Going with the (irregular) flow for better power generation at graphene-fluid interface

Over the past decade, much research has focused on the use of flowing liquid, including intermittent droplets, moving over or through nanocarbon materials such as graphene and nanotubes to generate electricity. The mechanisms thought to be at play, such as momentum transfer, ion motion, and capacitive charge and discharge, have not been conclusively explained, but theories have become focused on the interaction between a liquid’s charge fluctuations and graphene’s electronic excitation.

Takeda et al. conducted experiments using fluidic chips and numerical calculations to better understand how flow conditions can generate greater electromotive force (EMF) to enhance electrical output. The chip design included a top plate with water inlets, a fluidic channel, and a graphene substrate.

“We wanted to investigate what flow-chip shape would maximize power generation and found that slightly modifying the inlet shape to generate irregular flow doubled the EMF,” said author Takeru Okada.

The research revealed that, while changing the inlet shape to channel irregular flow was very determinative to generating EMF, the Reynolds number, a dimensionless quantity representing the ratio of inertial to viscous forces, was not. It also opened a relatively new channel of inquiry — flow conditions — to explore the mechanisms at play, and to further enhance power generation potential.

“When water flows over graphene, an electrical current flows, and while this phenomenon can be applied as a power generation device, many aspects remain unknown,” said Okada. “It is a fascinating finding that such a minor change in inlet geometry produces such a significant difference, and we believe this is an important insight for future power generation system design.”

Source: “Enhancing electricity generation at graphene-fluid interface under disturbance flow conditions,” by Hikaru Takeda, Mitsuhiro Honda, Masaki Tanemura, Ichiro Yamashita, Atsuki Komiya, and Takeru Okada, AIP Advances (2025). The article can be accessed at https://doi.org/10.1063/5.0294593 .