Micro/nano structures of colloidal nanoparticles attached to an electret substrate and method for producing such micro/nano structures

A process of manufacturing a binary micro/nanostructure formed of two types of colloidal nanoparticles, comprising:

• a first monolayer assembly of colloidal nanoparticles of the first type, which are attached to an electret substrate, having a first freely chosen and predetermined geometric shape, and
• a second monolayer or multilayer assembly of colloidal nanoparticles of the second type, which are attached to the electret substrate, having a second freely chosen and predetermined geometric shape, at least the first layer of which is compact in terms of absence of undesired gaps with a size greater than or equal to the size of two adjacent nanoparticles of the second type, preferably optionally greater than or equal to the size of one nanoparticle,
• wherein the process comprises the stages consisting in:
• in a first stage, providing the electret substrate composed of an electret material and having a free receiving surface, then
• in a second stage, writing, sequentially or in parallel, a surface electric potential on the receiving surface of the electret substrate according to a predetermined pattern of electric charges having a first sign and of electric charges having a second sign opposite the first, the pattern of charges being composed of a first subpattern of charges of the first sign, corresponding to the first monolayer assembly of nanoparticles of the first type, and of a second subpattern of charges of the second sign, corresponding to the second monolayer or multilayer assembly of nanoparticles of the second type,
• in a third stage, bringing the electret substrate having the receiving surface written with the surface potential into contact with a first colloidal dispersion for a first contacting time, the first colloidal dispersion comprising nanoparticles of the first type electrically charged according to the second sign and a first dispersing medium in the form of a liquid solvent or of a gas and the first contacting time being sufficiently long to allow the formation, on the first subpattern of charges written in the electret substrate, of the first monolayer assembly, having the desired first geometric shape, of nanoparticles of the first type bonded to the substrate under the action of electrophoretic forces created from the Coulomb interaction between the nanoparticles of the first type and the surface potential of the first subpattern of charges, then
• in a fourth stage, drying the electret substrate and the first assembly, together forming an intermediate micro/nanostructure of end of third stage, by removing the first dispersing medium, then
• in a fifth stage, bringing the dried intermediate structure into contact with a second colloidal dispersion for a second contacting time, the second colloidal dispersion comprising colloidal nanoparticles of the second type which are electrically neutral or quasineutral and electrically polarizable under the action of an external electric field and a second dispersing medium in the form of a liquid solvent or of a gas, substantially devoid of an electrical polarization action, in which the colloidal nanoparticles of the second type are dispersed, and
• the absolute value of the surface electric potential and the concentration of nanoparticles of the second type being respectively greater than or equal to a first surface electric potential threshold and greater than or equal to a second concentration threshold, the first and second thresholds each depending on the nature of the second dispersing medium and on the nature of the polarizable nanoparticles of the second type, such that
• after the second contacting time, which is less than 15 minutes, the second assembly obtained is the second monolayer or multilayer assembly having the second desired geometric shape, and at least the first layer of which is compact in terms of absence of undesired gaps with a size greater than or equal to the size of two adjacent nanoparticles, optionally greater than or equal to the size of one nanoparticle, the nanoparticles being bonded to one another and/or to the substrate under the action of dielectrophoretic forces created from the interaction between the polarizable nanoparticles and the surface potential of the second subpattern.

A process of manufacturing a binary micro/nanostructure formed of two types of colloidal nanoparticles comprising:

