Femtosecond-Laser Direct Writing based Laser-Induced-Graphene (LIG) on Wooden Materials for Green Electronics Applications

The importance of environmental sustainability has been on the rise, as issues like climate change and pollution continue to affect the planet. One area that has been heavily impacted by this trend is electronics manufacturing. In order to reduce the environmental impact of electronics production, researchers and engineers have been working to develop new materials and processes that are eco-friendly. One promising area of research is the development of green electronics, which use materials and manufacturing processes that are sustainable and environmentally friendly. To achieve green electronics, it is necessary to use precursors that are organic, inexpensive, and readily available. Additionally, the synthesis route must be economical and fast, and the resulting electronic materials must be suitable for low-cost manufacturing processes. Furthermore, the devices produced using these materials must be biocompatible and biodegradable. These criteria can be difficult to meet, but one class of materials that shows promise is wood-based materials. Wood is a renewable resource that is abundant, recyclable, and biodegradable. However, it is not a conductor, which limits its use in electronics. To overcome this limitation, researchers have been working on various methods for adding conductivity to wood such as carbonization or conducting materials coating. One of the most promising approaches is Laser-Induced-Graphene (LIG) formation technology, which was first introduced by the James Tour group in 2017. This technology uses Laser-Direct-Writing (LDW) to create graphene patterns on a variety of lignocellulosic materials, including paper, cork, potato skins, coconut shells, and leaves. Our group has confirmed that 3D porous LIG can be easily and quickly produced on wooden materials without special treatment in the air by ultrashort pulse laser irradiation. In this work, we report on high-quality Laser-Induced-Graphene formation on wooden materials in ambient air for green electronics applications using a femtosecond laser with a 1040 nm wavelength, 250-fs pulse width, and 200 kHz repetition rate. A Galvano scanner with a maximum 2,000 mm/s scanning speed is used for laser patterning. Various combinations of beam scanning speeds, laser power, and beam-line spacings are delivered onto natural and recycled wooden materials to optimize LIG quality. The lowest sheet resistance of LIG electrode achieved is 2.8 Ω/sq., and its properties are analyzed using scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. The LIG electrodes are applied for green electronics in smart homes or smart furniture, such as heaters, temperature sensors, and touch sensors. Furthermore, we demonstrate that interconnecting LIG electrodes can be made by irradiating the laser after physically combining two different wood blocks without any special chemical treatment. Additionally, the LIG touch sensor can easily control the heater and computer by synchronization. These technologies can be easily adapted to smart green homes or smart green furniture applications.