Concept for the Real-Time Monitoring of Molecular Configurations during Manipulation with a Scanning Probe Microscope

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