Abstract: A temperature sensor can include a resistor, a first electrical contact at a first end of the resistor, a second electrical contact at a second end of the resistor, and a resistance measuring device. The resistor can be formed of a matrix of sintered elemental transition metal particles interlocked with a matrix of fused thermoplastic polymer particles. The resistance measuring device can be connected to the first electrical contact and the second electrical contact to measure a resistance of the resistor.

Abstract: The present disclosure is drawn to 3D printing kits, multi-fluid kits for 3D printing, and methods of making 3D printed articles. In one example, a 3D printing kit can include a powder bed material, a fusible fluid, and a magnetic fluid. The powder bed material can include polymer particles. The fusible fluid can include water and a radiation absorber. The fusible fluid can be to selectively apply to the powder bed material. The magnetic fluid can include magnetic particles, and the magnetic fluid can be to selectively apply to the powder bed material.

Abstract: The present disclosure is drawn to 3D printing kits and methods of making 3D printed articles. In one example, a 3D printing kit can include a powder bed material, a fusible fluid, and an activator fluid. The powder bed material can include polymer particles. The fusible fluid can include a radiation absorber. The fusible fluid can be to selectively apply to the powder bed material. The activator fluid can include a non-conductive electroless metal plating activator. The activator fluid can also be to selectively apply to the powder bed material.

Abstract: A strain sensor can include a resistor, a first electrical contact at a first end of the resistor, and a second electrical contact at a second end of the resistor. The resistor can be formed of a matrix of sintered elemental transition metal particles interlocked with a matrix of fused thermoplastic polymer particles.

Abstract: In an example of a method for three-dimensional (3D) printing, a polymeric or polymeric composite build material is applied. A dielectric agent is selectively applied on at least a portion of the polymeric or polymeric composite build material. The dielectric agent includes a dielectric material having an effective relative permittivity (?r) value ranging from 1.1 to about 10,000. A fusing agent is selectively applied on the at least the portion of the polymeric or polymeric composite build material, and the polymeric or polymeric composite build material is exposed to radiation to fuse the at least the portion of the polymeric or polymeric composite build material to form a region of a layer of a 3D part. The region exhibits a dielectric property, a piezoelectric property, or a combination thereof.

Abstract: According to examples, a method of making a three-dimensional conductive printed part, including forming a layer of polymeric build material; selectively applying a fusing agent on a first selected area of the formed polymeric build material; selectively applying a conductive agent on a second selected area of the formed polymeric build material; and applying a solder receiving material to a portion of the first selected area and a portion of the second selected area; in which the solder receiving material is present on a surface of the conductive three-dimensional printed part is disclosed.

Abstract: A strain sensor can include a resistor, a first electrical contact at a first end of the resistor, and a second electrical contact at a second end of the resistor. The resistor can be formed of a matrix of sintered elemental transition metal particles interlocked with a matrix of fused thermoplastic polymer particles.

Abstract: In a three-dimensional printing method example, a pre-treatment coating is formed on a part precursor by applying and drying, alternatingly: a polycation solution including a chloride ion and a polyanion solution including a sodium ion to form at least two layers. An ink is selectively deposited on the pre-treatment coating.

Abstract: The present disclosure is drawn to 3D printing kits and methods of making 3D printed articles. In one example, a 3D printing kit can include a powder bed material, a fusible fluid, and an activator fluid. The powder bed material can include polymer particles. The fusible fluid can include a radiation absorber. The fusible fluid can be to selectively apply to the powder bed material. The activator fluid can include a non-conductive electroless metal plating activator. The activator fluid can also be to selectively apply to the powder bed material.

Abstract: According to an example, a three-dimensional (3D) printed heater may include a part body formed of fused thermoplastic polymer particles and an electrically resistive element formed of a matrix of conductive particles interspersed between a matrix of thermoplastic polymer particles. The conductive particles and the thermoplastic polymer particles may be provided at respective densities to cause the electrically resistive element to have a predetermined resistance level. The 3D printed heater may also include electrical contacts connected to the electrically resistive element, in which a current is to be applied through the electrically resistive element via the electrical contacts to cause the electrically resistive element to generate a predefined level of heat.

