ES2282009B1 - DEVICE AND PROCEDURE FOR THE GENERATION OF NANOEMULSIONS AND SINGLE AND DOUBLE MICROEMULSIONS BY MEANS OF ELECTRIFIED COAXIAL JETS IN DIELECTRIC LIQUID MEDIA. - Google Patents

Abstract

Device and procedure for generation of nanoemulsions and single and double microemulsions by electrified coaxial jets in liquid media dielectrics.

The present invention has as its object the description of the device and the method for generating single and double emulsions of micro and nano size by means of electrified coaxial jets in a dielectric liquid. In particular, two applications will be developed here focused on 1) the generation of double emulsions, of the type (o / w / o), of micro and nanometric size, in which capsules composed of a hydrophilic liquid containing another hydrophobic inside are dispersed in a continuous phase of a third liquid (also hydrophobic); this third liquid may be different from or the same as the encapsulated one and to 2) the dispersion within a hydrophilic liquid of micrometric and nanometric drops of a hydrophobic liquid and insoluble with the previous one, o / w type emulsions; The interest of this application lies in the fact that there are a good number of substances of high therapeutic value that are insoluble in water and that when they are administered to patients, the dissolution levels in the blood that are achieved are extraordinarily low unless this substance is be dispersed in very small sizes within an aqueous liquid in order to increase the surface between both liquids and facilitate the

dilution of one within the other. In case of the formation of liquid crystal monodisperse emulsions is another of the possible applications of interest.

Description

Device and procedure for generation of nanoemulsions and single and double microemulsions by electrified coaxial jets in liquid media dielectrics.

Object of the invention

The present invention describes a process for generating, via electrohydrodynamics, double emulsions, with drop sizes in the micro or submicron regime, of the water-oil-water (w / o / w) and oil-water-oil (o / w / o), and simple oil-water type emulsions (o / w). The procedure consists in the formation, in a bath of a dielectric liquid [liquid (1)], of a compound electrified jet, with a diameter in the micrometric or submicrometric range, formed by a liquid (2) and a liquid (3) ( with viscosities M 2 and M 3 respectively) that flows through the interior of the liquid jet (2), either in the form of drops or in the form of another internal jet. The liquid (2) is hydrophilic (conductivity conductor K2) and its nature is therefore different from that of the liquid in the bath (1), which is hydrophobic (dielectric liquid). The liquid (3) can be hydrophobic in nature, or even hydrophilic, although in the latter case the miscibility between the liquids (2) and (3) must be very low. The two liquids are injected through capillary needles (or feeding tips) located concentrically, or one inside the other. When the conductive liquid (2) flows at appropriate flow rates and is subjected to an electric field of the appropriate value, an electrified conical meniscus (Taylor cone) is formed from whose vertex a stationary jet flows by the action of the electric field . For appropriate values of the flow rate injected through the needle and the electric field, it is possible to ensure that the cone-jet structure remains stationary (Figure 1), see for example Barrero et al . J. Colloid. Interf. Sci. 272, 104-108, 2004 . This phenomenon is known in the electrohydrodynamic literature as stationary cone-jet electrospray . The diameter of the jet, which depends on the properties of the liquid (mainly electrical conductivity) and the flow injected, is between a few tens of nanometers and a hundred microns. If, under these conditions, a stationary flow of hydrophobic liquid (3) is injected through the inner needle, another meniscus is formed inside the anterior meniscus (2), see the photograph in figure 2. The arrangement of the needles is as that the dielectric liquid (1) partially or totally bathes the meniscus of the conductive liquid (2). The deformation of the inner meniscus by the action of the viscous forces of the movement of the liquid (2) that surrounds it causes it to adopt a conical shape like the one shown in the photograph in figure 2. If the hydrophobic liquid (3 ) small amounts of an appropriate surfactant are added, the interfacial tension between the liquids (2) and (3) decreases markedly and the viscous forces that the liquid (2) exerts on the liquid meniscus (3) break the conical tip of the inner meniscus to give rise to a second jet of liquid (3) that flows surrounded by the jet of liquid (2), see the photograph of figure 3 and figure 4a. The coaxial jet thus formed is unstable and breaks within the dielectric bath (hydrophobic liquid) giving rise to a hydrosol of composite drops in which the hydrophilic liquid (2) encapsulates one or more drops of the hydrophobic liquid (3). Sometimes, the intermittent rupture of the tip of the hydrophobic meniscus (3) produces a train of small drops, instead of a jet, which are carried along by the jet of liquid (2), see figure 4b. In this case, the breaking of the jet gives rise to capsules of liquid (2) that enclose one or more drops of liquid (3) (multi-nuclear capsules).

