Multi-material 3D printing of piezoelectric and triboelectric integrated nanogenerators with voxel structure

Flexible and highly filled piezoelectric nanogenerators with excellent performance play an indispensable role in portable electronic devices, while the bottlenecks are hard to improve the polarization efficiency and prepare three-dimensional (3D) amplifying effect structure. Compared with other typical 3D printing technologies, direct ink writing multi-material printing (DIW-M3D), can extrude multiple viscoelastic ink materials with a wide selection of materials, which has the advantage of integrated multi-material processing. However, there are fewer reports on the use of DIW-M3D technology to print functional composite materials. Inspired from Lego block structures, we utilized DIW-M3D technology to prepare fabrications with alternating arrangements of piezoelectric and conductive inks between layers. This voxel-isolated conducting network provided the superior polarization path and uniform distribution of polarization field, which sharply ameliorate the piezoelectric effect and output performance. Owing to this voxel-isolated structure, the V_OC and I_SC could reach 150 V and 16 µA respectively, with the jumping movements of the forefoot. This work paved a path of scale-up preparing piezoelectric devices with 3D amplification effect structure and enhanced the polarization efficiency of the devices.