• inverse pneumatic artificial muscles
• IPAM
• long gap esophageal atresia
• mechanotherapy
• minimally invasiveness
• soft robotics
• tissue traction forces

Esophageal Atresia (EA) is a neonatal abnormality affecting the esophagus; it represents one of the most common gastrointestinal birth defects with reported incidence from 1 in 4500 to 1 in 3000 newborns. Babies affected by EA do not present a continuous connection between the mouth and the stomach, but the esophagus grows into two separate segments ending in two blind pouches. For the treatment of EA, the most common therapy is represented by a surgical procedure called Foker technique. The Foker technique is based on the application of traction forces between each of the two esophageal segments through sutures; the application of this mechanical stimulus promotes the tubular tissue elongation through cellular proliferation. This surgical procedure allows the preservation of the native esophagus, which is associated with better long-term outcomes. However, the Foker technique presents three main drawbacks: the newborn is completely sedated for the whole duration of the treatment (approximately 14 days), the sutures could tear-out, with the consequent need for a second surgery and, finally, the newborn is subjected to daily X-rays to check the improvements in terms of gap reduction. The gap is defined as the distance between the two esophageal pouches. In the state-of-the art, different implants and solutions partially overcoming the disadvantages related with the Foker technique are described. The devices described in literature are based on technologies belonging to traditional rigid robotics. Some devices integrate DC motors, potentiometers and force sensors to actuate the system, and to continuously monitor both the gap length and the force applied. The main disadvantages are related to the necessity of two open chest surgeries for the positioning and removal of the implant, and to the potential damage of surrounding organs due to the presence of rigid components. Alternative devices use the magnetic attraction between two magnets positioned in the two esophageal pouches to reduce the gap length. However, the method based on magnets is associated with a high probability of having esophageal stenosis, a reduction of the esophageal lumen. Soft robotic implants, with respect to rigid ones, have the advantages of reducing the fibrotic response from the body upon implant, and the probability of being harmful for the surrounding organs and tissues.
The objective of this thesis is to design and develop a minimally invasive soft robotic implant for the treatment of EA. This novel device integrates Inverse Pneumatic Artificial Muscles (IPAMs) to apply tissue traction forces to the esophageal segments, promoting tissue regeneration. IPAMs are soft pneumatic actuators made of a pneumatic chamber and an external reinforcing structure to limit the radial expansion of the chamber upon pressurization. When the pressure in the pneumatic chamber increases, the IPAM elongates exerting a pushing force, when the pressure decreases, it shortens exerting a pulling force; the IPAM can be used in both the described modalities.
In this thesis a minimally invasive soft robotic device for the treatment of EA is presented. A study on IPAMs have been carried out, different soft actuators were tested to evaluate the impact of parameters related to the pneumatic chamber and to the reinforcing structure on the performance of the actuator itself. The device has been designed so to satisfy the technical requirements related to the clinical problem. Different design proposals are presented and discussed, in the end three prototypes are fabricated. The main advantage related with our device proposal with respect to solutions in the literature, is given by the low invasiveness of the implant: from one side the device is able to satisfy the technical requirements imposed by the clinical problem, from the other the anchoring method exploiting rigid structures of the oral cavity allows to insert and remove the device without the need of additional surgeries. In the future, the further development of a soft robotic device for the treatment of LGEA, could represent a new solution in the clinical practice allowing the overcoming of the drawbacks related to the currently available surgical solutions.