On-chip mass sensing at the physical limits of nanoelectromechanical systems

A tunable and self-regulating on-chip carbon nano-tube based mass balance is presented for small-size and low-cost environmental and healthcare applications. Tube stretching and a phase-locked loop topology make the system widely universal and invariant to nanotube characteristics. Operational for tube eigenfrequencies up to 385MHz, the circuit integration in a 180nm technology achieves instantaneous zeptogram resolution, while yoctogram precision is obtained within the tenth of a second. These figures of merit range at the physical limits of carbon nanotube resonators.