Direct Metal Printing of 3D Electronic Components and Circuits Using MetalJet

Printed electronics have been the focus of increasing attention in the past decade due to their wide range of diverse applications, including soft robotics, actuators, wearable electronics, biomedical applications, and human-machine interfaces. Considerable research has been devoted to nanoparticle-based inkjet printing as a large-scale fabrication method of such devices, and tremendous advances have been obtained. However, there are still process-related challenges to be addressed, including nozzle clogging, ink formulation, nanoparticle synthesis, drying, and sintering of the nanoparticles. Furthermore, higher electrical resistivity than the corresponding bulk metal, poor adhesion of printed traces to the substrate, and the coffee ring effect are common quality-related challenges associated with the process.<br/><br/>Drop-on-demand Metal Jetting (DoD-MJ is an emerging Additive Manufacturing technology that has the potential to fabricate 3D electronic components and flexible electronics whilst overcoming the challenges mentioned above. The metal jetting approach consists of dispensing and depositing individually-controlled droplets of molten metal onto a substrate at precise locations. DoD-MJ processes are classified based on the droplet generation actuation method. MagnetoHydroDynamic (MHD) actuators are the most advanced devices to date that have overcome the challenges of producing high-temperature droplets at high rates. One of the main advantages of DoD-MJ over inkjet printing is its simplified fabrication approach. This simplicity is granted by a wide availability of potential feedstock material, no residual impurities, and the elimination of the need for pre-processing and post-print processing.<br/><br/>MetalJet, the MHD-based system used in this study, has the capacity to produce molten micro-droplets (60–90 µm) at temperatures up to 2000 °C to form single and multi-material objects at frequencies up to 2 kHz. The work presented here reports that interface formation at the droplet substrate during the deposition of molten droplets embeds them into the substrate to obtain an acceptable level of adhesion. Moreover, strong metallurgical droplet-droplet bonding was obtained through remelting the interfaces. Consequently, the electrical resistivity of printed structures was comparable to that of the corresponding bulk metal. Overall, the work paves the way for the fabrication of next-generation electronics.