Silica aerogel is a lightweight porous foam with excellent thermal insulation. The bulk material of silica aerogel has been used in environmental technology, physical experiments or industrial catalysis.
Another feature of silica aerogel material is brittleness. Because brittleness can easily lead to fracture behavior, it is difficult to divide a larger aerogel block into small pieces, and the technical waste rate of directly solidifying the gel through a small mold is high. . These are the main reasons why silica aerogel materials can hardly realize small-scale applications.
Recent research results published in the subscription journal Nature reveal the breakthrough progress made in the manufacturing technology of micro-silica aerogels. The research team from the Swiss National Federal Laboratory (Empa) demonstrated how to achieve high-precision manufacturing of silica aerogel materials through ink direct writing 3D printing technology. This technology opens up new possibilities for thermal insulation applications in many high-tech industries, such as microelectronics, robotics, biotechnology and sensor technology.
Miniaturization application of aerogel
The research team has successfully used 3D printing to produce a stable and well-shaped micro-structured silica aerogel. The printed structure can be as thin as a tenth of a millimeter. The thermal conductivity of silica aerogel is just below 16 mW / (m * K), which is only half that of polystyrene, and even lower than the 26 mW / (m * K) of a non-flowing air layer many.
At the same time, the new 3D printed silica aerogel has better mechanical properties and can even be drilled and ground. This opens up new possibilities for the post-processing of 3D printed aerogels.
The research team uses the now patented method to precisely adjust the fluidity and curing performance of silica ink, thereby achieving 3D printing of self-supporting structures and thin-film structures. The lotus-shaped 3D printed silica aerogel sample in the picture is a dangling structure. Due to the hydrophobicity and low density of silica aerogel, the test object can float on the water, just like a natural lotus.
The new technology also makes it possible to print complex 3D multi-material microstructures for the first time.
Thermal management applications
Regarding the application direction of this technology, the research team also explored. One of the application directions is thermal management.
The mini-customized shield made of aerogel can effectively shield the heat of electronic components. These thermal images show how to shield the heat from the voltage controller on the motherboard (without insulation on the left, aluminum strip in the middle, and custom aerogel block on the right with 3D printing (far left); red/purple: high temperature; green /Blue: low temperature). Source: Empa
For example, it can be used for thermal shielding of temperature-sensitive components and thermal management of local "hot spots". Another possible application is to shield the heat source inside the medical implant so that the surface temperature of the heat source does not exceed 37 degrees, thereby protecting the human tissue.
Functional aerogel membrane
3D printing technology makes the production of multilayer/multi-material combinations more reliable and reproducible, and it is also feasible to manufacture new aerogel fine structures.
The researchers used a 3D printed aerogel membrane to construct a "thermal molecule" osmotic pump, which can operate without any moving parts and only powered by solar energy. The operating principle of this osmotic pump is based on restricted gas transport in a network of nanoscale pores or one-dimensional channels, with the pore walls being hot at one end and cold at the other. One side of the osmotic pump is doped with black manganese oxide nanoparticles.
Air purification
In the application of the above osmotic pump, the research team was able to transform the aerogel into a functional membrane through 3D printing technology. If this application is slightly changed, it can be applied to a wider range of fields.
For example, if the air is polluted by pollutants or environmental toxins (such as solvent toluene), the air can circulate through the membrane several times, and the pollutants are decomposed by a reaction catalyzed by manganese oxide nanoparticles. Due to its simplicity and durability, this kind of autocatalytic solution based on solar energy is particularly attractive in the field of small-scale air analysis and purification.
The title of the paper published by the research team is ‘Additive manufacturing of silica aerogels’. The ink direct writing 3D printing technology proposed by the research team can generate micro-silica aerogel objects from the silica aerogel powder slurry in the silica nanoparticle suspension (sol). Due to the high volume fraction of gel particles, the ink exhibits shear thinning behavior. This material easily flows through the nozzle during printing, but the viscosity increases rapidly after printing to ensure that the printed object maintains its shape. After 3D printing, the silica sol gels in ammonia gas. In addition, the paper proves the ease of combining functional nanoparticles and illustrates the potential of this technology in areas such as thermal management and micro air pumps.