About this Article
Written by: Kalin Higa
Written on: October 10th, 2009
Tags: aerospace engineering, lifestyle, material science, space
Thumbnail by: NASA/Wikimedia Commons
About the Author
In Fall 2009, Kalin Higa was a senior majoring in mechanical engineering at the University of Southern California's Viterbi School of Engineering. Born and raised on the island of Maui, Hawaii, he enjoyed spending his free time at the beach with his friends and family.
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Volume X Issue III > Aerogel - The Insulative Frozen Smoke
Aerogel, a material commonly referred to as "frozen" or "solid smoke," was originally developed in the 1930s, but has not received much attention until now. Scientists and engineers recently realized the possibilities of working with such an unusual substance, focusing on its strength-to-weight ratio and its thermal resistivity. These properties are a result of the material's molecular structure: it is composed of up to 99% air, with the remainder being a solid polymer network. With hundreds of proposed applications, this substance may be found in everything from building insulation to surfboards to space suits worn by future astronauts on Mars. As with most new technologies, however, the main obstacle to widespread use of aerogel is its relatively high cost.

The Miracle Material

Take a look into the house of the future: sleek, spacious rooms, furniture made from recycled material, and..."frozen smoke"? This frozen smoke, technically known as aerogel, is an extraordinary material that may find a way into your home sometime in the near future. As engineers discover ways to make this substance more affordable, the number of practical applications is increasing at an amazing pace. From home insulation and blankets to tennis rackets, ski jackets, and refrigerators, aerogel may revolutionize many facets of everyday life.
NASA/Wikimedia Commons
Figure 1: Aerogel is made of up to 95-99% air, with a density three times that of air.
So what exactly is aerogel? While some materials may exhibit a low density, high thermal resistivity, or high strength-to-weight ratio, only aerogel can claim all of these properties at once [1]. The name aerogel comes from the combination of the Greek word "aero", meaning air, and "gel", since aerogels are derived from gels. Normally, a gel is approximately 99% liquid, while the remaining 1% is a solid network that spans throughout the liquid and can allow the gel to maintain its shape. With a density only three times that of air, aerogel is what is left after replacing the liquid contents of a gel with a gas -- without shrinking it [2]. As shown in Fig. 1, the result is an opaque blue solid that is composed of anywhere from 95-99% air. The texture of aerogel is similar to a fine, dry sponge, but feels much lighter [1]. In fact, aerogel holds the record as the lightest solid in the world. When pressed softly, aerogel will return to its original form, but when pressed harder, a dimple forms. Put aerogel under too much pressure, however, and it will shatter like glass into many tiny pieces. Although it was first produced over 70 years ago, it has taken recent research and applications for it to be hailed as a "miracle material" [3].