The 2-D graphene holds enormous potential as a future candidate for gas sensors, not only coming from its vast surface area but also contributed by the highly active edges, which have promptly become a research hotspot. In this work, we developed a novel transferfree approach to prepare chemical vapor deposited edgeexposed multilayer graphene micromeshes by prepatterning the molybdenum (Mo) catalyst through photolithography. Our facile and efficient approach provides fewer steps, higher accuracy, and virtually unrestricted patternable features. It is also semiconductor manufacturing compatible with precise alignment and positioning for wafer-scale mass production. Graphene micromeshes with different thicknesses were prepared and studied for NO2 (∼1 ppm) gas sensing. Despite the reduction in the surface area, the micromeshes still delivered an enhancement of the overall response [for 20-min chemical vapor deposition (CVD) graphene, from 0.692% to 0.744%]. Based on our proposed calculation model, which hypothetically separates the response from the surface and edges, thinner multilayer graphene edges exhibited exceptionally high sensitivity compared with the surface due to higher reactivity and edge-facilitated gas adsorption. Our prepatterning method and study of graphene micromesh-based prototype gas sensors provide insights into the role of the edges of multilayer graphene, which could potentially be a vital part for future high-performance gas sensors.

Packaging is an indispensable part in microelectronics manufacturing industry, where transfer molding as an essential step is typically included for encapsulation. Recently, with the fruitful achievements of research on graphene in gas sensing, there is also urgent need for study on how the packaging process will affect the graphene, to develop compatible manufacture protocol for practical graphene-based gas sensor. In this work, we carried out experiments on how molding compound outgassing affects graphene for gas sensing. Our results show that although there is some impact on the electrical properties of the graphene, there is no change in the microstructure, and only a slight and manageable change in gas sensing abilities. This work suggests that graphene could maintain performances after epoxy molding packaging processes.