Julia L F Goldstein

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Silicon or Silicone? One Letter Makes All the Difference

Nov 11, 2018 by Julia L F Goldstein , in Materials

It amazes me that many educated people do not know the difference between silicon and silicone. I received an email that described a new type of windshield wiper blade supposedly made from silicon. I knew that couldn’t be right. The very idea made me think of fingernails on a chalkboard!

Silicon is an element with the chemical symbol Si. It’s a semiconductor, less electrically conductive than metals but still able to conduct electricity. Silicon is grey and shiny and looks metallic. Large, cylindrical crystals of silicon are sawn into the rigid silicon wafers that serve as the backbone for computer chips. The state-of-the-art microprocessors that power today’s advanced electronics contain many millions of silicon transistors.

 Printed circuit board. The large computer chips contain millions of silicon transistors.
Printed circuit board. The large computer chips contain millions of silicon transistors.

Silicon Valley got its nickname because of the prominent computer companies with headquarters in or near San Jose, California: IBM, HP, Apple, Intel. It’s not Silicone Valley! That locale is 400 miles further south, near Hollywood (just kidding).

Silicones, also known as polysiloxanes, are a class of polymer materials that contain atoms of silicon along with oxygen, carbon, and hydrogen. They do not conduct electricity. These materials are chemically non-reactive and work well at both high and low temperatures. Solid silicones remain soft and flexible when cooled to freezing and don’t melt in a 500-degree oven. Silicone rubber is used in applications as varied as caulk, gaskets, kitchen tools, and breast implants.

 Baster with silicone bristles Baster with silicone bristles

Silicon is ideal for electronics but would be a horrible choice for windshield wiper blades. Silicone rubber, on the other hand, is sufficiently flexible in the winter, won’t melt in the summer, and is water-repellent, and won’t scratch a windshield. The specific wiper blades that my email message mislabeled are made of silicone and feature a unique rectangular shape. The Kickstarter campaign for the project, whose website spells silicone correctly, is already funded at over 20 times the company’s goal.

If you were confused about silicon versus silicone, you’re not alone. Searching “silicone” on Pixabay.com brings up the same images of laptop computers, printed circuit boards, and quartz crystals as a search for “silicon.” Both searches also showed photos of silicone children’s toys and kitchen tools.

Why the photos of quartz? Quartz is a naturally occurring mineral that is a form of silica, or silicon dioxide (SiO2). Silicon does not occur naturally as a pure element but needs to be extracted from silica. Sand containing granules of silica goes through an extensive process involving very high temperatures, expending a great deal of energy to create silicon crystals. Growing the crystals large enough for use as silicon wafers requires yet more energy. As a result, silicon wafers are quite expensive, but not as expensive per ounce as gold.

Do you want to learn why gold costs so much, as well as ways to extract gold that are much less wasteful and toxic? If so, you will enjoy reading my book, Material Value, when it comes out early in 2019. I invite you to join my interest list to get a sneak peek.