Roland Piquepaille writes "Researchers from the Georgia Institute of Technology have created nanorings of single-crystal zinc oxide. Because of the semiconducting and piezoelectric properties of the material, these nanostructures could serve as nanometer-scale sensors, resonators and transducers, according to this article from nanotechweb.org. These perfectly circular nanorings range in diameter from one to four microns and are 10-30 nanometers thick. They could be used to build implantable sensors for real-time monitoring of such biomedical measures as blood pressure, blood flow rate and stress at the level of single cells. This overview contains more details and references. It also contains an image of such a beautiful zinc-oxide circular nanoring."