar. The resulting mixture was subsequently placed in an ultrasonic bath in order to provide good dispersion of the particles in the ethylene glycol.

[0182] The suspension was deposited on a glass slide and dried as in example 1. The glass slide comprising the layer of copper oxalate was subsequently placed in the laser lithography device as described in Example 1. Laser irradiation was carried out while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/layer of copper oxalate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 0.5 mm.Math.s.sup.1 approximately and the power density of the laser was 0.1610.sup.6 W/cm.sup.2 approximately.

[0183] The pattern to be irradiated was a line with a length of 5 mm and was preprogrammed on the lithography device.

[0184] Lines of copper metal and/or of re-oxidized copper with a width of 10 m approximately were formed.

Example 6: Manufacture of a Ceramic Microstructure Having a Rectangular Pattern According to the Process in Accordance with the Invention

[0185] An iron oxalate corresponding to the formula FeC.sub.2O.sub.4.2H.sub.2O and in the form of a powder of acicular particles with a mean length of 0.5 m and with a width of 50 nm was prepared according to the procedure described in Tailhades, Thesis, 1988, Universit Paul Sabatier.

[0186] 1 g of this iron oxalate was mixed with 4 g of ethylene glycol in an agate mortar. The resulting mixture was subsequently placed in an ultrasonic bath in order to provide good dispersion of the particles in the ethylene glycol.

[0187] The suspension was deposited on a glass slide and dried as in Example 1. The glass slide comprising the layer of iron oxalate was subsequently placed in the laser lithography device as described in Example 1. Laser irradiation was carried out while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/layer of iron oxalate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 1 mm.Math.s.sup.1 approximately and the power density of the laser was 0.4110.sup.6 W/cm.sup.2 approximately.

[0188] The pattern to be irradiated was a rectangular zone with dimensions of 18 mm15 mm and was preprogrammed on the lithography device.

[0189] The irradiated layer was analysed by X-ray diffraction (XRD) using an appliance sold under the trade name D4 by the company Brucker. FIG. 3 shows an image of the supported microstructure obtained by the process of the invention, said microstructure being in the form of a layer based on iron oxide.

[0190] The XRD analysis showed the presence of a predominant Fe.sub.2O.sub.3 phase. Traces of magnetite Fe.sub.3O.sub.4 and of iron oxalate were also observed, as is shown by FIG. 4.

Example 7: Manufacture of a Ceramic Microstructure Having a Pattern According to the Process in Accordance with the Invention

[0191] A mixed iron cobalt oxalate corresponding to the formula CoFe.sub.2(C.sub.2O.sub.4).sub.3 and in the form of a powder of acicular particles with a mean length of 1 m approximately and with a mean width of 0.3 m was prepared according to the procedure described in Le Trong H. et al., Solid State Sciences, 2008, 10(5), 550-556.

[0192] 1 g of this oxalate was mixed with 4 g of ethylene glycol in an agate mortar. The resulting mixture was subsequently placed in an ultrasonic bath in order to provide good dispersion of the particles in the ethylene glycol.

[0193] The suspension was deposited on a glass slide and dried as in Example 1. The glass slide comprising the layer of iron cobalt oxalate was subsequently placed in the laser lithography device as described in Example 1. Laser irradiation was carried out while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/layer of iron cobalt oxalate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 1 mm.Math.s.sup.1 approximately and the power density of the laser was 0.6410.sup.6 W/cm.sup.2 approximately.

[0194] The pattern to be irradiated was a rectangle with dimensions of 1815 mm.sup.2 and was preprogrammed on the lithography device.

[0195] A layer having a rectangular pattern, the structure of which was analysed by X-ray diffraction (XRD) using an appliance as described in Example 6, was formed.

[0196] The XRD analysis showed the presence of a spinel phase. This is because the diffractogram is characteristic of a spinel phase of CoFe.sub.2O.sub.4 type and of a monoxide phase of CoO type. The magnetic measurements carried out with a VSM device of Versalab model and of the Quantum Design trademark showed the presence of a ferrimagnetic phase. The coercive field was 1630 Oe at 300 K. After cooling, under a field of 3 T, from ambient temperature down to 100 K, the coercive field reached a very high value of 6130 Oe at 100 K. The hysteresis cycle was offset on the axis of the abscissae (exchange field of 1650 Oe), revealing a strong magnetic coupling between the spinel phase and the monoxide. This strong coupling also testifies to the intimate coexistence of these phases at the nanometric scale.

[0197] FIG. 5 represents the curves of the magnetization M (in emu/g) of the oxalate of formula (I) CoFe.sub.2(C.sub.2O.sub.4).sub.3 at 300 K (curve with the solid diamonds) and of the compounds obtained after irradiation at 300 K (curve with the solid squares) and 100 K (curve with the solid triangles), as a function of the magnetic field H (in KOe).

