First, it was a lone bacterium; then, a solitary virus. Now, scientists have pushed the limits of ultrasensitive detection even farther to determine the mass of a single DNA molecule. Such precise biosensor measurements could lead to faster and more-accurate early screening for HIV infection, cancer, and other diseases.
![](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2005/06/5092.jpg?resize=150%2C112&ssl=1)
The new biosensor, developed by Harold Craighead of Cornell University and his colleagues, consists of an array of microcantilevers made of silicon nitride, each one spotted on the end with gold.