When the capillary through which the liquid is injected (3) has an internal diameter considerably smaller than that of the capillary used to inject the liquid (2), the liquid (3) is ejected in the form of drops (see figure 4c) if the injected flow is below a threshold value ( dripping ), while for values higher than this it flows in the form of a jet with a diameter substantially equal to that of the capillary ( jetting ), which finally breaks into drops that are dragged by the liquid jet (2), see figure 4d. As in the previous case, the rupture of the liquid jet (2) gives rise to multi-nuclear capsules.

In all cases, the procedure described leads to a double emulsion of the o / w / o type in which drops of a hydrophilic liquid (2) containing a hydrophobic one inside (3) are scattered in a bath of another liquid as well hydrophobic (1) which can be the same or different liquid than the encapsulated (3). Compound drops, with a hydrophobic liquid (3) enclosed by the hydrophilic (2), resulting from the jet breaking are characterized by being uniform in size (small deviation Standard) and the range of its mean diameter, which is of the order of diameter of the jet, is in a range that, depending on the properties of liquids (mainly conductivity of the hydrophilic liquid), ranges from a few dozen nanometers, for the most conductive liquids, up to a hundred microns for the least conductive.

For the formation of simple emulsions type oil-water (o / w), is used as an electrode of reference a bath of hydrophilic liquid [liquid (4)] over which The dielectric liquid (1) rests, due to its lower density. Due at the loading of its drops, the hydrosol of compound drops is forced by the electric field to move towards the hydrophilic liquid bath (4). Once the droplets enter the bath, the outer liquid (2) dissolves in the liquid bath (4), giving rise to a micro- or nano-sized droplet emulsion of hydrophobic liquid (3) dispersed within the liquid (4).

The electric field is applied by establishing a potential difference between the needle if it is metallic (or tip power supply) and a reference electrode connected to ground or to a reference potential. The reference electrode can possess different geometric configurations, plate, ring, etc. Also, the reference electrode may not be solid; by For example, another conductive liquid (4) can also be used, different or not to the liquid (2), which is immiscible or poorly miscible with dielectric and is in contact with it through a interface.

The device and the procedure, objects of the present invention, can be applied to obtain nanoemulsions and encapsulation processes with applications in fields such as Materials Science (crystal nanoemulsions liquids and other complex fluids), Food Technology and Pharmaceutical Technology (emulsions and encapsulates), etc., where the generation and controlled manipulation of jets and drops of sizes micro or nanometric is an essential part of the process.

State of the art

Among the many procedures commonly used to generate stationary liquid jets and aerosols, this invention utilizes electrohydrodynamic forces (EHD). The phenomenon of dispersing a liquid in air by electrohydrodynamic forces has been known since ancient times. Among the many modes that are known, the one known as electrospray stands out for the properties of the resulting aerosol (drops with diameters in the nanometric range and average diameter of the highly uniform charged drops). As is known, under appropriate operating conditions, anchored to a needle (or feeding tip), metallic or not, a meniscus of a very approximately conical shape is formed from whose vertex a flow of liquid is emitted in the form of a micro or nanojet stationary. The breaking of said jet produces a cloud of charged drops called electrospray in a stationary cone-jet mode that has been widely studied (Cloupeau and Prunet-Foch, J. Electrostatics 22 , 135-159, Fernández de la Mora and Loscertales, J. Fluid Mech . 260 , 155-184, 1994; Gañán-Calvo et al . J. Aerosol Sci . 28 , 249-275, 1997; Hartman et al . J. Aerosol Sci . 30 , 823-849, 1999). Recently, using electrospray techniques, a procedure has been developed to produce electrified coaxial jets of liquids in which their breakage gives rise to an aerosol of drops composed of one liquid enclosing or encapsulating another, Loscertales et al . Science 295 , 1695-1698, 2002, and PCT / ES02 / 00047. When the solidification of one of the two liquids that make up the coaxial jet occurs before it breaks, the result consists of coaxial micro or nanofibers or micro / nanotubes. (Loscertales et. Al, J. Am. Chem. Soc . 126 , 5376, 2004). The above results refer to the dispersion of a liquid in a vacuum or in a gaseous atmosphere, but not to situations in which the dispersion process takes place within other liquids. In the liquid-liquid case, the development of cusps at the interface of two immiscible liquids when a sufficiently large electric field is applied has been analyzed by Oddershede and Nagel, Phys. Rev. Lett. 85 , 1234-1237, 2000. In any case, this work neither investigates nor establishes, therefore, the conditions necessary to form a stationary and stable electrospray, in the cone-jet mode, of a liquid within other. The electro-atomization of one liquid within another in the so-called dripping regime ( microdripping ) applying pulsed electric fields has also been considered by Tsouris, Neal, Shah, Spurrier and Lee, Chemical Eng. Comm. 160 , 175-197, 1997; Naturally, the use of non-stationary electric fields is incompatible with the stationary cone-jet mode (electrospray. Electrostatic atomization of dielectric fluids (such as air or organic solvents) within relatively conductive fluids (for example water) has been investigated also by Tsouris, Shin and Yiacoumi, Canadian J. Chem. Eng. 76 , 589-599, 1998; Sato, J. Colloid Interface Sci. 156 , 504-507, 1993; see also US Patent 5,762,775 and US Patent 4,508,265. This situation, in which various electrohydrodynamic phenomena occur, is also incompatible with the formation of a stable and stationary cone-jet structure.

