Acoustophoretic separation of lipid particles from red blood cells

1. A method of separating lipids from blood, the method comprising:

flowing the blood through a flow chamber, wherein the flow chamber has a source of acoustic energy with an initial shape and, on an opposing side of the flow chamber, a reflector of acoustic energy, and wherein the blood contains lipids;

driving the source of acoustic energy at a frequency that generates a higher order mode shape than the initial shape to create a plurality of three-dimensional standing waves in the blood; and

removing lipids trapped in the three-dimensional standing waves from the blood;

wherein each three-dimensional standing wave results in an acoustic radiation force with an axial force component and a lateral force component that are of the same order of magnitude.

2. The method of claim 1 , wherein the blood is continuously flowed through the flow chamber.

3. The method of claim 1 , wherein the standing waves create nodal lines and the lateral forces trap the lipids in the nodal lines.

4. The method of claim 3 , wherein the lipids trapped in the nodal lines coalesce or agglomerate such that the lipids are separated through enhanced buoyancy.

5. The method of claim 1 , wherein the lipids are collected in a collection pocket at the top of the flow chamber.

6. The method of claim 1 , wherein the blood is mediastinal blood collected via a suction.

7. The method of claim 1 , wherein the source of acoustic energy is an ultrasonic transducer comprising:

a housing with a top end, a bottom end, and an interior volume; and

a crystal at the bottom end of the housing with an exposed exterior surface and an interior surface, the crystal being able to vibrate when driven by a voltage signal; and

an air gap between the crystal and the top end of the housing.

8. A method of separating lipids from blood, the method comprising:

flowing the blood through a flow chamber, wherein the flow chamber has a source of acoustic energy with an initial shape and, on an opposing side of the flow chamber, a reflector of acoustic energy, and wherein the blood contains lipids;

driving the source of acoustic energy at a frequency that generates a higher order mode shape than the initial shape to create a plurality of three-dimensional standing waves in the blood; and

removing lipids trapped in the three-dimensional standing waves from the blood;

wherein each three-dimensional standing wave results in an acoustic radiation force with an axial force component and a lateral force component that are of the same order of magnitude; and

wherein the source of acoustic energy is an ultrasonic transducer comprising:

a housing with a top end, a bottom end, and an interior volume; and

a crystal at the bottom end of the housing with an exposed exterior surface and an interior surface, the crystal being able to vibrate when driven by a voltage signal, wherein a backing layer contacts the interior surface of the crystal, the backing layer being made of a substantially acoustically transparent material.

9. The method of claim 8 , wherein the substantially acoustically transparent material is balsa wood, cork, or foam.

10. The method of claim 8 , wherein the substantially acoustically transparent material has a thickness of up to 1 inch.

11. The method of claim 8 , wherein the substantially acoustically transparent material is in the form of a lattice.

12. The method of claim 7 , wherein an exterior surface of the crystal is covered by a wear surface material with a thickness of a half wavelength or less, the wear surface material being a urethane, epoxy, or silicone coating.

13. The method of claim 7 , wherein the crystal has no backing layer or wear layer.

14. The method of claim 7 , further comprising driving the crystal in a non-uniform displacement mode.

15. The method of claim 14 , further comprising driving the crystal in a higher order mode shape to produce more than one nodal trapping line.