Additive Manufacturing Special Report - November 2023 - 19

Multi-Material Digital Light Processing 3D Printing
A new method to 3D print metal-plastic composite structures has applications in smart
electronics, micro/nanosensing, IoT devices, and quantum computing.
Waseda University, Tokyo, Japan
I
n recent years, research interest
in the 3D printing of metal
patterns on plastic parts has grown
exponentially, due to its high
potential in the manufacturing of
next-generation electronics. But
fabricating such complex parts
through conventional means is not
easy. Now, researchers from Japan
and Singapore have developed a new
3D-printing process for the fabrication
of 3D metal-plastic composite
structures with complex shapes.
Three-dimensional 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
multi-material 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
said, " 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. "
ADDITIVE MANUFACTURING SPECIAL REPORT
Cu
Plastic
Ni Electrode
Ni
Au
Plastic
10 mm
10 mm
Selective
Plastic
Transparent plastic
10 mm
PZT elastic substrate
Ni
Metallization
Ni
10 mm
3.3 V
0 V
10 mm
Ni
Flexible resin
Resin
Substrate
Ni
10 mm
3 mm
5 mm
Examples of 3D metal-plastic composites that can be prepared by the new technology. (Image:
Waseda University)
The MM-DLP3DP process is a multistep
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 lightcured
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.
NOVEMBER 2023 19

Additive Manufacturing Special Report - November 2023

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