Lab talk
May 7, 2009
Study examines dynamics of polymerized CNTs
Polymerized carbon nanotubes (CNTs) are promising materials for polymer-based electronics and electromechanical sensors. Having a polymer nanolayer on CNTs widens the scope for functionalizing the structure in various ways. It is widely accepted that several solid-state nanoelectronic devices and sensors may be realized using polymerized CNTs. Understanding the behavior of polymerized CNTs in dynamically varying electromechanical environments holds the key to realizing efficient, cost-effective and commercially viable devices.
Researchers at the Department of Aerospace Engineering, Indian Institute of Science, have shown that the relative change in the resistance of a single isolated semiconductive nanotube is directly proportional to the axial and torsional dynamic strains, when the strains are small. Whereas in polymerized CNTs, the viscoelasticity of the polymer and its effective electrical polarization give rise to nonlinear effects as a function of frequency and bias voltage.
CNTs embedded in a background matrix of polymer mixed with carbon nanoparticles are considered in the latest research. For static strain and DC bias voltage, the electronic bandgap in CNTs is well understood. However, for dynamic strain sensing, there are two important physical aspects that have not been studied previously. One is the relative influence of constraint and strain rate effects in the polymer surrounding the CNTs and the other is the dynamic strain-dependent bandgap change in the CNTs. These two features give rise to an effective dynamic change in the resistance of the CNT-polymer system under consideration. With the help of experimental and analytical results, the nonlinearity due to strain amplitude and frequency in the current-voltage measurements can be explained.
The researchers presented their work in Nanotechnology.
About the author
The research was carried out at the Laboratory for Integrative Multiscale Engineering Materials and Systems (IMEMS), led by Prof. D Roy Mahapatra at the Department of Aerospace Engineering, Indian Institute of Science, Bangalore, India. Sandeep V Anand is a team member and research assistant at the Department of Aerospace Engineering, Indian Institute of Science. He has been a member of the IMEMS lab since September 2008. His current interests include CNT-based nano/micro devices for solid-state electronics, electromechanical and biochemical sensors and energy harvesting. Dr D Roy Mahapatra has been an assistant professor of Aerospace Engineering at the Indian Institute of Science since 2006. His current research interests are the mechanics of materials, smart structures and systems, dynamics, nano and bioengineering.
