Method and system for packed bed cell buoyancy separation

A method of performing a separation of a sample of a disperse fluid, comprising the steps of:

• i. providing a sample of a disperse fluid comprising particles dispersed in a fluid, wherein the particles comprise at least a first type of particle and at least a second type of particle, wherein the first type of particle has a first acoustic contrast relative to the fluid with a first absolute value, and the second type of particle has a second acoustic contrast relative to the fluid with a second absolute value, wherein the first absolute value is lower than the second absolute value, and wherein the first type of particle and the second type of particle either both have a positive acoustic contrast or both have a negative acoustic contrast;
• ii. positioning the sample in a microfluidic cavity;
• iii. subjecting the sample in the microfluidic cavity to an acoustic standing wave configured for causing the first type of particle and the second type of particle to congregate in at least one first region of the cavity, thereby causing the fluid to occupy at least one second region of the cavity, and thereby defining an interface between each first region and each second region;
• and
• iv. collecting at least a portion of each first region adjacent and along each interface to obtain the first type of particle.

A microfluidic system for performing a separation of a sample of a disperse fluid, the disperse fluid comprising particles dispersed in a fluid, and the particles comprising at least a first type of particle and at least a second type of particle, wherein the first type of particle has a first acoustic contrast relative to the fluid with a first absolute value, and the second type of particle has a second acoustic contrast relative to the fluid with a second absolute value, wherein the first absolute value is lower than the second absolute value, and wherein the first type of particle and the second type of particle either both have a positive acoustic contrast or both have a negative acoustic contrast, wherein the system comprises:

• a substrate with a microfluidic cavity formed in the substrate, the microfluidic cavity having an inlet configured for allowing the sample into the microfluidic cavity;
• an ultrasound transducer connected to the substrate and configured for generating an acoustic standing wave in the microfluidic cavity;
• a drive circuit connected to the ultrasound transducer and configured to drive the ultrasound transducer with a frequency that causes the particles to congregate in at least one first region of the cavity, thereby causing the fluid to occupy at least one second region of the cavity and thereby defining at least one interface between the at least one first region and the at least one second region;
• and
• a collecting device arranged and configured to collect at least a portion of each first region adjacent and along the at least one interface to obtain the first type of particle.