Example 8: Manufacture of a 3D Part According to the Process in Accordance with the Invention

[0198] A suspension of silver oxalate in ethylene glycol was prepared, deposited on a glass slide and dried under the conditions as described in Example 1. The sample obtained was subsequently irradiated while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/layer of silver oxalate interface. The diameter of the laser beam was 2 m approximately and the rate of displacement of the sample under the laser beam was 1 mm.Math.s.sup.1 approximately.

[0199] Formation of a First Layer

[0200] A first pattern forming a square with dimensions of 5 mm5 mm was irradiated over the whole of its surface at a power density of 0.1610.sup.6 W/cm.sup.2. The irradiation was carried out line-by-line along a longitudinal axis (0,x).

[0201] Then, inside this zone, a second square of 3 mm3 mm was irradiated over the whole of its surface, along a transverse axis (0,y), at a power density of 0.2210.sup.6 W/cm.sup.2, and then along a longitudinal axis (0,x), still at a power density of 0.2210.sup.6 W/cm.sup.2.

[0202] At this stage, the excess of non-irradiated material located outside the zone treated by the laser was removed.

[0203] The sample was subsequently placed back in the lithography device in order to carry out an irradiation of the second square of 3 mm3 mm while gradually increasing the power density of the laser (0.3210.sup.6 W/cm.sup.2, 0.6410.sup.6 W/cm.sup.2, 1.610.sup.6 W/cm.sup.2 and 2.710.sup.6 W/cm.sup.2) at the end of each irradiation series carried out alternately along the axis (0,x) and then the axis (0,y). For each power used, 2 scans were carried out.

[0204] On conclusion of these irradiation sequences, a well-defined square of silver was obtained which exhibits good adhesion to the glass substrate.

[0205] Formation of a Second Layer

[0206] Silver oxalate powder as used in Example 1 was subsequently added and compacted using a scraper and the application of a manual force to the square pattern of 5 mm5 mm.

[0207] The powder thus deposited was then irradiated three times as above to form a square of 3 mm3 mm, while still alternating a longitudinal scanning (0,x) at a power density of 0.1610.sup.6 W/cm.sup.2 on the square of 5 mm5 mm, and then a transverse scanning (0,y) followed by a longitudinal scanning (0,x) at a power density of 0.2210.sup.6 W/cm.sup.2 on the square of 3 mm3 mm. The non-irradiated powder was subsequently removed.

[0208] The sample was subsequently placed back in the lithography device in order to carry out an irradiation of the second square of 3 mm3 mm while gradually increasing the power of the laser (0.3210.sup.6 W/cm.sup.2, 0.6410.sup.6 W/cm.sup.2, 1.610.sup.6 W/cm.sup.2, 2.710.sup.6 W/cm.sup.2 and 3.210.sup.6 W/cm.sup.2) at the end of each irradiation series carried out alternately along the axis (0,x) and then the axis (0,y). For each power used, 4 scans were carried out.

[0209] Formation of a Third Layer and then of a Fourth Layer

[0210] The operations for the second layer were reproduced for the third and fourth layers. On conclusion of these different stages, a 3D object with a thickness in the region of 600 m approximately was obtained. This object consisted of pure silver metal, the sintering of which resulting from the irradiation by the laser beam provides the mechanical strength. The analysis by X-ray diffraction confirmed that silver metal was obtained.

Example 9: Manufacture of a Metal Microstructure Having Periodic Patterns According to the Process in Accordance with the Invention

[0211] The silver oxalate used in Example 1 was partially decomposed by heating it at 120 C. approximately in an oven for 20 hours approximately.

[0212] 1 g of this partially decomposed silver oxalate was mixed with 4 g of ethylene glycol in an agate mortar. The resulting mixture was subsequently placed in an ultrasonic bath in order to provide good dispersion of the particles in the ethylene glycol.

[0213] The suspension was deposited on a glass slide and dried as in Example 1.

[0214] The glass slide comprising the layer of partially decomposed silver oxalate was subsequently placed in the laser lithography device. Laser irradiation was carried out while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/layer of partially decomposed silver oxalate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 1 mm.Math.s.sup.1 approximately and the power density of the laser was 0.2210.sup.6 W/cm.sup.2 approximately.

[0215] The pattern to be irradiated was lines with a length of 5 mm and was preprogrammed on the lithography device. Lines of silver metal with a mean width of 10 m were obtained.

Comparative Example 10: Manufacture of a Metal Microstructure According to a Process not in Accordance with the Invention

[0216] 1 g of silver nitrate was mixed respectively with 1 g (mixture A) and 4 g (mixture B) of ethylene glycol in an agate mortar. The resulting mixtures A and B were respectively in the form of a colourless suspension A and of a colourless solution B (solubility limit of silver nitrate in ethylene glycol: 49.67 g per 100 g of ethylene glycol at 20 C. approximately).

