Photoswitchable Polymers for 2-Step Dry Transfer of 2D Materials

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Graphene and other atomically thin materials have very attractive mechanical, electrical and thermal properties and their mass production via chemical vapor deposition has greatly improved the opportunities to scale up the production of devices that employ them. However, before these materials can be used, they need to be transferred from their growth substrate to a target substrate for microelectronics devices. This award addresses the transfer step, which is a roadblock to manufacturing scalability. Historically, transfer has been accomplished by so-called wet methods, where the growth substrate is dissolved away. These are slow, wasteful, and often lead to relatively high levels of contamination. Dry transfer methods developed here provide an attractive rapid and “cleaner” alternative. Because these materials are so thin, they need to be supported at all times and polymers are an attractive medium for removing the materials from their growth substrate and depositing them on the target substrate. High and low adhesion is required for the first and second steps, respectively. The challenge being addressed in this award is the development of novel polymers, whose adhesion can be switched on or off by shining light on them. It is expected that successful development of such polymers will place the US in a leadership role in manufacturing these atomically thin materials and promote the fabrication of next generation electronics to be found in phones, computers, cars and televisions. There is extensive educational outreach to K-12 and STEM audiences that highlights switchable adhesion and the polymers developed in the course of the research.The goals of the research are to (i) develop a new class of photoswitchable adhesives that is tailored specifically to the 2-step, dry transfer of graphene via (ii) a thorough and deep characterization of the interactions of all the interfaces that play a role in the transfer process and (iii) the design and fabrication of a separation tool that is common to both transfer steps based on the understanding obtained in the first two steps. This multidisciplinary effort is highly coupled in that the development of this class of polymers will be guided by both the characterization and tool development efforts, which will both feedback into the fine tuning of composition, architecture and associated adhesion characteristics of the polymers. From a fundamental materials perspective, the impact of polymer composition and architecture (e.g., networks vs surface-bound brushes) on the photoresponsive change in order and topology will be unveiled and inform the design of next generation “smart” adhesives. These light-responsive adhesive characteristics will be judiciously characterized and applied to the efficient, large area 2-step dry (patterned) transfer of graphene using an innovative and efficient advanced manufacturing process.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.