Lock-In Amplified Fluorescence Spectroscopy in a Digital Microfluidic Configuration for Antibiotic Detection of Ciprofloxacin in Milk

Antibiotic detection in dairy is crucial, as introduction of antibiotics in food can lead to antibiotic resistance and cause allergic reactions in consumers. Dairy farmers risk monetary fines for shipping contaminated milk. Microfluidics is an appealing technology, as it is portable, can be implemented on-site, and is highly automated. This work presents a digital microfluidic dairy device for antibiotic detection. The digital microfluidic dairy device explores integration of a lock-in amplifier with droplet-based microfluidic techniques, being electrowetting actuation and droplet control. The lock-in amplifier setup is initially demonstrated for the fluorescent dye rhodamine B, to establish baseline operation. Ultimately, the lock-in amplifier setup is demonstrated for detection of ciprofloxacin in milk. The limit of detection is significantly lowered through the integration of the lock-in amplifier technology. Actuation of milk and water samples is shown, demonstrating full two dimensional control over the position of water and milk droplets, to enable a complete lab-on-a-chip system. The results show promise for modern dairy testing of antibiotic signatures. [2022-0120]