Fabrication of bimetallic nano actuators using nanotubes

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We have studied bimetal-type components consisting of a single nanotube with a platinum layer to realize heat-driven actuators at nanometer scale. The component was fabricated by electron beam deposition of Pt onto a boron nitride nanotube (BNNT) or a carbon nanotube (CNT). Thermal behavior during heating was examined by transmission electron microscopy equipped with a heating holder. As the result, Pt showed uniform thermal expansion at 673 K, however the bimetallic deformation of pristine Pt-nanotube components was hampered by the high rigidity of nanotubes and the plastic deformation of Pt layer due to the grain growth above 473 K. To solve this problem, individual nanotubes were treated by argon ion etching to control their rigidity. Accordingly, ion-treated Pt-nanotube components showed bimetallic deformation reversibly by the temperature swings between 293 and 373 K. In addition, it was confirmed that the smallest diameter to be operated as the bimetallic nanoactuator was 20 nm.