Mar 30, 2018
A team of researchers from the United States and China has found a way to print 3D structures composed entirely of liquids. The team’s all-liquid material could be used to construct liquid electronics that power flexible, stretchable devices.
Using a modified 3D printer, Dr. Tom Russell of Lawrence Berkeley National Laboratory and colleagues injected threads of water into silicone oil – sculpting tubes made of one liquid within another liquid.
They printed threads of water between 10 microns and 1 mm in diameter, and in a variety of spiraling and branching shapes up to several meters in length.
“It’s a new class of material that can reconfigure itself, and it has the potential to be customized into liquid reaction vessels for many uses, from chemical synthesis to ion transport to catalysis,” said Dr. Russell, the corresponding author of a paper published in the journal Advanced Materials.
The material owes its origins to two advances: learning how to create liquid tubes inside another liquid, and then automating the process.
For the first step, Dr. Russell and co-authors developed a way to sheathe tubes of water in a special nanoparticle-derived surfactant that locks the water in place. The surfactant, essentially soap, prevents the tubes from breaking up into droplets.
“This surfactant is so good at its job, we call it a nanoparticle supersoap,” they noted.
The supersoap 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.
In practice, 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. 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,” Dr. Russell said.
The researchers modified an off-the-shelf 3D printer by removing the components designed to print plastic and replacing them 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,” said first author Dr. Joe Forth, a postdoctoral researcher at Lawrence Berkeley National Laboratory.
“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.”
Joe Forth et al. Reconfigurable Printed Liquids. Advanced Materials, published online March 24, 2018; doi: 10.1002/adma.201707603