University of Nottingham Researchers Use UV Light to 3D Print Multi-Functional Devices

The process of integrating electronics into 3D printed devices starts with being able to 3D print multiple materials at the same time. Thanks to an innovation developed at the University of Nottingham, the ability to 3D print functional parts containing multiple materials is becoming a viable process. A team of researchers from the university’s Centre for Additive Manufacturing (CfAM) developed a single process to 3D print structures containing electrically conductive silver inks and insulative polymeric inks. The magic behind this innovation stems from a method that rapidly solidifies metallic and polymeric inks by using UV light as a single source of energy.

Fabricating dissimilar materials has been a challenge for 3D printing researchers due to the multiple steps required to solidify each material. In this case, metallic nanoparticles are contained in silver inks and dispersed in a solvent material. In order to form a layer of conductive silver, the solvents are evaporated from the ink and the nanoparticles are fused together. This requires the use of high temperatures, which are usually destructive to most polymeric inks. Silver nanoparticle inks are typically heated at 100-150^o C for ten minutes to convert the liquid ink into a conductive solid film.

Research Highlight: A schematic diagram showing how UV irradiation heats and solidifies conductive and dielectric inks to form the letter N with silver tracks that connect a green LED to a power source.

Dr. Ehab Saleh and colleagues from CfAM identified that silver nanoparticles in conductive inks are capable of absorbing UV light efficiently. The UV energy absorbed by the silver ink is converted into heat capable of evaporating the solvents and fusing the silver nanoparticles – and it doesn’t damage other material located next to it because it’s only focused on the conductive ink.

Printing apparatus with UV installed on the print-head assembly.

A solid, translucent dielectric polymer is formed by crosslinking photosensitive liquid monomers using the same UV source. This results in multi-functional 3D printed parts that contain conductive and non-conductive inks printed in a single process. The silver ink was sintered directly from the liquid stage, meaning no pre-processing (surface treatment, oven processing, etc.) was needed.

Chris Tuck, Professor of Materials Engineering and lead investigator of the study, talked about the potential of the breakthrough: “Being able to 3D print conductive and dielectric materials in a single structure with the high precision that inkjet printing offers, will enable the fabrication of fully customised electronic components. You don’t have to select standard values for capacitors when you design a circuit, you just set the value and the printer will produce the component for you.”

Research Highlight: Left: A conductive helix track printed within an isolative polymer which forms the basis of an antenna made up of complex shapes. Middle: A robotic car printed with electronic circuitry to power up two embedded motors and monitor printed sensors. Right: A microscopic cross-section of a printed structure showing a stack of conductive and insulating materials.

Professor Richard Hague, Director of CfAM, touched on the future of multi-functional additive manufacturing (MFAM): “Printing fully functional devices that contain multiple materials in complex, 3D structures is now a reality. This breakthrough has significant potential to be the enabling manufacturing technique for 21st Century products and devices that will have the potential for significant impact on both industry and the public.”

The study, 3D Inkjet Printing of Electronics Using UV Conversion, was published in the journal Advanced Materials Technologies.

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