3D-Printed Strain Sensors: Electro-Mechanical Simulation and Design Analysis Using Nonlinear Material Model and Experimental Investigation

This work is driven by the continuous improvement in additive manufacturing and the growing interest in developing flexible strain sensors with complex designs and structures. Characterization and analysis require not only understanding the mechanical behavior of the sensor but also the electrical behavior and the coupled electromechanical behavior. Traditionally, this coupled electromechanical behavior is determined using simplified approaches to establish a relationship between the electrical domain and mechanical domain. This work presents an experimental and numerical platform to characterize strain sensors and serves as a tool for design guidelines for these sensors. A nonlinear finite element COMSOL model is developed and validated against experiment. At 38% strain level the sensitivity is increased by 7% when the thickness,t, of the sensor decreased from t = 1.4 mm to t = 0.6 mm. A sensor with triangular embedded channels exhibits improved performance compared to square, hexagonal, and octagonal cross-sectional shapes. Three common channel patterns are examined including spiral, vertical serpentine, and horizontal serpentine patterns. Three commonly used materials for fabricating strain sensors are investigated including PDMS, EcoFlex, and NinjaFlex. At 35% strain level, a sensor with NinjaFlex substrate exhibits, approximately, 6% improvement in sensitivity, compared to a sensor with EcoFlex substrate.