Advanced Technologies in Soft Actuators

Dear Colleagues,

Soft robotics and actuators show great promise by enabling the control of machines and systems that rigid robots and actuators cannot achieve. Their flexibility and adaptability make them ideal for interacting with delicate objects and living organisms in complex and dynamic environments. Typically, soft actuators require a control signal and an energy source to function. These control signals cause the actuators to deform, converting input energy into mechanical motion used to operate machines or systems. Various stimuli, such as electrical or magnetic fields, heat, light, humidity, pH, chemicals, hydraulics, and pressure, can be used to activate the actuators. Soft actuators are typically made of stimuli-responsive materials with different mechanisms. For instance, ionic electroactive soft actuators bend when ions rearrange in response to external electrical fields. Photoactuators can deform through mechanisms such as thermal expansion/contraction, humidity adsorption changes, and molecular configuration variations. These stimuli-responsive soft actuators offer numerous advantages, including lightness, flexibility, compliance, complex motion capabilities, safety, low noise, minimal vibration, space efficiency, high degrees of freedom, and adaptability to environmental changes, which position them as potential replacements for rigid counterparts in various devices.

The aim of this Special Issue is to present those advanced technologies that are useful for the further development of soft actuators for real-world applications.

Dr. Mahato Manmatha
Dr. Jaehwan Kim
Guest Editors

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• IPMC
• EAP
• photo and thermally active actuators
• magnetoactive actuators
• SMA

Title: Design optimization of an origami linear soft actuator, based on internal reinforcement soft–structures
Authors: Med Amine Laribi and Eduardo Castillo Castaneda
Affiliation: Département Génie Mécanique et Systèmes Complexes, CNRS - Université de Poitiers
Abstract: The origami art in engineering applications allows the creation of light and compact structures that increase in size when unfolded. An example where these characteristics are being explored is in the development of soft pneumatic actuators which also demonstrates significant potential for achieving high forces and large displacements, all while maintaining ease of fabrication. This paper presents a design optimization of an origami soft actuator in terms of mobility and stiffness. The impact of the number of levels on the origami actuator is assessed through Finite Element Method (FEM) analysis. On the other hand, sheets and rings of soft internal reinforcing structures are proposed to increase the actuator stiffness. Furthermore, a kinematic model previously presented is numerically evaluated in the optimized actuator, achieving an accuracy of 97.4% with the FEM analysis and 98.3% with the manufactured actuator. Experimental evaluations were performed to the origami soft optimized actuator.

Title: Analysis of Collision Profiles in Collaborative Robots Using Mechanisms Actuated by Artificial Muscles
Authors: Dávid Kóczi, József Sárosi
Affiliation: University of Szeged, Faculty of Engineering (Hungary)
Abstract: In the safety technology of collaborative robots, standards differentiate between various collision profiles, the identification and differentiation of which are essential for ensuring safe operation. The objective of this paper is to develop and test a mechanism actuated by artificial muscle to examine the detection of these profiles in different collision scenarios. Utilizing the flexibility and rapid response of artificial muscles, different collision situations are simulated, and the results are analysed to assess the extent to which feedback from the artificial muscles can differentiate between collision types. The findings have the potential to enhance the safety of collaborative robots.