Most 3D printers print layers over and over again until a full object takes shape. But a whole new approach to 3D printing is capable of creating free-form metal objects and designs that emerge suspended in mid-air, thanks to a special kind of silver “ink.” The machine uses a high-intensity laser that heats tiny silver nanoparticles to form metallic shapes. As the nanoparticles are extruded from the nozzle they harden into fully formed 3D objects.
The 3D-printing technique was developed by a team of Harvard researchers at the Wyss Institute for Biologically Inspired Engineering and the Paulson School of Engineering and Applied Sciences. For now the team calls the system “laser-assisted direct ink writing” in its research publications, but there’s surely a catchier name on the horizon. The key to unlocking this new approach to printing metal was balancing the intensity of the laser and its proximity to the nozzle. Placing the laser too close to the printer system’s nozzle made the silver nanoparticles harden in the nozzle interior, instead of letting them ooze out to form unique metallic shapes.
Once researchers perfected the distance and timing between the laser and the nanoparticle nozzle, smooth metallic 3D printing was a cinch. The nozzle maps out its programmed path while pushing out the silver nanoparticles, and the laser follows the nozzle’s movement to solidify the particles into filament. The metallic product is incredibly delicate, composed as it is of a filament that is thinner than a single strand of human hair. A steady stream of nanoparticles within the nozzle ensures that the filament will be sturdy, without any breaks or imperfections.
This kind of delicate metal printing is particularly useful because of its freeform capabilities. The filament can be shaped into virtually any type of metal structure, which researchers expect will be useful in developing wearables, sensors, and even circuitry parts. Prototypes made with the silver nanoparticle printer are already demonstrating how useful custom 3D-printed wiring can be on intricate medical devices.