Finally, the dispersion of a conductive liquid in another dielectric applying alternating electric fields has been considered in the following patents: US Patent 5,503,372, by WG Sisson, MT Harris, TC Scott and OA Basaran; US Patent 5,738,821 by WG Sisson, OA Basaran and MT Harris; US Patent 5,759,228 by WG Sisson, MT Harris, TC Scott and OA Basaran. As indicated above, the application of an alternating electric field is naturally incompatible with obtaining the stable and stationary cone-jet structure that is claimed herein and that results in a monodisperse hydrosol of charged drops. More recently, Barrero et al . J. Coll. Interf. Sci . 272 , 104-108, 2004 has obtained stationary electrosprays of a conductive liquid within a dielectric bath.

Explanation of the invention

The novelty of the present invention lies in the formation of a hydrosol of charged drops, highly monodisperse, within a dielectric liquid (liquid (1)) from the breakdown of an electrified jet in which a conductive liquid (hydrophilic ), liquid (2), which flows on the outside completely surrounds another dielectric (hydrophobic), liquid (3), which flows on the inside; the drops formed by the breaking of the jet have a structure in which the liquid (2) encapsulates the liquid (3). Liquids are injected through two needles (or feeding tips) arranged concentrically, or one containing the other, and immersed inside the liquid bath. The conductive liquid (2) is injected through the annular space between the two needles or tips so that when an electric field is applied to it, an electrified conical meniscus is formed from whose vertex a jet of diameter in the micro / nanometric range flows. . The characteristic conical shape of the conducting meniscus is due to a balance between the interfacial tension forces and the electrical forces acting on the surface of the conducting meniscus. The movement of the liquid (2) is caused by the electrical tangential stress acting on the surface of the meniscus, driving the liquid (2) towards the tip of the Taylor cone. In the mode known in the literature as cone-jet mode, the above-described mechanical equilibrium is no longer satisfied in a region close to the vertex where the surface of the meniscus changes from conical to cylindrical (cone-jet). Inside this meniscus, another liquid (3) is formed, of a dielectric nature, anchored to the inner needle, by slowly injecting the liquid (3) through it. This meniscus is deformed by the action of viscous forces so that a cusp point is formed on its surface, from which a very thin jet is emitted when the viscous forces overcome the interfacial tension of the liquid (3), see figure 4a . Thus a composite jet structure is formed in which the conductive liquid (2), which flows outside the jet, completely covers the dielectric liquid (3), which flows inside. When the surface tension between both liquids (2 and 3) is not low enough, it is necessary to add a surfactant to break the surface of the innermost meniscus and get the liquid (3) to flow to form the structure of the coaxial jet. Naturally, to reach a steady state it is necessary to supply both liquids at flow rates equal to those ejected.

When there is a balance between viscous forces and interfacial tension, the meniscus oscillates intermittently between a shape with a rounded vertex (without mass emission) and another with a cusp point from which droplets of micro or nanometric, case of figure 4b.

