US researchers hope a new method of harvesting energy from flowing water could help create self-powered microsensors for discovering oil.
This energy should be enough to power tiny sensors that are placed in water or other fluids and pumped down into a potential oil well, said research leader Prof Nikhil Koratkar.
‘It’s impossible to power these microsensors with conventional batteries, as the sensors are just too small. So we created a graphene coating that allows us to capture energy from the movement of water over the sensors.
‘The advantage of the flexible graphene sheets is that they can be wrapped around almost any geometry or shape,’ he added.
‘We’ll wrap the graphene coating around the sensor and it will act as a “smart skin” that serves as a nanofluidic power generator.’
The water containing the sensors would be injected into the ground and flow through naturally occurring cracks, where the sensors could then detect any hidden pockets of oil and gas.
The sensors would remain active as long as water was flowing over the graphene coating, providing enough power to relay collected data and information back to the surface.
The research team demonstrated the creation of 85nW of power from a sheet of graphene measuring 0.03 by 0.015mm.
Chloride ions in the water stick to the surface of graphene but the flow of the water forces the ions to drift along the surface, dragging the free charges present in graphene with them and creating an internal current.
This means the oil companies would need to add chemicals to the water to create chloride ions and make the sensors work.
The team also tested the energy harvested from water flowing over a film of carbon nanotubes and found that graphene was twice as good at generating power.
Koratkar said the technology could one day lead to self-powered microrobots or microsubmarines. Another possibility is harvesting power from a graphene coating on the underside of a boat.