[0217] The abovementioned mixtures A and B were stored at 5 C. in order to prevent a change in colouration (from colourless to black) after a few hours.

[0218] 3 drops of the suspension A obtained above (respectively 3 drops of the solution B obtained above) were deposited on a glass slide with dimensions of 3 cm2.5 cm as substrate, in order to produce a smear. The assembly was placed in a freeze-drying device sold under the trade name Alpha2-4 by the company Christ in order to make possible the evaporation of the ethylene glycol. The compartment of the freeze dryer including the sample was sheltered from the light and brought from atmospheric pressure down to 10.sup.3 mbar approximately in 3 hours approximately. The temperature was 25 C. approximately throughout the operation. After bringing back to atmospheric pressure, the two deposits of silver nitrate deposited on the glass slide did not form a continuous layer and exhibited in particular surface heterogeneities.

[0219] The glass slide comprising the deposit resulting from the solution B (respectively comprising the deposit resulting from the suspension A) was subsequently placed in a laser lithography device as described in Example 1. Laser irradiation was carried out while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/deposit of silver nitrate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 0.5 mm.Math.s.sup.1 approximately and the power density of the laser was 0.910.sup.6 W/cm.sup.2 approximately.

[0220] The pattern to be irradiated was a grid of 200200 m.sup.2 for the deposit resulting from the solution B and that resulting from the suspension A, and was preprogrammed on the lithography device.

[0221] Subsequently, the samples were placed in a 4 mol/l aqueous ammonia solution in order to dissolve the silver nitrate present in the zones which were not irradiated.

[0222] For the deposit resulting from the solution B, all that remains on the glass slide is a grid of silver metal comprising silver wires with a width of 9-15 m approximately. FIG. 6 shows an image of the supported microstructure obtained by a process in accordance with the invention by replacing the solution B with a suspension of a silver oxalate and obtained according to the same irradiation conditions as those described above (FIG. 6a) and, by comparison, an image of the supported microstructure obtained by a process not in accordance with the invention and as described above (FIG. 6b). The microstructure of FIG. 6b is in the form of a grid of silver metal exhibiting numerous surface heterogeneities and discontinuities. Furthermore, observations by optical microscopy have shown, before treatment with ammonia, the formation of patterns of irregular dimensions due to strong surface heterogeneities observed, and to strong transformation heterogeneities.

[0223] For the deposit resulting from the suspension A, the treatment with ammonia did not make it possible to preserve the irradiated structure. Furthermore, observations by optical microscopy have shown, before treatment with ammonia, formed patterns very poorly defined due to strong surface heterogeneities observed, and to strong transformation heterogeneities.

Comparative Example 11: Manufacture of a Metal Microstructure According to a Process not in Accordance with the Invention

[0224] A solution of silver oxalate was prepared by recovering the supernatant from a suspension prepared under the same conditions as those described in Example 1 and separated by settling for 7 days.

[0225] The molar concentration of silver oxalate was extremely dilute, i.e. 0.025 mol/l approximately (i.e., a concentration by weight of 0.7%).

[0226] 3 drops of the solution obtained above were deposited on a glass slide with dimensions of 3 cm2.5 cm as substrate, in order to produce a smear. The assembly was placed in a freeze-drying device sold under the trade name Alpha2-4 by the company Christ in order to make possible the evaporation of the ethylene glycol. The compartment of the freeze dryer including the sample was brought from atmospheric pressure down to 10.sup.3 mbar approximately in 3 hours approximately. The temperature was 25 C. approximately throughout the operation. After bringing back to atmospheric pressure, the deposit of silver oxalate deposited on the glass slide did not form a continuous layer due to the small amount of silver oxalate deposited from the solution.

[0227] The glass slide comprising the deposit resulting from the oxalate solution was subsequently placed in a laser lithography device as described in Example 1. Laser irradiation was carried out while adjusting the focus of a laser with a wavelength of 405 nm at the glass slide/deposit of silver oxalate interface. The diameter of the laser beam was 2 m approximately, the rate of displacement of the sample under the laser beam was 1 mm.Math.s.sup.1 approximately and the power density of the laser was 0.910.sup.6 W/cm.sup.2 approximately.

[0228] The pattern to be irradiated was a line with a length of 5 mm and was preprogrammed on the lithography device.

[0229] A line of silver metal with a maximum width of 10 m was obtained.

[0230] However, the small amount of material deposited due to the use of an oxalate solution in place of an oxalate suspension did not make it possible to form a continuous line of silver after laser irradiation.