Ultrasonic Homogenizers for Liquid Processing

Particle Surface Cleaning

The surface of powder particles is a key factor for the interaction with the surrounding liquid. It is at such solid/liquid phase boundaries, where dissolving, chemical reactions or catalytical activity take place. Ultrasonic homogenization increases the exposure of particle surface to the liquid phase by uniform deagglomeration and particle size reduction. During catalytic and chemical reactions, the particle surface can be blocked by residue deposition, boundary layer formation, oxide layers and fouling. Ultrasonic cavitation causes high-speed liquid jets, high hydraulic shear and inter-particle collisions resulting in particle surface cleaning. Hielscher ultrasonic devices can be used in a batch or in-line to remove contaminations from particles in liquids.

Agitation

Stirring is an often-underestimated process and requires reliable equipment, especially for increasing viscosities and volumes. Conventional agitators such as paddle mixers or rotor-stator mixers are limited by various factors, including viscosity and scalability. Therefore, high power ultrasonicators are the right choice for your mixing process due to their advantages in higher through-put, time saving, lower operational costs, safe operation (no moving parts) and simple maintenance.

Hydrating

When mixing dry powders, such as, pigments, thickeners or gums with liquids, the powder particles tend to form agglomerates, lumps or so-called “fish-eyes” (partially hydrated powder with a dry powder core). Agitators and stirrers will wash the surface of such agglomerates, only. This results in long mixing times and poor product quality. Ultrasonic mixing breaks agglomerates and lumps leading to an agglomerate-free solution. Furthermore, sono-chemical effects are well known to activate the particle surface area, which leads to advantages such as faster reactions and enhanced product quality.

Sample Preparation

For measurements by analytical instruments (e.g. HPLC, atomic spectrometer, etc.), generally most samples have to be liquefied. If the sample is soluble, the solute (such as sucralose, salts, e.g. in powder or tablet form) can be dissolved in a solvent (e.g. water, aqueous solvents, organic solvents etc.) resulting in a homogeneous mixture, composed of only one phase. The dissolving process can be carried out by manual or mechanical stirring, which is time-consuming and inefficient. Related problems are sample losses due to manipulation or lacking reproducibility by random errors and uneven mixing.

Chemical Activation

To initiate a chemical reaction, energy is required. The so-called activation energy is the amount of energy required to initiate a reaction and carry on spontaneously. By the input of ultrasonic energy, chemicals reaction can be initiated as attractive forces are overcome and free radicals are created. Typical chemical reactions that benefit from ultrasound are sono-catalysis (e.g. phase transfer catalysis), synthetic organic reactions, sonolysis as well as sol-gel-routes. Furthermore, ultrasonic forces create highly reactive surfaces, which is an important technique to increase catalyst activity.

Shear-Thinning

The phenomenon of decreasing viscosity under increasing shear forces is termed shear thinning or thixotropic. The decrease of viscosity is of significant importance when the particle load of a medium should be modified. To achieve a higher solid load, in the first step viscosity must be lowered. After viscosity reduction, solids can be added and dispersed in the medium. High-shear forces created by ultrasonic cavitation cause shear-thinning and outstanding dispersing results. This application is mainly integrated before spray-drying or spray-freezing to increase the capacity of the spraying process or to influence the rheology of thixotropic material, e.g. polymers.

Wet Milling and Fine Grinding

Milling and particle size reduction are key processes in many industrial branches such as for paint & coatings, inkjet ink & printing, chemicals or cosmetics. The ultrasonic milling technology is proven for its reliable size reduction and dispersion in the micron- and nano-size range. Its unbeatable strength over bead, ball, and pebble mills lays in the avoidance of any milling media (e.g. beads/ pearls) that contaminate the final product due to abrasion. In contrary, ultrasonic milling is based on inter-particular collision – this means the particles to be milled are used as grist. Therefore the time-consuming cleaning of milling media is not any longer an issue. High viscosities and large volume streams can be processed resulting in a high quality product. For the integration into an industrial process line, Hielscher supplies the suitable solution: clusterizable systems, easy integration/ retrofitting, low maintenance, simple operation and high reliability. Read more about wet milling and fine grinding!

