The Development of an Interface-Locating Extraction Device for the Automated Application of Aqueous Two-Phase Systems to Rapid Paper-Based Assays

The clinical diagnosis of urinary tract infections (UTIs) faces challenges characterized by prolonged test results, contributing to over-prescription of antibiotics, and missed diagnoses. Point-of-care (POC) tests such as the lateral-flow immunoassay (LFA) attempt to alleviate this issue by providing patients with rapid results; however, their effectiveness is limited by low sensitivity. To improve the performance of the LFA, this thesis focuses on the development of an automated device that enables the addition of a sample preconcentration step at the POC using an aqueous two-phase system (ATPS). The device utilizes a photoresistor-based interface detection algorithm to selectively extract the bottom phase of the ATPS, containing concentrated biomarker, thereby avoiding the dispensing of the undesired top phase onto an LFA. The device incorporates a custom syringe pump module to apply the sample fluid to the LFA, and a gravity-based buffer dispensing module to facilitate the application of running buffer following sample addition. The affordability of the device is ensured through the use of reusable electrical components and cost- effective consumables, making it accessible to physician offices and mobile clinics at the POC. Experimental results demonstrate the successful automation of ATPS application onto the LFA, effectively extracting the bottom phase without any of the top phase. This advancement brings sample preconcentration using an ATPS one step closer to clinical adoption, offering a sensitive, rapid, and user-friendly UTI diagnostic solution.