Abstract: The present disclosure is drawn to fluid sets, material sets, and 3-dimensional printing systems. A fluid set can include a pretreat composition that includes a salt of an alkali metal with bromide or iodide. The fluid set can also include a conductive fusing agent composition including a transition metal for fusing thermoplastic powder when exposed to electromagnetic radiation.

Abstract: The present disclosure is drawn to material sets for 3-dimensional printing, 3-dimensional printing systems, and 3-dimensional printed parts. A material set can include a thermoplastic polymer powder having an average particle size from 20 ?m to 100 ?m, a photoluminescent ink including a photoluminescent agent, and a fusing ink. The fusing ink can include a fusing agent capable of absorbing electromagnetic radiation to produce heat.

Abstract: In an example, an apparatus includes processing circuitry comprising a model assessment module to identify an indication of a conductive element within object model data representing an object to be printed and a print instruction module to generate print instructions to generate the object. The print instructions may include an instruction to print conductive agent to form the conductive element and an instruction to print a fusing agent comprising an instruction to reduce an amount of fusing agent to be printed in a region of the conductive element compared to at least one other region of the object.

Abstract: The present disclosure is drawn to material sets for 3-dimensional printing, 3-dimensional printing systems, and 3-dimensional printed parts. A material set can include a thermoplastic polymer powder having an average particle size from 20 ?m to 100 ?m, an x-ray contrast ink including a jettable x-ray contrast agent, and a fusing ink. The fusing ink can include a fusing agent capable of absorbing electromagnetic radiation to produce heat.

Abstract: In a three-dimensional printing method example, a pre-treatment coating is formed on a part precursor by applying and drying, alternatingly: a polycation solution including a chloride ion and a polyanion solution including a sodium ion to form at least two layers. An ink is selectively deposited on the pre-treatment coating.

Abstract: The present disclosure is drawn to material sets for 3-dimensional printing. The material set can include a thermoplastic polymer powder having an average particle size from 20 ?m to 100 ?m, a conductive fusing ink comprising a transition metal, and second fusing ink. The second fusing ink can include a fusing agent capable of absorbing electromagnetic radiation to produce heat. The second fusing ink can provide a lower conductivity than the conductive fusing ink when printed on the thermoplastic polymer powder.

Abstract: In an example, a composition for three-dimensional (3D) printing includes a polymer build material and a non-conductive fusing agent dispensable onto the polymer build material to form a polymer-fusing agent composite portion when heated to a sintering temperature, a conductive agent dispensable onto on the polymer build material to form a polymer-conductive agent composite portion when heated at least to the sintering temperature, the conductive agent comprising: at least one conductive particulate present in an amount of from about 10% to about 60% of a total weight of the conductive agent; at least one co-solvent present in an amount of from about 10% to about 50% of a total weight of the conductive agent; and an additive present in an amount of from about 0% to about 10% of a total weight of the conductive agent.

Abstract: A temperature sensor can include a resistor, a first electrical contact at a first end of the resistor, a second electrical contact at a second end of the resistor, and a resistance measuring device. The resistor can be formed of a matrix of sintered elemental transition metal particles interlocked with a matrix of fused thermoplastic polymer particles. The resistance measuring device can be connected to the first electrical contact and the second electrical contact to measure a resistance of the resistor.

Abstract: The present disclosure is drawn to material sets for 3-dimensional printing. The material set can include a thermoplastic polymer powder having an average particle size from 20 ?m to 200 ?m, a conductive fusing agent composition including a transition metal, and nonconductive fusing agent composition. The nonconductive fusing agent composition can include transition metal oxide bronze particles.

Abstract: A 3-dimensional printed load cell part can include a part body formed of fused thermoplastic polymer particles, and a plurality of strain sensors separately formed of a matrix of conductive particles interlocked with a matrix of fused thermoplastic polymer particles. The plurality of strain sensors can have a first electrical contact at a first end and a second electrical contact at a second end. The particles of the plurality of strain sensors can be continuously fused to the particles of the part body.