Novel 3D printing method to fabricate complex metal–plastic composite structures

Three-dimensional (3D) metal–plastic composite structures have widespread potential applicability in smart electronics, micro/nanosensing, internet-of-things (IoT) devices, and even quantum computing. Devices constructed using these structures have a higher degree of design freedom, and can have more complex features, complex geometry, and increasingly smaller sizes. But current methods to fabricate such parts are expensive and complicated.

Recently, a group of researchers from Japan and Singapore developed a new multimaterial digital light processing 3D printing (MM-DLP3DP) process to fabricate metal–plastic composite structures with arbitrarily complex shapes. Explaining the motivation behind the study, lead authors Professor Shinjiro Umezu, Mr. Kewei Song from Waseda University and Professor Hirotaka Sato from Nanyang Technological University, Singapore state, “Robots and IoT devices are evolving at a lightning pace. Thus, the technology to manufacture them must evolve as well. Although existing technology can manufacture 3D circuits, stacking flat circuits is still an active area of research. We wanted to address this issue to create highly functional devices to promote the progress and development of human society.” The study has been published in ACS Applied Materials & Interfaces.

The MM-DLP3DP process is a multi-step process that begins with the preparation of the active precursors—chemicals which can be converted into the desired chemical after 3D printing, as the desired chemical cannot be 3D printed itself. Here, palladium ions are added to light-cured resins to prepare the active precursors. This is done to promote electroless plating (ELP), a process that describes the auto-catalytic reduction of metal ions in an aqueous solution to form a metal coating. Next, the MM-DL3DP apparatus is used to fabricate microstructures containing nested regions of the resin or the active precursor. Finally, these materials are directly plated, and 3D metal patterns are added to them using ELP.

The research team manufactured a variety of parts with complex topologies to demonstrate the manufacturing capabilities of the proposed technique. These parts had complex structures with multimaterial nesting layers, including microporous and tiny hollow structures, the smallest of which was 40 μm in size. Moreover, the metal patterns on these parts were very specific and could be precisely controlled. The team also manufactured 3D circuit boards with complex metal topologies, like an LED stereo circuit with nickel and a double-sided 3D circuit with copper.

“Using the MM-DLP3DP process, arbitrarily complex metal–plastic 3D parts having specific metal patterns can be fabricated. Furthermore, selectively inducing metal deposition using active precursors can provide higher quality metal coatings. Together, these factors can contribute to the development of highly integrated and customizable 3D microelectronics,” Umezu, Song, and Sato state.

The new manufacturing process promises to be a breakthrough technology for the manufacturing of circuits, with applications in a diverse variety of technologies, including 3D electronics, metamaterials, flexible wearable devices, and metal hollow electrodes.

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Reference

DOI: https://doi.org/10.1021/acsami.2c10617

Authors: Kewei Song¹, Yue Cui¹, Tiannan Tao¹, Xiangyi Meng¹, Michinari Sone², Masahiro Yoshino², Shinjiro Umezu^1,3, and Hirotaka Sato⁴

Affiliations:

¹Graduate School of Creative Science and Engineering, Department of Modern Mechanical Engineering, Waseda University

²Research and Development Division, Yoshino Denka Kogyo, Inc.

³Department of Modern Mechanical Engineering, Waseda University

⁴School of Mechanical and Aerospace Engineering, Nanyang Technological University

About Waseda University 
Located in the heart of Tokyo, Waseda University is a leading private research university that has long been dedicated to academic excellence, innovative research, and civic engagement at both the local and global levels since 1882. The University has produced many changemakers in its history, including nine prime ministers and many leaders in business, science and technology, literature, sports, and film. Waseda has strong collaborations with overseas research institutions and is committed to advancing cutting-edge research and developing leaders who can contribute to the resolution of complex, global social issues. The University has set a target of achieving a zero-carbon campus by 2032, in line with the Sustainable Development Goals (SDGs) adopted by the United Nations in 2015. 

To learn more about Waseda University, visit https://www.waseda.jp/top/en

About Nanyang Technological University, Singapore
A research-intensive public university, Nanyang Technological University, Singapore (NTU Singapore) has 33,000 undergraduate and postgraduate students in the Engineering, Business, Science, Medicine, Humanities, Arts, & Social Sciences, and Graduate colleges.

NTU is also home to world-renowned autonomous institutes—the National Institute of Education, S Rajaratnam School of International Studies, Earth Observatory of Singapore, and Singapore Centre for Environmental Life Sciences Engineering—and various leading research centres such as the Nanyang Environment & Water Research Institute (NEWRI) and Energy Research Institute @ NTU (ERI@N).

Under the NTU Smart Campus vision, the University harnesses the power of digital technology and tech-enabled solutions to support better learning and living experiences, the discovery of new knowledge, and the sustainability of resources.

Ranked amongst the world’s top universities, the University’s main campus is also frequently listed among the world’s most beautiful. Known for its sustainability, over 95% of its building projects are certified Green Mark Platinum. Apart from its main campus, NTU also has a medical campus in Novena, Singapore’s healthcare district.

For more information, visit www.ntu.edu.sg

About Professor Shinjiro Umezu
Dr. Umezu received his Ph.D. from Waseda University in 2006. He is currently a Professor at the Department of Modern Mechanical Engineering at Waseda University, Japan. He runs his lab, UMEZU Lab, which works on the fabrication of micro/nanomaterials. His research interests lie in 3D printing and microfabrication and their applications in bioengineering and green technology. He has 345 publications credited to him and 1,378 citations to his name.

About Professor Hirotaka Sato
Hirotaka Sato is a professor at the School of Mechanical & Aerospace Engineering (MAE), Nanyang Technological University (NTU), Singapore. He worked at UC Berkeley, University of Michigan, and Waseda University, during 2008–2011, 2007, and 2005–2006 respectively. He received his PhD in chemistry from Waseda University in 2005. His research focuses on MEMS, insect–computer hybrid robots (or cyborg insects), and electrochemical processes (metal plating, polishing). Web: https://hirosatontu.wordpress.com