Piezoelectric Soft Robotics: Designing Fully Sensing and Actuating Devices for Muscle Function Restoration and Next Generation Prosthetics

Volumetric Muscle Loss (VML) is a major clinical challenge due to the body’s limited regenerative ability and the lack of prosthetic systems capable of replicating the mechanical adaptability of natural muscle. This thesis explores the use of piezoelectric materials specifically poly(vinylidene fluoride trifluoroethylene) (PVDF-TrFE) to develop a soft robotic platform that mimics muscle function through integrated sensing and actuation. The project spans material choice, device fabrication, characterisation, system integration, and biological evaluation. First, novel PVDF-TrFE based strain sensors were fabricated using twisted and rolled nanofiber geometries. These were characterised across mechanical and electromechanical tests, demonstrating robust and reproducible voltage responses under tensile, bending, and dynamic loading conditions. The twisted configuration exhibited enhanced flexibility, while the rolled design showed superior durability and linearity in voltage force relationships. Subsequently, actuators were developed from PVDF films and characterised in terms of displacement and force output across variations in shape, size, thickness, signal type, and electrode composition. Experimental results were guided by using finite element simulations (ANSYS), confirming consistent electromechanical behaviour, and highlighting the influence of geometric design on performance. The sensors and actuators were then integrated into a closed loop-controlled system capable of regulating actuation levels in response to the current sensors measurements. A stepwise binning strategy using filtered sensor data enabled stable force classification with a ~10 s closed-loop classification and settling latency. The system demonstrated high repeatability, convergence, and classification accuracy across multiple actuation states. Finally, biocompatibility studies were performed using electrospun PVDF-TrFE scaffolds interfaced with both C2C12 myoblasts and human iPSC derived muscle cells. The scaffolds supported cell adhesion, viability, and early myogenic differentiation, suggesting their potential for bio integrated muscle restoration platforms. This thesis presents a novel system level demonstration of a soft robotic device integrating PVDF based piezoelectric sensors and actuators within a closed loop control framework for muscle function emulation. By combining high fidelity sensing, adaptive actuation, and biological compatibility, this work provides a proof of concept for next generation prosthetics and muscle repair systems with real time responsiveness.