Feb 11, 2009
Carbon nanotube-based nanoactuator
The amount of force generation at the tip of a bending carbon nanotube can be micro Newtons. To fabricate such a thermal bimorph actuator, a multiwall carbon nanotube (MWNTs) was stacked with a thin metal film only at one side of the nanotube, using pulsed laser deposition. The force generated from the tip was measured by Lateral force microscopy (LFM).
A nanoscale actuator or an array of such actuators can be used for many potential applications. For example, to investigate the effect of an external force on a cell (transfer of inter-cell signaling, and change of cell function), one must know how to generate and control the required force. In a recent study performed at the Stevens Institute of Technology, which was published in Nanotechnology, the authors used individual multiwall nanotubes (MWNTs) to create bimorph nanoactuators that generate the microNewton force.
The deflection and force generated at the tip of the bimorph nanoactuator are originated from the mismatch of coefficient of thermal expansion (CTE) between two constituting layered materials. To create such nanoscale bimorph structures, the researchers used a directional deposition method called pulsed laser deposition (PLD) technique to enable the deposition of a metal film on only one side of a MWNT exposing the other side as a bare MWNT surface. They measured the force from the nanoactuator by sweeping an AFM tip laterally at the middle of a bimorph.
The thermally generated force twisted the AFM cantilever further, and this amount appeared as an increase as the temperature was elevated by a thermal stage under the AFM. A vertical array of such bimorph nanoactuators can be fabricated using various sets of materials, if necessary, to elucidate the mechanochemical response of individual biological cell.
About the author
The work was performed at the mechanical engineering department at the Stevens institute of technology, at Hoboken, New Jersey, USA. Dr Onejae Sul is a postdoctoral scholar studying mechanics and actuation devices based on nanomaterials such as carbon nanotube, graphene and nanowires, under the supervision of Prof. EH Yang. Dr. Yang is currently an Associate Professor at Stevens Institute of Technology (Mechanical Engineering Department), and Director of Micro Devices Laboratory. Dr. Yang came from NASA's Jet Propulsion Laboratory, where he was a Senior Member of the Engineering Staff. He received a number of awards, including NASA ICB Space Act Awards, Bonus (Level B and C) Awards and Class 1 NASA Tech Brief Awards. In recognition of his excellence in advancing the use of MEMS-based actuators for space applications, he received the prestigious Lew Allen Award for Excellence at JPL. Dr. Yang is currently PI/Co-PI on grants from AFOSR, NSF, NASA SBIR, and US Army ARDEC. Dr. Yang holds 6 patents issued or pending. He is Associate Editor and member of Editorial Board of the IEEE Sensors Journal.