When the diameter of the internal capillary is very small compared to the external one, the injection of the liquid (3) into the liquid meniscus (2) results in a train of drops ( dripping ), figure 4c, or in a jet ( jetting ) that breaks into drops, figure 4d. Both modes give rise to drops with a diameter similar to that of the capillary.

The electrified jet breaks downstream by Varicose instabilities associated with surface tension giving place in a hydrosol, within the dielectric (1), of drops compounds or compound particles, of very uniform size, in the that the conductive liquid (2) encapsulates the dielectric liquid (3); In this way, emulsions of type oil-water-oil (o / w / o).

For the formation of simple emulsions type oil-water (o / w), is used as an electrode of reference a bath of hydrophilic liquid [liquid (4)] over which If its density is lower, the dielectric liquid (1) rests. Due to the charge of its droplets, the hydrosol of compound droplets is forced by the electric field to move into the liquid bath hydrophilic (4). Once the drops penetrate the bath, the outer liquid (2) that forms the capsules dissolves in the bath of liquid (4), releasing the liquid (3) and giving rise to a emulsion of micro- or nano-sized drops of liquid hydrophobic (3) dispersed within the liquid (4).

The electric field is applied by establishing a potential difference between the needle if it is metallic (or tip power supply) and a reference electrode connected to ground or to a reference potential. The reference electrode can possess different geometric configurations, plate, ring, etc. Also, the reference electrode may not be solid; by For example, another conductive liquid (4) can also be used, different or not to the liquid (2), which is immiscible or poorly miscible with the dielectric and is in contact with it through a interface.

It should be noted that it was not until 2004 (Barrero et al ., J Colloid Interface Sci . 272, 104-108, 2004) when an electrospray in cone-jet mode was stabilized for the first time in a dielectric liquid medium; that is, 90 years after Zeleny managed to do it for the first time on air. The main reason is that the ranges of values of the parameters are different since the hydrodynamics of the jet is substantially affected by the high values of density and viscosity, which are respectively 1000 times and a minimum of 40 times higher in this case, in which the dielectric external medium is a liquid, than when the medium is gaseous.

On the other hand, in this procedure, liquids (1) and (3) will be generally miscible or at least related, so that the liquid (2) must always remain as a barrier between the two so that the encapsulation of effective way. This is not always easy as liquids 1 and 3 they tend to come into contact, thus destabilizing the process. That is why the liquid (2) has to deform the meniscus M of the liquid (3) to form a compound jet J in which flow of coaxially between liquids 2 and 3. Several factors affect this process, but among them we will highlight the viscosity of the liquid (2) and the surface tension between liquids 2 and 3. On the one hand the liquid (2) must have a sufficiently high viscosity which allows you to effectively deform and drag the liquid (3). At the same time, the surface tension 2-3 does not must be too high, for which in many situations it must resort to the use of suitable surfactants to facilitate the process. Naturally, if the medium (1) was gaseous (case contemplated in other procedures described in the state of technique) this problem is not of such relevance, since the media 1 and 3 are different phases.

The advantages and innovative features of this electrohydrodynamic procedure compared to other techniques already existing are:

to)

The collection of the emulsion is done in a simpler way than in air, in which electrical neutralization of the spray to be able to extract it. When performing the process in a medium liquid, the viscosity compensates for the forces of electrical attraction and the hydrosol can be extracted together with the liquid (1) (for the case of double emulsions o / w / o) or liquid (4) (for simple emulsions of type o / w).

b)

Other The advantage of the invention stems from the fact that the breakage of the jet, micro / nanometric, produces droplets, micro / nanometric and charged. The charge of all drops is always of the same sign, which avoids, by Coulomb repulsion, the coalescence of the same. In addition, the local electric field acts on the net charge of each drop, helping very efficiently to extract the drops from the point where are produced, also preventing their coalescence.

c)

To the introducing the compound electrospray into a liquid bath is done single step emulsion generation possible. The generation from air would require longer and more complex processes to convert the aerosol generated in a hydrosol. The procedure here we claim allows the direct generation of the emulsion in a liquid medium.

d)

By carrying out the process in a dielectric liquid medium, corona-type electrical discharge is avoided, which in air sometimes limits the operating range in cone-jet mode.

and)

As It will be seen later, both types of emulsions (o / w) and (w / o / w) they can be generated using the same device.

