Everything about Microspheres
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  • Density Marker Beads Kit Now Available from Cospheric LLC

    Santa Barbara, CA, December 6, 2013 – Cospheric LLC, a microsphere manufacturing and distributing company, expanded their line of density marker beads which now offers six different densities including 1.02 g/cc (fluorescent green), 1.04g/cc (fluorescent orange), 1.06g/cc (fluorescent violet), 1.08 g/cc (dark blue), 1.09 g/cc (fluorescent red), and 1.13g/cc (fluorescent blue). Cospheric Density Marker Beads are now provided at a 20% concentration in an aqueous solution in 2.5ml vials, which makes the spheres easier to work with for the customers. Microspheres of different densities can be purchased individually or as a density marker beads kit.

    Microspheres of accurately known mass density are generally used as an external marker to facilitate the monitoring of the density gradient shape and range. Density marker beads enable excellent stratification and bright coloration for high visibility with the unaided eye. Historically density calibration beads in the size ranges of 212-250um or 250-300um are used. Unlike the discontinued density marker kits which used to be manufactured by GE Healthcare and sold by Sigma-Aldrich, Cospheric’s DMB density marker beads are ready for use right out of the vial, don’t need to be swollen, do not expire, and do not change density over time. Cospheric’s DMB microspheres will create Percoll gradients but will also work with any other centrifugation media. The colored microbeads may be recovered and stored for future use.

    The density marker beads provide a rapid, simple, and accurate method for measuring the density. Generally a set of several such beads, covering a range of densities, is used. In the biomedical industry researchers are sometimes looking for cells having targeted specific gravities. In order to locate these cells in test tubes it is useful to have colored marker beads which will show where the delineation between specific densities occurs. Density marker beads are also used for calibrating particles in other industries, such as agriculture, microbiology and others.

    About Cospheric LLC:
    Cospheric LLC develops, manufactures, and distributes high-quality microspheres in sizes from 10 micron to 1000 micron (1mm). Cospheric specializes in polyethylene microspheres and carries a large stock of polyethylene microspheres in many colors, fluorescent, phosphorescent, neutrally-buoyant, and paramagnetic properties. Cospheric also offers a selection of soda-lime and borosilicate glass, silica, metal-coated, and titanium dioxide-coated spheres, some available in spacer grades with very tight particle size distributions. Cospheric LLC welcomes inquiries for custom manufacturing of microspheres tuned to each customer’s unique specifications. Cospheric is an eco-friendly company that uses only recyclable materials and no solvents in the manufacturing process. For more information, pricing and sample requests visit www.cospheric.com.

    About Microspheres:
    Microspheres or beads are spherical particles usually between 1 to 1000 microns in diameter and are manufactured for wide variety of uses in research, medicine, consumer goods, paints and coatings, adhesives, personal care, household products, cosmetics, skin care, and other industries.

  • Bichromal Janus Particles, Microspheres, Microbeads – Stock selection or Custom-made

    Bichromal (half-white half-black or any other color) Microspheres, Janus Particles

    Bichromal (half-white half-black or any other color) Microspheres, Janus Particles. In this picture - Paramagnetic black microspheres with partial white coating - Magnification 40x.

    Cospheric offers unique capability to manufacture Janus microspheres and microparticles with partial coatings and dual functionality. Currently half-shell or hemispherical coatings can be applied to any sphere (glass, polymer, ceramic) in sizes 45micron in diameter and higher. Coatings can be customized for any color and coverage of between 20% to 60% of the sphere. Each coating is custom formulated for color, charge, magnetic, electric, and surface properties, and solvent resistance per customers’ needs.

    Half-coated glass microspheres - Partial coating on glass particles

    Half-coated glass microspheres - Partial coating on glass particles. In this picture - Soda lime glass microspheres with partial red coating - Magnification 40x.

    Hemispherical coatings of less than 1 micron with tolerances as low as 0.25 micron have been routinely demonstrated.  Color combinations are truly unlimited. White, black, silver, blue, green, red, yellow, brown, purple as well as transparent microspheres have been made. Sphericity of greater than 90% and custom particle size ranges are offered.

    We have successfully coated solid and hollow glass microsphere, including soda-lime, borosilicate, and barium titanate glass microspheres. We have also coated on silver.

    Half-coated Microspheres

    Half-coated Microspheres

    Optically anisotropic spheres and janus particles with magnetic half-shells have been originally developed for applications in electronic displays, such as e-paper, but are now widely used in numerous applications in diagnostics, medical research, microscopy and biotechnology, as well as electronics, due to their ability to orient themselves in response to electromagnetic field and show a visual response. This is achieved by making spheres both bipolar and bichromal, with dipole precisely aligned with two differently colored hemispheres. As the spheres align themselves, the viewer will observe the color of one hemisphere, while the other hemisphere will be hidden from view, providing an obvious strong visible indication of the presence of the field or other stimuli.  In alternating electromagnetic field, these microspheres have been proven to spin at hundreds of times per second.

  • PIV Seeding – Microparticle Recommendations

    Flow Visualization can best be accomplished with colored or fluorescent tracing particles of the same density as the fluid being studied.Particle image velocimetry (PIV) is the term used for imaging the fluid flow using colored tracer particles.  Through high speed particle imaging the velocity of the particles can be obtained and mapped.

