Aerogels are very lightweight materials, yet they can also be mechanically strong and conductive if the right materials are chosen. Multifunctional aerogels, which combine several useful properties, are particularly interesting. However, this area is not well-developed.

Yongping Chen, Hainan University, Haikou, China, Xuetong Zhang, Chinese Academy of Sciences, Suzhou, and University College London, UK, and colleagues have developed a multifunctional aerogel film composed of aramid nanofibers (ANFs), conductive carbon nanotubes (CNTs), and a hydrophobic fluorocarbon (FC) resin. The team first prepared dispersions of ANFs (Kevlar) and CNTs in dimethylsulfoxide (DMSO), which were mixed and deposited on a substrate (aluminum foil, polyethylene terephthalate sheets, or glass) using blade coating. The organic solvent was then displaced by water to create a hydrogel. This hydrogel was converted to an aerogel by freeze-drying. In a final step, the aerogel film was coated with a thin layer of fluorocarbon resin.

The fluorocarbon resin is hydrophobic and gives the film self-cleaning properties (similar to the lotus effect). This property is enhanced by the rough surface structure of the underlying nanofibers. The carbon nanofibers make the hybrid material electrically conductive. This allows the aerogel to be used as a safe electrical heater at low voltages. It can also be used to shield objects from electromagnetic interference (EMI). The aramid nanofibers give the material a high mechanical strength. According to the researchers, the aerogel could be useful, e.g., in smart clothing.

• Multifunctional Aramid Nanofiber/Carbon Nanotube Hybrid Aerogel Films,
  Peiying Hu, Jing Lyu, Chen Fu, Wen-bin Gong, Jianhe Liao, Weibang Lu, Yongping Chen, Xuetong Zhang,
  ACS Nano 2019.
  https://doi.org/10.1021/acsnano.9b07459