The objective of this research is the development of single wall carbon nanotube photo-mechanical actuators for the development of nanotube based sensors and actuators. Single wall carbon nanotubes have been recently demonstrated as a new class of actuator materials that require only small voltages for actuation. While much work has gone into the area of nanotube based electrical actuators, the field of optically driven nanotube actuators is at best nascent. The approach of this research is the fabrication and combination of nanotubes with material systems such as electro-active polymers to transduce the light energy that is incident on the nanotube sheet to actuate the polymer and develop wavelength selective photo-actuators. Finally.
Intellectual merit: The impact of this research is in the area of sensors and actuators. Currently piezoelectric and ferroelectric materials used for actuators require electronics that have to generate hundreds of volts for actuation. The photonic actuators are light- weight and can actuate remotely that can be utilized in interplanetary space missions. Further, the development of nanotube based micro-opto-mechanical systems can be utilized for label free genetic analysis of biomarkers in cells that can be used for monitoring autoimmune diseases with high ultra-high sensitivity
Broader impact: The success of this proposal will demonstrate the applications of this technology for micro-opto-mechanical systems for label free genetic analysis in cells. The research brings in opportunities for undergraduate and graduate student training in nanotechnology. Industrial partnerships through this research can potentially be used for commercialization of this technology and can bring greater benefit to the society and economy.
Both in natural and synthetic systems, actuator materials change their shape or dimensions upon external stimulus. The best-known materials for actuation are piezoelectrics, ferro-electrics, shape memory alloys, electrostrictive materials, liquid crystal elastomers, and conducting polymers. Recent additions include carbon nanotubes (CNTs) and porous metallic nanoparticles as they exhibit large stresses and strains from low voltage electromechanical actuation. While most materials undergo electrical actuation, only few materials undergo actuation when irradiated with light that is of any practical import. Compared to electrically/thermally/ionically/phase transition driven actuators, light driven actuators have several advantages including wireless actuation, electromechanical decoupling (and therefore low noise), elimination of electrical circuits at the point of use, and massive parallel actuation of device arrays from a single light source. This NSF CAREER project was awarded for developing new type of carbon nanotube based photomechanical actuators. Using nano-materials such as carbon nanotubes, we developed light driven actuators that can perform work that is comparable to electrically driven actuators. In five years, we have not only shown that carbon nanotubes and graphene based composites could be used as optically driven actuators, but also the mechanical response can be tuned using variety of factors including optical absorption, wavelength of light, dimenisonal state of the carbon, mixed dimenisonal carbons, percolation threshold, and geometric anisotropy. Variety of microsystems were created that utilized the optical absorption of nanotubes to perform useful work at the micro-meter length scales. Micro-electro-mechanical systems namely optically driven micro-gripper, micro-cantilever, and micro-mirrors were created. Such microsystems could find significance in precise positioning, energy scavenging and nanomanipulation systems. The educational aspects of the award incuded several undergraduate researchers, several graduate course offerings in nanotechnology, graduation of 2 PhD students and 3 MS students, minority and underrepresented students. The PI was able to establish relationships in depth with researchers at the University of Cambridge in England (Dr. Eugene Terentjev). Industrial collaborations were established with InsituTec company in North Carolina and NaugaNeedles in Kentucky. These relationships have led to new projects utilizing photomechanical actuators. The PI's past student Dr. Shoaxin Lu who worked on his dissertation in this project is now process engineer at Silicon Sensors in California. Mr. Ning Shao who worked on this project works for Applied Nanosystems in Boston. Mr. Ye Liu who worked on this project is currently a PhD student at the University of Wisconsin at Madison. Miss Vanessa Velasco who worked on the project is now a PhD candidate at the University of Louisville. Miss Lytzamed Santa, an undergraduate student at the University of Peurto Rico visited the PI's laboratory as an research experience for undergraduate and worked on the photomechanically actuated microsystems. Finally, Mr. James Loomis is in the final stages of completing his dissertation on graphene based photomechanical actuators. Mr. Nathan Bessler an undergrdauet student published his paper on graphene based photomechanical actuators and was an REU student funded by this project.
