Apr 8, 2008
Nanocomposite offers MEMS upgrade
Microcantilever actuators made from carbon nanotube (CNT)-polymer composites could dramatically improve the performance of microelectromechanical systems, according to scientists in Taiwan. The researchers from National Tsing Hua University have developed an easy to actuate material that rapidly suppresses unwanted oscillations thanks to a low quality factor.
"Lightweight and highly flexible CNT-composites provide fast electrothermo-actuation at low power," Weileun Fang told nanotechweb.org. "Moving the actuator from its original position to its pull-in position can be employed to define two different states such as 0/1 or on/off, which suits many applications in communications and displays."
The group's nanocomposite device has a pull-in voltage of just 50 V for a full deflection of 560 µm. As Fang explains, this value is very low compared with existing microcantilevers, which can demand at least 500 V to achieve a similar displacement. The researchers believe that CNT-based field amplification is responsible for the low pull-in voltage.
Next, the group turned its attention towards the actuator's damping properties. Images show that the aligned nanotubes are curled into spring-like structures that act as energy absorbers and help to reduce beam oscillation.
To make their composite material, the researchers first grow multiwalled CNTs on a iron-defined polysilicon substrate and then expose the substrate to polymer vapour. The CNT-polymer actuators are formed by removing the underlying polysilicon with vapour-phase XeF2.
The researchers presented their work in Nanotechnology.
About the author
James Tyrrell is editor of nanotechweb.org.