Danish physicists give the gift of world’s smallest Christmas record—in stereo

"Nanofrazor" cuts tiny single with first 25 seconds of “Rocking Around the Christmas Tree”

Physicists at the Technical University of Denmark (DTU) are bringing the Christmas cheer by using a 3D nanolithography tool called the Nanofrazor to cut the smallest record ever. The tune they "recorded," in full stereo no less: the first 25 seconds of "Rocking Around the Christmas Tree."

”I have done lithography for 30 years, and although we’ve had this machine for a while, it still feels like science fiction," said Peter Bøggild, a physicist at DTU. "To get an idea of the scale we are working at, we could write our signatures on a red blood cell with this thing. The most radical thing is that we can create free-form 3D landscapes at that crazy resolution.”

Back in 2015, the same DTU group created a microscopic color image of the Mona Lisa, some 10,000 times smaller than Leonardo da Vinci's original painting. To do so, 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 which colors of light were reflected, and the deformation in turn was determined by the intensity of the pulsed laser beam. For instance, low-intensity pulses only deformed the columns slightly, producing blue and purple tones, while strong pulses significantly deformed the columns, producing orange and yellow tones. The resulting image fit in a space smaller than the footprint taken up by a single pixel on an iPhone Retina display.

The DTU physics group acquired the Nanofrazor in order to sculpt precisely detailed 3D nanostructures quickly and relatively cheaply. The Christmas record was simply a fun holiday project for postdoc Nolan Lassaline to demonstrate the capability of shaping a surface with nanoscale precision. Instead of adding material to a surface, the Nanofrazor precisely removes material to sculpt the surface into the desired pattern or shape—a kind of gray-scale nanolithography.

"The Nanofrazor was put to work as a record-cutting lathe—converting an audio signal into a spiralled 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 lateral wriggles is the left channel, whereas the depth modulation contains the right channel. It may be too impractical and expensive to become a hit record. To read the groove, you need a rather costly atomic force microscope or the Nanofrazor, but it is definitely doable.”

The initial goal is to use the Nanofrazor to develop new kinds of magnetic sensors capable of detecting the currents in living brains. Lassaline plans to create "quantum soap bubbles" in graphene in hopes of discovering new ways of precisely manipulating the electrons in that and other atomically thin materials.  “The fact that we can now accurately shape the surfaces with nanoscale precision at pretty much the speed of imagination is a game changer for us," said DTU physicist Tim Booth. "We have many ideas for what to do next and believe that this machine will significantly speed up the prototyping of new structures."

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