טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
Ph.D Thesis
Ph.D StudentBerris Michelle
SubjectSelf-Propelled Bubble-Driven Locomotion for Robotic
Applications in Fetal Surgery
DepartmentDepartment of Mechanical Engineering
Supervisor Professor Moshe Shoham
Full Thesis textFull thesis text - English Version


Abstract

For a fetus diagnosed with a severe congenital anomaly, surgery may offer an alternative to abortion, intra-uterine death or a life with disability. Expertise is limited however, to few treatment centers worldwide and there are many technical hurdles including miniaturized instrumentation, real-time high-resolution imaging, and harmless fetal access. While the number of potential patients is low, research for implementation of robotics into the field of fetal surgery is justified by morbidity rates of current procedures, proven favorable outcomes with intervention, and educational value for extension to other medical disciplines.


A bubble-driven device is presented as a feasible, non-harmful solution for self-propelled locomotion within the pregnant uterus during fetal surgery applications. The millimeter scaled capsule releases gaseous bubbles to a surrounding volume of fluid containing a mixture of water and glycerine, thereby mimicking amniotic fluid.  High-speed imaging, particle image velocimetry (PIV), and computational fluid dynamics (CFD) are engaged to better understand the exact physics propelling the capsule. The role of surface tension, drag and bubble pinch-off are all considered with respect to the given scenario. Experiments were conducted by varying the diameter of the capsule orifice and the viscosity of the surrounding fluid, in order to generate empirical models and optimize performance. Results include trends in bubble growth and detachment time, maximum bubble radius and pressure profiles, along with a correlation between bubble release and capsule motion. The maximum bubble velocity achieved with the most recent prototype is 60 mm/sec.