Fingerprint-Inspired Strain Sensor with Balanced Sensitivity and Strain Range Using Laser-Induced Graphene

Area of Science:

• Materials Science
• Nanotechnology
• Sensor Technology

Background:

• Achieving high sensitivity and a broad strain range in flexible strain sensors presents a significant challenge, as improvements in one often compromise the other.
• The natural fingerprint pattern on human fingertips enhances tactile sensitivity and elasticity, offering a biomimetic design principle.

Purpose of the Study:

• To develop a novel resistive strain sensor inspired by the fingerprint structure of human fingertips.
• To investigate the performance characteristics, including sensitivity, strain range, response time, and reliability, of the developed sensor.

Main Methods:

• Fabrication of a fingerprint-structured laser-induced graphene (LIG) on a polyimide (PI) film in a single step.
• Transferring the LIG structure onto an Ecoflex substrate to create a flexible resistive strain sensor.
• Experimental evaluation of the sensor's response time, gauge factor across different strain ranges, and long-term reliability through cyclic testing.

Main Results:

• The fingerprint-inspired strain sensor achieved a rapid response time of approximately 70 ms.
• A balanced performance was observed with a notable gauge factor of 191.55 within a wide strain range of 42-50%.
• The sensor demonstrated excellent reliability, withstanding over 1500 cycles of stretching and releasing.

Conclusions:

• The fingerprint-inspired LIG strain sensor successfully overcomes the typical trade-off between sensitivity and strain range.
• The sensor's robust performance was validated through real-time monitoring of physiological signals (pulses) and human movements (gestures, voice recognition).
• This biomimetic design offers a promising pathway for developing advanced flexible electronics with enhanced sensing capabilities.