Relative displacements between the individual carbon molecules that are cylindrically nested and suspended using van der Waals forces within a multiwalled carbon nanotube (MWNT) have been demonstrated to provide exceptional performance as linear and rotary nanobearings, with an inherent position feedback capability. While prototype devices have previously proven concepts, the capability to controllably alter the as-synthesized closed-cap shell structure of MWNTs to form nanobearings in parallel represents a significant challenge towards their eventual manufacturability and commercialization.
Recent work at Prof. Bradley Nelson’s Institute of Robotics and Intelligent Systems (IRIS) at ETH, Zurich, has scaled this important technological barrier. By creating dielectrophoretically assembled MWNT nanostructure arrays with designs that ensure uniform joule heating, current-induced shell etching is used to form nanobearings with a high yield and low cycle time. Enabled by capabilities that are unique to the assembly process, sophisticated shell architectures that have previously been impossible, such as bi-directional linear bearings, nanoshuttles and multiple but independent high-density bearings from single nanotubes, have been demonstrated. This technique for constructing electromechanical building blocks is anticipated to be a fundamental unit process for manufacturing future NEMS. Some of the devices currently under development at IRIS include electromechanical transistors, combinatorial logic elements and GHz resonators.