With the increasing demand for wearable electronics, energy harvesting technologies have been developed by utilizing waste energies to supplement traditional power sources. Triboelectric nanogenerator (TENG) is a promising energy harvesting technology owing to its low cost, extensive material availability, simple design, and high output voltage. Based on the coupling effect of contact electrification and electrostatic induction, TENG can efficiently convert irregular mechanical energy into electricity. However, the triboelectric charge transfer process is significantly hindered in a humid environment owing to the charge neutralization with ions in water. Besides, high-permittivity triboelectric layers, which are developed for high surface tribo-charge density by introducing a second phase, are always accompanied by increasing dielectric loss, limiting the further improvement of or even reducing electric output. This study mainly focuses on material modification techniques for efficient, stable, and humidity-resistant tribo-charge transfer, which are of vital significance to obtain high-performance wearable TENGs for power supply and active sensing.

To eliminate the negative effect of humidity on triboelectric charge transfer, a bulk-phase fluorinated polydimethylsiloxane (PDMS) sponge (FPS)-based TENG (FPS-TENG) was developed. Both the sponge structure and the fluorine-terminated surface are intrinsically hydrophobic due to the air-trapping capacity of the porous structure and the low surface free energy of fluorine, respectively, endowing the FPS surface with nearly superhydrophobicity (water contact angle: 147.1°) and making the FPS-TENG humidity-resistant. Fluorine possesses a strong electron affinity, increasing charge transfer in contact electrification and improving electric output. Furthermore, fluorination performed on the sponge-structure dielectric enables bulk-phase modification; therefore, the increased electron affinity is stable under mechanical abrasion. The FPS-TENG delivers a maximum power density of 0.89 W m^-2, and the output voltage remains almost 90% under high relative humidity (85% RH) and heavy abrasion (1-mm-thick surface layer worn away). In addition, the FPS-TENG demonstrates the promising potential for self-powered sensing with high sensitivity (181.6 V kPa^-1). The notable sensitivity originates from the excellent deformability of the sponge structure, which provides a higher increment rate of the actual contact area before saturation as the external applied force increases compared with a solid structure.

In the second work, a triboelectric layer with improved relative permittivity and suppressed dielectric loss was developed via matrix–filler interface design. An amorphous carbon layer was coated onto the silver nanofiller to suppress dielectric loss of the triboelectric layer. The significant reduction in dielectric loss results from the unique characteristics of the amorphous C shell. Its low surface free energy enables the homogeneous distribution of silver fillers inside the PDMS matrix. Its moderate permittivity eliminates the permittivity mismatch between the filler and the matrix, resulting in a uniform local electric field at the interface. Additionally, its low conductivity prevents the formation of conducting channels. The mechanism behind the suppressed dielectric loss is investigated using finite element simulation. The triboelectric layer achieves a 50% decrease in dielectric loss and a 2.6-fold increase in relative permittivity. Consequently, a 302% increase in output current is achieved by the triboelectric layer enhanced TENG (TLE-TENG). Moreover, a wearable TLE-TENG was developed by pairing the enhanced triboelectric layer with a highly conductive flexible electrode. Self-powered sensing prototypes were realized with the flexible TLE-TENG, demonstrating extensive application scenarios for active sensing.

This thesis investigates high-performance wearable TENGs both experimentally and theoretically. Bulk-phase functionalization and dielectric loss manipulation were performed to optimize the triboelectric performance of wearable TENGs. In addition, the theoretical analysis was performed to understand the mechanism behind the performance improvement. This work is of great significance for the development of wearable self-powered systems, which can use low-frequency human motion for power supply and active sensing.