Aerogel was invented in the 1930s, and developed for insulation applications. It is among the lightest solid materials, fabricated from removing the liquid within gels through supercritical drying. Its excellent mechanical and chemical properties have attracted great attention from research institutions and industrial corporations.
Since the 1960s, aerogel has been used by NASA as the insulation layer for spacesuits. NASA has recently claimed that polymer-reinforced aerogels can be used for applications such as cryogenics or spacesuits. For consumer-level applications, aerogels have the potential to become the next-generation material for many applications beyond insulation such as electronics, packaging, and supercapacitors.
Properties of Aerogel
Aerogel material can potentially be up to 99.8% porous, meaning only 0.2% of the volume it occupies is non-air components. Typically, the density of aerogels range between 0.0011 and 0.5 g/cm3, averaging around 0.02 g/cm3. This average density of aerogel is only 15 times of the density of air, making aerogels one of the lightest types of materials humans discovered, only heavier than specialized materials such as metallic microlattices (0.9 mg/cm3) and aerographites (0.2 mg/cm3). Additionally to its low density, aerogels also offer the following advantages:
• Low mean free path of diffusion
• High specific surface area
• Low thermal conductivity
• Low refractive index
• Low dielectric constant
• Low coefficient of thermal expansion
• Low sound velocity
• High resistivity
Recent Scientific Discovery
Generally, a strong material can hardly be elastic. With aerogels, this has also been the case until a recent breakthrough in strong and elastic graphene aerogel. Researchers from Zhejiang University of China have fabricated exceptionally robust, conductive, and elastic graphene aerogel, inspired by an aquatic plant, Thalia dealbata. Hao Bai of Zhejiang University claims that he was inspired by the plant’s structure. Having small bridges within the body that helps connect its structural tubes, the plant makes itself capable of withstanding wild winds while having a strong backbone.
Bai’s laboratory moved forward with this inspiration and developed strong yet squishable graphene aerogel through a bidirectional freezing process, which can be applied to many other materials as well. The graphene aerogel fabricated can bounce back to its original shape after being squeezed to half its size. Moreover, 85% of its strength remains after 1000 squeezing cycles. This is a big step forward compared to other aerogel materials, which generally lose half of their strength after 10 cycles. Shown below is a picture of the squeezing process. The weight used in Bai’s experiments weighs 6000 times of the weight of the aerogel. The conductivity of this graphene aerogel can also be applied in various areas in the electronics industry from its excellent strength persistence. After further testing the conductivity of the aerogel, Bai claims that the aerogel has a high conductivity considering its low density, and the conductivity increases as the material is squeezed.
Impact on Industrial Market
Application of aerogels have been mainly in the area of insulation due to their light weight and low thermal conductivity. Aerogel Technologies, Aspen Aerogels, and Cabot are recognized manufacturers of aerogel products in the industry. Recently, a clothing manufacturer, Lukla, has raised almost $320,000 on Kickstarter for their aerogel filled winter jackets.
In addition to insulation, aerogels can also be used in many other areas. A recent report by IDTechEx predicts that over the next 10 years, the market size of aerogel products will grow to $910 million compared to $260 million for now. A forecast of application areas of aerogels is provided by IDTechEx. The company points out that the current price for aerogel is too high for it to capture a huge share of the market. With further development in manufacturing processes, the price may very well go down.
Regarding Bai’s achievement and his graphene aerogels, things may be different for the industry. Bai’s method of fabrication is low-cost and scalable, making the future of aerogels brighter than ever before. In addition to traditional application areas such as insulation, filtration, and absorption, aerogels now have the potential to be used in consumer electronics. Products like pressure sensor, cables, switches, and many others can benefit from this breakthrough in the future.
Image courtesy of NASA/JPL-Caltech.
