Figure 1

Schematic illustration of the microfluidic device. A. Overview and device settings. The top view of the device (upper side) and the cross section at the observation area (lower side) are illustrated. Each port from A to F was attached with a 2-mm silicone tube (black bar). Gray, yellow, and dark yellow areas indicate glass, PDMS, and the coverslip on the PDMS, respectively. Channels of white and sky-blue on the PDMS indicate the path of the air and the sample liquid, respectively. B. Photograph of the microfluidic device. C. Workflow of the chip. The illustrations indicate the cross section at the observation area of the chip. Vertical red and green arrows indicate the direction of the PDMS movement when directly and indirectly pressed by air, respectively. The horizontal red arrows in (1) and (4) indicate the flow direction of the sample liquid pressed by air. The observation of yeast cells is achieved with four cycle steps: (1) Injection, (2) Hold, (3) Release, and (4) Outflow. Yeast cells are softly held with PDMS pushed up by air pressure.