# Elliptical Electrode Designs in Quartz Crystal Microbalances: Enhancing Sensitivity in Liquid Biosensing Applications

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- Authors: Afri Ahamed, Chien Wei Ooi, Hui Jean Lim, N Ramakrishnan, Tridib Saha
- Journal: Available at SSRN 5094062
- Year: 2025
- DOI: 10.2139/ssrn.5094062
- Instrument used: openQCM Q-1

## Abstract

The demand for highly sensitive and versatile sensors is rapidly growing in biomedical applications, where specific, sensitive, and rapid detection are essential. Quartz crystal microbalance (QCM) is a popular analytical tool for such applications due to its high sensitivity and real-time monitoring capabilities. However, conventional QCM-based biosensing assays often suffer from poor sensitivity and high sample consumption, limiting their practicality. This study introduces a modified electrode design and a single droplet-based assay to enhance QCM-based bio-detection. Through extensive experiments, including contact angle analysis, damping, and viscosity measurements, we identified an optimal elliptical electrode design for single droplet-based liquid sensing. Using QCM crystals coated with molecularly imprinted polydopamine (MIPDA) sensing films containing recognition sites for detecting pepsin as a model protein, we demonstrate that QCM crystals with elliptical electrodes exhibit up to 10 times higher sensitivity than the industry-standard 1-inch circular QCM crystal. Additionally, the optimized QCM crystals showed linear sensitivity over a wider volume range, providing consistent detection at 250 Hz/μl compared to the circular crystal's narrower range at 50 Hz/μl. These findings establish a foundation for next-generation QCM platforms with superior sensitivity, reduced sample requirements, and broader adaptability, paving the way for advancements in biomedical diagnostics and environmental monitoring.

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