Thin film composite structured Janus membrane for fast gravity-driven separation of a trace of blood

Accurately monitoring blood glucose in real-time is highly required for diabetes. Utilizing membrane to realize fast separation of a trace of blood is significant for accurately testing blood glucose. In this work, we designed a Janus membrane with thin film composite structure by electrospinning polyurethane (PU) on Ca 3 (PO 4 ) 2 -coated nylon mesh. This Janus membrane exhibited directional liquid transport performance and liquid wastage reduction during separation through optimizing the surface wettability , pore parameters and asymmetric structures of membrane. When a trace of water with volume as small as 3 μL was dipped on the hydrophobic side with pore size of around 1.1 μm, this water droplet could easily penetrate through the Janus membrane within 2.9 s under only gravity and liquid wastage reduction was achieved at the same time (D 2 /D 1  = 1.27), suggesting an excellent liquid transportation performance. The blood glucose meter integrated with this Janus membrane could efficiently remove red blood cells from 10 μL blood within 7.2 s. As a result, the sensitivity of the blood glucose meter increased by 4.5%.