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.

Monodisperse Silica Microspheres

Scientists are always pushing the limits, and looking for more precise products and equipment to enable the next technology.   In an effort to provide those scientists with the right tools Cospheric LLC has added monodisperse silica microspheres to their broad product line.

Silica particles are now available in distributions of less than 10% CV in the sizes of 1.0 micron, 4 micron and 8 micron.

Silica Microsphere Products now available:

SIO2MS 1.0um  <10% CV

SIO2MS 4.0um <10% CV

SIO2MS 8.0um <10% CV

SIO2MS 4-6um  (2-19um range)

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.

Continue reading “Microparticles for simulating fish egg dispersion and recruitment” »

Microspheres as bond line spacers in epoxies

Today’s electronics are demanding tighter and tighter tolerances, and the assembly of many items require holding precise spacing between parts during assembly.  The spherical shape and precise sizes available make microspheres the ideal candidate as a precision spacer in various liquid adhesives and epoxies.

Important considerations:

1) The actual bond line will correspond to the largest spheres, not the average size.  Narrow size ranges of a few micron ensure the proper gap is maintained.

• If a 30um gap is required use a spacer grade size range of 27-30 micron.
• If a 40um gap is required use a spacer grade size range of 37-40 micron.
• If a 53um gap is required use a spacer grade size range of 50-53 micron.

3) Functionality gained from using different materials.

• Glass offers the best mechanical and chemical stability at a wide range of temperatures.
• Plastic such as PMMA can be used where some deformation is desirable.
• Metal coated glass spheres can be used where conductivity is desirable.
• Hollow Glass spheres can be used where assembly pressures are low, and reduced thermal conductivity is desired, available as uncoated hollow glass or silver coated hollow glass spheres.

4) The importance of sphere loading (% spheres by volume in the adhesive)

• Theoretical maximum loading by volume for a monolayer is 61%
• A mixture of about 5% by volume should work for most applications.
• Narrow bond lines with high assembly forces will require higher loadings
• Low crush strength spheres will require higher loadings.
• Proper dispersion in the adhesive will help to minimize the loading needed.

5) Adhesive / Epoxy selection

• High viscosity epoxies will help maintain sphere dispersion.
• For best results choose an adhesive that adheres to the spheres and the base material.
• Long pot-life materials work best, as they allow excess adhesive to flow out of the bond line during assembly.

6) Spacer Availability – Cospheric LLC stocks a wide variety of sizes and materials, and can custom produce spacer grade microspheres for your application.

• Spacer Grade Solid Glass Spheres, narrow 3um ranges, >95% in range, 22-53 micron
• Silver Coated Solid Glass Spheres, >90% in range, 22-110 micron sizes
• Soda Lime Glass Spheres, >90% in range, 27 micron to 3.4 mm sizes
• Solid PMMA Spheres, >90% in range, 20-150um sizes

Applications for Bond Line Spacers

Spacer Grade Glass Microspheres are presently used in gas plasma displays, automotive mirrors, electronic displays, flip chip technology, filters, sporting goods equipment, calibration standards and transformer manufacturing.  Every day engineers are finding new and innovative uses for bond line spacers.  One area that has had the most publications is in die attachment in the semi-conductor industry, a particularly interesting area is in using spacers for building multi-die packages. Continue reading “Microspheres as bond line spacers in epoxies” »

BioCompatability of Metal Coated Spheres

For those scientists who are looking to use silver coated materials such as silver coated microspheres in biomedical applications, it is important to understand whether they are bio-compatable.  A selection of abstracts and article references related to the biocompatability of silver follow:

The Biocompatibility of Silver²

The experiments reported have referred to some of the characteristics of the biocompatibility of Ag. Silver has been shown to display interactions with albumin, as an example of a plasma protein, quite different from those of most metals. Such studies shed further light on the complex issue of protein adsorption on biomaterials. It has also been demonstrated that Ag at concentrations < 1 ppm exerts a considerable influence on the activity of lactate dehydrogenase, this effect being reversed in the presence of albumin. A significant but transient increase in blood levels of Ag following intramuscular implantation of the metal has been observed. This is not reflected in any raised urine level. It is proposed that the richly vascular tissue immediately surrounding the implant in the acute phase of the response gives rise to the transient increase, but a subsequent decrease in vascularity reduces this possibility. It appears that Ag released from implants following this initial period substantially remains in the local area.²

Lack of toxicologocial side-effects in silver-coated megaprostheses in humans¹

Deep infection of megaprostheses remains a serious complication in orthopedic tumor surgery. Furthermore, reinfection gets a raising problem in revision surgery of patients suffering from infections associated with primary endoprosthetic replacement of the knee and hip joint. These patients will need many revision surgeries and in some cases even an amputation is inevitable. Silver-coated medical devices proved their effectiveness on reducing infections, but toxic side-effects concerning some silver applications have been described as well. Our study reports about a silver-coated megaprosthesis for the first time and can exclude side-effects of silver-coated orthopedic implants in humans. The silver-levels in the blood did not exceed 56.4 parts per billion (ppb) and can be considered as non-toxic. Additionally we could exclude significant changes in liver and kidney functions measured by laboratory values. Histopathologic examination of the periprosthetic environment in two patients showed no signs of foreign body granulomas or chronic inflammation, despite distant effective silver concentrations up to 1626 ppb directly related to the prosthetic surface. In conclusion the silver-coated megaprosthesis allowed a release of silver without showing any local or systemic side-effects.¹

Specific Article References for the biocompatability of silver are below: See the References