May 30, 2012
Carbon-based mixed-dimensional composites expand capability of adaptronics
Adaptronics, or smart structures, are terms that describe an emerging class of complex systems that adapt to changing environmental stimuli to facilitate motion, sensing or intelligence functions. The efficient and reliable operation of adaptronic structures requires a fundamental link between sensing and actuation elements. As the backbone of adaptronic systems, functional materials have properties that enable operation in both sensing and actuating roles. While a variety of these unusual materials already exist, the development of new classes of functional materials with enhanced properties will give researchers improved tools for engineering next generation adaptronic structures.
In recent work, researchers from the University of Louisville, US, have introduced a new class of functional materials based on carbon nanostructure thin-film polymer composites (TFPCs). Using polydimethylsiloxane, a common silicone elastomer, the team has fabricated composites with one-dimensional multi-wall carbon nanotubes (MWNTs), two dimensional single-layer graphene, two-and-a-half-dimensional graphene nanoplatelets and three dimensional highly ordered pyrolytic graphite. An evaporative mixing technique was utilized to achieve homogeneous dispersions of carbon in the polymer composites and their photomechanical responses to NIR illumination were studied.
For a given carbon concentration, both steady-state photomechanical stress response and energy-conversion efficiency were found to be directly related to the dimensional state of the carbon nanostructure additive. Actuation and relaxation kinetic responses were found to be related not to dimensionality, but to the percolation threshold of the carbon nanostructure additive in the polymer.
Studying the influence of the carbon nanostructure’s dimensional state on the mechanical response of the material could lead to new types of carbon-based mixed-dimensional composites for sensor and actuator systems. Furthermore, benefits of photomechanical actuation, such as wireless actuation, electromechanical decoupling (and therefore low noise) and massive parallel actuation of device arrays from a single light source, will provide researchers with an altogether different philosophy from which to pursue complex engineering challenges.
More information can be found in the journal Nanotechnology.
About the author
The study was conducted in the Small Systems Laboratory at the University of Louisville, Kentucky, US. Funding for this research was partially supported by the NSF CAREER award ECCS: 0853066 for one of the authors (BP). James Loomis is a PhD candidate in mechanical engineering. Dr Balaji Panchapakesan is a professor at the University of Louisville, and director of the Small Systems Laboratory.