3-dimensional printing

1. A method of 3-dimensional printing a printed part, the method comprising:

printing a first inkjet dopant composition at selected locations on a layer of build material comprising polymer particles, wherein the first inkjet dopant composition comprises a first dopant dispersed or dissolved in a first liquid carrier, wherein the first dopant comprises first dopant particles, and wherein the first dopant particles are selected from photoluminescent particles, dielectric particles, magnetic particles, ceramic particles, and semi-conductor particles;

printing an inkjet fusing composition onto selected areas of the layer of build material, wherein the fusing composition includes a fusing agent to absorb electromagnetic radiation to produce heat; and

exposing at least a portion of the layer of build material to electromagnetic radiation, thereby heating the selected areas of the layer of build material having the inkjet fusing composition printed thereon and fusing polymer particles at the selected areas of the layer of build material to form a fused polymer layer comprising the first dopant,

wherein the selected areas of the layer of build material include areas of the layer of build material that have not been printed with the first inkjet dopant composition.

2. The method as claimed in claim 1 , wherein the first dopant particles have a particle size of 1 to 200 nm.

3. The method as claimed in claim 1 , wherein the printed part comprises regions comprising the first dopant and regions in which the first dopant is absent.

4. The method as claimed in claim 3 , wherein the regions comprising the first dopant differ in at least one property from the regions in which the first dopant is absent, wherein the at least one property is selected from at least one of dielectric permittivity, magnetic permeability, refractive index, and photoluminescence.

5. The method as claimed in claim 1 , which further comprises forming a further layer of build material over the fused polymer layer; printing a second inkjet dopant composition at selected locations on the further layer of build material, wherein the second inkjet dopant composition comprises a second dopant dispersed or dissolved in a second liquid carrier; and fusing polymer particles at selected areas of the further layer of build material to form a further fused polymer layer comprising the second dopant.

6. The method as claimed in claim 1 , which further comprises forming a further layer of build material over the fused polymer layer, and fusing polymer particles at selected areas of the further layer of build material to form a fused polymer layer that is devoid of the first dopant.

7. The method as claimed in claim 1 , wherein the printed first inkjet dopant composition flows into at least some interstices between adjacent polymer particles in the layer of build material.

8. The method as claimed in claim 7 , wherein the printed first inkjet dopant composition penetrates into at least part of a depth of the layer of build material.

9. The method as claimed in claim 1 , wherein the first inkjet dopant composition is printed droplet by droplet, wherein each droplet has a volume of 5 to 20 pL.

10. The method as claimed in claim 1 , wherein the build material comprising polymer particles are thermoplastic polymer particles selected from at least one of a polyamide, a polyurethane, a polycarbonate, a polystyrene and polyolefin.

11. The method as claimed in claim 8 wherein the printed first inkjet dopant composition penetrates into at least 50% of the depth of the layer of build material.