A triboelectric nanogenerator coupled with internal and external friction for gesture recognition based on EHD printing technology

Surface charge density is a critical factor in determining the output performance of triboelectric nanogenerators (TENGs). However, enhancing the surface charge density is a relatively complex process characterized by high cost, fast charge dissipation, and inferior stability. Herein, a TENG with internal and external friction synergistic coupling enhancement that employed an electrohydrodynamic (EHD) printing technique for gesture recognition was proposed. Under the external force, the electrical performance of the triboelectric material could be improved via internal friction formed by the contact between the lines of silver nanowires (AgNWs) mixing with hydroxy propyl methyl cellulose (HPMC) (AgNWs (HPMC)) inside the tribolayer and the PDMS with microgrooves. The effects of dielectric layer thickness, micropore size, the number of micropore arrays, as well as the AgNWs content and the number of AgNWs (HPMC) lines on TENG output performance were analysed systematically. When the micropore arrays TENG (MA-TENG) size was 15 mm × 15 mm, the thickness of a dielectric layer was 240 µm, the number of micropore arrays was 36, and the number of AgNWs (HPMC) lines was 28, the charge transfer quantum of MA-TENG was 34.9 nC, which is about 5.8 times that of flat TENG. The peak power of the MA-TENG was 580 μW, which was about 10 times than that of the flat TENG. Finally, a self-powered gesture recognition was demonstrated successfully based on the developed MA-TENG and revealed its potential in the field of human-computer interaction. This work not only proposed a new method with the advantages of a simple process, low cost, and high output stability, to significantly increase the surface charge density, but also provided a new scheme for electronic skin and wearable devices.