A flexible and printable piezoelectric material that can convert mechanical pressure into electrical energy has been developed. It is 100,000 times thinner than a human hair and 800 percent more efficient than other piezoelectrics based on similar nontoxic materials. It can be easily fabricated through a cost-effective and commercially scalable method using liquid metals.
Until now, the best performing nanothin piezoelectrics have been based on lead, a toxic material that is not suitable for biomedical use. The new material is based on nontoxic zinc oxide, which is also lightweight and compatible with silicon, making it easy to integrate into current electronics. It is so efficient that only a single 1.1-nanometer layer of the material is required to produce all the energy required for a fully self-powering nanodevice.
The material’s potential biomedical applications include internal biosensors and self-powering biotechnologies, such as devices that convert blood pressure into a power source for pacemakers. The nanothin piezoelectrics could also be used in the development of smart oscillation sensors to detect faults in infrastructure like buildings and bridges, especially in earthquake-prone regions. Examples of energy-harvesting technologies that could be delivered by integrating the new material include smart running shoes for charging mobile phones and smart footpaths that harness energy from footsteps.
The material is produced using a liquid metal printing approach in which zinc oxide is first heated until it becomes liquid. This liquid metal, once exposed to oxygen, forms a nanothin layer on top like the skin on heated milk when it cools. The metal is then rolled over a surface to print off nanothin sheets of the zinc oxide skin. The technique can rapidly produce large-scale sheets of the material and is compatible with any manufacturing process including roll-to-roll processing.