A new approach for the development of mechanical biosensors is presented in Nature Communications this week. The scheme may enable new routes to low concentration detection of biomatter. Nanomechanical resonators are attractive for biosensing as their resonant frequencies depend very sensitively on changes to their mass, allowing them to detect the tiny masses associated with DNA and small molecules. Amit Lal and co-workers demonstrate a new device based on an array of vertical nanowires on a silicon membrane. Unlike existing nanoelectromechanical resonators or cantilevers, this structure forms a photonic crystal, so that the sensor is controlled by a laser. This enables remote activation of the device, while the large surface area of the silicon nanowires means that it achieves a far higher mass per area sensitivity than other types of mechanical sensor. This makes it a promising system for biosensors involving solutions with low concentrations of material, such as DNA.