Specialized Tools for Electrophysiology and Cell Biology Research

Introduction to Clark Capillary Glass

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Product Summary

Clark Electromedical Instruments has long been known for manufacturing micropipettes and microelectrode glasses used primarily in intracellular research.

High quality borosilicate glass
Five outside diameters
Thin or standard wall
Economical

Clark Electromedical Instruments has long been known for manufacturing micropipettes and microelectrode glasses used primarily in intracellular research. Warner Instruments continues to offer patch glass from Clark Electromedical through our affiliate, Harvard Apparatus, UK.

Borosilicate Capillaries

The properties of borosilicate glass make it the most popular material among researchers for the fabrication of electrodes and micropipettes. Its low softening temperature combined with its mechanical strength, chemical durability, high electrical resistivity, and ability to withstand thermal stress make these capillaries the most widely used in the world.

Clark Borosilicate Capillaries are offered in a variety of diameters and wall thickness (standard or thin walled), with or without an inner filament. They are available in fused multi-barrel configurations, as well as in theta style.

Single barrel glass is available in 75 mm (3 in), 100 mm (4 in) and 150 mm (6 in) lengths.

Composition	80.9% SiO₂, 12.9% B₂O₃, 4.4% Na₂O, 1.8% Al ₂O₃
Softening Temp.	815°C
Dielectric Const.	4.7

Aluminosilicate Capillaries

In recent years there has been developing interest in fabricating micropipettes from aluminosilicate glass. Like silicon, aluminum combines with oxygen to form tetrahedral networks and the Al-O bonds are very strong.

In comparison with borosilicate glass, aluminosilicate provides increased hardness, improved chemical durability, reduced electrical conductivity and a lower coefficient of thermal expansion. In addition, while the original ratio of a borosilicate capillarys inner to outer diameter will remain unchanged over its total taper length, aluminosilicate glass demonstrates a marked tendency to thin out as it is drawn to a tip. This behavior allows extremely fine tips to be formed.

Composition	51.9% SiO₂, 22.0% Al₂O₃, 7.8% P₂O₅, 7.7% MgO, 6.9% CaO, 2.1% B₂O₃, 1.4% BaO and 0.2% As₂O₃
Softening Temp.	950°C
Dielectric Const.	6.2

For more information:

Na/H Exchange, Vaughan-Jones, RD.; Grinstein Press, Ch.1 p.8.
Effects of intracellular and extracellular pH on contraction in isolated mammalian cardiac muscle, Bountra, C. & Vaughan-Jones, R.D.; Journal of Physiology, Volume 418 (1989).