Femtomolar sensitivity DNA photonic crystal nanowire array ultrasonic mass sensor

Femtomolar concentration DNA detection is important as this is the concentration needed for early-stage cancer and bacterial infection diagnosis application [1]. Here, we present the first-ever nanomechanical mass-sensing resonator with ordered vertical nanowire (NW) arrays on top of a Si/SiO₂ bilayer thin membrane acting as a photonic crystal. The device has a very high surface area-to-volume ratio of 10⁸ m^-1, enabling DNA sensing of femtomolar concentration. Moreover, the nanowire array forms a photonic crystal that shows strong light trapping and absorption over broad-band optical wavelengths, enabling high-efficiency broad-band opto-thermo-mechanical remote device actuation and biosensing on chip. This method represents a mass-based platform technology that can sense molecules at low concentrations.