F)

The generation of the hydrosol occurs in a single step and is not filtering or subsequent homogenization is necessary.

g)

Is possible to control the sizes and even the structure of the drops compound or simple by varying the flow rates Q2 and Q3 and the value of the conductivity K2 of the liquid 2.

Detailed description of the invention

This section is intended to description of the device and the procedure to generate single and double micro- and nano-size emulsions using electrified coaxial jets in a liquid dielectric. In particular, two applications will be developed here focused on 1) the generation of double emulsions, of the type (o / w / o), micro and nano-sized, in which capsules composed of a hydrophilic liquid containing another hydrophobic are dispersed in a continuous phase of a third liquid (also hydrophobic); this third liquid may be different or the same as encapsulation and 2) dispersion within a hydrophilic liquid of micrometer and nanometric drops of a hydrophobic liquid and insoluble with the previous one, type o / w emulsions; The interest of this application is that there are a good number of substances of high therapeutic value that are insoluble in water and that when administered to patients, dissolution levels in blood levels are extraordinarily low unless This substance is dispersed in very small sizes within a aqueous liquid with the aim of increasing the surface between both liquids and facilitate the dilution of one within the other. He case of the formation of monodisperse liquid crystal emulsions is another of the possible applications of interest.

The procedure and device is common for both applications and is based on the generation within a dielectric bath (liquid (1)) of a jet of a liquid electrified through whose interior co-flows another liquid, in the form of a stream or in the form of drops; the liquid exterior is hydrophilic in nature and good electrical conductor (liquid (2), with conductivity K2 and viscosity M2) and the that flows through the interior (liquid (3), of viscosity M3) is hydrophobe.

The different procedures for the generation of the emulsions are graphically described in Figures 4a to 4d. In a first procedure, the jets that emanate from the menisci M and C result in a coaxial jet that breaks downstream into composite drops in which the liquid (2) encapsulates the (3) (see fig. 4a). In the case of figure 4b, the meniscus M emits drops from its vertex ( tip-streaming ), which are dragged by the jet of liquid (2); the breaking of the jet J gives rise to compound drops in which the liquid (2) encapsulates the (3). It is also possible to produce compound drops by the procedure illustrated in figure 4c, where drops of liquid (3) emitted directly from tip B are entrained by jet J. Finally it is also possible, as illustrated in figure 4d, that a jet of liquid (3) is emitted from the tip B which breaks into drops within the jet J and forms compound drops after the latter breaks. These procedures can be combined with different electrode configurations depending on the application. In the case of wishing to generate double emulsions of the o / w / o type, a metallic electrode of the type observed in fig. 5. In the event that the objective is the generation of simple emulsions of type o / w, a liquid (4), miscible with the liquid (2), has to be deposited at the bottom of the bath so that the hydrosol H or the compound jet J dissolves and the liquid droplets (3) are dispersed in the liquid 4 forming the o / w type emulsion.

The device consists of two tips feed A and B, arranged concentrically, or one contained in the other, and located within a dielectric liquid (1), as is shown in figure 5. A flow rate Q2 of a liquid conductor (2), or conductive liquid suspension, is injected through the clearance between the tips. Feed tip B is connected to an electric potential V, through a source of electric potential HV, with respect to a reference electrode G. The reference electrode G, which can have geometric shapes varied (for example ring or conductive plate) is found immersed in the liquid (1) and facing the feeding tips A and B. If feed tip B is not metallic, the liquid conductor is connected to potential V through A. At the output of feed tip A forms an electrified meniscus C with a sensibly conical shape from whose vertex is emitted a stationary capillary jet J of liquid (2). A flow rate Q3 of a third liquid (3), immiscible or poorly miscible with the liquid (2) is injected at appropriate flow rates through the tip B, concentric with A. A second meniscus M of liquid (3), anchored at the exit of tip B, it is formed inside the meniscus C. The meniscus M develops a conical tip from which, depending of the interfacial tension of the liquids (2) and (3), a jet, or train of drops, of liquid (3), flowing into the inside the liquid jet (2). A jet is thus formed J composed of the liquids (2) and (3) that flow coaxially in the sine of the dielectric liquid (1). The diameter of the compound jet is between 500 microns and 15 nanometers while the diameter of the inner jet (liquid (3)), or of the droplets, is between 200 microns and 1 nanometer.

