Electromechanical Performance and Figure of Merit Optimization for Flexible Lead-Free PDMS-BaTiO ₃ Piezocomposites

In the modern era of the Internet of Things, the potential role of flexible piezoelectric generators (PEG) reflects the rapid increase in self-powered devices and wearable technologies. In this study, a casting process to elaborate the polydimethylsiloxane (PDMS)/barium titanate (BaTiO ₃) composite has been presented. The addition of 15 wt % BaTiO ₃ microparticles into the PDMS polymer greatly enhances the piezoelectric coefficient (d ₃₁ = 24 pC N^-1), leading to an increased output voltage of approximately 4 V under finger tapping force. The proposed flexible microgenerator yielded an excellent piezoelectric figure of merit (FoM ₃₁ = 13.1 × 10^-12 m² N^-1), significantly enhancing successfully the energy-harvesting performance (power density of 35 nW/cm²). Furthermore, the fabricated lead-free PEG exhibited an excellent flexibility figure of merit (fFoM) due to the low young modulus values (Maximum E = 3.4 MPa). These results indicate efficient energy conversion and demonstrate a favorable balance between the flexibility and piezoelectric properties of the composite, highlighting its potential for a wide range of applications in self-powered wearable sensors able to collect different human motions in applications such as gesture tracking and finger motion detection.