Isotropic Paper Directly from Anisotropic Wood: Top-Down Green Transparent Substrate Toward Biodegradable Electronics.

Flexible electronics have found useful applications in both the scientific and industrial communities. However, substrates traditionally used for flexible electronics, such as plastic, cause many environmental issues. Therefore, a transparent substrate made from natural materials provides a promising alternative because it can be degraded in nature. The traditional bottom-up fabrication method for transparent paper is expensive, environmentally unfriendly, and time-consuming. In this work, for the first time, we developed a top-down method to fabricate isotropic, transparent paper directly from anisotropic wood. The top-down method includes two steps: a delignification process to bleach the wood by lignin removal and a pressing process for removing light-reflecting and -scattering sources. The resulting isotropic, transparent paper has high transmittance of about 90% and high haze over 80% and is demonstrated as a nature-disposable substrate for electronic/optical devices. Adjusting the pressing ratio used changes the density of the resulting paper, which tunes the microstructure-related properties of the isotropic, transparent paper. This top-down method is simple, fast, environmentally friendly, and cost-effective, which can greatly promote the development of paper-based green optical and electronic devices.