Extraction and Cell Lysis

Cell disintegration or lysis is a common part of daily sample preparation in biotech laboratories. The goal of lysis is to disrupt parts of the cell wall or the complete cell to release biological molecules. The so-called lysate can consist in e.g. plasmid, receptor assays, proteins, DNA, RNA etc. Subsequent steps after lysis are fractionation, organelle isolation or/and protein extraction and purification. The extracted material (= lysate) has to be separated and is subject to further investigations or applications, e.g. for proteomic research. Ultrasonic homogenizers are a common tool for successful cell lysis and extraction. As the ultrasonic intensity can be leveled by adjusting the process parameters, the optimal sonication intensity – varying from very soft to highly intensive – can be set for each substance and medium. Read more about extraction and cell lysis!

Microbial Inactivation

Microbial inactivation is a key process in food processing. Due to the increasing demand for fresh, mild processed food, the industry follows the customers’ demand by replacing thermal preservation by milder processing methods. Ultrasonication is a non-thermal technique that allows for the inactivation of microorganisms at sublethal temperatures resulting in a better preservation of the sensory attributes, nutritional and functional properties of the product. As microorganisms are the main cause for food spoilage, the preservation technique must be targeted towards them. The advantage of sonication is the full control over sonication intensity and thus the adaptability to specific types of microbes and the product. Read more about microbial inactivation!

Degassing, Degasification or Deaeration

In many liquid products, dissolved gas such as air, oxygen or carbon dioxide, causes problems for down-stream processes or product quality. Dissolved gas can result in corrosion, foaming, the formation of micro-bubbles or microbial growth.
Under ultrasonic irradiation, the dissolved gas is extracted into the vacuum of cavitation bubbles (vacuum degasification). The gas filled bubbles subsequently float to the top and can thereby be removed. The gas content of a liquid can be decreased rapidly below natural equilibrium at atmospheric pressure using ultrasonic degassing. Read more about degassing!

Removal of Micro Bubbles

Suspended micro-bubbles in liquids and slurries are a significant quality issue for many products, as such bubbles can result in product impurity, microbial growth, haze in coatings, mechanical instability, or uneven printing results by gas-containing inkjet ink. Ultrasonic waves propagating through the liquid force suspended bubbles to merge into bigger bubbles that will float to the top and can thereby be removed. Ultrasonication helps bubbles to move through the liquid, e.g. water, oil or resin, leading to a faster and more complete deaeration. Read more about the removal of micro bubbles!

Defoaming

In many industrial processes, such as fermentation, digestion or chemical processes, foam causes great problems as it makes process less controllable. Mostly, foam is an unwanted by-product, which must be removed. Commonly used anti-foaming chemicals are expensive and contaminate the final product. In contrast, highly intense ultrasound waves (sono-defoaming) break the foam without contamination. The destruction of foam is a soft, low energy ultrasonic application. Specially designed plate sonotrodes create high amplitude air born waves, which destabilize the bubbles in the foam so they collapse. This can be achieved in a few seconds and does not have any residual effects. Read more about defoaming!

Heating

Although heating is mostly not the main purpose of sonication, the side effect of heat generation in the treated medium should not be neglected. Controlled heating is advantageous as many processes are improved by heat. During many processes, e.g. preservation or chemical reactions, the ultrasonic treatment is purposely supported by elevated temperature, known as thermo-sonication. For heat-sensitive materials, targeted cooling during the sonication secures stable temperatures during ultrasonic processing. By implementing ice baths, flow cells with cooling jackets and integrated heat exchangers in the setup, Hielscher offers the solution for your individual targets.