Due to capillary instabilities, jet J breaks in a hydrosol of compound drops H so that the liquid (3) is encapsulated by liquid (2). The average size of the drops compounds is substantially uniform and is comprised in a range of values that vary between 500 microns and 15 nanometers.

The hydrosol is carried away by the outgoing flow Q, of liquid (1) that is extracted from the bath and the emulsion is collected in an attached device, see figure 5; the same liquid flow (1) is simultaneously injected into the bath.

The power tips A and B of the device They must have a diameter between 0.01 mm and 5 mm and 0.002 mm and 2 mm respectively.

The liquid feed rate (2) (Q_ {2}) that flows through the gap between the tips of feed A and B is between 10 -15 m 3 / s and 10-7 m 3 / s.

The liquid feed rate (3) that flows through feed tip B is between 10 -15 m 3 / s and 10 -7 m 3 / s.

When the distance between the tip of supply A and reference electrode G is comprised between 0.01 mm and 50 cm, the applied electric potential must be between 10 V and 300 KV.

Thus, the device object of the invention consists of:

a) Two feeding tips A and B located concentrically, or one of them contained in the other; by the tip B is fed a flow Q3 of a liquid (3) while by the clearance between A and B injects a flow rate Q2 of the liquid (2); leads A or B are connected to an electric potential V, if it is some of them metallic. If the tips are not metallic, the electrical contact can be made directly to the conductive liquid (2).

b) An RE container (see fig. 5) in which the dielectric liquid (1) resides, arranged so that the tips supply lines A and B are submerged in the liquid (1) and the potential V is a differential value with respect to an electrode G, also immersed in the liquid (1) and connected to a source of HV potential. Liquids (1) and (2) are immiscible or poorly miscible. At the outlet of the feed tip A a electrified capillary meniscus C, substantially conical in shape, from whose vertex a stationary capillary jet J of liquid (2), so that the liquid (1) completely surrounds the liquid (2). A second M liquid meniscus (3), anchored to the exit of tip B, is formed inside the meniscus C. The Meniscus M develops a conical tip from which a jet of liquid (3), or a train of drops of the same liquid, which co-flow with the liquid (2) to form a jet composed of both liquids. Said compound jet J has a diameter between 500 microns and 15 nanometers. The diameter of the liquid jet (3), or its drops, is comprised between 200 microns and 0 nanometers; this last situation corresponds to case where no liquid (3) is injected through the tip of feeding B.

The object of the present invention is procedure and device for generating jets compounds and the hydrosol formed spontaneously by the breakdown of the compound jet.

Another object of the present invention is the described procedure for the generation of jets and hydrosols when, instead of a conductive solid, a liquid is used conductor (4) as a reference electrode G. Liquids (1) and (4) must be immiscible and must form a separating interface the heaviest liquid being below this interface.

Brief description of the figures

Figure 1. Photograph of a simple electrospray of glycerin anchored in a metal needle. In this case I don't know injects fluid through the inner needle that is seen in the Photography. Note the very long jet of glycerin that is emitted from the vertex of the electrified conical meniscus.

Figure 2. Photograph of an electrospray of glycerin containing inside a meniscus of oil of silicone. Note the deformation of the oil meniscus silicone, which takes the shape of a conical tip, produced by the glycerin movement.

Figure 3. Photograph of a compound jet electrified in which the glycerin flowing through the outside contains another jet of petroleum jelly with a certain surfactant concentration (Span 80).

Figure 4. Schematic of the device used to produce electrified composite jets. (a) The cusp of the inner meniscus emits a stationary jet of liquid (3) that flows into the electrified jet of liquid (2). (b) The cusp of the inner meniscus emits a train of liquid droplets (3) that flow into the electrified jet of liquid (2). (c) When the inner capillary has a diameter significantly smaller than the outer capillary and the flow rate injected through it is less than a certain threshold value, the liquid (3) is injected in the form of drops ( dripping ) that flow through the inside the electrified jet of liquid (2). (d) When the inner capillary has a diameter significantly smaller than the outer capillary and the flow rate injected through it is greater than a certain threshold value, the liquid (3) forms a jet at the outlet of the capillary ( jetting ) that breaks by capillary instabilities in drops that flow inside the electrified jet of liquid (2).

Figure 5. Schematic of the device used to produce coaxial liquid jets of micro and nano sizes, in another liquid to obtain double emulsions, with extraction of the fluid bath and the resulting hydrosol.

