Development and Characterization of Freestanding Poly (Methyl Methacrylate)/Monolayer Graphene Membrane

Graphene-polymer based materials are gaining more popularity among researchers due to its mechanical properties that are found to be suitable to be used in various micro/nanoscale application requiring highly sensitive sensors. This research ventured into the fabrication and characterization process of a freestanding poly (methyl methacrylate) (PMMA) on monolayer graphene (Gr) yielding a (PMMA/Gr) membrane. In the process of transferring the chemical vapor deposition (CVD) graphene film over a cavity that was developed on a silicon substrate, the wet transfer method was used. Five repetitions of the nanoindentation testing had been carried out on the flexible membrane which resulted in a reproducible deflection, when exerted with a maximum loading of 10 mN. The indented (PMMA/Gr) membrane showed an identical elastic behavior with Young's modulus of 0.18 GPa. The highest deflection of approximately 22 μm at 1.6 mN maximum loads and the tensile stress of 0.58 MPa was obtained from the indentation testing analysis. The combination of PMMA-Graphene materials as a membrane has shown impressive changes to its mechanical properties. Besides maintaining its viscoelastic-plastic behavior which contributed to its flexibility, the presence of a graphene layer provided strong support to prevent damages to the membrane. Meanwhile, PMMA properties with low elastic modulus have contributed to the increased of the mechanical sensitivity of the membrane. Based on this research, the mechanical sensitivity of (PMMA/Gr) is reported to be 0.15 nm/Pa, which is much higher compared to a typical conventional membrane. It was proven that the hybrid (PMMA/Gr) membrane was extremely sensitive to the subjected pressures, thus, shown its potential to be applied as a micro-electro-mechanical systems (MEMS) capacitive pressure sensor.