After the collection, about 10 ml of DNA and RNA free DI water was pipetted onto the hydrophobic film as observed in Figure 1 . To collect breath samples on the hydrophobic film, one only needs to use the pipette to touch the DI water droplet, and then drag the DI water droplet to scroll over the entire surface. The DI water droplet would move with the pipette without an extra step. The materials collected on the surface would be subsequently scavenged into the water droplet. After this operation, the collected EBC samples in the form of bigger liquid droplet as shown in Figure 1D were transferred to a sterile tube by a pipette for subsequent analysis. The samples collected without the exhaled breath from human subjects are used as the negative controls. The EBC collection efficiency and biological analysis of collected samples were performed as outlined in the experimental procedure shown in Figure S1 (Supporting Information).