Femtosecond Laser Etching：Removing PI Coating on Medical CGM Sensors

With the rapid advancement of manufacturing processes, the complexity of miniaturized devices continues to increase. In cutting-edge industries such as microelectronics, healthcare, and photonics, micro-devices often adopt multilayer stacked structures of different materials to achieve increasingly complex multifunctional requirements.

Particularly in the medical field, the application of Continuous Glucose Monitoring (CGM) systems has brought breakthroughs for diabetic patients. By providing real-time blood glucose data, CGM significantly enhances the efficiency of blood sugar management. However, CGM sensor manufacturing involves extremely complex and rigorous processes: as the sensor is implanted subcutaneously and exposed to body fluids long-term, its biocompatibility, micro-nano precision, and durability are critical. Take the processing of Pt/Ir alloy needle sensors (key CGM components): it requires precise subtractive manufacturing to etch away PI (polyimide) coating in specific areas, leaving only the necessary electrode regions at the micrometer scale.

Why Remove the PI Coating?

The CGM needle sensor (0.19mm in diameter) features a platinum-iridium (Pt/Ir) alloy base layer, ideal for precision medical implants due to its high inertness, biocompatibility, corrosion resistance, low impedance, and high charge transfer capability. The surface PI (polyimide) coating serves as an insulator with extremely low leakage current and excellent dielectric properties.

To enable the needle to accurately sense blood glucose signals and facilitate efficient electrochemical reactions with interstitial fluid, specific areas of the Pt/Ir alloy must be exposed to form clear conductive pathways and sensing interfaces. Thus, selective and precise removal of the PI coating—while preserving the Pt/Ir alloy's functionality—represents a core challenge in CGM needle manufacturing.

Will Femtosecond Lasers Damage the Pt/Ir Surface?

MONO LASER 's  femtosecond laser fixed-depth etching equipment addresses this challenge with revolutionary advantages, especially for micro-nano processing of complex curved surfaces.

Case: Etching Depth 0.05mm, Accuracy ±1μm

Precise Depth Control & Substrate Protection
Femtosecond laser etching uses ultra-short pulses (femtosecond scale) for "cold processing," where energy is instantaneously absorbed and vaporized on the surface, minimizing heat diffusion to the underlying Pt/Ir alloy. This enables:

1、Nanometer-level precision: Etching depth control within ±1μm (minimum depth ≤0.1μm), ensuring the PI coating is removed exactly to the target depth without damaging the Pt/Ir layer.

2、Ultra-smooth surface: The processed Pt/Ir surface achieves roughness Ra < 0.2μm, crucial for medical implants to reduce friction, minimize biofouling, and ensure stable electrochemical signal transmission.

Overcoming Curved Surface Stitching Challenges
Traditional methods struggle with patterned processing on curved surfaces, often causing "stitching gaps" and metal residues that lead to circuit failures. Femtosecond laser systems support large-format processing with stitching accuracy ≤±1μm, enabling seamless etching on complex surfaces and maintaining functional integrity.

Comparison with Traditional Processes

Coating removal techniques like chemical stripping, thermal ablation, or plasma etching face critical limitations for high-precision devices:

· Chemical stripping: Difficult to control at the micrometer scale; solvents may corrode the substrate and leave residues.

· Thermal ablation/traditional laser: Causes significant heat-affected zones, leading to molten residues, edge carbonization, and severe thermal damage.

· Plasma etching: Complex, expensive, and maintenance-intensive, suitable mainly for mass production.

Conclusion

Femtosecond laser etching technology, with its superior processing performance, not only provides solid technical support for the innovation of implantable medical devices but also drives the development of "extreme manufacturing" in miniaturized, high-precision device fabrication. Its ability to balance precision, material compatibility, and process flexibility positions it as a cornerstone for next-generation micro-nano manufacturing.