    Photo Courtesy of Wiki-CommonsFor PIV experiments in water there are a wide variety of 1g/ml microspheres available as seeding particles, Cospheric offers polyethylene seeding particles in a variety of colors (fluorescent and non-fluorescent) and sizes from 10-20um, on up to 1mm.

    Particle size selection is important to ensure that observations can be accurately made.  For imaging systems without any magnification or unaided human observation it is recommended to use micro-spheres that are larger than 200um.   Human eyes can resolve features down to about 75um, at 200um+ the particles will be large enough to be discernible.

    Correctly seeding the system is also important.  For most applications loadings of 0.1-0.3% are sufficient.  This is the equivalent of about 1 gram of particles per gallon of fluid in systems of 10-50 gallons (40-200 liters) .  Exact loading levels will depend on the individual experiment requirements.

    For aqueous systems, polyethylene micro-particles will require a surfactant to wet properly.  For general flow studies pre-wetting the PE microspheres with Simple Green concentrated cleaner works well.  For biological systems a bio-compatable surfactant such as Tween 20 or Tween 80 is recommended.

    Seeding particle color selection is important to ensure that sufficient contrast is achieved during testing.  Very bright fluorescent micro-particles are available in densities of 1g/cc  these offer not only bright testing under daylight conditions, but also the option of illumination with lasers or uv lights for increased system contrast.

    The recommended PIV seeding particles are available from Cospheric.

    For green lasers (530nm)  we recommend UVPMS-BR
    For dark backgrounds: UVPMS-BY, UVPMS-BG, BLPMS, ORGPMS, BSPMS, or WPMS
    For light backgrounds: GRYPMS, VIOPMS, UVPMS-BR, UVPMS-BO

  • Calculating microspheres per gram

    During scientific experiment design and analysis it is common to need to know the number of spheres per gram of dry material.  We have put together the table below to help speed up the process.

    If you have material of a density different from those listed in the table, divide the number of spheres per gram in the density ~1.0 g/cc column by the true particle density of your material to get an estimate of the number of spheres per gram.

    Product Size Polyethylene
    Density ~1.0 (g/cc)
    Soda Lime Glass
    Density ~2.5 (g/cc)
    Lower (um) Upper (um) Spheres per Gram Spheres Per Gram
    20 27 147,162,715 58,630,564
    27 32 74,393,558 29,638,868
    32 45 33,467,185 13,333,540
    45 53 16,233,536 6,467,544
    53 63 9,788,528 3,899,812
    63 75 5,813,720 2,316,223
    75 90 3,401,258 1,355,083
    90 106 2,029,192 808,443
    106 125 1,239,525 493,835
    125 150 734,672 292,698
    150 180 425,157 169,385
    180 212 253,649 101,055
    212 250 154,941 61,729
    250 300 91,834 36,587
    300 355 54,371 21,662
    355 425 32,196 12,827
    425 500 19,305 7,691
    500 600 11,479 4,573
    600 710 6,796 2,708
    710 850 4,025 1,603
    850 1000 2,413 961
    1180 1400 890 354
    1400 1700 513 204
    1700 2000 302 120
    2000 2360 184 73
    2360 2800 111 44
    2800 3350 66 26

    Note: This table assumes the mean diameter is half way between the upper and lower size.

  • Microparticles for simulating fish egg dispersion and recruitment

    Understanding survival and mortality of fish in the early life stages has been a fundamental issue in biology and a central problem in fisheries oceanographic study for more than a century. It has been argued that most marine fishes begin life as an egg that floats in the sea, and, during their evolutionary history, the early life of fishes has surely been shaped to ensure the “continued existence of species” by the sheer pressure of natural selection, and stated that a fish to survive must deal with and exploit its physical and biological environments. However, although we are now in the 21st Century, there still remains a lot to be made scientifically clear in the early life of fishes. In the present lecture, I will talk about fundamental issues in the isolated floating eggs of marine fish, which many pelagic species spawn in thousands, millions, or sometimes almost billions during a life of an individual female. The topics contain description and discussion on the egg size, buoyancy and rising speed. Measurements on the eggs naturally spawned in aquaculture systems are firstly introduced. Several examples of egg vertical distribution, accumulation and dispersion observed through field surveys will be shown to consider how the egg size and buoyancy are adaptive to survive in the pelagic environment.1

    UVPMS-BG 180-212um - 40x MagnificationScientists who study fish require artificial micro-particles to simulate fish eggs and their dispersion behavior in water. In order to accurately simulate the dispersion of fish eggs it is important to use particles of the proper size and buoyancy/density. Particles with accurate size ranges and densities are now available from Cospheric LLC. Densities from 1.00g/cc up to 1.12 g/cc are available in size ranges from 10-27um on up to 0.85-1.0mm. Sea water particles of 1.025g/cc (UVPMS-BG-1.025), and fresh water beads of 1.00g/cc are in stock and available for quick delivery.

    Most fish eggs are in the size of 0.5-5mm1 with the typical size of 1mm being the most common.   Salt water fish eggs tend to be slightly less dense than medium saltwater at a density of about 1.020g/cc1.

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