3D printing of PVDF-based piezoelectric nanogenerator from programmable metamaterial design: Promising strategy for flexible electronic skin

The high-performance piezoelectric nanogenerator (PENG) with good flexibility, tunability and sensitivity is desirable for the next-generation of wearable electronics. However, the 3D printing of unique architectures and arbitrary shapes could endow the conformal electronic sensors with excellent flexibility and functionality. In this work, the self-poled PENG were successfully fabricated by incorporating the oriented ionic salt-montmorillonite (IS-MMT) co-fillers into poly (vinylidene fluoride) (PVDF) matrix and then performing 3D printing. This hence could give the 3D printed PENG the locked interfacial piezoelectric polarization. More importantly, the self-adaptive conformal PENG based on auxetic metamaterial has also been developed, which is beyond the practicability of the traditional 2D PENG. The effect of various architectures of the metamaterial on the mechanical and piezoelectric responses was particularly discussed. The tailoring of the 3D printed cell with metamaterial of serpentine geometries shows the appealing advantages of high sensitivity to structure variation, thus being beneficial for easier regulation of piezoelectric output. When mounted on the joints as a wearable healthcare monitoring device, this 3D printed PENG could accurately detect the movement of muscles, demonstrating its potential in motion tracking and sign-language interpretation. Obviously, this work could provide a new idea for design and fabrication of programmable wearable electronics.