Nano spray dryer
Encyclopedia
Nano spray dryers refer to using spray drying
to create particles in the nanometer range. Spray drying is a gentle method for producing powder
s with a defined particle size out of solutions, dispersions, and emulsions which is widely used for pharmaceuticals, food, biotechnology, and other industrial materials synthesis.
In the past, the limitations of spray drying were the particle size (minimum 2 micrometre
s), the yield (maximum around 70%), and the sample volume (minimum 50 ml for devices in lab scale). Recently, minimum particle sizes have been reduced to 300 nm, yields up to 90% are possible, and the sample amount can be as small as 1 ml. These expanded limits are possible due to new technological developments to the spray head, the heating system, and the electrostatic particle collector. To emphasize the small particle sizes possible with this new technology, it has been described as "nano" spray drying. However, the smallest particles produced are in the sub-micrometre range common to fine particles rather than the nanometer scale of ultrafine particles
.
The drying gas enters the system via the heater. A new kind of heater system allows for laminar air flow
. The spray head sprays the fine droplets with a narrow size distribution into the drying chamber. The droplets dry and become solid particles. The solid particles are separated in the electrostatic particle collector. The exhaust gas is filtered and sent to a fume hood or the environment. The inlet temperature is controlled by a temperature sensor.
This technique is widely used in the pharma market. Because of the small sample amounts and the high yields it is ideal for spray drying expensive substances in basic research. The following list shows examples of what is possible:
Materials science:
This new technique offers new prospects in materials science
, specially in the nanomaterial field. Now it is possible to spray dry fine particles. The following list shows examples of what is possible:
Food:
Also in the field of food science
this technology offers new possibilities. Especially in the currently vibrant field of functional food
, the following list shows examples of what is possible:
A piezoelectric system precisely vibrates a fine mesh
. Vibration produces fine droplets with a narrow size distribution
.
The laminar flow is produced by pressing the air through a porous metal foam
.
The electrostatic particle collector charges the dry particles' surface and deflects them with an electrical field. To produce the electrical field, a high voltage (16 kV) is applied to a round collector tube. The electrical field builds up between the inner wall of the collector tube and the tips of a grounded star electrode. To have a low level of energy in the system the current is very low.
After getting deflected the particles stay at the inner wall of the particle collector tube and are completely uncharged. This separation method works fine for all kinds of materials.
The efficiency of the electrostatic particle collector is very high: 99% of all particles that enter the system are collected.
Spray drying
Spray drying is a method of producing a dry powder from a liquid or slurry by rapidly drying with a hot gas. This is the preferred method of drying of many thermally-sensitive materials such as foods and pharmaceuticals. A consistent particle size distribution is a reason for spray drying some...
to create particles in the nanometer range. Spray drying is a gentle method for producing powder
Powder (substance)
A powder is a dry,thick bulk solid composed of a large number of very fine particles that may flow freely when shaken or tilted. Powders are a special sub-class of granular materials, although the terms powder and granular are sometimes used to distinguish separate classes of material...
s with a defined particle size out of solutions, dispersions, and emulsions which is widely used for pharmaceuticals, food, biotechnology, and other industrial materials synthesis.
In the past, the limitations of spray drying were the particle size (minimum 2 micrometre
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...
s), the yield (maximum around 70%), and the sample volume (minimum 50 ml for devices in lab scale). Recently, minimum particle sizes have been reduced to 300 nm, yields up to 90% are possible, and the sample amount can be as small as 1 ml. These expanded limits are possible due to new technological developments to the spray head, the heating system, and the electrostatic particle collector. To emphasize the small particle sizes possible with this new technology, it has been described as "nano" spray drying. However, the smallest particles produced are in the sub-micrometre range common to fine particles rather than the nanometer scale of ultrafine particles
Ultrafine particles
Ultrafine particles are nanoscale, less than 100 nanometres. Regulations do not exist for this size class of ambient air pollution particles, which are far smaller than the regulated PM10 and PM2.5 size classes and are believed to have several more aggressive health implications than those classes...
.
Functional principle
The functional principle is basically the same as with normal spray dryers. There are just different technologies that are used to do similar things.The drying gas enters the system via the heater. A new kind of heater system allows for laminar air flow
Laminar flow
Laminar flow, sometimes known as streamline flow, occurs when a fluid flows in parallel layers, with no disruption between the layers. At low velocities the fluid tends to flow without lateral mixing, and adjacent layers slide past one another like playing cards. There are no cross currents...
. The spray head sprays the fine droplets with a narrow size distribution into the drying chamber. The droplets dry and become solid particles. The solid particles are separated in the electrostatic particle collector. The exhaust gas is filtered and sent to a fume hood or the environment. The inlet temperature is controlled by a temperature sensor.
