Microparticles

Microparticles are particles between 0.1 and 100 μm in size. Commercially available microparticles are available a wide variety of materials, including those made of ceramics, glass, polymers, and metals. One encounters microparticles everyday in nature with items such as pollen, sand, and dust. Many Microparticles can be found in your kitchen as well with items such as: flour, and powdered sugar.

Microparticles have a much larger surface-to-volume ratio than at the macroscale, and thus their behavior can be quite different. For example, metal microparticles can be explosive in air.

Microsphere are spherical microparticles, and are used where consistent and predictable particle surface area is important.

In biological systems, microparticles are small membrane bound vesicles circulating in the blood derived from cells that are in contact with the bloodstram such as platelets and endothelial cells. (see Endothelial microparticle). Because they retain the signature membrane protein composition of the parent cell, microparticles carry useful information and can be detected and characterized by Flow cytometry.

Alternative definitions for size

Although the generally accepted definition of 0.1 to 100 μm complements the size definition of nanoparticles, there are other ways to define the size.

Mathematical: as the term "micro" refers to 10 ^{− 6}, the range for micro would then be 10 ^{− 7.5} to 10 ^{− 4.5}, or roughly 31.6 nm to 31.6 micrometers. However, general acceptance considers particles smaller than 100 nm nanoparticles.

Rounding: rules of rounding in mathematics provide an alternative for the definition. Anything larger than 0.5 μm and anything smaller than 0.5 mm is considered microparticles.

Convenient/popular: Very often particles with dimensions more than 100 nm are still called nanoparticles. The upper range may be between 300 to 700 nm, so this would give a size definition for microparticles of 0.3 to 300 μm or 0.7 to 700 micrometers.

Applications

Most people are familiar with home pregnancy test - a color appears if the test is positive. These tests make use of gold microparticles.

Manny applications are also listed in the Microsphere article.