Figure 6. Scheme of the two possible settings for the creation of type emulsions oil-in-water (emulsions type o / w). (a) Formation of a hydrosol H and precipitation of the droplets charged on the liquid electrode by electrical forces and gravitational. (b) Compound electrified jet impacting directly onto the liquid reference electrode.

Figure 7. Current emitted through the jet as a function of the dispersed conductive liquid flow rate.

Realization example 1

The basic apparatus used in this example consists in:

(a) Liquid (2) is supplied through a metallic capillary A with an external diameter of 0.8 mm and a 0.4 mm inside diameter; in this example, the liquid (2) was glycerin

(b) The dielectric liquid (3) is supplied to through a capillary B with external diameter of 0.36 mm and internal 0.15 mm; in this case the liquid (3) was petrolatum oil with a certain concentration of oil-soluble surfactant;

(c) A container RE to hold the liquid bath dielectric (liquid (1)), immiscible with liquid (2), and very low electrical conductivity; in this case it has been used hexane. The ends of tubes B and A through which they flow respectively the liquids (3) and (2) are immersed in the liquid (1);

\hbox{distancia de 1 cm;}

(d) A reference electrode G, such as a metal plate or ring, located opposite the end of the tube
bo A and also immersed in the liquid (1). The end of A and the reference electrode G were one

 \ hbox {distance of 1 cm;}

(e) A high voltage HV source, with one of the poles connected to tube A and the other connected to the electrode of reference G that is in contact with the liquid (1). The difference of applied potential was in this case 3 KV, as can be seen in figure 5.

By way of illustration, table I gives values experimental tests of the intensity of current carried by the compound jet formed by a jet composed of liquid (3) that flows through another jet of conductive liquid (2) that surrounds it completely and flows coaxially with the liquid (1).

1

These data are collected in Figure 7 where represents on the ordinate axis the emitted current and the root square of the flow on the abscissa axis. Experimental data represented thus follow very approximately the experimental law I? Q 1/2, which is common to all electrospray in mode stationary cone-jet. As in electrosprays in gaseous or vacuum atmosphere, our experiments in dielectric liquid atmospheres indicate that obtaining the stationary cone-jet mode requires operating with flow rates between two values. Lower one, which corresponds to the minimum ejectable from a liquid tip and another upper that is set by the maximum load density compatible with the existence of a stationary jet.

Jet breakage gives rise to compound droplets formed by a glycerin cover that encloses or encapsulates the Vaseline oil. Drops that have a very medium size uniform are dispersed in a dielectric liquid (1) and give rise to a double emulsion (oil of petrolatum-glycerin-hexane) of the type oil-water-oil (o / w / o).

Realization example 2

In this case the device is intended Disperse a hydrophobic liquid in a hydrophilic one maximizing the contact surface between both liquids, thus creating a oil-in-water emulsion (o / w). To do this, a device which is basically the same as in the example of embodiment 1, only in this case the dielectric liquid of the bath (liquid (1)) rests on a layer of a fourth liquid, liquid (4), which is a conductor (water for example) that connects electrically grounded. There is thus a layer of hexane located on top of another layer of water as seen in Figure 6.

The basic device used in this example consists in:

(a) Liquid (2) is supplied through a metallic capillary A with an external diameter of 0.8 mm and a 0.4 mm inside diameter; in this example, the liquid (2) was glycerin

(b) In the same way, the dielectric liquid (3) is supplied through a capillary B of external diameter 0.36 mm and internal 0.15 mm; in this case the liquid (3) was petroleum jelly oil with a certain concentration of surfactant oil soluble;

(c) A container RE1 containing a volume of a conductive liquid, liquid (4) (water in this example), on the resting the dielectric liquid in the bath (liquid (1)); in this case hexane has been used. The ends of the feeding tips B and A through which the liquids (3) and (2) flow respectively they are immersed in the liquid (1);

(d) The end of feed tip A is immersed in the liquid (1) and located at a distance of 1 cm of the liquid (4);

(e) A high voltage HV source, with one of the poles connected to the supply tip A and the other connected to the liquid (4) that is in contact with the liquid (1). The applied potential difference was in this case 3 KV.

The breakage of the jet (petroleum jelly by the inside and glycerin outside) ejected from the menisci gives rise to compound droplets formed by a glycerin coating that encloses or encapsulates petroleum jelly. The drops compounds dispersed in a dielectric liquid (1) are charged electrically and fall into the water under the simultaneous action of the gravity and electric field. Once the hydrosol drops compounds H reach the water, the glycerin coating disappears because it is soluble in water and submicron drops of petroleum jelly dispersed in the liquid (4), see figure 6th.

