“…20,21 When combined with rGO, several common metal oxides, including ZnO, SnO 2 , WO 3 and CuO, demonstrated improved gas sensing capabilities compared to base metal oxides. [22][23][24][25] Despite this, the non-uniform hybridization between rGO and metal oxides leads to a ring-like deposition because particles are concentrated on droplet edges as a result of the coffee ring effect. 26,27 Consequently, the sensitivity and repeatability of the manufactured sensors are severely reduced.…”