A Small-Scale Soft Linear Actuator for Tool Feeding with Intrinsic Force Sensing

The evolution of soft robotics has unlocked new design possibilities for adaptable and safe robotic systems, particularly in medical applications. Among these advancements, fluid-driven soft actuators offer compact, lightweight, and energy-efficient solutions suitable for minimally invasive surgical (MIS) and endoluminal procedures. In this work, we introduce a completely soft hydraulic actuator for tool feeding. Conventional soft actuators for tool insertion often rely on bulky components, which limit use at smaller scales and constrain the integration of direct force-sensing methods. In applications where controlled contact forces are essential, recent research has focused on estimating or intrinsically sensing forces without relying on external sensing devices. We characterize the soft actuators’ nonlinear mechanical behavior and employ methods of determining tool contact and force exerted on a target from pressure and volume relationships over the actuators’ workspace. Furthermore, we demonstrate effectiveness in controlling tool advancement and retraction in free space and into varying shore hardness silicone phantoms.