3D printing aerogel microstructures for sensors and insulation

3D printing aerogel microstructures for sensors and insulation

Technology News |
By Nick Flaherty

A team at EMPA in Switzerland has developed a technique to 3D print microstructures using insulating silica aerogels.  

The team led by Shanyu Zhao, Gilberto Siqueira, Wim Malfait and Matthias Koebel have 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 millimetre. The aerogel can be used to insulate small electronic components and even build small pumsp and sensors.

The thermal conductivity of the silica aerogel is just under 16 mW/(m*K), half that of polystyrene and even significantly less than that of a non-moving layer of air at 26 mW/(m*K). At the same time, the 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.

Such structures would make it simple 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”. 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.

Next: 3D printing an aerogel pump for a sensor 

The 3D printing technique allows multilayer/multi-material combinations to be produced much more reliably and reproducibly. Using a printed aerogel membrane, the researchers constructed a “thermos-molecular” gas pump. This 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.

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 suitable as an air sensor and purifier.

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

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