Stabilization

High power ultrasound contributes to mechanical as well as microbial stabilization. Ultrasonically generated high shear forces provide an extremely fine mixing so that inter-particle bondings are overcome and mechanical stabilization is achieved. The durability of the stability depends on the formulation: some emulsions and dispersions are self-stable due to the very fine and even homogenization, whilst other mixtures must be supported by the addition of stabilizing agents. If stabilizers are needed, ultrasound is a very reliable tool to mix the stabilizer into the mixture.
For biological and food-related products, ultrasound is dependable technique of microbial inactivation to achieve product stability and preservation. Ultrasonic microbial stabilization is a non-thermal preservation alternative that convinces by efficient microbial deactivation and only mild heat generation. Ultrasound has been demonstrated to be very effective on the destruction of food-borne pathogens, like E.coli, Salmonellae, Ascaris, Giargia, Cryptosporidium cysts, and Poliovirus.

Particle Surface Functionalization

The structure of a particle’s surface is important for the particle characteristics. The specific Surface area of a particle becomes larger in correlation with the reduction of the particle size. Thus, by decreasing particle size, the surface properties become increasingly prominent – especially during nanonization. For the usage of such materials, surface characteristics are as important as the properties of the particle core. This means that the functionalization of nanomaterials enables a broad range of applications such as polymers, nanofluids, biocomposites, nanomedicines, and electronics. This makes the size reduction, deagglomeration, and functionalization an essential step in particle treatment. Hielscher ultrasonicators are widely used for the treatment of micron- and nano-particles in order to mill, deagglomerate, disperse and modify their structure. By the modification of the particle surface, an unwanted aggregation of particles can be avoided. In downstream steps, the ultrasonically modified particles can be mixed into composites, where sonication achieves a homogeneous distribution within a matrix. This is very important for manifold industrial applications regarding long-time stability or mechanical properties of hybrid materials.

Erosion Testing

Cavitation erosion resistance is an important aspect of material durability and lifetime. To ensure material functionality, erosion propensity and material fatigue must be tested for quality assurance. Erosion resistance is of high relevance for materials used in demanding environments such as ship propellers, (marine) coatings, pumps, engine components, hydraulic turbines, hydraulic dynamometers, valves, bearings, diesel engine cylinder liners, hydrofoils, and in internal flow passages with obstructions etc. To perform cavitation erosion testing in accordance with ASTM Standard G32-92, controllable and reproducible ultrasonication is inevitable. Hielscher ultrasonic devices can be used for the direct and indirect erosion testing of samples. The same ultrasonic equipment can be used for both, the direct and the indirect tests. During direct testing a specimen is mounted to the sonotrode, whilst for indirect erosion testing the specimen is fixed in the beaker. The erosion tests can be carried out under fully controlled environmental conditions and in almost every fluid. By adjusting the ultrasonic intensity, the erosive power can be adapted to the test requirements. Read more about erosion testing!

Wire, Cable & Continuous Strand Cleaning

Endless materials such as wires, cables, tapes, rods, and tubes have to be cleaned of lubricant residues before they can be further processed downstream, such as galvanizing, extrusion or welding. Cleaning of endless materials is often the bottleneck of the production line. Hielscher Ultrasonics offers an unique ultrasonic cleaning process for efficient inline cleaning, which can handle even high throughput speed. The effect of the cavitation generated by the ultrasonic power removes lubrication residues like oil or grease, soaps, stearates or dust. In addition, the pollution particles are dispersed into the cleaning liquid. By that, a new adhesion to the material to be cleaned is avoided and the particles are flushed away. Advantages of ultrasonic cleaning at a glance: proven & reliable, efficient, environmental-friendly, less or none chemical cleaning agents, plug-and-play, modular systems, simple operation, low maintenance, 24/7 operation, small footprint, retrofittable, customizable. Read more about continuous strand cleaning!

