Here, the basic building block is a metal nanoparticle linked to two electrodes by an organic ligand and a nanoswitch. The net charge delivered by this nanostructure exhibits a sharp resonance when the alternating potential applied between the electrodes has the same frequency as the periodic variation between the on and off conductance states induced on the nanoswitch. This resonance can be used to process an external signal by selectively extracting the weight of the different harmonics.
Tackling tolerance issues
Due to the nature of the fabrication process, the nanostructures will inevitably show a significant variability in their physical characteristics. By using a phenomenological model that takes this variability into account, as well as the stochastic nature of electron transference, and the thermal noise, the group has demonstrated that reliable signal processing can still be achieved by adapting the number of nanoswitches per bit of information (circuit redundancy) to suit the tolerance of the nanostructure (device variability).
A moderate level of redundancy could compensate for significant nanostructure variability in future devices. Alternatively, local interactions among the redundant nanostructures associated with each bit could lead to a co-operative behaviour among nearest neighbours to enhance majority rules. Additional work along these lines is in progress.