▎ 摘　　要

A layered graphene (G) composite was prepared onto an ITO/PEN substrate to develop a novel low-cost, transparent, and flexible biosensor. This layered structure comprises of graphene oxide (GO) on the top layer acting as a sensing surface, and G on the bottom layer featuring a high conductivity for transmission. The O-2/H-2 low damage plasma treatment (O/H-LDPT) was utilized for atomic layer oxidation of bilayer G to form layered composite GO/G. After immobilization, the resistance variation was measured at different concentrations (10 pM-100 nM) of micro ribonucleic acid-21 (miRNA-21). A high sensitivity and detection accuracy was confirmed with a linearity of 0.9825 and detection limit as low as 16.1 pM. In addition, different sequences of target were detected to ensure the selectivity. While detecting the 4-base mismatched target, the rate of resistance variation decreased from 16.4% to 4.49%, indicating a certain specificity for target miRNA-21. Additionally, in the bending test for devices, after a 24 h continuous bending with a bending radius of 12.3 mm, the device maintained its original high sensitivity to detect the target miRNA-21.