CAREER: Investigation of Mechanical Properties of Carbon Nanotube Macro-Films in Integrated Systems

Since their discovery in 1991, carbon nanotubes (CNTs) have stimulated the interest of scientists and engineers in the nanoscience and nanotechnology field. The fundamental properties of CNTs have been extensively explored, which have led to the development of miniaturized CNT-based devices. However, the unavailability of a more appropriate technology to manipulate the ultra-small individual CNTs has proved to be a serious bottleneck for developing CNT-based devices. To circumvent this bottleneck and in turn make nanotechnology a real technology in realistic applications, it is important that the nanoscale features are linked to macroscale materials and devices that can be handled by conventional manufacturing technology. Recently, macrostructures of two-dimensional CNT assemblies (e.g., CNT macro-films or buckypaper) with up to centimeter dimensions and nanoscale features have attracted extensive attention for this purpose. However, the superior properties displayed by individual CNTs do not warrant that similar capabilities can be expected from CNT macro-films. In order to utilize CNT macro-films in potentially transformative applications, it is, therefore, indispensible to examine their fundamental properties and behaviors. The research goal of this CAREER proposal is to understand the mechanical properties of CNT macro-films in integrated systems. Main research targets at (I) stand alone CNT macro-films, (2) film/substrate interface, and (3) CNT macro-films/substrate system. Intellectual Merit: The primary research tasks of this CAREER proposal are (1) to investigate mechanical properties of stand alone CNT macro-films; (2) to identify interfacial strength between CNT macro-films and substrates; and (3) to achieve deformability of CNT macro-films in integrated systems. This CAREER proposal will propose a multiscale approach to capture the intrinsic multiscale nature of CNT macro-films, namely macroscopic features with nanoscale details, e.g., morphologies of inter-bundle junctions. To enable fully deformable CNT macro-films without sacrificing their electrical properties upon deformation, a buckling method involving buckled thin films on compliant substrates is proposed, which will be also used in the proposed buckling-induced delamination method to measure the interfacial strength and the deformable energy storage devices made from buckled CNT macro-films. Advances made in this research carry significant potential in the development of a design guideline for the assembly of macroscopic CNT networks with desired properties that can significantly impact new applications. Broader Impact: The proposed research will facilitate our understanding of fundamentals in macro-structured CNTs in integrated systems and has great potential to lead to a range of transformative and innovative applications using CNT macro-films. By advancing knowledge in how to control the mechanical properties and deformability of CNT macro-films, new engineered CNT macro-films with desired properties can be realized in integrated system that will impact nanoscience and nanoengineering fields, and in turn contribute to the "Grand Challenges for Engineering" in the 21" century. The education component will focus on increasing enrollment and retention of underrepresented students and engaging the public through unique outreach programs initiated by the PI and in partnership with: (1) the Arizona Science Center, and (2) Phoenix Elementary School District. A new course is also proposed based on this research.