Ultra-Low Power Batch-Fabricated Pd-Au Nanogap Hydrogen Sensor Node for Sub-PPM Detection Operating at Room Temperature

This letter presents a uniform 5-nm Pd-Au nanogap sensor, fabricated using a batch-fabrication wafer-scale process, enabling sub-ppm hydrogen (H2) detection for operating at room temperature with ultra-low-power operation in an in-field-deployable sensor node. The nanogap sensor was integrated into a compact size of 58 × 52 mm 2 that combines a Pd-Au nanogap sensor, signal processing unit, and wireless communication unit, while all units being powered by a coin cell battery (220 Ah). The nanogap sensor unit operates in a normally off mode, consuming 12 pW in standby, while the complete system including processing and communication units consumes 51.40 µW. Upon detecting ≥0.46 ppm H2, the Pd layer expands to close the nanogap, switching the node on to an active the state to wirelessly transmit detection alerts. This wake-up operation reduces average power consumption to 67.84 µW with one detection event per week, supporting up to 59 weeks of operation. At 1 ppm of H2, the sensor shows a response time of ≤5 seconds for detection and a recovery time of ≤3 minutes for resetting, thus, multiple H2 leak measurements can be achieved. The development of this compact Pd-Au nanogap sensor node is expected to advance the safety of H2 transportation and storage infrastructure where even sub-ppm levels of highly flammable H2 gas leaks is concerned.