Morphology-Guided Nonlinear Structural Evaluation of a Hybrid Bio-Inspired Soft Robotic Actuator

Soft robotic actuators exploit structural compliance to produce adaptive motion, but their response depends strongly on the interaction between geometry, material distribution, specific reinforcement, and actuation. This manuscript presents a bio-inspired hybrid soft actuator based on the elongated, continuously deformable morphology of the arrow worm and evaluates whether its bending response can be programmed through structural morphology. Four force-controlled nonlinear static finite element studies were performed in SOLIDWORKS Simulation using a hyperelastic Ogden model for the EcoflexTM 00-50 body and orthotropic models for the Thermoplastic Polyurethane (TPU) 68D reinforcement spine and Acrylonitrile styrene acrylate (ASA) pressure pad. Across the analysed force activation levels, maximum resultant displacement increased from 0.948 mm to 17.88 mm, equivalent strain from 0.005268 to 0.06833, and maximum von Mises stress from 0.596 MPa to 5.447 MPa. Simultaneously, effective-average incremental stiffness decreased from 0.21097 N/mm to 0.04846 N/mm, corresponding to a 77.03% reduction. These findings demonstrate progressive nonlinear softening and the transformation of mechanical input into a guided global shape change. A representative comparison with existing measurements of the fabricated actuator was additionally used to quantitatively cross-check the predicted bending response. The result of the morphological calculation was also the creation of a morphological map for quantitative and qualitative assessment of normalized morphological descriptors of the actuator.