Development and Characterization of Passivation Methods for Microneedle-based Biosensors

Area of Science:

• Biomedical Engineering
• Materials Science
• Analytical Chemistry

Background:

• Microneedles (MN) enable painless skin penetration to access dermal interstitial fluid.
• Interstitial fluid contains biomarkers, making MN-based biosensors valuable for diagnostics.
• Effective passivation of MN substrate areas is crucial to prevent background interference.

Purpose of the Study:

• To evaluate four distinct passivation techniques for microneedle substrate areas.
• To assess the performance of SiO2, PMMA, adhesive film, and varnish.
• To identify the optimal passivation method for microneedle biosensor applications.

Main Methods:

• Fabrication of microneedles with four different substrate passivation layers.
• Optical microscopy and Scanning Electron Microscopy (SEM) for structural analysis.
• Electrochemical measurements to quantify electrical isolation and sensor performance.

Main Results:

• Varnish application yielded the highest electrical isolation manually.
• Spin-coating a 5 μm PMMA layer demonstrated superior performance and manufacturability.
• Passivation techniques significantly impacted the electrical insulation of the microneedle substrates.

Conclusions:

• Substrate passivation is critical for improving microneedle biosensor functionality.
• PMMA offers a promising balance of performance and scalability for MN fabrication.
• Optimized passivation will enhance the reliability of non-invasive continuous monitoring systems.