DMREF/Collaborative Research: Conductive Protein Nanowires as Next Generation Polymer Nanocomposite Fillers

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Stretchable electronics have the potential to enable new innovations in technologies for communications, healthcare, security and beyond. Soft-filler, soft-matrix nanocomposites are desired for most stretchable electronics applications. Conventional nanocomposites embed thin, hard, and brittle conductive materials such as metal nanowires or carbon nanotubes into stretchable elastic polymers, which provide electronic function, but fail during stretching cycles due mechanical mismatch. This Designing Materials to Revolutionize and Engineer our Future (DMREF) award supports research for the understanding, development and manufacture of a new class of soft electronics. This work is a collaborative computational-experimental research approach to understanding the fundamental processing-microstructure-property relationships in conductive protein nanowires, and to design nanoscale protein wires to be highly conductive, mechanically soft fillers that match the host polymer properties to create a superior nanocomposite. Calculations of protein-polymer interactions will inform the synthesis and fabrication of protein-based nanocomposites with enhanced elasticity and conductivity, which will be confirmed by advanced microscopy, electronic, and mechanical testing. This research merges disciplines including microbiology, polymer chemistry, materials processing, electronics, and molecular modeling in a powerful feedback loop. This award also supports educational activities which emphasize participation from groups traditionally underrepresented in STEM, including a multi-day workshop series on innovation, team building, work-life balance, and entrepreneurship through which participants gain the confidence and skills necessary to succeed as scientists, engineers, and entrepreneurs, thus promoting future economic and societal advancement. This work has the potential to bring the U.S. to the forefront of flexible electronics development, while training the next generation workforce to maintain this competitive advantage.Advancing soft electronics requires a nascent class of filler that exhibits high conductivity yet remains chemically and mechanically compatible with the host matrix. Conductive protein nanowires or pili function as the conducting element of protein-based soft electronics. Molecular simulations with coarse-grained models will survey the interplay of pili amino acid sequences and exposed surface peptide residues with soft materials chemistry to create a data-rich system that establishes foundational design principles for pili fillers in soft polymer matrices. The inherent aqueous dispersion properties of conductive pili enable the design, characterization, and production of both bulk pili-polymer nanocomposites and electrospun pili-polymer nanofiber mats with well-distributed filler. Advanced electron and scanning probe microscopy will interrogate the structural and electronic properties of the pili and provide a feedback loop that refines the molecular models. Directed agglomeration of pili into bundles and electrospun pili-elastomer fibers will also enable studies on the scalability of this new nanocomposite platform. Molecular models will ultimately unveil surface peptide sequences that improve processability and functionality of new pili strains and pili-polymer nanocomposites that are validated by rheology, microscopy, transport, and tensile testing methods.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.