Kirigami-processed cellulose nanofiber films for smart heat dissipation by convection

Abstract

Heat dissipation has become increasingly important in electronics. Conventional convection cooling systems have significant material and dimensional constraints, and they have difficulty meeting the heat dissipation, miniaturization, and flexibility requirements of next-generation smart electronics. Here, we used kirigami (the traditional art of paper cutting) with a thermally conductive cellulose nanofiber film to propose a flexible cooling system through convective heat dissipation. By stretching the Amikazari (net decoration) pattern produced by kirigami and allowing air convection through its aperture at 3.0 m/s, the thermal resistance was reduced to approximately one-fifth of that without kirigami and convection. The kirigami apertures defined the outlet air velocity, resulting in a significant increase in the heat-transfer coefficient. Our kirigami heat dissipation concept enables the design of electronics using a variety of film materials as shape-variant cooling structures, which will inspire a wide range of thermal engineering and electronics applications.

Elastocaloric Kirigami Temperature Modulator

“…The programmable kirigami designs can provide ultrahigh stretchability and flexibility not only to papers but also to rigid materials, which reveals a variety of engineering opportunities in the fields of electronics and materials science. [ 22–30 ] Although many kirigami patterns are possible, [ 31 ] in this study, we focus on the simple design consisting of periodically displaced multiple slits in a rectangular sheet (Figure 1b). Here, we show that elastocaloric materials with the kirigami structure exhibit focused heat release and absorption simultaneously due to nonuniform internal stress, and the cooling and heating distributions can be tuned by cutting patterns, which cannot be realized if a plain (referred to as “unpatterned” hereinafter) elastocaloric material is stretched.…”

“…The programmable kirigami designs can provide ultrahigh stretchability and flexibility not only to papers but also to rigid materials, which reveals a variety of engineering opportunities in the fields of electronics and materials science. [22][23][24][25][26][27][28][29][30] Although many kirigami patterns are possible, [31] in this study, we focus on the simple design consisting of periodically displaced multiple slits in a rectangular sheet (Figure 1b). Here,…”

Thermal Diffusion Films with In-Plane Anisotropy by Aligning Carbon Fibers in a Cellulose Nanofiber Matrix

“…Recently, thin and flexible paper-like electronic devices have been developed. − As their performance improves, the problem of heat exhaustion will become more serious. Because thin devices cannot be equipped with conventional bulky heat sinks, thermal diffusion to the substrate and convective heat dissipation by kirigami processing are considered to be promising for cooling the devices. Thermal diffusion through the substrate in contact with the heat-generating device is the most important method for heat dissipation, and thus it is essential to improve the thermal conductivity of the substrate material in the in-plane direction .…”

Resilient Mechanical Metamaterial Based on Cellulose Nanopaper with Kirigami Structure

“…We evaluate the mechanical resilience by the residual strain. The results reveal the dependence on the maximum strain and the number of iterations in the tensile test, which has not been addressed in the only existing study of Kirigami on nanopaper which focuses on the specific functionality of heat dissipation [ 35 ]. Whereas the existing reports on the mechanical properties of nanopapers are rather focused on the stiffness, we report the new aspect of mechanical characteristics.…”