Strategically placed cuts to structural films can create 3D nanostructures when force is applied to the films, similar to how kirigami cuts made to paper can create pop-up structures.
PHOTO: JENNIFER M. MCCANN/PENN STATE MRI

Enhancing the Japanese artform of origami, kirigami involves folding paper to create 3D structural designs by strategically incorporating cuts to the paper prior to folding.

“We used kirigami at the nanoscale to create complex 3D nanostructures,” says Daniel Lopez, Penn State Liang Professor of Electrical Engineering and Computer Science, and leader of the team that published this research in Advanced Materials. “These 3D structures are difficult to fabricate because current nanofabrication processes are based on the technology used to fabricate microelectronics which only use planar, or flat, films. Without kirigami techniques, complex three-dimensional structures would be much more complicated to fabricate or simply impossible to make.”

Lopez says that if force is applied to a uniform structural film, nothing really happens other than stretching it a bit, similar to when paper is stretched. But when cuts are introduced to the film, and forces are applied in a certain direction, a structure pops up. The geometry of the planar pattern of cuts determines the shape of the 3D architecture.

“By introducing minimum changes to the dimensions of the cuts in the film, we can drastically change the three- dimensional shape of the pop-up architectures,” Lopez says. “We demonstrated nanoscale devices that can tilt or change their curvature just by changing the width of the cuts a few nanometers.

“This kirigami technique will allow the development of adaptive flexible electronics that can be incorporated onto surfaces with complicated topography, such as a sensor resting on the human brain.”

Lopez will focus his future research on applying these kirigami techniques to materials that are one atom thick, and thin actuators made of piezoelectrics. His goal is to work with other researchers at Penn State’s Materials Research Institute (MRI) to develop a new generation of miniature machines that are atomically flat and more responsive to environmental changes.

“By incorporating ultra-thin piezo and ferroelectric materials onto kirigami structures, we will develop agile and shape-morphing structures. These shape-morphing micro-machines would be very useful for applications in harsh environments and for drug delivery and health monitoring.”

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Other authors on the study include Xu Zhang from Carnegie Mellon University and Haogang Cai from New York University, both former postdoctoral fellows with Lopez. Lior Medina and H. Espinosa from Northwestern University and Vladimir Askyuk from the National Institute of Standards and Technology also are part of the team. The research was supported by the U.S. Department of Energy.