Figure 1. Schematic diagram of the dual-flow cell model. (A) The flow system. Arrowheads indicate the direction of the flow. The system is connected by 14-gauge Masterflex tubing (Cole-Palmer, Vernon Hills, IL, USA). For pulsed treatment of biofilms with KSL, a syringe pump (KD Scientific, Holliston, MA, USA) with 2 injectable syringes containing respective treatment and control solutions was directly connected to each of the flow chambers through a three-way valve. (B) The dual-flow cell. The flow cell consists of 2 parallel flow chambers, each of which contains 3 recesses for holding Ge disks. The inner diameter and depth of each recess are 10.25 mm and 2.0 mm, respectively. Holes with a diameter of 2.0 mm for flow inlets and outlets are drilled in each end of the flow chamber. The flow chambers are contained on one side by the polycarbonate bottom plate, and on the other side by an aluminum cover plate containing 2 parallel 60 mm x 24 mm no. 2 cover glasses. (C) Cross-section of the flow chamber, showing the dimensions of the flow channel (0.4 mm deep, 13 mm wide, and 25 mm long).