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  • Does Density of Microspheres Matter for your Research Application?

    Posted on February 28th, 2020 Microsphere Expert

    Monthly Newsletter of Cospheric LLC

    Does Density of Microspheres Matter?

    There are a lot of variables for the researcher to consider when selecting the right material for their project. What properties of the material are critical? Particle size? Formulation? Color? Fluorescence? Phosphorescence? Coating? Reflective Index?

    Our technical support team starts by asking two questions:
    1 – Do you need a particle of specific diameter?
    2 – Do you need a particle of specific density?

    Typically, researchers have a good idea of what size particles they need to work with,
    but many misunderstand how critical density is to the success of their project.

    When is particle density important?

    Density controls the buoyancy of an object and its behavior in a system or process.

    Let’s look at three scenarios:

    – Scientists often need to suspend the particles in a specific fluid (to stay suspended, to float, or to sink). In this situation the delta between the densities of the particle and of the fluid need to be precisely controlled. If there is a mismatch in density, the microspheres will either sink or float. The smaller the microspheres the less sensitive they are to the density mismatch. For larger microspheres (such as close to 1mm in diameter) to stay suspended for some time, the density delta needs to be at most 0.001g/cc. Even slight changes in the temperature of the fluid might change its density and determine whether the particles will stay suspended.

    – Scientists are studying fluid flow, performing flow visualizations, or particle image velocimetry. The particles are used as flow tracers or seeding particles and must be clearly visible as they follow the flow of the fluid. In these applications, not only does the density of the particle needs to match the density of the fluid exactly, the particle needs to also be small enough to stay suspended, and be color-stable and visible to the observer under the specified illumination (laser, UV light, daylight, etc).

    – Scientists are simulating/modeling objects with specific density. Whether studying the flow of fish eggs in a stream, the spread of pollen in forest, or the flow of semen in artificial insemination, many experiments start with a computer model that is based on an assumption of a spherical particle of specific density. Being able to obtain such particles to test and validate the model is often a key step towards understanding the process and making breakthroughs in understanding how our world functions.

    Cospheric products are unique because every product we manufacture is produced and qualified to a specific density grade and tolerance. Density of every lot of material is thoroughly characterized with our proprietary process prior to being offered for sale.

    Precision Density Microspheres – Density Marker Beads

    Density Marker Beads are small colored microspheres of known mass density that are used for calibrating density gradients and determining density in gradient columns.  Density gradient are often used for separation and purification of cells, viruses and subcellular particles.  Generally, a set of several density marker beads covering a range of densities used.

    The gradient is calibrated with beads that float at different heights within the column.  When a test sample is added to the column, it drops until the point
    of natural buoyancy and the density is determined from the calibration chart.  Density gradient column can be used to measure the density of any sample.

    Density Marker Beads are engineered for exceptional precision and uniformity of true particle density. These specialized microspheres pass much tighter density tolerances than any other microspheres on the global marketplace
    and are often used as density standards for calibration or creating of density
    gradients.

    Cospheric Density Marker Beads are spherical particles of diameter between 200micron and 300micron. There are seven unique color-density combinations, provided in an aqueous solution (20% concentration). Density marker beads are ready for use right out of the vial.

    Ask a Scientist:

    Q: What is the difference between bulk and true particle density? Which one matters to me?

    A: Bulk density (or tapped density) of powders is often referenced in literature but is not an intrinsic property of material and can be misleading. The reason for this is that bulk density can vary widely depending on the packing efficiency of material and can change over time as the powder settles in the container and the volume it occupies becomes smaller while the weight stays the same.

    True particle density (or skeletal density) specifies the unique density of the material that the particles are made of. When properly measured, it is a characteristic property of material. This allows scientists and engineers to accurately model and predict performance of these particles in specific applications.

    All Cospheric particles are characterized for true particle density by utilizing our proprietary density measurement technique which relies on NIST-calibrated gas pycnometry and high precision NIST-calibrated scale. To best support our customers’ research needs, every Cospheric product offered for sale is listed on our website with true particle density as part of product description.

