Experimental set-up for the characterization of 3D printed realistic phantoms of medium-large calibre arteries

Compliance is a parameter that describes the ability of blood vessels to expand and then recoil towards its initial form as a response to pressure changes. It can be used to give an estimation of the vessels elasticity and it represents an important cardiovascular risk factor, as compliance decreases with age. In particular, it is related to the arterial stiffness occurring as a consequence to vascular wall pathologies such as atherosclerosis or other wall degenerative changes. Therefore, it is important to be able to measure it accurately and reliably in experimental mock loop reproducing the function of the cardiovascular system. The present thesis aims at developing and testing a low cost and easy to use set-up able to estimate the compliance of vascular vessels models, when inserted in a hydraulic system that replicates realistic conditions. Thus, the developed test bench includes the PD-1100 pulsatile pump from BDC Laboratories (CO, United States), two cameras from mobile phones positioned above and next to the phantom that record the external diameter deformations over time as the fluid flows, four piezoresistive pressure sensors placed in pairs upstream and downstream of the vessel model that are connected to the circuit by two 3D printed tube connectors, and a flow meter. The external diameter deformations have been carried out through the optical system and an ad-hoc developed MATLAB code. A LabVIEW scheme coordinates the simultaneous acquisition of video and pressure signals. The first aim of this thesis work was the development of the acquisition system. The latter is composed by smartphones cameras, so it is usable by anyone who owns a device with high performances. It is compact, easy to use, low cost, and it does not require additional instrumentation. Then, the developed system has been tested in a wide range of operating conditions. The system allows to capture the diameter variation profile over time occurring as a consequence of the pulsatile inflow. After this preliminary phase, all sources of uncertainty in the measurements were carefully considered and quantified. Then, the set-up was then used to obtain the compliance of a silicone tube. The developed set-up can be applied to arterial phantoms manufactured with 3D printing technology. In future developments, this set-up will be exploited to assess the compliance of 3D printed vessel-like structures, where two different printing material with different Shore hardness will be used in combination. The developed set-up will be used to verify which combination of materials provides a mechanical behaviour similar to the one characteristic of human arteries. Thanks to 3D4MED Laboratory at Policlinic San Matteo (Pavia), many models have been designed and printed using a Stratasys Objet 260 Connex 3 printer. This technology creates objects by depositing thin layers of photopolymer cured with UV light. Pig descending aorta samples have also been collected by 3D4MED Laboratory and they could also be studied using the created experimental set-up. Subsequently, their results could be compared to the 3D printed models’ ones.