3D Printing of Polyvinylidene Fluoride and Layered MoS₂ Composites for Piezoelectric Sensing

Flexible and stretchable piezoelectric sensors have numerous applications in wearable electronics, healthcare, and structural health monitoring. Most of them are made from piezoelectric polymer materials such as polyvinylidene fluoride (PVDF) and it's copolymers that have limited piezoelectric response. Recent discoveries in two-dimensional materials as high-performance piezoelectric materials provide a promising route to formulating novel composites for sensors and actuators. Here, we develop nanocomposites using PVDF and layered molybdenum disulfide (MoS₂) into 3D printable, stretchable, and flexible piezoelectric sensors. Ink is formulated by distributing layered MoS₂ into PVDF by high-power vacuum mixing to achieve desired rheological properties for direct ink writing (DIW) 3D printing. We harness the shear stress-induced PVDF dipole mechanical poling and nanomaterial alignment during DIW printing for piezoelectric sensitivity enhancement. A remarkable 87.5% improvement in piezoelectric coefficient is achieved in 3D printed PVDF compared with casted samples. Furthermore, we observe enhancement up to 8.1 and 4.3 times increment in the piezoelectric coefficient for nanocomposites with 8 wt% MoS₂ loading over casted and 3D printed neat PVDF. We thoroughly examine the piezoelectric response enhancement of PVDF by β phase enhancement mechanism as a function of MoS₂ fraction as well as the heterogeneous strain distribution in PVDF-MoS₂ nanocomposite via numerical simulations. In this presentation, we will discuss the experimental analysis and its mechanistic study along with the piezo sensor performance from 3D printed MoS₂-PVDF composite.