Development and Characterization of a 3D-Printable PDMS Composite With BaTiO3 for Enhanced Force Sensing in Soft Robotics

Abstract Polydimethylsiloxane (PDMS) is widely used in flexible electronics and soft robotics due to its mechanical flexibility and biocompatibility. These properties make PDMS particularly suitable for applications involving wearable devices and biomedical technologies. However, conventional methods for fabricating PDMS structures, such as dip casting and spin coating, impose limitations on design flexibility, as they restrict the complexity and scalability of the fabricated structures. Integrating PDMS with advanced 3D printing techniques offers a promising approach to overcome these limitations, allowing for more complex and customizable structural configurations. This method also enables the incorporation of multiple materials within a single processing step, creating opportunities for multifunctional device designs. When combined with piezoelectric ceramics, PDMS composites show significant potential for creating low-cost, flexible tactile sensing devices. This study explores the efficacy of barium titanate (BaTiO3) as a piezoelectric additive in a PDMS matrix to develop a flexible sensor suitable for prosthetic applications. The piezoelectric sensor was fabricated by mixing 7 parts SE1700 PDMS with 3 parts SYLGARD™ 184 base, each at a 10:1 base-to-curing agent ratio. To this blend, 40% BaTiO3 powder by weight (2.4g) was added and mixed thoroughly for 15 minutes. The composite was cured at 80°C for 1.5 hours, then layered between Kapton tape and silver conductive ink to ensure electrical insulation and conductivity. Force-induced voltage output was measured using an oscilloscope and force gauge. Rheological properties were evaluated to assess shear-thinning behavior, which is critical for 3D printability. A flow sweep was conducted to calculate the shear-thinning coefficients (K and n), and a three-interval thixotropy test (3iTT) was performed to examine the material’s recovery rate post-printing. BaTiO3 dispersion within the PDMS matrix was visualized via scanning electron microscopy (SEM). Finite element analysis (FEA) was conducted to simulate the sensor’s voltage response under force. The PDMS-BaTiO3 composite sensor displayed a linear relationship between applied force and voltage output, indicating effective piezoelectric behavior. Rheological analysis confirmed the material’s shear-thinning properties, supporting its suitability for 3D printing. The SEM analysis revealed a homogeneous dispersion of barium titanate within the PDMS matrix. The 3iTT results demonstrated a robust recovery rate post-shear, essential for achieving high-quality print fidelity. The FEA simulation of piezoelectric sensors illustrated the variation in voltage as a function of applied force. This research presents a novel 3D-printable PDMS-BaTiO3 composite piezoelectric sensor that holds promise for applications in prosthetics, leveraging its flexible design, single-step fabrication, and piezoelectric responsiveness.