Methods and device for manipulating objects

1. A method for manipulating objects in a cavity comprising a liquid, said method comprising:

a) providing objects in at least one region of the cavity;

b) forming an aggregate of the objects within a levitation plane by submitting them to an acoustic field; and

the objects are light absorbing objects in a given wavelength range, and said method further comprising the step of:

c) disrupting the aggregate within the levitation plane by submitting said aggregate to a light beam emitting at the said given wavelength range, the objects migrating along the levitation plane and being gradually expulsed from the aggregate itself.

2. The method according to claim 1 , wherein a power of the light beam is ranging from 10μW to 200 mW.

3. The method according to claim 1 , wherein an amplitude of the acoustic field is ranging from 0.1 V to 50 V.

4. The method according to claim 1 , wherein a volume fraction of the objects within the liquid is ranging from 0.025% to 65%.

5. The method according to claim 1 , wherein the acoustic field ( 8 ) is a pulsed acoustic field.

6. The method according to claim 1 , wherein a frequency of the acoustic field is in the range from 0.5f o to 1 . 5 f o , wherein f o is a resonance frequency of the cavity.

7. The method according to claim 1 , wherein the objects are fluorescents.

8. A method for separating objects in a cavity comprising a liquid, said method comprising:

a) providing in at least one region of the cavity objects comprising a first plurality of objects capable of absorbing light in a first wavelength range and a second plurality of objects not capable of absorbing light in the first wavelength range;

b) forming an aggregate within a levitation plane of the first plurality of objects and the second plurality of objects by submitting them to an acoustic field; and

c) expulsing within the levitation plane the first plurality of objects from the aggregate by submitting the aggregate comprising first plurality of objects and second plurality of objects to a light beam emitting at the said first wavelength range, the first plurality of objects migrating along the levitation plane and being gradually expulsed from the aggregate itself.

9. The method according to claim 8 , further comprising the steps of:

flowing the liquid within the cavity; and

recovering the expulsed objects in a first outlet.

10. The method according to claim 8 , wherein the second plurality of objects absorbs light in a second wavelength range not overlapping with the first wavelength range.

11. The method according to claim 10 , further comprising the step of submitting the aggregate to a light beam emitting at the second wavelength range.

12. The method according to claim 8 , wherein the first plurality of objects has a same acoustic contrast factor than the second plurality of objects.

13. A method for acquiring at least one image of objects in a cavity comprising a liquid, said method comprising:

a) manipulating or separating the objects by using the method as claimed according to claim 1 ;

b) illuminating the at least one region of the cavity; and

c) acquiring at least one image of said illuminated objects through a transparent wall of the cavity.

14. A device for separating objects in a liquid, said device configured for performing the method of claim 1 and comprising:

at least one cavity extending along a longitudinal axis, having a cross-section that present a width (w) measured along a first transverse axis and a height (h) measured along a second transverse axis perpendicular to the first transverse axis; the cavity having first and second walls along the second transverse axis, at least a first inlet in liquid communication with the cavity and at least first, second and third outlets in liquid communication with the cavity, wherein the first outlet is arranged on the first transverse axis between the second and third outlets;

at least one acoustic wave generator which generates acoustic field in a first region of the cavity from one of the walls; and

at least one light source is arranged to emit simultaneously to the acoustic field a light beam in the first region of the cavity, the at least one light source being placed opposite to or on the same wall from which is generated the acoustic field, said light source being configured to emit a light beam at a wavelength corresponding to the absorbing wavelength range of the objects.

15. The device according to claim 14 , further comprising second and third inlets, wherein the first inlet is arranged on the first transverse axis between the second and third inlets.