Label-free and compact approach for bacterial detection in beverages using a dielectrophoresis-integrated 65-GHz inductor-capacitor-oscillator array sensor chip1

Food safety remains a critical concern, with bacterial contamination in beverages posing significant health risks due to rapid bacterial proliferation. Traditional bacterial detection methods, such as plate culture, require days of cultivation, while molecular and optical techniques demand complex pretreatment and specialized equipment, limiting their practicality for routine food inspection. To address these challenges, we developed a rapid, label-free bacterial detection method using a dielectrophoresis (DEP)-integrated 65-GHz inductor-capacitor (LC) oscillator array sensor chip. The sensor chip, fabricated using 65 nm CMOS technology, consists of 1488 sensor elements arranged in a zigzag pattern, each incorporating 5-μm DEP electrodes and a 50-μm LC oscillator. The set up allows for distributed bacterial collection and measurement. We evaluated the sensor's DEP collection patterns for Escherichia coli (E. coli) and Saccharomyces cerevisiae, optimizing conditions for E. coli detection in various beverage matrices, including mineral water, green tea, and bovine milk. The method achieved detection limits of 1.3 × 10⁵ bacterial cells/mL in mineral water and green tea and 5.4 × 10⁶ cells/mL in bovine milk, with an enrichment rate reaching up to 20-fold. The entire detection process was completed within 30 min without the need for pretreatment, external analyzers, or temperature control. Overall, we demonstrated the utility of our simplified and cost-effective bacterial detection technique that enables efficient separation and enrichment of bacteria from food matrices. The sensor's compact design, reusability, and speed make it well-suited for on-site industrial food safety inspections, laying the groundwork for further improvements in real-world applications.