Alignment of Thermally Conducting Nanotubes Making High-Performance Light-Driving Motors

Light-actuating devices
that can produce selective motions at small
scales are highly desired for on-demand manipulation. For conventional
photothermal motors that mostly encounter the homogenous light-induced
heat diffusion at the liquid/air interface, it is challenging to effectively
control the actuating direction and enhance the actuating speed. To
this end, here, we explore aligned thermally conducting one-dimensional
nanomaterials to make light-driving motors where the light-induced
heat can be transmitted to the water surface along the length direction
of the aligned one-dimensional nanomaterials to generate a localized
surface tension gradient for high spatial resolution propulsion. When
multiwalled carbon nanotubes were studied as a demonstration, the
aligned active layer generated sufficient propulsion to drive a centimeter-sized
motor that was 10 000 times higher in mass of the actuating layer
on water. In addition, the actuating direction had been accurately
controlled by varying the illuminated region of the active aligned
nanotube layer. The resulting light-driving motors can move as fast
as 4.19 cm/s (or 5.2 body length per second), which exceeded the previous
motors based on the light activation.