3D Printing Optical Illusions at the Nanoscale

Cytosurge is a spin-off company from ETH Zurich, and it has become known for its FluidFM 3D printing technology, which was commercialized and made consumer-friendly via the FluidFM 3D printer. FluidFM is a metal 3D printing technique capable of creating components at the nano level. It involves a moveable pipette, mounted on a cantilever leaf-spring, through which a liquid metal solution flows and exits through an aperture of 300 nanometers. An electrode produces a voltage under the aperture, which solidifies the metal as it exits the nozzle. Once the gap between the surface and the pipette is filled with solid metal, the pipette moves to the next position and repeats the process. In this way a 3D object is built.

FluidFM technology has been applied to many applications, from metal nanoprinting to medical research, and now it has been applied to something new: so-called impossible objects. Not to be confused with the company Impossible Objects, an impossible object is an optical illusion of a two-dimensional object that is interpreted by the viewer as a 3D image. It also appears to have an entirely different shape when viewed from different perspectives. The drawings of M.C. Escher are examples of such objects, and now Professor Kokichi Sugihara, a mathematical scientist at Meiji University, has found a way to 3D print these objects, using FluidFM technology.

Sugihara has a long history in mathematical engineering, having received a Bachelor, Master and Doctor of Engineering from the University of Tokyo. He worked at the Electrotechnical Laboratory in the Ministry of International Trade and Industry of Japan, Nagoya University and the University of Tokyo before moving into his current position at Meiji University. He has done a lot of work with computer vision, and that work led him to experimentation with impossible objects or impossible solids.

“A trompe l’oeil, referring to an art genre, is painted by using optical illusions,” Sugihara explains. “One day, I tried to confirm if my software determines that it is impossible to construct solids from stereoscopic objects depicted in a trompe l’oeil. Unexpectedly, the software reconstructed solids that we never could imagine are possible through human eyes. This interesting result inspired me to create ‘impossible solids’. We visualize a 3D object from a 2D drawing based on the preconceived assumption that is obtained through common sense and visual experience. The stereoscopic objects in the trompe l’oeil are painted by exploiting these preconceived assumptions and appear unlikely to our eyes to exist. However, the computer is not influenced by any assumption. The computer examines every possibility in order to reconstruct a 3D object and concludes that it is ‘Able to do it.’ I applied this theory also to create impossible motion.”

Sugihara won the Best Illusion of the Year contest three times, and finished in second place twice. Now he has teamed up with Cytosurge to 3D print one of those illusions, in three nanoscale sizes: 0.1 mm diameter, 0.03 mm and 0.01 mm, or the size of a red blood cell. The tiny objects were 3D printed from copper. The objects have been imaged at high resolution with an electron microscope, and you can see the illusion from different angles below:

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