Applications
Pharmaceuticals:This technique is widely used in the pharma market. Because of the small sample amounts and the high yields it is ideal for spray drying expensive substances in basic research. The following list shows examples of what is possible:
- InhalableInhalationInhalation is the movement of air from the external environment, through the air ways, and into the alveoli....
drugs for Dry Powder InhalerInhalerAn inhaler or puffer is a medical device used for delivering medication into the body via the lungs. It is mainly used in the treatment of asthma and Chronic Obstructive Pulmonary Disease . Zanamivir , used to treat influenza, must be administered via inhaler...
s (DPI‘s) - Nano- and microencapsulation of liposomeLiposomeLiposomes are artificially prepared vesicles made of lipid bilayer. Liposomes can be filled with drugs, and used to deliver drugs for cancer and other diseases. Liposomes are composite structures made of phospholipids and may contain small amounts of other molecules...
s - Stabilization of heat-sensitive vaccineVaccineA vaccine is a biological preparation that improves immunity to a particular disease. A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe or its toxins...
s, insulinInsulinInsulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
, growth hormones - EncapsulationEncapsulation- Chemistry :* Molecular encapsulation, in chemistry, the confinement of an individual molecule within a larger molecule* Capsule , in pharmacy, the enclosure of a medicine within a relatively stable shell for administration...
of nanoparticleNanoparticleIn nanotechnology, a particle is defined as a small object that behaves as a whole unit in terms of its transport and properties. Particles are further classified according to size : in terms of diameter, coarse particles cover a range between 10,000 and 2,500 nanometers. Fine particles are sized...
drugDrugA drug, broadly speaking, is any substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.In pharmacology, a...
s for high bioavailabilityBioavailabilityIn pharmacology, bioavailability is a subcategory of absorption and is used to describe the fraction of an administered dose of unchanged drug that reaches the systemic circulation, one of the principal pharmacokinetic properties of drugs. By definition, when a medication is administered... - Nanocapsules of biodegradable polymers (lactides, glycolides)
- Porous drug carriers for nanoparticle suspensions
- Excipients for controlled drug release studies: trehaloseTrehaloseTrehalose, also known as mycose or tremalose, is a natural alpha-linked disaccharide formed by an α,α-1,1-glucoside bond between two α-glucose units. In 1832, H.A.L. Wiggers discovered trehalose in an ergot of rye, and in 1859 Marcellin Berthelot isolated it from trehala manna, a substance made...
, mannitolMannitolMannitol is a white, crystalline organic compound with the formula . This polyol is used as an osmotic diuretic agent and a weak renal vasodilator...
, lactoseLactoseLactose is a disaccharide sugar that is found most notably in milk and is formed from galactose and glucose. Lactose makes up around 2~8% of milk , although the amount varies among species and individuals. It is extracted from sweet or sour whey. The name comes from or , the Latin word for milk,...
, HPMC, PVAPVAPVA may refer to:* Paralyzed Veterans of America* Patrick Van Aanholt , a Dutch footballer playing for Chelsea F.C.* Patterned vertical alignment, an LCD technology* Penn Virginia Corporation * Perkiomen Valley Academy...
, chitosanChitosanChitosan is a linear polysaccharide composed of randomly distributed β--linked D-glucosamine and N-acetyl-D-glucosamine...
, dextrine, PLGAPLGAPLGA or poly is a copolymer which is used in a host of Food and Drug Administration approved therapeutic devices, owing to its biodegradability and biocompatibility. PLGA is synthesized by means of random ring-opening co-polymerization of two different monomers, the cyclic dimers of glycolic...
, starchStarchStarch or amylum is a carbohydrate consisting of a large number of glucose units joined together by glycosidic bonds. This polysaccharide is produced by all green plants as an energy store...
, gelatinGelatinGelatin is a translucent, colorless, brittle , flavorless solid substance, derived from the collagen inside animals' skin and bones. It is commonly used as a gelling agent in food, pharmaceuticals, photography, and cosmetic manufacturing. Substances containing gelatin or functioning in a similar...
Materials science:
This new technique offers new prospects in materials science
Materials science
Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates...
