3D-printed all-liquid structures promise liquid electronics
Such all-liquid materials, say the scientists, could be used to construct liquid electronics that power flexible, stretchable devices that conform to their surroundings. To create the structures, they used a modified 3-D printer to inject threads of water into silicone oil — sculpting tubes made of one liquid within another liquid.
Using this technique, the researchers have printed threads of water between 10 microns and 1 millimeter in diameter, and in a variety of spiraling and branching shapes up to several meters in length. In addition, they say, the material can conform to its surroundings and repeatedly change shape.
“It’s a new class of material that can reconfigure itself,” says Tom Russell, a visiting faculty scientist in Berkeley Lab’s Materials Sciences Division. “And it has the potential to be customized into liquid reaction vessels for many uses, from chemical synthesis to ion transport to catalysis.”
In developing their method, the researchers first found a way to sheathe tubes of water in a special nanoparticle-derived surfactant – a substance that reduces the surface tension of a liquid in which it is dissolved – that locks the water in place. The surfactant, which is essentially soap, or as the the scientists call it, a “nanoparticle supersoap,” prevents the tubes from breaking up into droplets.
This was achieved by dispersing gold nanoparticles into water and polymer ligands into oil – the gold nanoparticles and polymer ligands want to attach to each other, but they also want to remain in their respective water and oil mediums. Soon after the water is injected into the oil, dozens of ligands in the oil attach to individual nanoparticles in the water, forming a nanoparticle supersoap. These supersoaps jam together and vitrify, like glass, which stabilizes the interface between oil and water and locks the liquid structures in position.
“This stability means we can stretch water into a tube, and it remains a tube,” says Russell. “Or we can shape water into an ellipsoid, and it remains an ellipsoid. We’ve used these nanoparticle supersoaps to print tubes of water that last for several months.”
The researchers automated the process by modifying an off-the-shelf 3D printer by replacing its components designed to print plastic with a syringe pump and needle that extrudes liquid. They then programmed the printer to insert the needle into the oil substrate and inject water in a predetermined pattern.
“We can squeeze liquid from a needle, and place threads of water anywhere we want in three dimensions,” says Joe Forth, a postdoctoral researcher in Berkeley Lab’s Materials Sciences Division. “We can also ping the material with an external force, which momentarily breaks the supersoap’s stability and changes the shape of the water threads. The structures are endlessly reconfigurable.”
For more, see “Reconfigurable Printed Liquids.”
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