Practical Considerations for Laser-Induced Graphene Pressure Sensors Used in Marine Applications

Area of Science:

• Materials Science
• Oceanography
• Sensor Technology

Background:

• Small, low-power, inexpensive marine depth sensors are crucial for maritime security and environmental monitoring.
• Laser-induced graphene (LIG) piezoresistive sensors offer rapid fabrication and a large dynamic range.
• Exploring LIG integration into fieldable deep ocean (1 km) depth sensors is essential.

Purpose of the Study:

• Evaluate the practicality of bulk LIG integration into deep ocean depth sensors.
• Characterize the piezoresistive response of LIG sensors under ocean conditions.
• Investigate methods to mitigate thermal sensitivity and improve seawater isolation.

Main Methods:

• Design of Experiments (DOE) to optimize LIG fabrication parameters (line length, width, speed, power).
• Uniaxial compression and thermal testing (0-25 °C, up to 10.3 MPa) of LIG sensors.
• Evaluation of polydimethylsiloxane (PDMS) encapsulation for thermal and electrical isolation.

Main Results:

• Bare LIG sensors exhibited higher resistance changes with temperature (ΔR ≈ 30 kΩ) than pressure (ΔR ≈ 1-15 kΩ).
• PDMS encapsulation significantly dampened thermal effects (ΔR ≈ 0.3 kΩ).
• LIG/PDMS composite structures show potential for improved deep ocean depth sensing.

Conclusions:

• Conformal coatings are necessary to thermally insulate and electrically isolate LIG traces from seawater.
• PDMS encapsulation offers a viable solution for thermal dampening in LIG-based depth sensors.
• Further research is recommended to validate LIG/PDMS platforms for global deployment.