In-Situ Vertical-Contact Engineering of Laser-Induced Graphene Nanotips for Ultra-Sensitive Humidity Sensors

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Conventional lateral-contact laser-induced graphene (LIG) humidity sensors have limited responsivity due to subsurface current pathways.
• A need exists for highly sensitive and stable humidity sensors for advanced applications.

Purpose of the Study:

• To develop a novel vertical-contact architecture for ultra-sensitive humidity detection using LIG nanotips.
• To explore the performance of this new sensor design in different operating modes.
• To demonstrate the sensor's potential for real-time respiratory monitoring in wearable devices.

Main Methods:

• Fabrication of vertically aligned LIG nanotips using single-pulse laser irradiation.
• Creation of in-situ vertical contacts between LIG nanotips and graphene electrodes.
• Operation of the sensor in Contact Mode (resistance modulation) and Remote Mode (field ionization).

Main Results:

• The vertical-contact sensor achieved high responsivity (40% in Contact Mode, 14,000% in Remote Mode).
• Demonstrated rapid response and recovery times (<1 s), excellent stability, and high gas selectivity.
• Successfully integrated into wearable face masks for real-time respiratory monitoring up to 156 bpm without signal degradation.

Conclusions:

• The novel vertical-contact LIG nanotip architecture significantly enhances humidity sensor performance.
• This technology offers a simple, scalable strategy for high-performance humidity sensors.
• The developed sensors are suitable for next-generation wearable healthcare applications, particularly respiratory monitoring.