Fig. 1

Overview of the acoustophoretic microchip, preserved proliferation capacity and cell size distributions of PDX cells and PBPCs. A The schematic illustration shows the acoustophoresis principle. The sample is infused through the inlet (a) at 100 µL/min and enters the prealignment channel where the 5 MHz acoustic standing wave induces 2D-alignment of the cells in two lines (b). Buffer is centrally infused at 300 µL/min to laterally position the cells close to the side walls, maximizing the lateral migration in the separation channel and hence separation performance. As the cells enter the separation channel (actuated with a 2 MHz transducer), the acoustic force in the standing half-wavelength field induces a movement of the particles towards the channel center (c). The effect of the radiation force on the cells is dependent on the cells’ acoustophysical properties, i.e., larger and denser cells (red) move faster in the acoustic field and are directed to the center outlet, while less affected cells are collected in the side outlet (blue, Additional file 1: Equations 1 and 2, Figure S1). B Photograph of the silicon-glass chip as used in this study. Visible are the microchip in the open holder, the temperature sensor, transducers, as well as prealignment (b), and separation channel (c). Arrows indicate inlets (a) and outlet positions. C Cell size distributions of PDX cells in different passages (P) and one representative measurement of PBPCs. Cell counts are presented as normalized numbers to the total number of cells acquired per sample. Inserts show representative images of the different PDX cells growing in free 3D spheroid cultures, scale bars represent 200 µm. D Analysis of PDX cell proliferation capacity for non-sorted, sham-sorted and acoustically separated PDX-1 cells seeded at identical numbers. Data are normalized to initially seeded cell numbers (dashed line) counted after one week culture (n = 3, mean ± SD). Ordinary one-way ANOVA with Kruskal–Wallis multiple comparisons test identified no statistical significances between the different treatments (ns)