Structure-property relationships in novel conjugated mixed conductors

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Nontechnical description: Soft materials that have the ability to transport both ions and electrons are of great interest for use at the interface between electronics and biology. Indeed, biology works by shuttling ions while electronic systems work by moving electrons. Mixed conductors, that transport both ions and electrons, can act as translators between biological signals and electronic devices. Potential applications of these materials include biosensors, neural probes, and drug delivery systems. In this project, new plastic materials exhibiting mixed conduction are studied. In particular, the structure of these materials is correlated with their ability to transport ions and electrons. Advanced materials characterization techniques using X-rays and electron beams are used to analyze the structure of these plastics down to the molecular level, in order to determine what limits their performance. Ultimately, these insights allow to design and synthesize higher performance materials. Scientific advances resulting from the project are incorporated in undergraduate and graduate classes. The educational outreach is completed by enrolling undergraduate students to join the project during the Summer Quarter, with a focus on recruiting through the Engineering Diversity Program. An additional program, the Art + Science program at Stanford is leveraged to broaden the undergraduate experience through interactions with the Cantor Museum aimed at studying the materiality of art objects. Finally, the interdisciplinary nature of the research project provides a broad educational training to the graduate student involved in it, which greatly facilitates the student's insertion in the biotech industry workforce.Technical description: Polymers that exhibit mixed ionic and electronic conduction have the ability to transduce ionic fluxes, the language of biology, into electrical currents, which can be manipulated by conventional electronics. The goal of the project is to understand how ion penetration and electronic carrier transport are affected by the microstructure of a new family of polymeric mixed conductors. In particular, the effect of crystalline texture, degree of crystallinity and mesoscopic organization of the crystallites is studied. Advanced X-ray diffraction techniques and a new scanning nanobeam microscopy technique are used to analyze the microstructure. The microstructure is correlated to performance, as characterized using electrochemical methods. The ultimate goal is to determine materials design rules, which will be confirm by studying potentially high-performing materials. Healthcare is being revolutionized by the confluence of engineering and medical sciences. Soft materials that exhibit mixed conduction have a role to play because of their outstanding electrical properties combined with a low modulus. New high-performance materials are ideally placed to play an important role in this space. Finally, the project trains a student with an interdisciplinary outlook, ready to enter this nascent industry.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.