Mechanical flexibility is a key factor determining the stability and durability of porous carbon materials. The compressive brittleness of porous carbon materials has been well resolved. However, reversible stretchability property remains a major challenge due to the weak connections of the three-dimensional porous carbon networks.

In a study published in Advanved Materials, a team led by Prof. YU Shuhong from University of Science and Technology of China (USTC) developed a super-elastic porous carbon material with both high compressibility and stretchability, called "carbon spring". Its unique microstructure and properties make it an ideal material for manufacturing intelligent vibration and magnetic sensors.

Inspired by the elastic deformation of arched bow, the researchers introduced a unique long-range lamellar multi-arch microstructure to solve both compressive and tensile brittleness problems of porous carbon materials. The carbon springs developed based on this microstructure can achieve reversible tensile and compressive deformation in the large strain range of -60% to 80% and can fully rebound. This elastic behavior is similar to that of a real metallic spring.

Strain sensors made from carbon spring. Credit: Gao Huailing.

Using the carbon spring as a key component, the researchers developed a strain sensor that can detect tiny vibration. The strain detection limit of the vibration sensor was at least ± 0.5%, and the maximum vibration frequency detected was at least 1000 Hz. The vibration sensor can make sensitive response to a variety of complex vibration patterns such as simulated seismic vibrations. In addition, by co-assembling Fe₃O₄ nanoparticles into the carbon spring, the researchers obtained a magnetic carbon spring that can be driven by magnetic field. Based on this carbon spring, a new type of magnetism sensor was manufactured which could make a stable response to a small magnetic field with the detection limit of as tiny as 0.4 mT. These two sensors could both work stably in temperature ranging from -100 to 350 °C.

This work provides an effective way to construct novel intelligent vibration and magnetism sensors and a new strategy to create highly stretchable and compressible porous materials for extreme applications from other inorganic components.

This article originally appeared in USTC News Center of August 27, 2021.

Reference:

1. Gao, H. L., Wang, Z. Y., Cui, C., Bao, J. Z., Zhu, Y. B., Xia, J., ... & Yu, S. H. (2021). A Highly Compressible and Stretchable Carbon Spring for Smart Vibration and Magnetism Sensors. Advanced Materials, 2102724. DOI: 10.1002/adma.202102724.