The piezoelectric transducer has been excited via an arbitrary function generator (AFG3011C, Tektronix ). The motion of the yeast cells has been captured at 12 -17 frames/s using an inverted microscope (IX81, Olympus). To account for the varying size of yeast cells, multiple frames of the recordings were averaged. All data required for individual qualitative evaluations of design or process parameters has been collected in single experimental sessions to ensure comparability and to prevent inter-device discrepancies such as in the distance between the transducer and the PDMS device.