Genetically encoded actuators for acoustic manipulation

A method of sorting a population of cells, comprising:

• flowing a fluid sample through a microfluidic channel, wherein the microfluidic channel comprises one or more flow stream(s) introduced in the microfluidic channel via one or more inlet channel(s) and exiting the microfluidic channel via two or more outlet channels, wherein the fluid sample comprises a population of cells, wherein the population of cells has been incubated with gas vesicles (GVs), wherein cells of the population of cells have varying capacity to uptake said GVs, and wherein population the cells is capable of uptaking GVs in a context-dependent manner, wherein the levels of GVs within a cell increases the compressibility (3) and reduces the density (ρ) of said cell, thereby modulating the acoustic contrast ((D) of said cell relative to the fluid in the microfluidic channel, wherein the uptake of GVs above a threshold level of uptake imparts a threshold negative acoustic contrast on said cell, and wherein the population of cells comprises or is suspected of comprising:
• (i) a first subpopulation of cells having a nonnegative acoustic contrast or a negative acoustic contrast below the threshold negative acoustic contrast, or (ii) a second subpopulation of cells having a negative acoustic contrast at or above the threshold negative acoustic contrast;
• and applying ultrasound to the microfluidic channel, wherein applying ultrasound comprises generating acoustic standing wave(s) in the microfluidic channel, wherein the acoustic standing wave(s) position pressure antinode(s) in the microfluidic channel, wherein the second subpopulation of cells is actuated towards flow stream(s) comprising the pressure antinode(s), and wherein the method does not comprise buoyancy purification of the population of cells.