Maskless fabrication of micro-gradient patterned ion density enhanced moisture-driven power generation using a phase spatially shaped femtosecond laser

Moisture-driven power generation and sensing technology holds significant practical significance, as it enables microwatt-level power generation primarily for wearable or medical sensors with limited power consumption, and the gradient structures play a pivotal role in this domain. Achieving patterned gradient machining within defined parameters represents a formidable challenge, posing a significant hurdle to attaining high precision across a small scale and extensive range. In response to these challenges, we introduce a flexible, maskless 3D fabrication method for processing micro-scale gradient moisture-driven power generation. This method leverages a femtosecond laser with phase spatial shaping capabilities, enabling the laser to transition from a Gaussian distribution to laser fluence gradient field distributions. Additionally, our investigation incorporated a systematic reduction of graphene oxide films through the modulation of laser power within the range of 1–2.8 mW. This approach enhances processing versatility and elevates the ionization sites of the humidity-driven generator through precise patterning, thereby amplifying ion density and consequently improving the overall performance of the moisture-driven power generation. This process resulted in a shift of the carbon‑oxygen ratio from 2 to 6, Furthermore, we conducted comprehensive humidity sensor tests encompassing pressure and specialized environmental performance evaluations. Remarkably, the humidity sensor exhibited a rapid peak voltage of 372 mV within approximately 250 milliseconds when subjected to pressure, returning promptly to baseline when the pressure was removed. It consistently maintained stable performance under varying environmental conditions, allowing environmental assessments to be based on the voltage curve. Moreover, we demonstrated the method's flexibility by effortlessly creating diverse patterned structures, including representations of pandas, school badges, and more. These achievements hold profound significance across a variety of domains. © 2024 Published by Elsevier Ltd on behalf of The Society of Manufacturing Engineers.