• artificial ventricle simulator
• pneumatic artificial muscle
• self sensing
• soft actuators
• soft robotics

Nowadays, cardiovascular diseases, including heart diseases and stroke, are the primary cause of death worldwide. There are different solutions that are clinically available. They can consist of either a pharmacological treatment or a substitution of part or the entire organ, in the most severe cases. Unfortunately, when the transplant is the only solution, the limited availability of donors represents the most incident problem. These issues led to the development of mechanical circulatory support devices, such as ventricular assist devices (VADs), direct cardiac compression devices (DCCs) and Total Artificial Hearts (TAHs). However, due to the presence of rigid mechanical parts that come in contact with blood, commercially available devices present different drawbacks, such us the necessity of long-term blood-thinning medications. Indeed, today there is only one TAH that is FDA approved, but only as a bridge to transplantation therapy. This is mainly due to the fact that they are composed of hard materials and bulky sensors, which makes them not safe to be integrated in a human body. Furthermore, they fail to reproduce the physiological movement of real human heart due to their inflexible structure.
For these reasons, recently, the field of soft robotics has attracted considerable attention. Soft materials, indeed, represent a promising solution to current issues. Being inexpensive, lightweight, and intrinsically safe, they present advantageous characteristics for the development of TAHs and soft cardiac assistive devices. Indeed, softness may improve the adaptability of the system to the human body. To realize active soft devices, it is necessary to employ actuators presenting the same intrinsic nature. Emerging soft actuators enable applications in robotics, health care, haptics, assistive technologies, and many other areas. In this field, Inverse Pneumatic Artificial Muscles (IPAMs) represent a promising technology, especially for the wider motion range compared to traditional positive pneumatic actuators. IPAMs in the state of the art can reach up to 300% of strain. When they are pressurized, they elongate, while, when the pressure is decreased, their return elastic force is exploited for actuation in a reverse mode. To realize a complex and controllable device, a sensorization of the actuation system is needed. Besides self-sensing is a recognized highly desirable property for soft actuators to enable proprioception and to facilitate the soft robot's control, a self-sensing strategy for a soft inverse pneumatic muscle was still missing.
The first objective of this thesis consisted in the optimization of the performances of an inverse pneumatic artificial muscle, that was designed in a previous study. In this initial phase, different prototypes of the IPAM were realized to select the most performant material for the body of the actuator. Their performances have been evaluated in terms of stroke and maximum return elastic force they are able to exert, when the internal pressure is set to 0 bar. The fabrication process reported is easy and makes use of commercial materials and components. The second objective consisted in the realization of the first totally soft Self-sensing Inverse Pneumatic Artificial Muscle (Self-sensing IPAM). In the newly developed Self-sensing IPAM, the reinforcing but compliant element that guides its motion during actuation has not only a mechanical function but, being also electrically conductive, it endows the actuator with self-sensing. To realize it, a polymeric conductive wire was employed. The sensing of the actuator current deformation was possible thanks to the measurement of the resistance variation of the wire with the actuator stretch. The material employed for the realization of the main body of the Self-sensing IPAM was chosen considering its interaction with the polymeric wire. The results of the electro-mechanical characterization experiments performed both on the polymeric wire itself and on the Self-sensing IPAM are presented. In addition, we demonstrate its self-sensing capability in a dynamic setting, by predicting the actuator strain from its electric resistance variation, through a calibration model. Finally, the applicability of the developed IPAM for the realization of the actuating system of a soft robotic artificial ventricle simulator is demonstrated. Moreover, a dimensioning of the actuation layer for both a left and a right artificial ventricle is presented, together with an optimization of the simulator in terms of encumbrance and volume of air needed for actuation.