Rational Design of Soft Yet Elastic Lamellar Graphene Aerogels via Bidirectional Freezing for Ultrasensitive Pressure and Bending Sensors

To enhance the sensitivity of graphene aerogel-based piezoresistive sensors by weakening their compressive strength while keeping their elasticity, lightweight and lamellar graphene aerogels (LGAs) with high elasticity and satisfactory electrical conductance networks are fabricated by bidirectional-freezing of aqueous suspensions of graphene oxide in the presence of small amounts of organic solvents, followed by lyophilizing and thermal annealing. Because of the lamellar structure of the LGA, its compressive strength along the direction perpendicular to the lamellar surface is much lower than those of both isotropic and unidirectionally aligned graphene aerogels with similar apparent densities, leading to an ultrasensitive LGA-based piezoresistive sensor with a high sensitivity of -3.69 kPa(-1) and a low detection limit of 0.15 Pa. The ultrahigh sensitivity and low detection limit of LGA-based piezoresistive sensor contribute to detecting subtle pressure at room temperature and in liquid nitrogen with ability to detect dynamic force frequency and sound vibration. Besides, thanks to the fewer junction points between the graphene lamellae, LGAs slices can be integrated as a wide-range and sensitive bending sensor, which can detect arbitrary bending angles from 0 degrees to 180 degrees with a low detection limit of 0.29 degrees, and is efficient in detecting biosignals of wrist pulse and finger bending.

Automated summary

The researchers have achieved an ultrahigh sensitivity and low detection limit piezoresistive sensor with lightweight lamellar graphene aerogels (LGAs), which can detect subtle pressure in liquid nitrogen and serve as a sensitive bending sensor for detecting arbitrary bending angles. The sensor is also efficient in detecting biosignals such as wrist pulse and finger bending.