  Atomic force spectroscopy and microscopy (AFM) are invaluable tools to
characterize nanostructures and biological systems. Most experiments, including
state-of-the-art images of molecular bonds, are achieved by driving probes at
their mechanical resonance. This resonance reaches the MHz for the fastest AFM
micro-cantilevers, with typical motion amplitude of a few nanometres.
Next-generation investigations of molecular scale dynamics, including faster
force imaging and higher-resolution spectroscopy of dissipative interactions,
require more bandwidth and vibration amplitudes below interatomic distance, for
non-perturbative short-range tip-matter interactions. Probe frequency is a key
parameter to improve bandwidth while reducing Brownian motion, allowing large
signal-to-noise for exquisite resolution. Optomechanical resonators reach
motion detection at 10^(-18) m.(Hz)^(-1/2), while coupling light to bulk
vibration modes whose frequencies largely surpass those of cantilevers. Here we
introduce an optically operated resonating optomechanical atomic force probe of
frequency 2 decades above the fastest functional AFM cantilevers while Brownian
motion is 4 orders below. Based on a Silicon-On-Insulator technology, the probe
demonstrates high-speed sensing of contact and non-contact interactions with
sub-picometre driven motion, breaking open current locks for faster and finer
atomic force spectroscopy.
