In recent years, soft robotics technologies enabled the development of a new generation of biomedical devices. The combination of elastomeric materials with tunable properties and muscle-like motions paved the way toward more realistic phantoms and innovative soft active implants as artificial organs or assistive mechanisms. This review collects the most relevant studies in the field, giving some insights about their distribution in the past ten years, and their level of development, and opening a discussion about the most commonly employed materials and actuating technologies. The reported results show some promising trends, highlighting that the soft robotics approach can help replicate specific material characteristics, in the case of static or passive organs, but also reproduce peculiar natural motion patterns for the realization of dynamic phantoms or implants. At the same time, some important challenges still need to be addressed. However, by joining forces with other research fields and disciplines, it will be possible to get one step closer to the development of complex, active, self-sensing and deformable structures able to replicate as closely as possible the typical properties and functionalities of our natural body organs.

A textile-based strain sensor for measuring the length of a McKibben pneumatic actuator has been developed. McKibben actuators are flexible, lightweight, and widely used in all those applications where compliance and safety are required, e.g. soft robotics and power assisting device. The actuator length needs to be measured to control the device accurately. However, properties such as flexibility and lightness might be lost if rigid sensors such as potentiometers or linear encoders are directly attached to the actuators. For this reason, flexible and stretchable sensors are necessary. In this study, a flexible sensor using conductive textile is proposed to actively measure the length of manufactured McKibben actuators. Firstly, the electro-mechanical characteristics of the proposed sensor were obtained and a model to compensate its nonlinearities was evaluated. Secondly, an estimation of the accuracy was performed during dynamic actuator contractions. The results showed that, using this sensor, a direct measurement of the actuator axial displacement can be obtained within 20% error, without affecting its performances in terms of contraction.

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