EAGER: Transforming Flexible Device Manufacturing by Bottom-up Growth of Nanocarbons Directly on Polymers

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This EArly-concept Grants for Exploratory Research (EAGER) award focuses on revealing the fundamental principles underlying laser-induced nanocarbon formation, LINC, which is a new nanomanufacturing process capable of rapidly growing a diverse set of nanostructured carbon materials directly on polymers. This approach enables patterning of functional nanocarbons that are needed for a number of emerging applications in healthcare, biomedical, automotive, consumer electronics, and defense. This project enables customization of the nanocarbon type with precise spatial distribution to rapidly create optimized structures for different devices on the same substrate without the need for multiple inks and successive printing steps. Instead of top-down deposition or printing of nanocarbons such as graphene and nanotubes/nanofibers from ink, this research focuses on bottom-up thermochemical synthesis of different nanocarbons from polymers, which act as the carbon source under highly localized laser heating. This project impacts a multibillion-dollar market for flexible electronics where a major challenge is the integration of multiple functionalities, such as sensing, energy storage and circuits onto the same flexible substrate. LINC is a facile, scalable pathway to manufacturing of conformal/wearable and other devices, which benefits US economy. The main goal of this EAGER project is to show a proof-of-concept for scalable direct patterning of different nanocarbons with tailored morphologies and properties on flexible substrates based on dynamic laser processing of polymers. The laser-induced nanocarbon (LINC) method requires an understanding of the mechanisms and kinetics of thermochemical carbonization of polymers and of the tunability of the electrical properties of grown nanocarbons for sensing and other functionalities. Hence, this project generates new knowledge by elucidating the influence of the spatiotemporal evolution of optical energy (laser) flux and the ensuing photothermal heating on the content of graphitic carbon as well as on the transition between forming isotropic porous morphology and aligned filamentary structures. As a result, this project constructs the causal relation between gradients of laser energy density and the temperature-dependent multiphysics phenomena of absorption, heat transfer, splashing dynamics, phase transitions and chemical transformations, which dictate the formation of different nanocarbons such as graphene, carbon nanofibers, and carbon nanotubes. In addition to explaining the mechanisms of alignment and self-organization among carbon nanofilaments, the project tests the fabrication and performance of kirigami-based strain sensors directly on polyimide films. Moreover, the scalability of this new approach is tested by continuous manufacturing of strain sensors based on combining fast fiber laser scanning using a galvo system with roll-to-roll processing.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.