The recent mergence of Human-machine interaction and flexible electronics has heralded a revolutionary era that changes the communication pattern between people and the environments. To pursue a more fascinating and convenient life, expansion of command capacity is inevitable towards multiple functionalities. However, traditional flexible sensors, which collect the user requirement and convert to electrical commands, are binary inputs (idle status for ‘0′ and applied stimuli for ‘1′) and the expansion possibility is restricted. In view of this, we developed a flexible sensor which can precisely perceive the bidirectional stimuli even under a small bending angle of ± 5°. Upon inward bending, the optimized microflakes/cilia enabled more contact points for resistance decrease, while an outward bending generated increased resistance due to the applied strain. With the non-overlapping signals, ternary inputs ‘1′, ‘0′, and ‘− 1′ could thus be defined by the bending direction from human joints, e.g. the wrist. The ternary-based devices exhibited overall superiorities when compared with the binary system, e.g. effective Morse code communication, intuitive robotic control, and expanded capacity for logic outputs and mouse system. The study raises a facile strategy to design the ternary bridge between human and machine that meets the growing pursuit for an intelligent future.