Sieving, Screening, Filtration

Separation of particles by size difference requires agitation of the screen or mesh. Ultrasonic agitation for sieving and screening is a proven tool, which increases sieving capacity and saves time as powders are enabled to pass the sieve faster and more complete. The result is a better final product quality with less material loss due to incomplete separation – and all within a shorter processing time. Read more about sieving and screening!

Water Treatment

The control of bacteria and algae growth in water is for many industries a highly relevant upstream- or downstream-process for production. Powerful ultrasound waves are known for their effects on cell structures causing cell lysis and cell death as well as for their cleaning capability due to mechanical impact.
Furthermore, tanks, barrels, vessels and even filters can be successful cleaned from biofilms, residues, and debris in a very simple but efficient sonication step. Ultrasonically generated mechanical vibrations and cavitational shear forces remove the contamination. In general, cleaning agents are not necessary and the removed residues can be easily flushed away.

Precipitation (Bottom-Up-Synthesis)

The precipitation or bottom-up synthesis describes the controlled formation of atoms, molecules and ions into larger chemical compounds. Precipitation is also useful for the purification of products. The advantage of precipitation is that by this method smallest particles of almost uniform form, particle/ crystal size and morphology are obtained. For the production of nano particles of high purity, precipitation and self-organization of molecular components is often the only way to achieve the desired quality. As precipitation is a very fast reaction, the efficient mixing of the reactants is essential. Ultrasonic mixing is the key for an even and fine mixed solution. Hielscher Ultrasonics supplies highly reliable ultrasonic equipment that guarantees complete control over the process parameters and a full reproducibility. Read more about precipitation!

Sono-Catalysis

Catalysts increase the conversion rate of chemical reactions and are needed to initiate a reaction or to keep the reaction running until a complete conversion is achieved. The fact that catalytic reactions are often slow and incomplete can be changed by high power ultrasound. Ultrasonication contributes to both, the homogeneous and heterogeneous catalysis and achieves faster conversion rates and higher yields. Ultrasonic forces create highly reactive surfaces and thereby increase the catalytic activity. Even though catalysts are not consumed themselves, surface depositions can lower the catalyst’s activity over the time. As solid catalysts often require rare and expensive metals, a long lifetime is an economically essential aspect. Ultrasound is a proven technique to remove fouling from the catalyst surface for reactivation to full catalytic capacity. Read more about sono-catalysis!

Sono-Chemistry

Chemical reactions are often slow and incomplete, thus the achievement of fuller utilization of the precursors is desirable. High-power ultrasonics cause physical effects in liquids, for instance enhanced mass transfer, emulsification, bulk thermal heating, and a variety of effects on solids (milling, deagglomeration, surface activation, modification). These physical effects significantly influence chemical reactions. In consequence, ultrasound contributes to manifold chemical reaction such as catalysis, synthesis & precipitation, sol-gel routes, emulsion chemistry and polymer chemistry. Hielscher ultrasonic devices are ideal for sonochemical application as Hielscher systems are capable to handle solvents, acids, bases and explosive materials (ATEX rated ultrasonicator UIP1000hd-Exd). All systems can be used for batch sonication as well as for inline sonication. A broad assortment of devices and accessories allows for matching the process requirements. Read more about sono-chemistry!

Sol-Gel Routes

Ultrafine nano-sized particles and spherical shaped particles, thin film coatings, fibers, porous and dense materials, as well extremely porous aerogels and xerogels are highly potential additives for the development and production of high performance materials. Advanced materials, including e.g. ceramics, highly porous, ultra light aerogels and organic-inorganic hybrids can be synthesized from colloidal suspensions or polymers in a liquid via the sol-gel method. The material shows unique characteristics, since the generated sol particles range in the nanometer size. Via the ultrasonic sol-gel route, gels (so-called sono-gels) with smallest particle size, highest surface area and highest pore-volumes can be created. The broad range of Hielscher’s ultrasonic equipment offers the ideal device configuration for specific materials and volumes. Read more about sol-gel processes!

