Research - Goal

Aim 1: Equipment development (testing equipment and specialized 3D printer)
It is necessary to develop new and upgrade existing mechanical testing machines. Also, for the best precision of 3D printed stents, a 3D printer needs to be optimized and assembled for stent printing.

Aim 2: Development of constitutive models of 4D printed polymer and silicone material
Using biaxial, pressure-extension, creep, and dynamic tests on 4D printed and silicone square and tube specimens, a constitutive model will be chosen, and material parameters fitted based on experimental data. The first verification of the 4D printed material constitutive model will be performed, and adjustments will be made, using data from the three-point bending test and uniaxial tension test on the stent geometry. Additionally, the maximal stretch that chosen material can withstand while retaining its original shape after reverting and the time needed for reversion will be determined.

Aim 3: Development of G&R model of the stented artery
he existing G&R model of aortic adaptation in FEAP will be adjusted to the carotid artery. This implies adjusting geometrical and structural parameters, as well as other model parameters (i.e., constituent mass production rate parameters) to obtain relevant results. The adapted model will be validated with clinical observations and longitudinal studies available in the literature, including carotid intima-medial thickening with aging with comparison for women and men, and geometric changes of the carotid artery with age.

Aim 4: Verification of the stent constitutive model and experimental evaluation of stent efficiency
Stent specimens and silicone tubes (both non-stenosed and with various degrees of stenosis) representing arteries will be 3D printed. Stents will be stretched at increased temperature, cooled down to body temperature, and placed into silicone arteries. Changes in luminal and outer diameters will be measured. This will give us the initial evaluation of stent efficiency.

Aim 5: Numerical evaluation of medical performance
Finally, using an optimized and verified G&R model of the carotid artery from Objective 3 and a verified material model of the stent, evaluation of stent performance is possible. The stent material model developed and implemented into FEAP will be coupled with the arterial G&R model. Evaluation of the medical performance of 3D printed thermal shape memory polymer carotid stent will be investigated. Hypotheses on factors causing in-stent restenosis formed in Aim 3 will be checked. xisting G&R model of aortic adaptation in FEAP will be adjusted to the carotid artery. This implies adjusting geometrical and structural parameters, as well as other model parameters (i.e., constituent mass production rate parameters) to obtain relevant results. The adapted model will be validated with clinical observations and longitudinal studies available in the literature, including carotid intima-medial thickening with aging with comparison for women and men, and geometric changes of the carotid artery with age.