, specially in the nanomaterial field. Now it is possible to spray dry fine particles. The following list shows examples of what is possible:
- Fine metal particles for novel catalysts
- Fine magnetic powders
- Carbon nanotubeCarbon nanotubeCarbon nanotubes are allotropes of carbon with a cylindrical nanostructure. Nanotubes have been constructed with length-to-diameter ratio of up to 132,000,000:1, significantly larger than for any other material...
s as additives - High performance ceramicCeramicA ceramic is an inorganic, nonmetallic solid prepared by the action of heat and subsequent cooling. Ceramic materials may have a crystalline or partly crystalline structure, or may be amorphous...
s with novel structures and high specific surface area - Titanium oxideTitanium oxideTitanium oxide may refer to:* Titanium dioxide , TiO2* Titanium oxide , TiO, a non-stoichiometric oxide* Titanium oxide , Ti2O3* Ti3O* Ti2O* δ-TiOx...
particles - Nanoparticle suspensions for agglomerationAgglomerationIn the study of human settlements, an urban agglomeration is an extended city or town area comprising the built-up area of a central place and any suburbs linked by continuous urban area. In France, INSEE the French Statistical Institute, translate it as "Unité urbaine" which means continuous...
- Silicon oxideSilicon oxideSilicon oxide may refer to either of the following:*Silicon dioxide, SiO2, very well characterized*Silicon monoxide, SiO, not very well characterized...
nanoparticle agglomerates - Finest pigmentPigmentA pigment is a material that changes the color of reflected or transmitted light as the result of wavelength-selective absorption. This physical process differs from fluorescence, phosphorescence, and other forms of luminescence, in which a material emits light.Many materials selectively absorb...
s for paintPaintPaint is any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film. One may also consider the digital mimicry thereof...
s and coatingCoatingCoating is a covering that is applied to the surface of an object, usually referred to as the substrate. In many cases coatings are applied to improve surface properties of the substrate, such as appearance, adhesion, wetability, corrosion resistance, wear resistance, and scratch resistance...
s
Food:
Also in the field of food science
Food science
Food science is a study concerned with all technical aspects of foods, beginning with harvesting or slaughtering, and ending with its cooking and consumption, an ideology commonly referred to as "from field to fork"...
this technology offers new possibilities. Especially in the currently vibrant field of functional food
Functional food
Functional food is a food where a new ingredient has been added to a food and the new product has a new function ....
, the following list shows examples of what is possible:
- Nano food – Functional additivesFood additiveFood additives are substances added to food to preserve flavor or enhance its taste and appearance.Some additives have been used for centuries; for example, preserving food by pickling , salting, as with bacon, preserving sweets or using sulfur dioxide as in some wines...
- Encapsulation of fruit aromas, flavours, or perfumePerfumePerfume is a mixture of fragrant essential oils and/or aroma compounds, fixatives, and solvents used to give the human body, animals, objects, and living spaces "a pleasant scent"...
s - Spray drying of fine powder aromas for pet food
- Encapsulation of fish oil for smell protection
- Vitamins, other food additives, etc.
Spray head
One of the three new technologies that makes "nano" spray drying possible is the spray head.A piezoelectric system precisely vibrates a fine mesh
Mesh
Mesh consists of semi-permeable barrier made of connected strands of metal, fiber, or other flexible/ductile material. Mesh is similar to web or net in that it has many attached or woven strands.-Types of mesh:...
. Vibration produces fine droplets with a narrow size distribution
Particle size distribution
The particle-size distribution of a powder, or granular material, or particles dispersed in fluid, is a list of values or a mathematical function that defines the relative amounts of particles present, sorted according to size...
.
Heating system
In the field of "nano" spray drying a new heating system is used to provide the drying gas to produce the particles. The gas flow in the system is laminar and not turbulent as in common spray drying. The advantage of a laminar flow is that the particles fall straight down from the spray head and do not stick to the glass wall.The laminar flow is produced by pressing the air through a porous metal foam
Metal foam
A metal foam is a cellular structure consisting of a solid metal, frequently aluminium, containing a large volume fraction of gas-filled pores. The pores can be sealed , or they can form an interconnected network . The defining characteristic of metal foams is a very high porosity: typically...
.
Electrostatic particle collector
To collect the very fine particles a new technology is used in the field of "nano" spray drying. The reason is that common cyclone technology depends on the particle mass; particles smaller than 2 μm can’t be separated and instead exit the system along with the exhaust gas.The electrostatic particle collector charges the dry particles' surface and deflects them with an electrical field. To produce the electrical field, a high voltage (16 kV) is applied to a round collector tube. The electrical field builds up between the inner wall of the collector tube and the tips of a grounded star electrode. To have a low level of energy in the system the current is very low.
After getting deflected the particles stay at the inner wall of the particle collector tube and are completely uncharged. This separation method works fine for all kinds of materials.
The efficiency of the electrostatic particle collector is very high: 99% of all particles that enter the system are collected.