• a first monolayer or multilayer assembly of colloidal nanoparticles of the first type, which are attached to an electret substrate, having a first freely chosen and predetermined geometric shape, and
• a second monolayer or multilayer assembly of colloidal nanoparticles of the second type, which are attached to the electret substrate, having a second freely chosen and predetermined geometric shape, at least the first layer of which is compact in terms of absence of undesired gaps with a size greater than the size of two adjacent nanoparticles of the second type, optionally greater than the size of one nanoparticle of the second type,
• wherein the process comprises the stages consisting in:
• in a first stage, providing the electret substrate composed of an electret material and having a free receiving surface, then
• in a second stage, writing, sequentially or in parallel, a first surface electric potential on the receiving surface of the electret substrate according to a first predetermined subpattern of electric charges having a first sign, corresponding to the first assembly of nanoparticles of the first type, the first subpattern making up a first part of a pattern of charges which also comprises a second predetermined subpattern of electric charges having a second sign opposite the first sign,
• in a third stage, bringing the electret substrate having the receiving surface written with the first surface potential into contact with a first colloidal dispersion for a first contacting time of less than or equal to 15 minutes, the first colloidal dispersion comprising nanoparticles of the first type, either electrically charged according to the second sign or substantially neutral and electrically polarizable, and a first dispersing medium in the form of a liquid solvent or of a gas and the first contacting time being sufficiently long to allow the formation, on the first subpattern of charges written in the electret substrate, of the first assembly, having the first monolayer or multilayer geometric shape, of nanoparticles of the first type bonded to the substrate, either under the action of electrophoretic forces created from the Coulomb interaction between the nanoparticles of the first type and the surface potential of the first subpattern of charges, when the nanoparticles of the first type are electrically charged according to the second sign, or under the action of dielectrophoretic forces created from the interaction between the polarizable nanoparticles and the surface potential of the first subpattern of charges when the nanoparticles of the first type are substantially neutral and electrically polarizable,
• in a fourth stage, drying the electret substrate and the first assembly, together forming an intermediate micro/nanostructure of end of third stage, then,
• in a fifth stage, writing, sequentially or in parallel, a second surface electric potential on the receiving surface of the electret substrate of the dried intermediate structure outside the regions covered by the first assembly, according to the second predetermined subpattern of electric charges having the second sign, then
• in a sixth stage, bringing the intermediate structure written with the second surface potential into contact with a second colloidal dispersion for a second contacting time, the second colloidal dispersion comprising colloidal nanoparticles of the second type, which are electrically neutral or quasineutral and electrically polarizable under the action of an external electric field, and a second dispersing medium in the form of a liquid solvent or of a gas, which is substantially devoid of an electrical polarization action, in which the colloidal nanoparticles are dispersed, and
• the value of the electric surface potential and the concentration of nanoparticles of the second type being respectively greater than or equal to a first surface electric potential threshold and greater than or equal to a second concentration threshold, the first and second thresholds each depending on the nature of the second dispersing medium and on the nature of the polarizable nanoparticles of the second type, so that,
• after the second contacting time, the second assembly obtained is the second monolayer or multilayer assembly having the second desired geometric shape, at least the first layer of which is compact in terms of absence of undesired gaps with a size greater than or equal to the size of two adjacent nanoparticles of the second type, optionally greater than or equal to the size of one nanoparticle of the second type, the nanoparticles being bonded to one another and/or to the substrate under the action of dielectrophoretic forces created from the interaction between the polarizable nanoparticles and the surface potential of the second subpattern.

A micro/nanostructure formed of colloidal nanoparticles comprising:

• an electret substrate composed of an electret material and having a free receiving surface, in which a surface electric potential is written on the receiving surface of the electret substrate according to a pattern of positive and/or negative electric charges,
• an assembly of colloidal nanoparticles which are attached to the electret substrate, having a geometric shape,
• wherein:
• the colloidal nanoparticles are electrically neutral or quasineutral and electrically polarizable under the action of an external electric field, and
• the polarizable nanoparticles are positioned as a monolayer or multilayers, being directly bonded to one another and/or to the substrate under the action of dielectrophoretic forces created by the interaction existing between the polarizable nanoparticles and the surface potential of the pattern of charges, and
• the pattern of electric charges of the same polarity written in the electret substrate corresponds to the geometric shape of the monolayer or multilayer assembly of nanoparticles, and
• the absolute value of the surface electric potential created by the pattern of charges is greater than or equal to a first surface electric potential threshold which depends on the nature of the polarizable nanoparticles and such that at least the first layer of the assembly of colloidal nanoparticles is compact in terms of absence of undesired gaps with a size greater than the size of two adjacent nanoparticles, optionally greater than the size of one nanoparticle.

A micro/nanostructure formed of colloidal nanoparticles of two different types comprising, in the form of a binary assembly,

• an electret substrate composed of an electret material and having a free receiving surface,
• a first monolayer or multilayer assembly of colloidal nanoparticles of the first type, which are attached to the electret substrate,
• a second monolayer or multilayer assembly of colloidal nanoparticles of the second type, which are attached to the electret substrate,
• wherein:
• the electret substrate comprises a surface electric potential written on the receiving surface of the electret substrate according to a predetermined pattern of electric charges having a first sign and having a second sign opposite the first sign, the pattern of charges being composed of a first subpattern of charges of the first sign and of a second subpattern of charges of the second sign, and
• the nanoparticles of the first type forming the first monolayer or multilayer assembly are either electrically charged according to the second sign and bonded to the electret substrate under the action of Coulomb forces created by the interaction existing between the nanoparticles of the first type and the surface potential of the first subpattern of charges written in the electret substrate or substantially neutral and electrically polarizable and bonded to one another and/or to the substrate under the action of dielectrophoretic forces created from the interaction existing between the nanoparticles of the second type and the surface potential of the first subpattern of charges written in the electret substrate, and
• the colloidal nanoparticles of the second type forming the second monolayer or multilayer assembly are electrically neutral or quasineutral and electrically polarizable under the action of an external electric field and bonded to one another and/or to the substrate under the action of dielectrophoretic forces created from the interaction existing between the nanoparticles of the second type and the surface potential of the second subpattern of charges written in the electret substrate, and
• the second subpattern of electric charges of the second sign written in the electret substrate corresponds to the geometric shape of the second monolayer or multilayer assembly of nanoparticles, and
• the absolute value of the surface electric potential created by the pattern of charges is greater than a first surface electric potential threshold which depends on the nature of the polarizable nanoparticles, and such that at least the first layer of the second assembly of colloidal nanoparticles is compact in terms of absence of undesired gaps with sizes greater than or equal to the size of two adjacent nanoparticles, optionally greater than or equal to the size of one nanoparticle.