    PDF version of the newsletter

  • Overview of 2019 Quality Show – Quality Management in Laboratories and Manufacturing Operations

    Posted on November 13th, 2019 Microsphere Expert

    By Allen Licha, PMP, Cospheric LLC

    Last month Cospheric attended the Quality Show in Rosemont, IL. As a global supplier of precision spherical particles, striving to provide the highest quality microparticles on the market, quality is a huge part of what we do at Cospheric. Performing accurate measurements is vital to our business.  Metrology, the science of measurement, is how we ensure that we can confidently compare the results of measurements made worldwide.

    The Quality Show offered an opportunity to learn more about how quality fits with other organizations, what are their challenges, and what are the tools/solutions being used in the industry.

    When I think of Quality, I think of many different aspects, including Quality Planning, Quality Assurance, and Quality Control.  I also think of a Quality Management System, which is a set of policies, processes and procedures required for planning and execution in the core business area of an organization (i.e., areas that can impact the organization’s ability to meet customer requirements).   The Quality Show focuses on Quality in the manufacturing environment, specifically on measurements, or metrology/CMM.  If you are looking for the latest technologies/trends in measurement tools, this show is great!

    This is only the third time they have put on this show, so I do believe that future shows will have more emphasis on all areas of quality. The show is well run and very affordable (free for attendees if you register early).

    Below are the summaries of the four presentations that I found particularly valuable.

    Quality Show Keynote – Building a Culture of Quality by Deb Andree, Northrop Grumman

    The keynote presentation, Building a Culture of Quality, delivered by Deb Andree of Northrop Grumman was very powerful! She talked about how Northrop Grumman, who’s Palmdale facility was awarded Quality Plant of the Year, gets employees to put quality first by communicating the importance of quality in all functions, across all programs and at every level withing the organization.  Three key points she touched on were:

    • Quality is a journey – Quality is on-going project, striving for continuous improvements over the previous results, as customers specifications and market demands are contstantly evolving.
    • Quality is personal – Does each employee in the organization know where they fit in a culture of quality? Is every employee giving a personal guarantee on the outputs they are producing? The actions of each person has a huge impact throughout the organization. The mindset at Northrop Grumman when it comes to quality is that employees are their biggest asset. Employees are highly recognized for their commitment to quality and encouraged to speak up if something does not seem right or they are unsure.
    • Quality is a commitment – Executive management support is one of the biggest indicators of whether or not a project will be successful.  At Northrop Grumman there is commitment to quality from leadership at every level.

    Setting Calibration Intervals with Confidence by Eric Gasper, PQ Systems

    Performing regular calibrations on measuring equipment is vital to ensure trust with the equipment and the product produced as a result of those measurements.  Gasper dived into the importance of having properly defined intervals.  Why is this important? If you calibrate too often, then it is a waste of time and money. If you do not calibrate often enough, then you risk using faulty equipment to measure your product. So how do we determine the proper calibration frequency? Gasper recommends performing a stability study to determine if your measurement system is stable (i.e. in control).  “We are looking to catch when the measurement tool has an issue or becomes unstable prior to the scheduled calibration date.  We are also looking at the results to see if it remains stable between calibrations.”  The whole point of this study is to build evidence to support lengthening or shortening the calibration frequency.  In either case you will save time by reducing rework/rechecks if calibrations are not frequent enough or save time in performing calibrations if they are too often.

    Cospheric Team reflected on this presentation and used it to provide validation for the Calibration/Verification Module that we have recently developed as part of our in-house Manufacturing Execution System. In our system we pre-define Verification Intervals for each piece of equipment, which will prevent the operator to record data for the equipment that has passed its verification date. We also pre-define control limits which will automatically tell us whether the equipment passed verification (and will be released for use) or fails verification, in which case it will be off-line for troubleshooting and/or calibration. Equipment will not be released for use until a successful verification has been performed. This way we ensure that we only recalibrate when equipment is outside the control limits. We also verify the performance of equipment regularly to ensure that a product will not be released with a faulty measurement.

