Designing information-rich and space-efficient sensors is a key challenge for soft robotics, and crucial for the development of safe soft robots. Sensing and understanding the environmental interactions with a minimal footprint is especially important in the medical context, where portability and unhindered patient/user movement is a priority, to move towards personalized and decentralized healthcare solutions. In this work, a pulsating fluidic soft sensor (PFS) capable of determining location, pressure and contact area of press events is shown. The sensor relies on spatio-temporal resistance changes driven by a pulsating conductive fluid. The sensor demonstrates good repeatability and distinction of single and multiple press events, detecting single indents of sizes greater than 1 cm, forces larger than 2 N, and various locations across the sensor, as well as multiple indents spaced 2 cm apart. Furthermore, the sensor is demonstrated in two applications to detect foot placement and grip location. Overall, the sensor represents an improvement towards minimizing electronic hardware, and cost of the sensing solution, without sacrificing the richness of the sensing information in the field of soft fluidic sensors.

Achieving compact and biocompatible actuators 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 capable of measuring both force and displacement in static and dynamic conditions is presented. Pressure and resistance are shown to be interchangeable in predicting load and sensor-actuator height, and showed good repeatability and distinction between the loaded and constrained conditions tested. Furthermore the sensor-actuator is demonstrated in a probe application and showed comparable findings to a tensile test machine when tested on three objects of varying stiffness. Overall, this sensor-actuator has the potential to be a key building block for biomedical robots that require large expansion, as well as continuous monitoring of both displacement and force.

Soft robots are known for their ability to comply and having superior extensibility. However, one of the limitations of most of these robots is that they can stand only a limited amount of load before buckling, and they feature a non-negligible initial height. Hybrid soft-rigid actuators seem to offer a trade-off between compliance and the amount of load they can withstand, but only a few simple models have been proposed to describe the behavior of these actuators. In this paper, we propose a design, model and experimental validation of a soft actuator based on stackable Hyperelastic Ballooning Membranes (HBMA). This actuator shows an extensibility higher than 179%, as well as an ability to stand more than 20 times its own weight at a pressure as low as 35 kPa. Two models, giving the dynamic behavior of the HBMA in terms of displacement and pressure, have been derived from different hyperelastic models (Neo-Hookean and Mooney-Rivlin) and compared in terms of accuracy and robustness. Finally, an example of a hybrid soft-rigid continuum ballooning robot built with HBMAs is presented and characterized experimentally.