Chemical Degradation

Chemical waste imparting its recovery and degradation are a severe problem of industrial processes such as mining, chemicals manufacturing and landfill sites. Waste and pollutants (e.g. in soil, waste water…) have to be processed in terms to recycling, waste reduction or deposition. Sonochemical degradation is a highly potential process, which is characterized besides its outstanding and unique results by environmental friendliness and easy operation. Sonication can result in the cleavage of bondings, chain length reduction, molecular modification or activation. Thereby, it contributes to oxidation, sorption, sonolysis and leaching. Characteristic features of ultrasonically-assisted degradation are an increase of the chemical conversion rate as well as ultrasonic cavitation and the sonochemical effects provide a better mixing, initiation of reactions by energy input, creation of functional group (e.g. cleavage –OH hydroxyl groups) and radicals (e.g. H₂O -> H+ and HO-).

Polymerization

Sonication has various effects on polymers: the effects of physical nature include mixing (such as emulsification, dispersing, deagglomeration, encapsulation) and bulk heating, whilst chemical effects create free radicals and change molecular structures. Ultrasound contributes in several ways to polymerization: High power ultrasound waves produce and disperse nano-size particles, emulsify non-miscible liquid phases and create free radicals which contribute to emulsion polymerization. Polymer nanocomposites and hydrogels can produced successfully by ultrasound. Furthermore, the surface functionalization of polymers plays an important role to enhance the performance of basic polymers and offers new approaches toward the development of tailored materials. The improvement of surface properties of commodity polymers is of high economical interest. Thereby, sonochemistry is the right way for successful polymer treatment.

Catalyst Reclamation / Regeneration

When reagents react at a catalyst particle surface, the products of the chemical reaction accumulate at the contact surface. This together with fouling and passivating layers blocks other reagent molecules from interacting at this catalyst surface. By ultrasonic cavitation and the thereby caused inter-particle collision, the residues on the particle surface are broken-off and washed away by ultrasonic streaming in the liquid. Cavitational erosion on particle surfaces generates unpassivated, highly reactive surfaces. Short-lived high temperatures and pressures contribute to molecular decomposition and increase the reactivity of many chemical species. Hielscher ultrasonic reactors can be used in the preparation, reclamation and regeneration of catalysts.

Sonoluminiscence

Sonoluminiscence describes the phenomenon of short bursts of light emission generated by imploding ultrasonic cavitation bubbles in a liquid medium. Although there are different theories that try to unveil the phenomenon of sonoluminiscence, until today scientists could not prove their theories, which include hotspot, bremsstrahlung radiation, collision-induced radiation and corona discharges, nonclassical light, proton tunneling, electrodynamic jets and fractoluminescent jets, quantum explanation (which is related to the Unruh or Casimir effect) or thermonuclear fusion reaction.

DNA, RNA & Chromatin Shearing

Deoyxribonucleic acid (DNA), ribonucleic acid (RNA) and chromatin are – along with proteins – the major macromolecules for all forms of life. DNA and RNA are the molecules that encode the genetic instructions of organisms. Chromatin is the combination of DNA and proteins where from the content of the cell nucleus is built. For research purpose, it is necessary to fragment these molecular building blocks into smaller components to investigate and analyze them or to rearrange them during immunoprecipitation and crosslinking. For DNA, RNA and chromatin shearing, the fragment size is very important. By full control over all important parameters, ultrasound enables for targeted molecule fragmentation. For instance, the ideal chromatin fragment length ranges between 200 and 1000 bp. Ultrasonic shearing is achieved by bursts in pulse mode. Due to intelligent devices and accessories, processing needs such as direct or indirect sonification, sample cooling, digital process recording are provided by Hielscher’s ultrasonic equipment. This ensures successful microbiological processing and operation comfort.