Method for producing microcarriers and for performing biological assays

1. A method for producing at least a microcarrier, the method comprising the following steps:

a) providing a wafer having a sandwich structure comprising a bottom layer, a top first sacrificial layer and an insulating layer located between said bottom and top layers;

b) structuring the first sacrificial layer to form a first mask delineating a first three dimensional negative pattern;

c) depositing a first structural layer over the first sacrificial layer so as to form a first three dimensional structure complementary to the first three dimensional negative pattern;

d) depositing a second sacrificial layer over the top surface of the first structural layer;

e) structuring the second sacrificial layer to define a second mask delineating a second three dimensional negative pattern on the top surface of the first structural layer;

f) depositing a second structural layer in the second three dimensional negative pattern so as to form a second three dimensional structure on the upper surface of the first structural layer;

g) etching away from above the first and second structural layers down to the insulating layer to delineate lateral walls of bodies of microcarriers, each body comprising at least a first lower and a second upper three dimensional structures; and

h) etching away the insulating layer, the bottom layer and the sacrificial layers to release the microcarriers.

2. A method according to claim 1 , wherein the first and/or the second three-dimensional structures comprise at least one spacing element protruding from the corresponding surface of the body onto which they are formed.

3. A method according to claim 1 , further comprising, before step c, a step of depositing a first active layer on the first sacrificial layer and onto the first three dimensional negative pattern.

4. A method according to claim 1 , further comprising the following steps, before step g:

a) etching away the second sacrificial layer; and

b) depositing a second active layer over the first and second structural layers.

5. A method according to claim 3 , wherein at least one of the first active layer or the second active layer comprises a material having optical or magnetic properties, polycrystalline silicon and/or polytetrafluoroethylene, or a metallic layer having a high reflective index.

6. A method according to claim 5 , wherein the first active layer and/or the second active layer comprise an oxide or a nitride, or a metal layer.

7. A method according to claim 1 , wherein at least one of the first three dimensional structure and second three dimensional structure of each microcarrier comprises at least a diffraction grating.

8. A method according to claim 1 , further comprising before step d, a step of polishing the upper surface of the first structural layer so as to form a flat upper surface.

9. A method according to claim 1 , wherein the insulating layer and the first sacrificial layer form a single layer.

10. Method according to claim 1 , wherein at least one of the sacrificial layers is made of or comprises silicon nitride or photoresist material.

11. A method according to claim 1 , wherein the first and second structural layers comprise silicon.

12. A method according to claim 6 , wherein said oxide is silicon dioxide.

13. A method according to claim 9 , wherein said single layer comprises silicon nitride.

14. A method according to claim 11 , wherein said silicon is amorphous silicon.

15. A method according to claim 11 , wherein said silicon is polysilicon.