Everything about Microspheres
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  • 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.

  • Phosphorescent Microspheres – Long Afterglow Particles

    Phosphorecent Beads - Yellow Green Afterglow Spheres

    Phosphorecent Beads - Yellow Green Afterglow

    Phosphorescent microspheres in particle sizes 10 to 600 microns are now available from Cospheric LLC. These phosphorescent particles are 90% spherical and appear to be off-white under ordinary daylight or regular room illumination.  However, when the lights are turned off these phosphorescent particles exhibit phosphorescent yellow-green after-glow.

    The spheres have tight particle size distributions and are > 90% within size range.  Polymer spheres that incorporate proprietary phosphorescent ingredient have a melting point of 115°C , and are mechanically stable past 90°C.  Phosphorescent beads are also inert in most solvents.

    Phosphorescent Decay CurveIntensity of Phosphorescent Afterglow:

    Intensity according to DIN 67510-1

    800 mcd/m2 at 1 minute
    180 mcd/m2 at 5 minutes
    90 mcd/m2 at 10 minutes
    12 mcd/m2 at 1 hour
    5 mcd/m2 at 2 hours

    Excitation and Phosphorescent Emission Curve:
    Excitation and Emission Spectra

  • Microspheres for Medical Devices – MDDI Magazine – January 2011

    The Microsphere of Influence

    Published: January 2011, MDDI

    Published on MDDI Magazine
    By: Yelena Lipovetskaya

    Find more content on: Feature, Nano and Microtechnology, Technology, Testing and Inspection

    Microspheres come in many different grades and sizes, and are usually solid particles that are composed of polymers, glass, and ceramics. All images courtesy of COSPHERIC LLC

    Microspheres are round microparticles that typically range from 1 to 1000 μm in diameter. In the pharmaceutical and cosmetics industry, microspheres are well known for their ability to deliver active materials. This process usually involves the microencapsulation of a drug or an active cosmetic ingredient to protect it from the deteriorating effects of the environment or for optimal release and performance in the final product. Active ingredients are released by dissolution of the capsule walls, mechanical rupture (rubbing, pressure, or impact), melting, or digestion processes. Solid microspheres are widely used as fillers and spacers in a variety of industries.

    Microspheres used to manufacture and test medical devices are typically solid particles that are made from robust and stable raw materials such as polymers, glass, and in some cases, ceramics. Different types and grades of microspheres are available and selected based on specific application requirements.

    They are often used as tracers and challenge particles in medical devices. In these situations, it is beneficial to use larger microspheres with sphere diameters greater than 50 μm that are vividly colored (red, blue, black, yellow, or green), since they provide contrast with the background material and visibility to the naked eye in daylight. Colored microspheres are typically used in the testing of filtration media and systems, vial and container cleaning evaluations, flow tracing and fluid mechanics, centrifugation and sedimentation processes, pharmaceutical manufacturing, and contamination control.

    Fluorescent microspheres are recommended for applications that require the use of particles that emit distinctive colors when illuminated by UV light and offer additional sensitivity for observation through the use of microscopes, lasers, and other analytical methods. Examples include microcirculation and biological research, imaging, and flow cytometry. Fluorescent microspheres can be excited and detected by a wide range of methods and are useful as experimental particles for acoustical and optical analytical systems.

    Continue reading “Microspheres for Medical Devices – MDDI Magazine – January 2011” »

  • ParaMagnetic Microspheres

    Paramagnetic microspheres have the ability to increase in magnetization with an applied magnetic field and loose their magnetism when the field is removed. Neither hysteresis nor residual magnetization is observed and that provides the end use two very practical advantages:

    • When the filed is removed, the microspheres demagnetize and re-disperse easily. This property allows efficient washing steps, low background and good reproducibility.
    • The behavior of the microspheres is always the same whatever the magnetization cycles may be. Such behavior is a key point for automated instrument.
    Black Paramagnetic Microspheres

    106-125um Magnetic Microspheres

    Recently black paramagnetic microspheres have been produced in larger sizes of 10 micron to 1mm (1000um) and in dry form enabling scientists to leverage the benefits of paramagnetic particles in new applications. These highly spherical polyethylene microspheres offer the flow-ability of standard microspheres, with the ability to be separated from other materials for re-use and cleanup.

    One use of paramagnetic microspheres as large as 1mm in diameter to simulate salmon eggs, Scientists are able to place them in a natural habitat, observe how they move with the water currents and then use their magnetic properties to clean them up.

    SuperParamagnetic microspheres, sometimes just called magnetic microspheres or paramagnetic microspheres have become widely used in the life sciences industry (<10um diameters) for applications such as:

    • Solid Phase Immunoassays
    • Bacteria Detection
    • High Throughput screening
    • Rapid Tests
    • Cell Sorting
    • Biosensors
    • Nucleic Acids Technology
    • Microfluidics1

    Super paramagnetic microspheres used in the life science industry are supplied in solution form.

    1. Merck Estapor Super Paramagnetic Microspheres Brochure

  • Fluorescent Microspheres – Properties and Applications

    Fluorescent microspheres are round spherical particles that emit bright colors when illuminated by UV light. Ability to emit intense color under UV (black light) illumination provides contrast and visibility of microspheres relative to background materials. In addition to the benefits of conventional high quality microspheres, such as sphericity, smoothness and spreadability among others, fluorescent spheres offer extra sensitivity and detectability for analytical methods. For example, fluorescent microbeads are often used as traces to simulate spread of viruses in medical research.

    Typical applications of fluorescent spheres include: testing of filtration media and systems, vial and container cleaning studies, flow tracing, flow visualization, and fluid mechanics studies, medical imaging and flow cytometry, fluorescence microscopy and photography, as well as biomedical technology research, qualification and validation of medical devices, biomedical diagnostics, process troubleshooting and process flow among others. Specifically fluorescent microspheres are often used for water- and air-flow testing and bead-based diagnostic applications. New unique applications of fluorescent spheres are being discovered daily.

    75-90um Dual Response - Daylight & 365nm UV  20um-1000umFluorescent spheres have a unique ability to appear translucent (clear) and practically invisible under ordinary light, and emit intense visible color when energized by ultraviolet (UV) light. This effect allows scientists and engineers to design blind tests and controlled experiments (e.g. simulate spread of viruses) where the microspheres are invisible to the operator doing the procedure until after the fact, therefore, eliminating any operator bias and uncertainty in the validity of experiment. This unique feature of fluorescent microspheres has numerous applications in biomedical research and process troubleshooting. Continue reading “Fluorescent Microspheres – Properties and Applications” »