Physicists at the Technical University of Denmark (DTU) are bringing Christmas cheer by breaking the smallest record ever using a 3D nanolithography tool called Nanofrazor. The tune they “taped”, no less in full stereo: the first 25 seconds of “Rocking Around the Christmas Tree”.
“I’ve been into lithography for 30 years, and even though we’ve had this machine for a while, it still feels like science fiction,” said Peter Bøggild, a physicist at DTU. “To give you an idea of the scale we’re working on, we could use this thing to put our signatures on a red blood cell. The most radical thing is that we can create freeform 3D landscapes with this crazy resolution.”
As early as 2015, the same DTU group created a microscopic color image of the mona lisa, around 10,000 times smaller than Leonardo da Vinci’s original painting. To do this, they created a nanoscale surface structure consisting of rows of columns covered by a 20 nm thick layer of aluminum. How much a column was deformed determined the colors of light that was reflected, and the deformation in turn was determined by the intensity of the pulsed laser beam. For example, weak pulses deformed the columns only slightly, producing blue and violet tones, while strong pulses deformed the columns significantly, producing orange and yellow tones. The resulting image fits in a space smaller than the footprint occupied by a single pixel on an iPhone Retina display.
The DTU physics group acquired the Nanofrazor to sculpt precisely detailed 3D nanostructures quickly and relatively cheaply. The Christmas platter was simply a fun holiday project for postdoc Nolan Lassaline to demonstrate the ability to sculpt a surface with nanoscale precision. Rather than adding material to a surface, the Nanofrazor precisely removes material to mold the surface into the desired pattern or shape — a sort of greyscale nanolithography.
“The Nanofrazor was used as a lathe to cut vinyl records – it converted an audio signal into a spiral groove on the surface of the medium,” said Bøggild, who is also an amateur musician and vinyl record enthusiast. “In this case, the medium is a different polymer than vinyl. We even encoded the music in stereo – the sideways shake is the left channel while the depth modulation contains the right channel. It can be too impractical and expensive to be a hit. Reading the groove requires a fairly expensive atomic force microscope or the Nanofrazor, but it’s definitely doable.”
The initial goal is to use the Nanofrazor to develop novel magnetic sensors that are able to record the currents in living brains. Lassaline plans to create “quantum soap bubbles” in graphene in hopes of discovering new ways to precisely manipulate the electrons in this and other atomically thin materials. “The fact that we can now accurately shape the surfaces with nanoscale precision and pretty much at the speed of our imaginations is a game changer for us,” said DTU physicist Tim Booth. “We have many ideas about what to do next and believe that this machine will greatly speed up the prototyping of new structures.”