Suppose that you had to build a tiny spring, antenna or other structure for use in a microelectronic device such as a biomedical implant… how might you go about doing it? Well, a new 3D printing technique developed at Harvard University would certainly make the process easier. It allows people to essentially draw minuscule metal items in mid-air.
Created at Harvard's Wyss Institute for Biologically Inspired Engineering and the John A. Paulson School of Engineering and Applied Sciences, the technology incorporates an ink composed of silver nanoparticles.
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That ink is extruded through a tiny glass nozzle along x, y and z axes. Although it's initially in a gel-like form, it's hit by a laser almost as soon as it comes out, the heat causing the silver to harden into a solid. The spacing between the nozzle and the laser is crucial. If they're too far apart, the strand of ink will sag before it hardens – if they're too close together, the laser will heat the nozzle itself, causing the ink to solidify within it.
As it is, though, the result is free-standing three-dimensional structures made from electrically-conductive silver nanowires that are thinner than the width of a human hair. These can take on whatever shape is programmed into the printer – as can be seen above, they can even be made to look like butterflies.
The research was led by Prof. Jennifer Lewis, and is described in a paper that was published today in the journal Proceedings of the National Academy of Sciences. The process can be observed in the following video.