We performed experiments without flow to observe the forces acting on the bacteria and determine suitable excitation frequencies. We changed the frequency in steps of 1 kHz in a range from 1 to 4 MHz to experimentally determine resonance frequencies that lead to bacteria attraction. As the strongest observable particle attraction occurred at a frequency of 1.89 MHz, this parameter was applied for all subsequent experimental procedures. To perform medium exchange with the device, we operated it while applying a flow of cells. Specifically, we implemented a three-step protocol including a capture step during which the bacterial cells are trapped at the wall by the acoustic forces, resulting from the ARF, and the drag forces, resulting from the acoustic streaming, followed by a wash step in which the surrounding medium is exchanged while the acoustic and drag forces still trap the cells, and finally, a release step in which the forces are no longer applied and cells can re-suspend into the surrounding liquid (Fig. (a)). We ran the protocol and determined the efficiency of each step (ESI † video 2). We observed accumulation of cells at the acoustic pressure nodes at the vibrating wall (Fig. ). Over three experiments, on average, we were able to capture 70% of the cells that passed through the corresponding channel section during the time of application of acoustics. An additional 20% of the captured cells were lost in the washing step, indicating that wash duration and flow rate require further optimization. Finally, up to 52% and on average 47 ± 3% of the cells that entered the chip initially were successfully washed and released into the new medium (Fig. ).