CHARM3D paves the way for the efficient printing of
free-standing 3D structures that offer high electrical
conductivity, self-healing capabilities and recyclability — a
boon for electronics in healthcare, communications and
security
SINGAPORE, July 29,
2024 /PRNewswire/ -- Unlike traditional printed
circuit boards, which are flat, 3D circuitry enables components to
be stacked and integrated vertically — dramatically reducing the
footprint required for devices. Advancing the frontiers of 3D
printed circuits, a team of researchers from the National University of Singapore (NUS) has
developed a state-of-the-art technique - known as tension-driven
CHARM3D - to fabricate three-dimensional (3D), self-healing
electronic circuits. This new technique enables the 3D printing of
free-standing metallic structures without requiring support
materials and external pressure.
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The research team led by Associate Professor Benjamin Tee from the Department of Materials
Science and Engineering in the NUS College of Design and
Engineering used Field's metal to demonstrate how CHARM3D can
fabricate a wide range of electronics, allowing for more compact
designs in devices such as wearable sensors, wireless communication
systems and electromagnetic metamaterials.
In healthcare, for instance, CHARM3D facilitates the development
of contactless vital sign monitoring devices — enhancing patient
comfort while enabling continuous monitoring. In signal sensing, it
optimises the performance of 3D antennas, leading to improved
communication systems, more accurate medical imaging and robust
security applications.
The team's findings were published in the journal Nature
Electronics on 25 July 2024.
Assoc Prof Tee is the corresponding author of the research
paper.
A more streamlined approach to 3D circuit
manufacturing
3D electronic circuits increasingly underpin modern electronics,
from battery technology to robotics to sensors, enhancing their
functionalities while enabling further miniaturisation. For
example, 3D architectures, with their large effective surface
areas, improve battery capacity and enhance sensor sensitivity.
Direct ink writing (DIW), a promising 3D printing technique
currently used to fabricate 3D circuits, poses significant
drawbacks. The crux lies in its use of composite inks, which have
low electrical conductivity and entail support materials to aid in
solidification after printing. The inks are also too viscous,
limiting printing speed.
Enter Field's metal, a eutectic alloy of indium, bismuth and
tin. Eutectic alloys melt and freeze at a single temperature lower
than the melting points of their constituent metals — offering an
attractive alternative material for 3D printing. With a low melting
point of 62 degrees Celsius, a high electrical conductivity and low
toxicity, Field's metal, unlike composite inks, solidifies rapidly
— a crucial characteristic that enables the printing process to
eschew support materials and external pressure.
Leveraging the low melting point of Field's metal, the CHARM3D
technique exploits the tension between molten metal in a nozzle and
the leading edge of the printed part, culminating in uniform,
smooth microwire structures with adjustable widths of 100 to 300
microns, roughly the width of one to three strands of human hair.
Critically, phenomena such as beading and uneven surfaces —
characteristic of pressure-driven DIW — are also absent in
CHARM3D.
Compared to conventional DIW, CHARM3D offers faster printing
speeds of up to 100 millimetres per second and higher
resolutions, offering greater level of detail and accuracy in
circuit fabrication. CHARM3D forgoes post-treatment steps and
enables the fabrication of complex free-standing 3D structures,
such as vertical letters, cubic frameworks and scalable helixes.
Moreover, these 3D architectures exhibit excellent structural
retention with self-healing capabilities, meaning they can
automatically recover from mechanical damage and are
recyclable.
"By offering a faster and simpler approach to 3D metal printing
as a solution for advanced electronic circuit manufacturing,
CHARM3D holds immense promise for the industrial-scale production
and widespread adoption of intricate 3D electronic circuits," said
Assoc Prof Tee.
Far-reaching applications
The researchers successfully printed a 3D circuit for wearable
battery-free temperature sensors, antennas for wireless vital sign
monitoring and metamaterials for electromagnetic wave manipulation
— capturing the diversity in applications enabled by CHARM3D.
Traditional hospital equipment such as electrocardiograms and
pulse oximeters require skin contact, which can cause discomfort
and risk infections. Through CHARM3D, contact-free sensors can be
integrated into smart clothing and antennas, providing continuous,
accurate health monitoring in hospitals, assisted-living facilities
or home settings.
Furthermore, arrays of 3D antennas or electromagnetic
metamaterial sensors — fabricated via CHARM3D — could optimise
signal sensing and processing applications. This leads to improved
signal-to-noise ratios and higher bandwidths. The technique opens
up the possibility of creating specialised antennas for targeted
communication, enabling more accurate medical imaging, such as
microwave breast imaging for early tumour detection, and advanced
security applications, such as detecting hidden devices or
contraband emitting specific electromagnetic signatures.
Other collaborators in this work include Dr Zhuangjian Liu from
Agency for Science, Technology and Research's Institute of High
Performance Computing and Professor Michael
Dickey from North Carolina State
University's Department of Chemical and Biomolecular
Engineering.
Next steps
The research team envisions that this technique can be extended
to other types of metals and structural applications. The team is
also looking for opportunities to commercialise this unique
approach for metal printing.
Read more here:
https://news.nus.edu.sg/nus-researchers-develop-technique-to-fabricate-three-dimensional-circuits/
Watch the video here:
https://www.youtube.com/watch?v=wf0gnm0R4TM
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SOURCE National University of
Singapore