Iso-acoustic focusing
Analyzing cells' acoustic properties
![A cancer cell, a lymphocyte and neutrophil is seen, where the cancer cell has the lowest acoustic impediance and the neutrophil has the highest.](/fileadmin/biomedicalengineering/Personal_folders/Per_Augustsson/Research/csm_IAF_schematic_baf270bcbf.png)
In iso-acoustic focusing (IAF), individual cells are analyzed based on the previously uncharted parameter of effective acoustic impedance [Augustsson et al., Nature Communications, 2016]. This equilibrium method can be viewed as a microfluidic analog to density gradient centrifugation or iso-electric focusing. Cells flowing through a microchannel migrate sideways, influenced by an acoustic field, into flow streams of ever increasing acoustic impedance. Finally, the individual cells reach their iso-acoustic point (IAP), at which the acoustic contrast between the cell and the surrounding liquid becomes zero, and the sideways displacement ceases. Cell-specific differences in effective acoustic impedance translate to a spatial dispersion of the cell population transverse to the flow, enabling continuous label-free analysis of individual cells.
![The neutrophils and the monocytes have been seperated along the vertical flow direction.](/fileadmin/_processed_/8/3/csm_csm_cellOverlay_75afde8a7b_816dfa2521.gif)
![Before the inlet, there is Histopaque with whole blood on its sides. Before the outlet, the whole blood is divided in focused red blood cells and plasma, respectively.](/fileadmin/_processed_/c/b/csm_alsved_illustration_a8709b9ed8.jpg)
Separating cells based on acoustic properties
By this approach, we recently presented the first one-step acoustic separation of mononuclear cells (MNCs) from undiluted human whole blood [Alsved et al. Microtas, Basel, 2019 (PDF)].