Action-potential-inspired osmotic power generation nanochannels

The action potential across biological membranes formed by osmotic gradient induced by external conditions plays a key role in the signal transmission of life processes, which can inspire researchers to develop artificial osmotic power generation device with multi-stimuli controllable power output. Herein, an adaptive 2D nanochannel membrane is fabricated by stacking of montmorillonite nanosheets co-modified with a laboratory synthesized cationic surfactant containing spiropyran species and a commercially cationic surfactant of dioctadecyldimethylammonium bromide. Similar to biological action potentials, the osmotic power generation of 2D nanochannel membranes can be regulated by external multiple stimuli such as light, pH and temperature based on the adaptive ion selectivity and ion flux of nanofluidic channels relying on the surface charges of spiropyran species and the phase state of surfactants. Impressively, the control of temperature rising to 60 °C significantly boosted the maximum power density of 2D nanochannel membrane from ∼0.81 W/m² to be ∼7.12 W/m² by 8.8 times at a gradient of artificial sea water and river water resulting from the enhanced ion flux by phase transition of surfactants, which is the highest value among those of clay-based nanochannel membranes and ion exchange membranes. Our results implies that the development of adaptive 2D nanochannel membranes is a new strategy for improving the power output of osmotic energy conversion devices.