Environment-Friendly Triboelectric Nanogenerator Based on 3D-Printed Nanocellulose Films for Human Motion Monitoring

Triboelectric nanogenerators (TENGs) have drawn much interest in self-powered sensors or wearable electronics, particularly those based on nanocellulose (NC) films fabricated by manual casting. Herein, we introduce the 3D-printing technique to directly 3D-print (3DP) NC suspension on polycarbonate substrates, followed by cleanroom drying (relative humidity: 45%; temperature 25 °C). The 3DP NC films show high flexibility, transparency, a tensile strength of 139.92 ± 5.3 MPa, a Young’s modulus of 5.74 ± 0.32 GPa, and a strain at break of 6.13 ± 0.15%, much higher than manually cast NC films (tensile strength: 66.29 ± 8.12 MPa; Young’s modulus: 4.02 ± 0.11 GPa; strain at break: 2.42 ± 0.09). Eco-friendly 3DP NC films, without surface modification, are used to fabricate 3DP-NC-TENGs, demonstrating output powers of 16.85 μW at 20 Hz and significantly higher outputs of 19.4 μW at the same frequency, surpassing previously reported manually cast NC film-based TENGs. Finally, the 3DP-NC-TENG is applied as a self-powered sensor that demonstrates stable and sustainable performances across various human motion monitoring, such as walking (4.38 V), jumping (26.7 V), and finger tapping (9.4 V). 3D-printing technology can be preferred over traditional manual casting methods for fabricating environmentally friendly and high-performance NC-based TENGs.