A bold vision in nanofabrication is the assembly of functional
molecular structures using a scanning probe microscope (SPM). This
approach requires continuous monitoring of the molecular configuration
during manipulation. Until now, this has been impossible because the
SPM tip cannot simultaneously act as an actuator and an imaging probe.
Here, we implement configuration monitoring using experimental data
other than images collected during the manipulation process. We model
the manipulation as a partially observable Markov decision process
(POMDP) and approximate the actual configuration in real time using
a particle filter. To achieve this, the models underlying the POMDP
are precomputed and organized in the form of a finite-state automaton,
allowing the use of complex atomistic simulations. We exemplify the
configuration monitoring process and reveal structural motifs behind
measured force gradients. The proposed methodology marks an important
step toward the piece-by-piece creation of supramolecular structures
in a robotic and possibly automated manner.
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