The ordered structure of a graphene aerogel (left) mimics that of a strong, flexible aquatic plant stem (right) with parallel layers that are connected by short bridges.
Credit: ACS Nano
Ultralight and exceptionally strong, graphene aerogels are attractive materials for use as catalysts, electrodes, and flexible electronics. But so far it has been hard to make them both strong and elastic. Researchers have now overcome that hurdle by making a squishable graphene aerogel that mimics an aquatic plant’s highly ordered porous structure (ACS Nano 2017, DOI: 10.1021/acsnano.7b01815).
The new, conductive aerogel springs back to its original shape after being squeezed to half its size with more than 6,000 times its weight. The aerogel retains 85% of its original strength even after being squeezed more than 1,000 times. In comparison, aerogels with random pore structures that the researchers made and tested lost more than half of their strength after just 10 compression cycles. The combination of low density, strength, super elasticity, and conductivity are critical for applications in which the material undergoes large volume changes, such as an absorbent that soaks up chemicals or an electrode that takes up and releases ions.
Scientists have typically made graphene aerogels by chemically reducing graphene oxide flakes suspended in water and freeze-drying them. More recently, scientists used 3-D printing with graphene inks to make porous, compressible graphene aerogels.
To assess the material’s potential for use in sensors and electronics, the team tested its conductivity and how it varies with compression. When they connected the aerogel to a light-emitting diode in a circuit, they found that squeezing the aerogel increased conductivity as they expected, demonstrated by the LED glowing brighter. “The conductivity of the aerogel is high considering its low density,” Bai says. “With higher density, the aerogel should be more conductive.”
This is a clever, low-cost, and scalable freezing process to generate a new aerogel microstructure, says Peter Pauzauskie of the University of Washington. “This kind of detailed graphene microstructure would be very expensive and difficult to achieve” using other methods, including 3-D printing, he says
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