    Technical Learning in the Workplace by Aliesha Anderson, ZEISS Industrial Quality Solutions

    In this learning session, Anderson covered the impact of Industry 4.0 on Quality and Manufacturing.  She talked about how the manufacturing industry has changed dramatically in recent decades due to new and emerging technologies.  Many open positions are vacant due to a skill shortage.  Anderson presented data from the Deloitte Millennial survey, which found that 43% of Millennials envision leaving their jobs within two years and only 28% seek to stay beyond 5 years.  In a recent national survey 87% of Millennials cited professional development /career growth as being very important to their decision to stay of leave a company.  What does that mean for companies today? It would be in their best interest to view employee training as an investment instead of an expense.

    Benefits and Challenges of ISO/IEC 17025 Accreditation for Laboratories in Manufacturing Facilities by Melanie Ross, Training Products Specialist, ANSI National Accreditation Board (ANAB)

    ISO/IEC 17025 is a company level accreditation based on a standard published by the International Organization for Standardization (ISO) titled “General requirements for the competence of testing and calibration laboratories.”

    So, what is the difference between ISO 9001 and ISO/IEC 17025?

    Ross explains that ISO 9001 is focused on the general management system where an organization demonstrates the ability to provide consistent products and services that meet requirements. ISO/IEC 17025 focuses on the management system with technical laboratory requirements. You demonstrate competency of the laboratory.  Once key difference between the two is that ISO 9001 is a certification, where ISO/IEC 17025 is an accreditation.

    Why should you seek this accreditation?

    More agencies are requiring this accreditation, including DOD, DOA, FDA, FAA, and state governments.  Another thing that Ross mentions, is that if you already have an QMS, then you are already 80% there to having your ISO/IEC 17025 accreditation. You can find more information on accreditation and training by visiting www.anab.org.

  • Are Microplastics Toxic to the Environment? Literature Review

    Posted on October 24th, 2019 Microsphere Expert

    by Nathan Garnica, Cospheric LLC

    What are microplastics?

    Microplastic is a broad term used to describe microscopic plastics with sizes ranging from 1µm to 3mm1. The shapes of microplastics can vary from fragments, fibers, pellets, film, and spheres2. Anything less than that can be considered nanoplastic, which is also prevalent in the ocean. The properties such as the size, shape, and charge are constantly changing which affects the bioavailability, or circulation into living organisms1. The plastic production generated in 2016 was estimated at 335 million metric tons and the demands continue to increase2. It is estimated that over 5 trillion plastic particles weighing over 250,000 tons resides in the ocean1. The most common forms of polymer microplastics are polyethylene (PE), polystyrene (PS), polypropylene (PP), polyester (PES), polyvinylchloride (PVC), polyamide (PA), acrylic polymers (AC), polyether (PT), cellophane (CP), polyurethane (PU), and others that are not specified2.

    How are microplastics being accumulated in the ocean?

    Microplastic accumulated in the ocean can be divided into two categories. The primary means of accumulation of microplastic is released directly into the environment via domestic use, industrial effluents, spills, and sewage discharge2. The secondary means involves the gradual degradation and fragmentation of larger plastic particles already present in the environment. About 80% of marine plastic debris derives from land-based sources including beach litter4. Roughly 18% of marine plastic debris comes from the fishing industry4. These particles can continue to degrade into nanoparticles that can range from 1nm to 100nm2.

    Are microplastics toxic?

    The toxicity of microplastics in living organisms has been largely debated in scientific literature. Research has shown conflicting results regarding entry and harm to organisms.

