When it comes to 3D printed folding research, we hear most often about projects inspired by origami. But as new research coming out of the Chinese Academy of Sciences shows, we shouldn’t discount the ancient Chinese art of kirigami, also known as jianzhi and paper-cuts, for 3D printed inspiration.
Kirigami involves cutting patterns into flat paper before folding into 3D shapes, and while artistically, this traditional art is used most often in ceremonies, festivals, and window decorations, it’s also found technological and scientific uses in designs for biomedical devices, micro- and nano-electromechanical systems (MEMS/NEMS), and solar arrays.
Recently, Dr. Li Jiafang, from the Academy’s Institute of Physics (IOP) and his collaborative team of researchers from the Academy, MIT, and the South China University of Technology applied kirigami to make a model for advanced 3D nanofabrication. The researchers were specifically inspired by a traditional kirigami design called “pulling flower,” and created their own direct nano-kirigami method to work at the nanoscale level with flat films.
The team recently published a paper, titled “Nano-kirigami with giant optical clarity,” in the journal Science Advances; co-authors include Zhiguang Liu, Huifeng Du from MIT, Li, Ling Lu, Zhi-Yuan Li from the South China University of Technology, and MIT’s Nicholas X. Fang. The Academy, the National Science Foundation of China, the Ministry of Science and Technology of China, the Chinese Scholarship Council, and multiple US government grants provided support for the study.
The abstract reads, “Kirigami enables versatile shape transformation from two-dimensional (2D) precursors to 3D architectures with simplified fabrication complexity and unconventional structural geometries. We demonstrate a one-step and on-site nano-kirigami method that avoids the prescribed multistep procedures in traditional mesoscopic kirigami or origami techniques. The nano-kirigami is readily implemented by in situ cutting and buckling a suspended gold film with programmed ion beam irradiation. By using the topography-guided stress equilibrium, rich 3D shape transformation such as buckling, rotation, and twisting of nanostructures is precisely achieved, which can be predicted by our mechanical modeling. Benefiting from the nanoscale 3D twisting features, giant optical chirality is achieved in an intuitively designed 3D pinwheel-like structure, in strong contrast to the achiral 2D precursor without nano-kirigami. The demonstrated nano-kirigami, as well as the exotic 3D nanostructures, could be adopted in broad nanofabrication platforms and could open up new possibilities for the exploration of functional micro-/nanophotonic and mechanical devices.”
The team cut a very precise pattern in a free-standing gold nanofilm with a focused ion beam (FIB), which was later used to slowly pull the nanopattern into a complex 3D shape. During FIB irradiation, both heterogeneous vacancies and the implanted ions introduced tensile and compressive stresses to induce these pulling forces within the nanofilm. The team was able to create several versatile 3D shape transformations in the nanostructures, like complex rotation, downward bending and upward buckling, and twisting, by taking advantage of the topography-guided stress equilibrium inside the nanofilm.
A theoretical model was also developed by the researchers, in order to further explain the dynamics at play during nano-kirigami fabrication. While previous studies focused more on intuitive designs, this model will allow other researchers to successfully design 3D nanogeometries based on desired optical functionalities.
Other functional kirigami device fabrication attempts mostly centered around realizing mechanical functions, instead of optical ones, and used complex sequential procedures. But this team’s new method for nano-kirigami can perform several optical functions, and only requires one fabrication step.
The researchers made a 3D structure not dissimilar to a pinwheel, with giant optical chirality, for a proof of concept. The nano-device, as explained by the Academy, was able to achieve “efficient manipulation of “left-handed” and “right-handed” circularly polarized light and exhibited strong uniaxial optical rotation effects in telecommunication wavelengths.”
This proof of concept was able to show a valid multidisciplinary connection between the nanomechanics and nanophotonics fields, which could be a precursor to a whole new direction for kirigami research. The team’s concept could lead to more broad nanofabrication platforms, and even be used to create complex optical nanostructures for biomedical, computation, MEMS/NEMS, and sensing devices.
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