Quantum dot LED 3D printed using five various materials

3D printing will spark manufacturing revolution, if it hasn't already. This method of constructing objects by building them up, one layer at a time, has yielded a 30kW power inverter, a rocket thruster and a car composed of 3D printed components made of tiny pellets of plastic infused with carbon fibre. Now, Princeton University researchers said they did something new. They fabricated a quantum dot LED (QD-LED) with five different materials using a custom 3D printer.

To date, 3D printing has been limited to specific plastics, passive conductors and a few biological materials. Developing the ability to 3D print various classes of materials possessing distinct properties is said to enable the freeform generation of active electronics in unique functional, interwoven architectures.

The 3D printed QD-LED is composed of the following materials: emissive semiconducting inorganic nanoparticles, an elastomeric matrix, organic polymers as charge transport layers, solid and liquid metal leads, and a UV-adhesive transparent substrate layer, as cited in a paper published by American Chemical Society.

Exhibiting pure and tunable colour emission properties, the QD-LED demonstrates that diverse classes of materials can be 3D printed and fully integrated into device components with active properties. According to ExtremeTech, the researchers took six months to build the $20,000 printer used to build the QD-LED.

The QD-LED's base layer is made up of silver nanoparticles that are ideal for connecting the LED to an electronic circuit. Above them are two polymer layers, which drive the current towards the next layer—the nanoscale semiconductor crystals. Composed of cadmium selenide nanoparticles enveloped in a zinc sulphide shell, these crystals produce green or orange light upon contact with an electron. The colour can be controlled by modifying the size of the particles. The uppermost layer is a gallium indium that functions to lead the electrons away from the LED.

The fabrication approach involves three core steps, reported NanoWerk. First is to initially identify electrodes, semiconductors and polymers that possess required functionalities and exist in printable formats. These materials are then dissolved in orthogonal solvents in order to preserve the identity of underlying layers during the layer-by-layer printing process. Lastly, to achieve interwoven patterning, the materials are directly dispensed in a CAD-designed construct.