A Soft Fluidic Sensor-Actuator for Active Sensing of Force and Displacement Applied to Tissue Probes and Implants

Achieving compact and biocompatible advanced technologies with sensing capabilities is a key challenge for the safety critical and highly patient-specific biomedical field. In this study, a compact and versatile soft fluidic sensor-actuator (SA) capable of measuring both force and displacement in static and dynamic conditions is presented. Pressure and resistance are shown to be interchangeable, although best used in combination, when predicting the load on the SA, and show good repeatability and distinction between the loaded and constrained conditions. Using a single sensing medium and across the different diameters tested, the best estimated resolution of just under 4g and 0.07mm is achieved with the 12mm sensor, filled with 1.5mL using pressure sensing only. Furthermore, the SA is demonstrated in two probe applications and as part of a soft robotic implant for tissue-loading based tissue regeneration. The SA showed the ability to distinguish between different objects or areas of varying stiffness, as part of both a rigid-bodied and soft-bodied probe, as well as being able to predict force and displacement from the lengthening and retraction of a soft implant. Overall, this SA has the potential to be a key building block for biomedical robots’ monitoring of both displacement and force.