Prof. Jerry Fuh is a Professor at the Department of Mechanical Engineering, National University of Singapore (NUS) and the Founding Director and Advisor of NUS Centre for Additive Manufacturing (AM.NUS), Singapore. He is a Fellow of SME and ASME, USA and a PE from California, USA. Prof. Fuh has devoted himself to the research of Additive Manufacturing (AM) processes or 3D Printing (3DP) since 1995. He and his colleagues have established the NUS’s cross-faculty  R&D programme focusing on AM/3DP-enabled biomedical applications and set up SGD$20M+ advanced AM laboratories through several agencies’ and University grants, incl. NAMIC, EDB, NRF and A*STAR with industrial collaborations.

He has produced numerous technical publications, incl. 450 papers, 5 monographs and 30 IPs/patents (with 19,000+ of citations and h-index of 76 in Google Scholar) in advanced manufacturing, materials and design, and supervised over 100 graduate students with over 60 PhD students. He also serves in more than 10 refereed journals as Editor, Associate Editor or Editorial Board Member related to design, manufacturing, material, and AM.

Topic title: 3D Printing of Field’s Metal for High-performance Sensors and Electronics

Abstract:

3D printing technologies can build functional 3D structures with high resolution, high precision, and low cost. Among them, extrusion-based direct ink writing (DIW) is one of the most attractive 3D printing methods, as they have excellent compatibility with a variety of printable materials with various viscosity. However, traditional DIWs are restricted by low printing speed and are typically unable to print high-aspect-ratio free-standing 3D structures without support. Moreover, conventional printable inks exhibit low electrical conductivity and require post treatments to enhance conductivity, hindering their applications in high-performance multifunctional electronics.

To address all the gaps, herein, a DIW approach is presented to directly print complex free-standing structures with liquid Field’s metal. Field’s metal is a eutectic alloy with a low melting point of 62 °C and high electrical conductivity of 2 × 104 S cm-1. To avoid the beading issue due to the high surface tension of molten metal, the DIW is driven by shear for 2D planar writing and by tension for 3D out-of-plane printing. This technique achieves a high printing speed of up to 100 mm s-1 and shows excellent compatibility with various rigid and soft substrates. Furthermore, rapid solidifying of Field’s metal after printing enables direct printing of free-standing structures without support. Free-standing metal wires can be printed at any slope angles from 0° to 90° with high aspect ratio of up to 750 and even horizontal over-handing structures can be printed readily. Various free-standing 3D architectures have been printed, such as vertical letters, cubic frameworks, and scalable helical structures, exhibiting high electrical conductivity, self-healing capability, and recyclability. To illustrate its versatility in the fabrication of 3D electronics, a multilayer circuit was created for battery-free temperature sensing and hemispherical helical antennas for contact-free vital sign monitoring. The developed DIW printing technology can facilitate the development of high-performance multifunctional electronics.