Perla · Percolation and conductivity in fluids containing rod-like particles

The PERLA project aims at developing electrically conductive fluids containing rod-like particles. Their novelty is based on the formation of dynamical system-spanning networks in fluid flow. It is well established that rod-like particles do not simply align, but do tumble and rotate in shear or elongational flow. However, the consequences of this tumbling on the percolation and electrical conductivity of suspensions are still unknown. This behaviour is expected to promote collisions and electrical connectivity throughout the suspension. PERLA will validate this fundamental hypothesis, and provide thereby new concepts for the development of conductive fluids with low viscosity, high and tunable conductivity. Systems of carbon nanotubes and short carbon fibers will be used as conductive Brownian and non-Brownian rods. They will be processed and optimized based on the longstanding expertise of the investigators in carbon chemistry and fiber processing. The structure, rheological and electrical properties of the suspensions will be characterized in depth in various flow conditions, from dilute to concentrated regimes. The latter will be of particular interest with the formation of liquid crystalline phases in which tumbling is also well established. The basic knowledge gained in PERLA will be exploited in examples of applications, including flow capacitors, capacitive water desalination and soft electronic sensors and vibrational energy harvesters. These applications are particularly promising regarding energy and environmental issues. However, they are currently limited by the use of highly viscous slurries made of spherical particles, or of heavy and poorly stable liquid metals. The fluids in PERLA will circumvent these limitations, and provide new degrees of freedom due to original effects related to their response to oscillatory pressures, or presence of particles of different sizes.