    Clear Polyethylene Microspheres from Cospheric LLC, 0.96g/cc - Various Sizes 1um to 1700um (1.7mm)

    Clear Polyethylene Microspheres from Cospheric LLC, 0.96g/cc – Various Sizes 1um to 1700um (1.7mm)

    A recent article published in Marine Pollution Bulletin utilized a wide range of sizes of polyethylene microspheres, such as those produced by Cospheric LLC (USA), and showed that polyethylene microplastics used in this study were not toxic to the unicellular marine organisms exposed at environmentally relevant concentrations or even at higher concentrations6.  In this study non-fluorescent low-density and high-density polyethylene microparticles were used in sizes from 1micron to 500micron in diameter. The authors state that ”in this study, bacteria luminescence inhibition and micro algal growth were not affected by either the virgin or the oxidized PE-MPs at concentrations of up to 25 mg/L. These results confirm previous data on the absence of ecotoxicological effects included in standard test guidelines in decomposers and primary producers exposed to MPs.” The authors refer to prior publications by other researchers who also investigated ecotoxicological effects of plastic microparticles in the same bacterium as well as several microalgae and did not find any toxic effect at environmental concentrations.

    Due to limited number of studies in this area, the questions remain. For example, would nanoplastics (particles smaller than 1um in diameter) would behave differently and have a stronger effect? Are we measuring the right parameters? Do we need to investigate alternative responses to detect the potential risk and influence on plastics on unicellular organisms?

    It is important to note that, as they disperse and degrade in the ocean, polymer microparticles undergo changes which can alter their bioavailability and access into living organisms.

    The dispersal determines which depth and area of the ocean and which organisms are impacted. The density, size, and surface properties determine the depth and distance microplastics particles travel. Any given microparticle can take weeks to years to reach the ocean floor1. This dispersal directly impacts the marine communities inhabiting that area.

    Factors that influence degradation of microplastics include chemical additives, water permeability chemical composition, molecular weight, morphology, porosity, size, and more3. Additives define the outer surface which change the overall properties of particles. Porous particles allow cells to migrate into the pores which can help in the degradation process3. Nonporous particles degrade more slowly than porous particles3.

    Do microplastics alter the ocean ecosystem?

    The effect on the ecosystem could potentially happen indirectly by altering the environment around marine life.

    Polystyrene Microspheres from Cospheric LLC, Crosslinked, 1.07g/cc - Diameters between 9.5um and 105um

    Polystyrene Microspheres from Cospheric LLC, Crosslinked, 1.07g/cc – Diameters between 9.5um and 105um

    A study shown in “Interactions of Microplastics throughout the Marine Ecosystem” by Galloway et al. observed the digestion effects of polystyrene microspheres in zooplankton. The fecal pellets of zooplankton are a vital carbon source for marine life in the deep depths of the ocean1. The polystyrene fecal pellets took 53 days longer to reach the bottom of the ocean1. This delay in carbon supply impacted deep ocean life that is dependent on this maintenance of carbon flux. The experiment used polystyrene microspheres but polyethylene and polypropylene, which are more abundant in the ocean, are less dense and may take even longer to sink1.

    Fertility and fecundity were greatly reduced in oysters during an 8-week exposure experiment to polystyrene microparticles 1.  The findings showed a decrease in sperm motility, oocyte production, and size of oocytes1. Similar effects were found in offspring not exposed to microspheres1. The study suggested that the microspheres were present where the food should have been and had adverse biological impacts1. A similar result in Daphnia magna led to immobilization1. The energy production was most likely inhibited using the 1µm polyethylene experimental particles 1.

    Biofilms, which are communities of bacteria surrounded by their extracellular matrix, colonize microplastics1. A typical colonizer of microplastics are the ubiquitous Vibrios1. Vibrio crassostrea is a common pathogen that can colonize microplastics which can then be ingested by oysters1. The bacteria can then cause infections to the oysters1.

    It is difficult to define a specific threshold of harmful microplastics due to the changing nature of material properties over time. A harmless microplastic may degrade to become toxic or a toxic microplastic may degrade to become passive.

    How can we limit microplastic pollution?

    There are many strategies to help reduce the amount of microplastic accumulation. The public can reuse, recycle, and recover plastics5. Alternatives to biodegradable products can be made such as polylactatide (PLA), polyhydroxyalkanoates (PHA)5. Laundry balls can help catch microfibers from falling off clothes in the washer.

