Patent Application
20100247760
The invention relates to a multi component particle generating system.
In the art, producing multicomponent particles is complex when aiming to produce smaller particle volumes in larger quantities. EP1364718 discloses a concentric nozzle arrangement to produce a mixed or encapsulated particle. However, the tuning of relative viscosities and fluid pressures of the two components is complex and limits the application possibilities. Furthermore, U.S. Pat. No. 4,341,310 teaches an arrangement of two systems generating streams of droplets arranged at an angle, to selectively eject a droplet from one of the droplet streams by a droplet of the other of the droplet streams. This arrangement is aimed at generating precisely timed collisions by use of polarity adjustment of the fluid. It is difficult to produce large quantities of multicomponent particles in this manner.
U.S. Pat. No. 5,230,735 discusses a system for mixing powder particles with fluid material via a wetted inner wall. This system easily leads to clogging and coagulation of powder particles. Therefore, the provision of individually generated multicomponent particles is not possible. A similar mechanism is illustrated in U.S. Pat. No. 2,067,908.
Furthermore, EP0563402 discloses a granule coating apparatus wherein a powder nozzle is formed to have a central powder blowout opening and a concentrically arranged tapered coating liquid blowout path. This system is provided to form good intermixing with the powder and the liquid, however, due to the form of the blowout jet, selected isolated coating control of particles is not possible; thus easily leading to clogging.
In one aspect, the invention aims to provide a multicomponent particle generating system that mitigates the problems discussed above and that can provide for coating and/or intermixing of isolated particles. To this end, a continuous particle generating system is provided according to the features of claim 1. In particular, a multicomponent particle generating system is provided comprising first and second pressure systems comprising first and second nozzles respectively, for pressurizing first and second fluids respectively. The first nozzle is constructed to generate at least one isolated particle of first fluid; wherein said second nozzle is arranged to generate a generally uninterrupted fluid jet; said first and second nozzles arranged to have said isolated particle collide with the fluid jet so as to encapsulate said particle of first fluid by the second fluid.
In addition, the invention provides a method of generating a multicomponent particle comprising: generating at least one isolated particle of a first material; generating a generally uninterrupted fluid jet of a second material; and colliding said isolated particle with the fluid jet so as to combine said particle of first material with the second material.
By colliding the particles in the above described manner, a large volume of special purpose multicomponent particles can be created.
Other features and advantages will be apparent from the description; in conjunction with the annexed drawings, wherein:
The outlet channel 42 of the pressure system 40 connects with a damper 43. The outlet of the damper 43 is connected to the print head 12 via channel 10. The channel in the print head 12 is provided with at least one outflow opening, nozzle 14 through which the fluid material 4 exits under pressure in the form of a jet breaking up into drops, in order for these drops, after being selectively deflected, or directed, towards fluid jet 300. A transverse dimension of the nozzle 14 can be in the interval of 5-300 micron.
In this example, the channel 10 comprises a portion downstream of the nozzle 14 which is provided with a cock 15. By opening the cock 15, the printhead 12 can be flushed with a flushing material/flushing ink which is present in the channel.
The illustrated apparatus 2 is a printer of the continuous jet-type, whereby a continuous stream of drops to be printed is formed. However, the invention may be also applicable in a drop-on-demand type printer system where drops are delivered through the outflow opening only if the printhead has been activated to that effect. For the purpose of forming a jet breaking up into drops, the apparatus 2 is provided with a pressure regulating mechanism for varying the pressure of the material 4 upstream of the outflow opening.
The apparatus 2 in this example may be provided with a pre-treatment system 16.1, 16.2 enabling the drops to be pretreated. To that end, the pre-treatment system 16.1, 16.2 is provided, for instance, with a heater, cooler, a drying system, gas treatment, radiation treatment (UV treatment) by means of which the drops can be pretreated. Further, the apparatus 2 may be provided with a collector 18 by which particular drops can be captured. Clearly, the collector 18 is shown to be able to collect the isolated droplets after collision, typically, after having flown in a free flight sufficiently to be able to collect the particles substantially individually, for example, after a dry-out phase or a chemical reaction phase in free flight.
The pressure generating means 40 may be constructed for providing a printing pressure in an interval of 0.1-3000 bars. Accordingly, high-viscous materials 4, for instance in a range of 0.1-800 mPa·s may be passed under a predetermined pressure through the channel in the direction of the nozzle 14. Under this pressure, viscous fluid 4 accommodated in the reservoir is forced through the channel 10 to the nozzle 14 in the printhead 12. Next, the viscous fluid 4 is forced through the nozzle 14 to fly as droplets 30 in free flight towards the collector 18 arranged in a flight trajectory of the particle 30.
