We are developing sustainable flexible electronics from waste coffee powder (WCP) using femtosecond laser-induced graphene (fs-LIG) technology.

A femtosecond laser directly converts waste coffee powder into porous and conductive graphene-like structures, which are then integrated into flexible sensors through PDMS packaging. The fabricated sensors provide both bending and pressure sensing capabilities, enabling real-time monitoring of robot joint motion and gripper force.

This approach combines biowaste upcycling, laser manufacturing, and flexible sensing, providing an eco-friendly platform for smart robotic and industrial monitoring systems.

(In collaboration with Prof. Young-Jin Kim's group at KAIST, and Prof. Liandong Yu's group at China University of Petroleum.)

We fabricate metal-doped LIG by drop-casting a small amount of metal solution onto wood surfaces followed by fs laser irradiation.

Metal-doped LIG is applied as a green gas sensor, demonstrating rapid detection of CH₄, NH₃, CO, and NO₂ gases. By integrating a CNN-based machine learning algorithm, we enhance gas classification accuracy and improve detection precision.

This technology has been validated for applications in wildfire monitoring and gas detection from fertilizers.

(In collaboration with Prof. Young-Jin Kim's group at KAIST, and Prof. Inkyu Park’s research group at KAIST.)

We are developing a sustainable and eco-friendly fabrication process for metal-doped LIG. 

In this approach, metal powder is evenly spread over pre-fabricated LIG using a brushing technique, followed by a second laser irradiation step to achieve metal doping.

This method eliminates chemical waste as the excess metal powder can be fully recycled. Additionally, it requires minimal additional processing, enabling a fast and efficient metal doping process.

The resulting metal-doped LIG has been demonstrated for applications in gas sensors and triboelectric nanogenerators (TENGs).

(In collaboration with Prof. Inkyu Park’s research group and Seunghwa Ryu's research group at KAIST.)

We precisely irradiate fs laser on wood surfaces to create hydrophobic LIG electrodes.

This technology enables the development of an eco-friendly, multifunctional hydrophobic roofing system that is water-resistant, facilitates rapid drying of surrounding wood, and provides de-icing capabilities.

Additionally, we integrate LIG electrodes onto glass substrates by applying polyimide (PI) tape to glass surfaces and irradiating them with UV ns lasers. Once the tape is removed, a transparent glass-based electrode is formed.

This innovative approach is applied to temperature sensing, defogging, and solar light absorption, creating an efficient sunlight absorber that enhances heat retention while maintaining clear visibility.

We are developing carbon electrodes by irradiating fs laser to the natural wood and plywood (recycled wood) and applying them to smart home technologies.

When fs laser pulses are applied to wood, the existing molecular bonds break, combusting other materials while leaving behind carbon. This remaining carbon reorganizes into aromatic carbon rings, forming laser-induced graphene (LIG)—a three-dimensional porous carbon electrode.

Utilizing LIG electrodes, we aim to develop heaters, temperature sensors, alternative electrical wiring, boilers, and touch sensors, contributing to the realization of a green smart home.