For creating 3D microstructures and nano tools, Kirigami cuts can be used.
Paper snowflakes, children’s pop-up books and artful paper maps are not for hobbyists alone.
To build a nifty alternative to 3D printing, a team of engineers at Northwestern University is using concepts from the art of paper folding.
Kirigami comes from the Japanese words ‘kiru’ (to cut) and ‘kami’ (paper) and is a traditional art form in which paper is precisely cut and transformed into a 3D model. By drawing inspiration from the practice, engineers may create a wide range of complex structures using thin layers of material and software that selects accurate geometric cuts.
A study paper published in 2015 showed promise for the “pop-up” fabrication model of Kirigami.
The ribbon-like structures produced by the cuts were open shapes in this iteration, with minimal capacity to achieve closed shapes. Other study, based on the same inspiration, mainly shows that with simple materials such as paper, kirigami can be implemented on a macro scale.
But in the journal Advanced Materials, new research published Dec. 22, 2020, takes the process a step further.
Horacio Espinosa, a professor of mechanical engineering at the McCormick School of Engineering, said his team was able to apply nanostructures to the principles of design and kirigami.
The research was led by Espinosa, and James N. and Nancy J.
Farley, Professor of Entrepreneurship and Manufacturing.
“By combining nanomanufacturing, in situ microscopy experiments and computer modeling, we have unraveled the rich behavior of kirigami structures and identified conditions for their use in practical applications,” Espinosa said.
Using state-of-the-art semiconductor manufacturing techniques and carefully positioned “kirigami slices” on ultra-thin films, researchers are beginning to create 2D structures. Structural instabilities induced by residual stresses in the films then generate well-defined 3D structures.
In a variety of applications, engineered kirigami structures could be used, from microscale grippers (e.g. holding cells) to spatial light modulators to flow control in aircraft wings.
These capabilities place the technology in biomedical devices, energy storage, and aerospace for future applications.
Usually, the number of shapes with a single kirigami motif that can be produced is limited.
However, the team was able to illustrate the bending and twisting of the film by varying the cuts, resulting in a wider range of shapes, including both symmetrical and asymmetrical configurations.
For the first time, researchers showed that microscale structures with film thicknesses of tens of nanometers can achieve unusual 3D shapes and exhibit wider functionality.
Electrostatic micropincers, for instance, snap shut, which for soft samples can be very uncomfortable.
In comparison, tweezers based on kirigami can be designed to control gripping force accurately by changing the degree of stretch.
It is possible to design intersections and model structural actions based on computer simulations in this and other applications, reducing trial and error and saving time and money.
Espinosa says that, as the research progresses, his team aims to explore the large space of Kirigami designs, including array configurations, to achieve a greater number of potential functionalities.
Embedding distributed actuators for Kirigami deployment and control is another field for future study.
As the technology is further explored, the team claims that kirigami can be used in architecture, aerospace, and environmental engineering.
By Xu Zhang, Lior Medina, Haogang Cai, Vladimir Aksyuk, Horacio D. Reference, ‘Kirigami Engineering-Nanoscale Structures Exhibiting a Variety of Controllable 3D Configurations’
Espinosa, Advanced Materials.DOI: 10.1002/adma.202005275, and Daniel Lopez, Dec. 22, 2020.
The U.S. sponsored the paper, “Kirigami engineering: nanoscale structures exhibiting a range of controllable configurations,”
Energy Department (contract number DE-AC02-06CH11357).
Espinosa and Penn State’s David Lopez are the co-first authors.