Dual-Mode Variable-Stiffness Soft Gripper Based on Electrorheological Fluids

The adaptability to various operating conditions represents a crucial aspect of soft robotics, and variable-stiffness mechanisms have demonstrated promise in achieving this flexibility. This article proposes a dual-mode variable-stiffness soft gripper based on electrorheological fluids (ERFs), enabling rapid, wide-ranging, and high-precision stiffness adjustments. The key advantage of this approach lies in the introduction of two distinct stiffness mechanisms and the ability to switch between them. The first mode relies on fluid flow, wherein the controlled opening and closing of valves enable fluid flow, resulting in an extremely low stiffness resembling a fluidlike state. Conversely, the second mode depends on activating the ERFs to enhance the stiffness, exhibiting elastic deformation akin to a solid. Thereby, the dual-mode changes of the stiffness can be manipulated to grip fragile objects using a fluidlike state while generating substantial gripping forces for rigid objects via a solidlike state. In addition, the combined use of these two modes also enables the soft gripper to conform tightly to irregular object surfaces with exceptionally low stiffness, surpassing conventional soft structures before delivering significant gripping forces.