Direct Laser Writing of Laser-Induced-Graphene (LIG) on Recycled Wood for Smart Furniture Applications

About 30% of the earth's land is covered by forests, which are mostly composed of trees. As such, wood is naturally abundant and inexpensive; thus, it has been used for a variety of purposes, including furniture, paper, buildings, and vehicles for thousands of years. Today, it is mainly utilized in thermal power plants as a fuel material. Recently, strong interest in green technology has risen around the world, so extensive studies are being conducted on transparent wood formation and wood-based carbonization filter production. Since recycling is more spotlighted for carbon naturalization to save the earth, the global wood recycling market also keeps expanding. However, the key applications of recycled wooden biomass or waste woods have been limited to manufacturing the packaging boxes, fuel biochips for cogeneration plants, fertilizers, and synthetic woods. Biochip production is the largest portion of the wood recycling market, but substitute renewable energy sources, such as solar power, wind power, and tidal power technologies are being actively developed. Therefore, more attractive wood recycling technology needs to be developed. Direct laser writing of Laser-Induced-Graphene (LIG) is considered as one of the technology candidates for taking eco-friendly and economical benefits of waste woods into new markets. Our group reported that high-quality three-dimensional porous multilayer graphene can be formed by illuminating femtosecond laser pulses in ambient air without additional fire-retardant treatment or an inert gas environment. Here, we report femtosecond-laser-direct-writing (FsLDW) of LIGs on recycled waste wood for realizing smart furniture. We tested the LIG formation on particleboards, medium-density fiberboards, and oriented strand boards, as the recycled wood examples. Ytterbium-doped fiber femtosecond laser with a 250-fs pulse duration, a 1040 nm center wavelength, and a 200 kHz repetition rate was used as the light source with a beam-scanning Galvano scanner with a maximum scanning speed of 2.0 m/s. Various combinations of laser power, wavelength, and beam scanning speeds were delivered onto the recycled wood samples for optimizing the LIG quality then monitored the resulting chemical composition and electrical conductivity. A low sheet resistance of 5.8 Ω/sq was attained on a medium density fiberboard; this is the best value to our best knowledge. A series of chemical composition tests, including SEM (Scanning Electron Microscope), TGA (Thermogravimetric analysis), XRD (X-ray diffraction), XPS (X-ray Photoelectron Spectroscopy), and Raman spectroscopy were performed, which confirmed the successful graphene formation. This LIG electrode will be applied to a joule heating-based heater for a stove warmer on a dining table application, a pulse sensor installed on chair armrests, and power switches without electrical metal-wire interconnects for green and smart furniture applications