  Nanomechanical resonant sensors that are based on detecting and tracking the
resonance frequency deviations due to events of interest are being advocated
for a variety of applications. All sensor schemes currently in use are subject
to a basic trade-off between accuracy and speed, while there is great interest
in improving both in order to enable unprecedented and widespread applications.
Based on a thorough understanding of the characteristics of current resonant
sensor architectures, we propose adaptive and flexible sensor schemes. Unlike
recently proposed time-resolved mechanical detection methods, the proposed
schemes do not require ensemble averaging of the resonator response for many
independent identical stimuli. Distinct one-time events can be detected in
real-time with high time resolution with an accuracy that then improves
considerably with elapsed time. While the proposed adaptive schemes also need
to abide by the fundamental speed versus accuracy trade-off, we show that there
is still "some room at the bottom" for improvement with sensor architecture
innovations. Pareto optimal performance that reaches a bound that is imposed by
the fundamental thermomechanical noise can be achieved.
