<p>The fabrication of arterial flow phantoms for fluid dynamics studies suitable for particle image velocimetry (PIV) techniques has presented challenges. Current 3D-printed blood flow phantoms with suitable transparency for optical PIV (laserPIV) are restricted to rigid materials far from those of arterial properties. Conversely, while soft 3D-printed phantoms demonstrate promise for sufficient acoustical transparency for ultrasound PIV (echoPIV), their optical translucency presents challenges for laserPIV applicability. This dual-modality approach leverages the high spatial resolution of laserPIV for in-vitro applications and the ability of echoPIV to quantify flow in both in-vivo and in-vitro application (also inside stents), providing a more comprehensive understanding of flow dynamics. In this study, we present a series of coated thin-walled 3D-printed compliant phantoms suitable for dual-modality PIV flow imaging (i.e., laserPIV and echoPIV) methods, overcoming current 3D-printable material limitations. Stereolithographic (SLA) 3D printing was used to fabricate pipe flow phantoms from a set of commercial soft resins (flexible and elastic) as vascular tissue surrogates. To overcome low transparency and poor surface finish of soft resins, we coated the 3D-printed flow phantoms with a soft, optically transparent, photo-activated polymeric coating. The feasibility of performing dual-modality PIV was tested in an in-vitro flow setup. Our results show that the average normalized root mean square errors obtained from comparing laserPIV and echoPIV velocity profiles against the analytical solutions were 3.2% and 5.1%, and 3.3% and 5.3% for the flexible and elastic phantoms, respectively. These results indicate that dual-modality PIV flow imaging is feasible in the 3D-printed coated phantoms, promoting its future use in fabricating clinically-relevant flow phantoms.</p> Graphical abstract <p></p>