Another way of operating is to reduce appropriately the separation distance between tips of power supply and the liquid reference electrode [liquid (4)] so that jet J reaches the liquid (4) before breaking (see figure 6b), so that the emulsion is obtained directly drops of Vaseline oil dispersed in water (emulsion o / w).

Claims (9)

1. Procedure to produce coaxial jets electrified micro and submicron diameter within dielectric liquids and generate the emulsion resulting from breakage varicose micro / nano jet consisting of the injection of a flow rate Q2 of a liquid (2) through a tip of feed A; where A encompasses another feed tip B through which a flow rate Q3 of a liquid (3) flows; where said feed tips are immersed in a dielectric liquid (1), and connected to a potential electrical V relative to an immersed reference electrode also in the liquid (1); where for a range of values of Q2 and V we shape, anchored at tip A, a capillary meniscus C with a shape sensibly conical from whose vertex a capillary jet is emitted liquid stationary (2); where the liquid (3) forms a capillary meniscus M anchored at B from whose vertex a jet is emitted that flows coaxially with the liquid (2), resulting in a compound jet capillary, stationary, so that the liquid (2) surrounds or encapsulates the liquid (3) and such that said jet has a diameter between 500 microns and 15 nanometers, which is appreciably less than the characteristic length of the liquid meniscus electrified from which it emanates. 2. The method of claim 1 where the liquid (3) forms a capillary meniscus M anchored at B from whose vertex is emitted a train of drops that flows coaxially with the liquid (2), resulting in a capillary compound jet, stationary, so that the liquid (2) surrounds or encapsulates the liquid (3) and such that said jet has a diameter comprised between 500 microns and 15 nanometers, which is significantly less than the characteristic length of the electrified liquid meniscus of which emanates. 3. The method of claim 1 wherein drops of liquid (3) are emitted from tip B, which flow coaxially with the liquid (2) resulting in a compound jet capillary, stationary, so that the liquid (2) surrounds or encapsulates the liquid (3) and such that said jet has a diameter between 500 microns and 15 nanometers, which is appreciably less than the characteristic length of the liquid meniscus electrified from which it emanates. 4. The method of claim 1 where from tip B a jet of liquid (3) is emitted, which flows coaxially with the liquid (2) resulting in a compound jet capillary, stationary, so that the liquid (2) surrounds or encapsulates the liquid (3) and such that said jet has a diameter between 500 microns and 15 nanometers, which is appreciably less than the characteristic length of the liquid meniscus electrified from which it emanates. 5. Device for producing compound jets electrified micro and submicron diameter within dielectric liquids and generate the emulsion resulting from breakage varicose micro / nano jet, according to claims 1 to 4, consisting of a feed tip A through which a flow rate Q2 of a liquid (2) and that encompasses another tip of feed B through which a flow rate Q3 of a liquid flows (3); where said feed tips are immersed in a dielectric liquid (1), and connected to a potential electrical V with respect to a reference electrode also immersed in the liquid (1). 6. Device for producing electrified compound jets of micro and submicron diameter within dielectric liquids and generating the emulsion resulting from varicose breakage of the micro / nano jet, according to claim 5, characterized in that the 2 feeding tips have diameters between 0.01mm and 5mm. 7. Device for producing electrified compound jets of micro and submicron diameter within dielectric liquids and generating the emulsion resulting from varicose breakage of the micro / nano jet, according to claims 5 and 6, characterized in that the flow rates that flow through the tips feed are comprised between 10 <-15> m <3> / s and 10 <-7> m <3> / s. 8. Device for producing electrified compound jets of micro and submicron diameter in dielectric liquids and generating the emulsion resulting from varicose breakage of the micro / nano jet, according to claims 5 to 7, characterized in that for a distance between each tip of power supply and the reference electrode between 0.01 mm and 50 cm, the applied electric potential V is between 10 V and 300 KV. 9. Device for producing electrified compound jets of micro and submicron diameter in dielectric liquids and generating the emulsion resulting from varicose breakage of the micro / nano jet, according to claims 5 to 8, characterized in that the reference electrode is a liquid conductor (4) immiscible with the dielectric liquid (1).