Low-Defect Laser-Induced Graphene from Lignin for Smart Triboelectric Touch Sensors

Laser-induced graphene (LIG) has emerged as a versatile carbon material for broad applications. However, the synthesis of high-quality LIG materials, especially with low defects, remains underexplored. This study was thus focused on developing a facile and cost-effective alternative to producing low-defect LIG, especially using lignin as a renewable precursor. The results showed that lignin treated by methyl ethyl ketone yielded LIG with a markedly low-defect level (I-D/I-G ratio of 0.12) by direct laser writing under ambient conditions. The triboelectric tactile sensor fabricated from low-defect LIG electrodes exhibited exceptional durability (over 15,000 cycles), accurate and real-time responsiveness (<0.01 s), wide-ranged touch frequencies (1-6 Hz), and ultrasensitivity to pressure (5-300 kPa). Moreover, the sensor was successfully demonstrated for the wireless control of LEDs. This work indicated that lignin-derived low-defect LIG has great potential for smart electronics applications.