Toward roll-to-roll transfer of large-scale graphene for flexible electronics fabrication
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Graphene is a promising material for flexible electronics due to its extraordinary electrical, mechanical, and optical properties. One of the biggest challenges today is to transfer large-scale graphene sheet to flexible substrates with minimal quality degradation. In this thesis, a bilayer polymer support for graphene transfer is proposed. Liquid PDMS (polydimethylsiloxane) is first coated on graphene to conform to its surface morphology. A flexible plastic substrate is then pressed on PDMS as a durable support. After PDMS is cured, electrochemical delamination is used to separate graphene from the copper foil. Due to the extremely low work of adhesion between graphene and PDMS, the graphene film on PDMS can be further transferred onto silicon wafer or other flexible substrates by simple adhesion. An added benefit of the PDMS layer is its strain isolation effect, which could protect graphene-based devices from breaking under external loads applied on the flexible substrate. The strain isolation effect of PDMS is verified with an analytical model and finite element analysis. The design of a prototype roll-to-roll graphene transfer machine is also presented.