Aerogel: the micro structural material of the future
Thermal insulation for miniature components -printed in 3D

Date:
August 20, 2020
Source:
Swiss Federal Laboratories for Materials Science and Technology
(EMPA)
Summary:
Aerogel is an excellent thermal insulator. So far, however,
it has mainly been used on a large scale, for example in
environmental technology, in physical experiments or in industrial
catalysis. Researchers have now succeeded in making aerogels
accessible to microelectronics and precision engineering: A new
article shows how 3D-printed parts made of silica aerogels and
silica composite materials can be manufactured with high precision.



FULL STORY ========================================================================== Behind the simple headline "Additive manufacturing of silica aerogels" --
the article was published on July 20th in the scientific journal Nature
-- a groundbreaking development is hidden. Silica aerogels are light,
porous foams that provide excellent thermal insulation. In practice,
they are also known for their brittle behaviour, which is why they
are usually reinforced with fibres or with organic or biopolymers for large-scale applications. Due to their brittle fracture behaviour, it is
also not possible to saw or mill small pieces out of a larger aerogel
block. Directly solidifying the gel in miniaturised moulds is also not
reliably -- which results in high scrap rates. This is why aerogels have
hardly been usable for small-scale applications.


========================================================================== Stable, well-formed microstructures The Empa team led by Shanyu Zhao,
Gilberto Siqueira, Wim Malfait and Matthias Koebel have now succeeded
in producing stable, well-shaped microstructures from silica aerogel by
using a 3D printer. The printed structures can be as thin as a tenth of a millimeter. The thermal conductivity of the silica aerogel is just under
16 mW/(m*K) -- only half that of polystyrene and even significantly less
than that of a non-moving layer of air, 26 mW/(m*K). At the same time,
the novel printed silica aerogel has even better mechanical properties and
can even be drilled and milled. This opens up completely new possibilities
for the post- processing of 3D printed aerogel mouldings.

With the method, for which a patent application has now been filed, it
is possible to precisely adjust the flow and solidification properties
of the silica ink from which the aerogel is later produced, so that both
self- supporting structures and wafer-thin membranes can be printed. As
an example of overhanging structures, the researchers printed leaves and blossoms of a lotus flower. The test object floats on the water surface
due to the hydrophobic properties and low density of the silica aerogel --
just like its natural model. The new technology also makes it possible
for the first time to print complex 3D multi-material microstructures.

Insulation materials for microtechnology and medicine With such structures
it is now comparatively trivial to thermally insulate even the smallest electronic components from each other. The researchers were able to
demonstrate the thermal shielding of a temperature-sensitive component and
the thermal management of a local "hot spot" in an impressive way. Another possible application is the shielding of heat sources inside medical
implants, which should not exceed a surface temperature of 37 degrees
in order to protect body tissue.

A functional aerogel membrane 3D printing allows multilayer/multi-material combinations to be produced much more reliably and reproducibly. Novel
aerogel fine structures become feasible and open up new technical
solutions, as a second application example shows: Using a printed
aerogel membrane, the researchers constructed a "thermos- molecular"
gas pump. This permeation pump manages without any moving parts at all
and is also known to the technical community as a Knudsen pump, named
after the Danish physicist Martin Knudsen. The principle of operation is
based on the restricted gas transport in a network of nanoscale pores
or one-dimensional channels of which the walls are hot at one end and
cold at the other. The team built such a pump from aerogel, which was
doped on one side with black manganese oxide nanoparticles. When this
pump is placed under a light source, it becomes warm on the dark side
and starts to pump gases or solvent vapours.

Air purification without moving parts These applications show the
possibilities of 3D printing in an impressive way: 3D printing turns
the high-performance material aerogel into a construction material for functional membranes that can be quickly modified to suit a wide range
of applications. The Knudsen pump, which is driven solely by sunlight,
can do more than just pump: If the air is contaminated with a pollutant or
an environmental toxin such as the solvent toluene, the air can circulate through the membrane several times and the pollutant is chemically broken
down by a reaction catalyzed by the manganese oxide nanoparticles. Such sun-powered, autocatalytic solutions are particularly appealing in the
field of air analysis and purification on a very small scale because of
their simplicity and durability.

Empa researchers are now looking for industrial partners who want to
integrate 3D-printed aerogel structures into new high-tech applications.

Video: https://www.youtube.com/watch?v=Yl8yz28xQbw&feature=emb_logo

========================================================================== Story Source: Materials provided by Swiss_Federal_Laboratories_for_Materials_Science_and
Technology_(EMPA). Original written by Rainer Klose. Note: Content may
be edited for style and length.


========================================================================== Journal Reference:
1. Shanyu Zhao, Gilberto Siqueira, Sarka Drdova, David Norris,
Christopher
Ubert, Anne Bonnin, Sandra Galmarini, Michal Ganobjak, Zhengyuan
Pan, Samuel Brunner, Gustav Nystro"m, Jing Wang, Matthias M. Koebel,
Wim J.

Malfait. Additive manufacturing of silica aerogels. Nature, 2020;
584 (7821): 387 DOI: 10.1038/s41586-020-2594-0 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/08/200820102459.htm

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