The apparatus 2 according to
In addition, a second pressure system 20 is provided comprising a second nozzle 140. The second nozzle 140 is arranged to generate a generally uninterrupted fluid jet 300.
Preferably the second nozzle 140 is slitted to produce a sheet form or curtain form uninterrupted fluid jet having a relatively thin thickness of about several microns, preferably less than 1500 micron, to arrive at smaller thicknesses. Typically, the sheet form jet, at a particle traversing place has a thickness which is relatively thin so that the particles can traverse without being caught by the jet. The jets may have varying forms such as concentric forms flat shapes or curved shapes, but are essentially not disturbed near a particle traversing location, contrary to, for example, such as in EP0563402 by transverse directed flows of additional jets. A cross-section of the second nozzle 140 may be formed having broadened opposite sides. The second pressure system 20 is arranged to direct the fluid jet 300 at an angle relative to the direction of the beam of the isolated droplets 30 generated by the nozzle 14 of the fluid pressure system 2. Clearly, as follows from the described embodiments and related figures, in this context, the term “isolated” refers to the feature that particles are generated substantially separate from each other, and that, although having arbitrary incidence frequency, particles will be spatially separated when directed towards the jet. Although the invention can be practiced with other particle generating devices, for fluid particles, drop on demand or continuous droplet generating devices based on the Rayleigh break up mechanism are suitable since these devices can impart sufficient kinetic energy to the droplets to collide with a jet and maintain their individuality. Depending on the angle, the fluid nozzle 14 and second nozzle 140 are arranged to have the isolated droplets 30 collide with fluid jet 300 generated by the second nozzle, either in transmissive mode or in reflective mode. Accordingly, as will be further illustrated in the examples a combined droplet is formed of the first fluid (in any phase state) with the second fluid of the fluid jet 300 to provide a multicomponent droplet. Printhead 120 of pressure system 20 is depicted with heating element 340; inlet channel 100; cock 150 and fluid material 400, to produce fluid jet 300.
Although it will be illustrated further with reference to
Referring to
In this first embodiment a “true encapsulation” of the droplets 30 with fluid jet material 300 is formed, optionally also by additional fluid jets 310 and higher. Thus, the droplets are formed as a core having an encapsulation formed around the core. Accordingly, complex multilayered/multimaterial particles 32 can be formed according to one aspect of the invention. Since the droplet generating arrangement 14 is of a continuous type this can produce higher volumes and will be interesting for industrial applications. It should be note that the droplets 30 are formed by ejecting a liquid but may become a solid before or after traversing fluid jet 300, for example pending on a preprocess 50 that may be performed on the droplets 30. Such pretreatment can be heating or cooling or drying or gas treatment or a radiation treatment, for example UV-treatment or any technique that may be feasible to pretreat the droplets 30 prior to colliding them with the fluid jet 300. Applications can be for example toner fillings or photography related applications or an application where uniform droplet sizes are of importance for example for providing solder paste. In one embodiment solder balls can be formed by emitting solder droplets and having them coated with the flux provided by a fluid jet. With this process solder balls can be coated with a small amount of flux to generate highly efficient solder paste. Another application can be in food, feed, pharma, cosmetics and other areas where a stabilization or protection of sensitive ingredients is needed. For example by encapsulating these with a permeation-limiting shell material. These ingredients can be protected from degradation by the aforementioned parameters, in order to increase the shell-life of certain products or to enable the use of hitherto unusable ingredients. In this respect the fluid jet material can be chosen to provide a chemically protective encapsulation, or to provide a UV-protective encapsulation. In this respect the protection is designed against an unexpected chemical treat or physical treat of the ingredients, for example but not limited to UV-light, or oxygen, water, PH, ions or chemicals. In addition the encapsulation can be provided to shield reactive ingredients, for example reactive polymers or glues or epoxy resins from environments. In this respect the first material is arranged to be chemically reactive with a for a predetermined environment parameter, for example but not limited to UV-light, oxygen, water, PH, ions or other chemicals. Degradation or rupturing of the encapsulation material may lead to release of the core material which would be able to provide materials that are self-repairing where such particles may be embedded in a matrix material or premixed two-component glue.
The first droplet material may stay in any desired phase depending on material parameters including gas phase, liquid phase or solid phase. For example liquids such as water maybe encapsulated by a solid encapsulation to provide particles filled with water. These might be used to generate instant ready meal without the need of adding extra water. The advantage of having encapsulated is that the water releases when it is necessary and not beforehand.
Another application could be wherein these second materials arranged to be chemically reactive with the predetermined chemical reactant, to provide a triggered release of the first material embedded in the encapsulation. Also the second material can be designed to have suitable material properties to have a predetermined permeability to the first material that is encapsulated inside to provide a time delayed release of the first material. In particular, depending on shell material, particles 31 can be made that can be used as slow or triggered release applications. By selecting a shell material that has a degree of permeability the payload can diffuse out of the particles with a diffusion rate depending on the permeability of the shell.
