A Review on Soft Planar Mechanisms: Modeling and Actuation for Robotic Applications

Soft planar mechanisms combine compliant materials, bio-inspired designs, and hybrid actuation strategies to extend classical planar kinematics into adaptive robotic systems. This review is based on studies that were published between 2020 and 2025, and sourced from Scopus, Web of Science, and Google Scholar databases. It is a synthesis of recent advances in actuation technologies, such as pneudraulic actuators, Organic Photovoltaic–Dielectric Elastomer Actuators (OPV-DEAs), and McKibben textile muscles, and biologically inspired structures, such as avian claws and origami-based exoskeletons. It further discusses the development of intelligent modeling and control, such as Koopman-based Model Predictive Control (MPC) and biLSTM neural networks that can be used to increase real-time flexibility and accuracy. Important constraints associated with reproducibility, fatigue performance, and variability of fabrication are taken care of by benchmarking activity and new standardization. The review concludes with a roadmap focusing on embedded sensing, sustainable materials, and scalable deployment for rehabilitation, wearable robotics, and adaptive soft systems.