Faculty Affairs and Academic Programs
Soumya Bose
Engineering and Computer Science
Electrical and Computer Engineering
UC Santa Cruz
Self-Powered In Situ Fog Sensing in California’s Redwood Forests
Fog is a vital part of California’s climate, regulating temperature, reducing drought stress, and providing essential water to the state’s iconic redwood forests. Its steady decline in recent years threatens forest health, water availability, and increases wildfire risks. Yet fog monitoring in forest ecosystems remains limited, relying mainly on satellite imagery and distant weather stations. To address this gap, we propose developing the first energy-autonomous, ultra-compact in situ fog sensor capable of continuous, battery-free operation within forests. The sensor uses a complementary metal-oxide-semiconductor (CMOS)-integrated capacitive detection system with interdigitated metal-oxide-metal (MOM) capacitors. Fog flow through exposed electrodes alters capacitance, measured in real-time by on-chip circuits to quantify fog density. A “piezo-leaf” energy harvester is introduced to convert wind, fog flow, and tree vibrations into 100nW-1uW of electrical energy, sustainably powering the sensor. The project advances several critical innovations: • CMOS capacitive sensor design for fog monitoring, • Ultra-low-power on-chip capacitive sensing circuits, • Multi-input power converters for cm-scale motion energy harvesting. By combining these, the proposed chip-scale sensing system achieves orders of magnitude lower power consumption than conventional optical visibility-based fog sensors, enabling battery-free, continuous monitoring in remote ecosystems. This breakthrough provides unprecedented, high-density data on fog patterns, offering new insights for climate research, redwood conservation, and early drought and wildfire risk prediction across the state of California.