Alternatively a shell material can be selected that is impermeable until made permeable by a certain trigger (e.g. water, enzymes, pH, temperature, mechanical energy . . . ). This will then result in a release of the payload as described above. In addition, complete and instantaneous release of the payload may also be achieved as a result of a trigger.
Applications for these types of systems can be found in food, feed, and pharma, where release in specific areas in a digestive tract is required; this can be achieved by the action of enzymes present in the various parts of the in a digestive tract.
Another application may be in personal care, where a body cream may contain particles (e.g. perfume, deodorant) that, upon heating, rupture or melt to release an ingredient (e.g. menthol or ethanol), that will produce a cooling or soothing effect.
Other applications may be found in the slow release of fragrances (cosmetics, home care), antibacterial (paint, anti fouling coatings), antioxidants (food, feed).
As shown in
Such morphologies can be of interest since the non-symmetrical aspect ratio can provide oriented or aligned particles 32 as in
It should be noted that the materials 30 and 300 may be a pure liquid or any other suitable forms of fluids that may already be mixed or emulsified or any other condition.
In a first embodiment 350, if droplets 30 comprise of e.g. an oil in ethanol then shooting drops 30 through a screen 300 (e.g. water) will result in a mixing of the ethanol and the water and a demixing of the ethanol and oil, ultimately giving an emulsion of oil in an ethanol/water mixture. (Note: also other solvents and mixtures are possible)
The advantage of such a setup might lie in the fact that the emulsion might be very homogeneous, in that the oil droplets within all of the ethanol/water drops might have very similar sizes. To keep the oil droplets within a single drop separated, a stabilizer (surfactant) may be required.
If the demixing process described above results in the formation of a single oil droplet within each ethanol/water drop then the size of this droplet will be smaller than the original ethanol/oil droplet that was printed. Inherent to the system, each ethanol/water droplet will contain an identical oil droplet. This means that this method can be used to make uniform oil droplets (or other particles) of a size that is not limited by the (lowest possible) size of the printer nozzle.
Applications may be found in pharma where emulsions are frequently used. The potentially small particle size would result in a large surface area per weight, and hence a faster dissolution or better uptake in vivo, potentially leading to higher bioavailability (administration: dermal, pulmonal, mucosal, oral).
The same holds true for food, feed, and cosmetic applications. In addition, smaller emulsions are of interest for pharma, food, and cosmetics as the sensory perception of such small emulsions may be more desirable.
Other applications of these types of emulsions may be found in the paint industry where emulsions are frequently used.
Solidification of the small (inner) droplets might result in interesting nanomaterials, or particles that may have applications in heterogeneous catalysis.
In a second embodiment 360, similar to the previous system, droplets 30 may comprise a solid compound (non-water-soluble) dissolved in ethanol. Printing drops of this solution through screen 300 (e.g. water) would then result in precipitation or crystallization of the solid compound. Analogously to the emulsion system, the size of the solid particles might well be very small, allowing the formation of nanoparticles or nanocrystals. In addition the particle size might be very monodisperse. (Note: crystallization may also be induced by a change in pH, salt concentration or some other parameter.)
Small particles have large surface area per weight and therefore are interesting for applications in pharma, food, feed, and cosmetics as explained for the emulsion system (i.e. bioavailability). Also the sensory perception argument holds true.
Again this system may be interesting for the production of catalyst particles or (nano)particles with nanomaterial applications.
In a third embodiment 370 rather than leading to emulsification or precipitation, the mixing of solution 1 and 2 may result in gelation of the particle. An example of this may be to print drop of a Na-alginate solution through a Ca2+ solution screen, thus producing microgel-particles. Microgel particles are being investigated widely for various applications ranging from drug delivery devices to environmental applications in which they may be used as nanosponges.
In addition, the use of a printing setup allows one to start with a relatively viscous solution (i.e. a concentrated polymer solution), resulting in gel particles with a very high solid content not easily attainable by other methods.
As gels generally consist of two separate but each continuous phases, the removal of one of the two phases would result in a micro/macroporous material of well defined size (monodisperse) that would have zeolite-like properties.
In a fourth embodiment 380, the mixing of several reactants by coalescence of droplets 31 and fluid jet 300 can be used to carry out chemical reactions. Each drop would function as a microreactor, giving many of the advantages for which microfluidic devices are currently being investigated. Heat effects and dangerous compounds would be easier to control, however, the continuous process would still allow the production of significant quantities of material.
It should be noted that the mixing embodiments 350, 360, 370 and 380 can be used in addition to the encapsulation embodiment discussed in
In addition, they may be used as additives for self-stratifying layers. When for example embedded in apolar matrix, the polar part of the particles will make them diffuse to the surface.
