Epidermal electronics are extensively used in human–machine interfaces and wearable sensors. However, managing sweat and gas permeability at the skin–device interface to ensure comfort and prevent skin damage during prolonged use remains a key challenge. Inspired by the fog collection mechanism of cactus spines and trichomes, this work develops a biomimetic, flexible epidermal electronic device with high gas permeability and unidirectional water transport capability. The device exhibits excellent flexibility (Young’s modulus: 0.02 MPa), breathability (electrode: 3551.63 g day–1 m–2, substrate: 3795.38 g day–1 m–2), unidirectional water transport (1.09 s), and antigravity water transport (2.50 s). Notably, during continuous sweating (5 h) and extended wear (7 days), it demonstrates outstanding electromyography (EMG) signal acquisition, with a signal-to-noise ratio (SNR) approximately 58 times higher than that of commercial electrodes. This offers promising potential for advancing high-performance, wearable human–machine interface electronics.