Evaluation of the Adhesion Strength of Ultrathin Gold Coatings on Substrates of Soda-Lime Glass and Cyclo-Olefin-Polymer by Cross-Cut and Scratch Tests under the Influence of a Thermal Shock Test for Use in Biosensors

Rebecca Vornweg ¹, Mona Roser ¹, Alexander Fromm ²

⁰Institute for Micro Integration (IFM), University of Stuttgart, Allmandring 9B, 70569 Stuttgart, Germany.

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January 27, 2025

View abstract on PubMed

Summary

This study investigated adhesion strength for gold coatings on glass and cyclo-olefin-polymer (COP) substrates, crucial for optical biosensors. Optimal configurations were identified to enhance sensor performance by minimizing adhesion layers.

Area Of Science

Materials Science
Nanotechnology
Biomedical Engineering

Background

Demand for sensitive optical sensors in biodiagnostics drives development of ultrathin metal coatings.
Adhesion layers can attenuate signals in plasmonic sensors, necessitating investigation into robust coating adhesion.
Understanding factors affecting adhesion is key for fabricating reliable diagnostic optical sensors.

Purpose Of The Study

To evaluate adhesion strength of ultrathin gold coatings on glass and cyclo-olefin-polymer (COP) substrates.
To identify optimal configurations for high adhesion, potentially eliminating or minimizing adhesion layers.
To assess the impact of plasma pretreatment, titanium adhesion layers, and thermal shock on coating integrity.

Main Methods

Utilized cross-cut and nano scratch tests for qualitative and quantitative adhesion assessment.
Investigated effects of oxygen plasma pretreatment and ultrathin titanium adhesion layers.
Performed thermal shock tests to evaluate coating integrity under temperature cycling.

Main Results

On glass, highest adhesion strength was achieved with an adhesion layer, with or without plasma treatment.
On COP, high adhesion was observed with an adhesion layer alone or no pretreatment; plasma treatment reduced adhesion.
Thermal shock testing altered adhesion strengths, with cyclo-olefin-polymer (COP) showing disparate results possibly due to its thermal expansion properties.

Conclusions

Adhesion layer presence and substrate type significantly influence gold coating adhesion for optical sensor applications.
Plasma treatment negatively impacts adhesion on cyclo-olefin-polymer (COP) but can be beneficial on glass with an adhesion layer.
Further research into substrate-specific pretreatments and adhesion layers is needed for robust sensor fabrication.