    There is also research that shows great promise towards reducing microplastic through new technologies or through bioremediation strategies. Improved water filters can help catch microplastics in wastewater treatment facilities before the water enters rivers and the ocean5. Several species of microbes and fungi have been found to degrade polymers5. Polyethylene, polypropylene, polystyrene, and Polyethylene terephthalate have been found to be degraded by Bacillus and Enterobacteria along with several different fungi5. Polyethylene, polypropylene, polystyrene are considered nonbiodegradable5. These promising developments demand collective support from industry, government, and the general public if we are to move away from a plastic ocean.

    1. Galloway, T S, et al. “Interactions of Microplastics throughout the Marine Ecosystem.” Nature Ecology and Evolution, vol. 1, no. 5, 20 Apr. 2017, doi: 10.1038.
    2. Sá, Luís Carlos De, et al. “Studies of the Effects of Microplastics on Aquatic Organisms: What Do We Know and Where Should We Focus Our Efforts in the Future?” Science of The Total Environment, vol. 645, Dec. 2018, pp. 1029–1039., doi:10.1016/j.scitotenv.2018.07.207.
    3. Sá, Luís Carlos De, et al. “Studies of the Effects of Microplastics on Aquatic Organisms: What Do We Know and Where Should We Focus Our Efforts in the Future?” Science of The Total Environment, vol. 645, Dec. 2018, pp. 1029–1039., doi:10.1016/j.scitotenv.2018.07.207.
    4. Wu, Wei-Min, et al. “Microplastics Pollution and Reduction Strategies.” Frontiers of Environmental Science & Engineering, vol. 11, no. 1, 2016, doi:10.1007/s11783-017-0897-7.
    5. Wu, Wei-Min, et al. “Microplastics Pollution and Reduction Strategies.” Frontiers of Environmental Science & Engineering, vol. 11, no. 1, 2016, doi:10.1007/s11783-017-0897-7.
    6. Gambardella, Chiara, et al. “Microplastics Do Not Affect Standard Ecotoxicological Endpoints in Marine Unicellular Organisms.” Marine Pollution Bulletin, vol. 143, 2019, pp. 140–143.
  • Suspension of Hydrophobic Particles in Aqueous Solution – Density Gradients

    Posted on April 10th, 2019 Microsphere Expert

    Fluid Flow Visualization using Microspheres, Spherical Particles

    Fluorescent polyethylene microspheres for flow visualization in aqueous systems. Suspension of beads in aqueous solutions.

    Background Information

    Many materials are hydrophobic (water-fearing) in nature. Due to their non-polar chemical structure, hydrophobic particles want to minimize contact with polar (water) molecules and, as a result, tend to aggregate on the surface of the water and resist going into suspension. This presents a challenge to scientists and engineers who would like to be able to work with hydrophobic particles suspended in aqueous solution.

    Examples of the applications are using fluorescent polyethylene microspheres for flow visualization in aqueous systems, creating density gradients, filtration and contamination control studies.

    Fortunately, there is a simple way to overcome the hydrophobic effect. It is called a surfactant, a detergent, or simply “soap.” Surfactant is a magical molecule that has both hydrophobic and hydrophilic properties, which coats the particles and helps them mix into water. The same mechanism applies when we use soap to wash greasy dishes or stained clothes.

    Selection of the surfactant depends purely on your process and product requirements. Dishwashing liquid works great, so does Simple Green. For scientists working on biological applications we recommend the use of Tween surfactants. Tween is the commercial name for Polysorbate non-ionic surfactants, which are stable, nontoxic, and often used in pharmacological, cosmetic, and food applications. Non-ionic detergents are considered to be “mild” detergents because they are less likely than ionic detergents to denature proteins. By not separating protein-protein bonds, non-ionic detergents allow the protein to retain its native structure and functionality.

    Tween 20 and Tween 80 are frequently used. Both surfactants are yellowish, water-soluble viscous liquids. Primary difference between the two is viscosity. Tween 20 has lower viscosity and is easier to work with.

    Suspension Process

    There are many ways to suspend the particles (e.g. put a few drops of dish detergent into water and shake with the particles).

