Fig. 4
Measured liquid distribution data (360o circular angle) for a 250-mL shake flask containing 40 mL of an aqueous 5 μM fluorescein solution with 100 mM phosphate buffer (pH 8). Measurement conditions are 400 rpm of shaking frequency and 25 mm of shaking diameter. a shows the output voltage [V] relative to the maximum values of the output voltage [Vmax] detected. The leading edge (LB) and tail of the bulk liquid (TB) are observed at varying heights starting from 2 mm to 57 mm (with an increment of 5 mm) from the base of the shake flask. The heights of 2 mm to 12 mm refer to the torus of the flask; the heights of 17 mm to 57 mm refer to the conical part (see Fig. 1). b depicts the three-dimensional (3D) bulk liquid positions for LB (green solid circle and line) and TB (red solid triangle and line) at the shake flask’s wall based on determined angle values [o] at varying heights. The location of the optical fiber is referred at the 0o circular angle of the shake flask. The direction of the centrifugal force is pointing from left to right. The LB and TB are observed at azimuth and elevation angles of 180o and 6o, respectively