Finger-powered bead-in-droplet microfluidic system for point-of-care diagnostics

In this paper, we present a versatile `human-powered´ microfluidic system that encapsulates microbeads within droplets to perform a medical diagnostics assay. Point-of-care (POC) microfluidic devices hold great promise for medicinal applications throughout the world. In particular, portable, low-cost systems that can be operated by non-medical personnel without electrical supplies are desired. Here we present a PDMS microfluidic device (2.8 cm × 1.9 cm × 0.8 cm) to achieve four distinct accomplishments: (i) pressing force from a single human finger simultaneously actuates the flow for three distinct solutions/suspensions in parallel, (ii) functionalized “detection” microbeads (ø = 15 μ m) and biological reagents are simultaneously encapsulated together within microdroplets (ø ≈ 50 μm), and (iii) novel trapping architectures are utilized to ultimately immobilize the microbead-containing microdroplets for fluorescence detection. The presented system was employed to detect the inflammatory cytokine, interferon-gamma (IFN-γ), via aptamer beacons conjugated to microbeads - which represents the first time IFN-γ detection has been achieved using microbeads inside microdroplets.