Photo-patternable and transparent films using cellulose nanofibers for stretchable origami electronics

Abstract

Substantial progress in flexible or stretchable electronics over the past decade has extensively impacted various technologies such as wearable devices, displays and automotive electronics for smart cars. An important challenge is the reliability of these deformable devices under thermal stress. Different coefficients of thermal expansion (CTE) between plastic substrates and the device components, which include multiple inorganic layers of metals or ceramics, induce thermal stress in the devices during fabrication processes or long-term operations with repetitions of thermal cyclic loading-unloading, leading to device failure and reliability degradation. Here, we report an unconventional approach to form photo-patternable, transparent cellulose nanofiber (CNF) hybrid films as flexible and stretchable substrates to improve device reliability using simultaneous electrospinning and spraying. The electrospun polymeric backbones and sprayed CNF fillers enable the resulting hybrid structure to be photolithographically patternable as a negative photoresist and thermally and mechanically stable, presenting outstanding optical transparency and low CTE. We also formed stretchable origami substrates using the CNF hybrid that are composed of rigid support fixtures and elastomeric joints, exploiting the photo-patternability. A demonstration of transparent organic light-emitting diodes and touchscreen panels on the hybrid film suggests its potential for use in next-generation electronics.

Ultraflexible and Lightweight Bamboo‐Derived Transparent Electrodes for Perovskite Solar Cells

“…The b‐CNF/IZO electrodes show a tensile strength of 230 MPa and Young's modulus of 7.3 GPa. Figure b exhibits the comparison of the b‐CNF/IZO electrodes with other reported results . The b‐CNF/IZO electrodes show better mechanical properties than other reported CNF films and plastic films.…”

“…It is worthy of noting that the square resistance of the b‐CNF/IZO electrode keeps well after more bending cycles. It could illustrate that the b‐CNF/IZO electrode exhibits a better mechanical durability, which attributes to a better Young's modulus . Furthermore, we compare mechanical durability of b‐CNF/IZO electrodes with other reported biomass‐based wearable flexible electrodes (Table S1, Supporting Information).…”

Smart Sensing Systems Using Wearable Optoelectronics

“…j) The schematic illustrations of a rigid‐soft hybrid structure for providing mechanically stable forms. c,j) Reproduced with permission . Copyright 2016, Springer Nature.…”

“…The conventional, singular cellulose nanofiber film has a high Young's modulus (>100 GPa), and it is hard to form complex, fine designs and is limited in mechanical deformations. Ji et al described a cellulose nanofiber–epoxy hybrid film that was fabricated using the electrospinning method, as shown in Figure c . The fabricated hybrid film overcomes various constraints and can be applied to complex, fine designs with mechanical resistance in bending (10 000 cycles at a 0.5 mm bending radius) and a stretching test (<50% stretching).…”

Research on flexible display at Ulsan National Institute of Science and Technology

“…These designs are based on engineered substrates that are composed of materials with different values of elastic modulus. [9][10][11] These "engineered substrates" can be designed to manipulate the distribution of mechanical strain by patterning the rigid regions to take advantage of the huge difference in elastic modulus, as shown in Fig. 3a.…”