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.

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

Scientists 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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Neutrally Buoyant in Water – Microspheres with Specific Gravity of 1g/cc

Cospheric offers polymer microspheres with specific gravity of 1g/cc are specifically designed to match the density of water for optimal suspension of particles. Suspension of microspheres in water enables the visualization and characterization of fluid flow and testing the capability of devices to withstand particulate matter in the fluid stream, ensuring that microspheres do not settle and do not float on the surface.  Most of these polymer microspheres are at least moderately opaque and clearly visible in water, clear or translucent liquids.

Many Colors are available in sizes from 10um up to 1180um,  of polyethylene microspheres are available with specific density of 1g/cc, designed for optimum suspension in water for fluid flow visualization.  Colors include Violet, Orange, Yellow, Fluorescent, Grey, Pink, Blue.

Phosphorescent Microspheres – Long Afterglow Particles

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.

Intensity 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:

Microspheres for Medical Devices – MDDI Magazine – January 2011

The Microsphere of Influence

Published: January 2011, MDDI

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.

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