When applied in such coatings the shape of the particles and their organization in the layer can result in optical effects or a lotus effect.
Suitably the tube diameter of the second part 63 at the start of the converging flow is 8-12 times larger than the tube diameter at the end of the converging flow, i.e. at the release opening 65 of the tube. To establish this, the diameter of the second part 63 converges over the length of said part in respect of the central axis of said second part in an angle in the range of from 2-90°. More preferably, between 5° and 90°, most preferably between 5-45°.
Suitably, part 63 has a length in the range of from 0.5-150 cm. Preferably, the second part 63 has a length in the range of from 0.5-100 cm.
Accordingly, converging part 63 focus and accelerate the carrier gas flow containing particles 30. Suitably, the carrier gas can be normal air but can also be selected from the group consisting of nitrogen, hydrogen, argon or a mixture thereof.
A characterization of the gas flow is through the Stokes number. It will be appreciated that the Stokes number (St) of a particle in a gas flow, in our case droplets, is defined as follows:
wherein ρp is the particle density; Dp the particle diameter; Cc the correction factor (=1); Uo is the characteristic velocity; μf is the fluid viscosity; and Lc is the typical length scale.
To prevent disturbances of the fluid jet 300, a carrier gas deflector system 62 is arranged to deflect the gas flow before collision with the fluid jet 300, so as to have said particle collided with the fluid jet 300 substantially free from the gas flow. Typically, the gas deflector system is formed by a flow channel deflecting the gas stream away from a particle collision direction. At the end of the converging first part 63, the gas stream guiding system comprises a first release opening 65 for releasing the gas into the gas deflector system 62.
Accordingly, in this embodiment, in converging part 63 a steady gas flow is maintained over a first period of time, wherein the Stokes number of the droplets in the gas stream is less than 1 during the first period of time. Which will make the particles follow the gas flow and they will accelerate substantially equal with the gas acceleration. Subsequently, the steady flow of the droplets in the gas stream is converted into a converging flow and maintaining the converging flow of the droplets over a second period of time, whereby the Stokes number of the droplets in the gas stream increases up to a value higher than 10 during the second period of time, near the end of part 63 leading to part 65. Typically, the first and second periods of times may be in the range of from 0.1-10 seconds and 0.01-1 seconds respectively. In the second period, the particles will not be further accelerated but will follow their own course, towards second release opening 66.
In this embodiment, the deflector is formed by a flow channel deflecting the gas stream away from a particle collision direction and wherein, in the flow channel, along a particle collision direction and opposite the first release opening 75; a second release opening 66 is provided for providing passage to the particle 30. Due to the high Stokes number the kinetic energy of the particles will be dominant and they will follow their own trajectory through opening 66. Typically, to direct the volumetric gas flows away from the second release opening 66, the first release opening 65 is larger than the second release opening 66. Pumps 61 may be provided in a counter flow path between the second part and the first part, to maintain the carrier gas stream in almost a closed system, (re)injecting the gas into the first part 64, after flowing from the second part 63.
In the above illustrated examples a method has been demonstrated for generating a multicomponent particle comprising generated at least one isolated particle 30 of a first material, generating a generally uninterrupted fluid jet of a fluid jet 300 of a second material and colliding said isolated droplet 30 with the fluid jet 300 so as to combine said droplet of the first material with the second material. In this respect it is noted that the term “generally uninterrupted” refers to a fluid jet, without dividing up into separate droplets by Rayleigh break up effect or by any other disturbance such as mixing or combining of flows when collided, except, of course the collision of the particle itself. However, more downstream of the jet such could be taking place without consequences for the particle encapsulation. By providing curtain form liquid of a generally planar shape a generally large impact area can be provided so that a plurality of particle beams can be aimed at the fluid jet and large quantities of particles can be produced. The planarity of the fluid jet can be increased by having a cross-section of the fluid jet nozzle 140 in a slip form having broadened opposite sides. Further, applied pressures can range from 0.1-3000 bars and applied temperatures can range from −200 to +1800° C. Viscosities may range from 0.5 10−3 to 3000 10−3 Pa.s upon exit. In addition, the term “fluid” may encompass, without limitation, a liquid or liquid mixtures; solutions; emulsions; dispersions or melts, and may include gasses or liquefied gasses. Furthermore, although the invention has been described with fluid particles as embodiments, other types of particles may be applied likewise, such as solid grains or seeds etc. The invention has been described on the basis of an exemplary embodiment, but is not in any way limited to this embodiment. Diverse variations also falling within the scope of the invention are possible.
| Number | Date | Country | Kind |
|---|---|---|---|
| 07112887.0 | Jul 2007 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/NL08/50456 | 6/7/2008 | WO | 00 | 6/1/2010 |