    The process below is specific for using the minimum amount of Tween for biologically sensitive applications.

    Safety:

    • Gloves and eye protection are to be worn at all times during solution preparation and use.
    • Care should be taken when handling hot objects/liquids and immersion blender.
    • Centrifuge should be properly balanced and allowed to come to a full stop before opening.

    Recommendations:

    • We recommend using distilled water to minimize impurities.
    • We recommend boiling the water to sterilize and to make it easier to disperse a small amount of surfactant uniformly. This also increases shelf-life of prepared solutions and suspensions.
    • We use an immersion blender to disperse the surfactant in water quickly and effectively.

    Process:

    Preparing Tween Solution:
    • Fill a heatproof container with distilled water.
    • Ensure the water level is high enough to cover the immersion blender.
    • Heat water to boiling and leave boiling for 5 minutes.
    • Weigh out 0.1g of Tween per 100ml of water used (creating 0.1% solution).
    • Slowly add Tween to boiled water while mixing with immersion mixer (~30 seconds).
    • Some bubbles will form during mixing.
    • Bubbles will dissipate on cooling and solution will appear clear.
    Suspending particles in Tween solution.
    • Place the desired amount of particles into a container.
    • Dispense prepared Tween solution on top of particles.
    • We recommend at least five times greater volume of solution to the volume of particles.
    • Cover tightly and place containers into a centrifuge.
    • Centrifuge on highest setting for at least 5 minutes.
    • If some particles are still floating on the surface of water, more centrifuging may be necessary.
    • A small quantity of particles may accumulate on the top surface and not enter solution despite additional centrifugation. Typically, these particles will go into suspension over time (hours).
    Other Considerations
    • A greater length of centrifuging or larger volume of Tween solution may be necessary to suspend certain materials and particle sizes.
    • As a 0.1% Tween solution is sufficient for most applications, concentration levels could be raised to support particles that are more resistant to entering solution.
    • Once the particles are suspended, solution can may be diluted further to increase the volume.
    • Particles can be recycled and reused as necessary. The suspension might need to be repeated.
    • If no centrifuge is available, it is possible to shake the container by hand (up and down, upside down) to achieve the same result.

    Here is an example of Cospheric fluorescent beads 150 to 180micron in diameter being dispersed in a pilot bioreactor.

    About Cospheric

    Our extensive product line consists of more than two thousand unique spherical microparticle and nanoparticle products, all developed based on customer demand. We work with each individual customer to find a creative solution for their unique needs ­– tight particle size ranges, wide selection of colors, densities, properties and formulations. We are the sole global supplier for the majority of our products. We developed a disruptive technology which is redefining the microsphere market and creating a new category of precision spherical particles. Our research department is always excited to tackle new challenging projects. Explore at www.Cospheric.com.

    Other Information

    The information contained in this document is correct to the best of our knowledge at the date of publication. It should not be viewed as all inclusive, but as a guide only. It does not represent any guarantee of the properties of the product. Cospheric LLC shall not be held liable for any damage resulting from handling of or from contact with the above product. For these reasons, it is important that product users carry out their own tests to satisfy themselves as to the suitability of the safety precautions for their own intended applications.

  • Fluorescent Microspheres Used for Experiments in Plant Canopies

    Posted on December 19th, 2018 Larisa Lipovetskaya

    Fluorescent Microspheres - Polymer Spheres - 1g/cc

    Fluorescent Microspheres – Polymer Spheres – 1g/cc

    The University of Utah in collaboration with USDA Labs in Corvallis, OR performed five field campaigns in commercial vineyards in Oregon’s Willamette Valley.  Among the methodologies developed over the five-years experiment was the use of fluorescent microsheres as a fungal spore analog.  The microspheres used were inert fluorescing polyethylene micropsheres in four separate colors manufactured by Cospheric.

    The article attached below outlines the technology developed as well as microspheres sampling and meteorological equipment used in the experiments.  The authors of the article conclude that “these techniques have enabled for incredibly detailed research into particle plume dynamics in a vineyard.”

    NMiller_Poster_Methods