Hydraulically Steerable Micro Guidewire Capable of Distal Sharp Steering.

Current steerable catheters or guidewires often cannot advance into small diameter vessels due to their large diameters or lack of sharp steering capacity. This paper proposes a hydraulically steerable guidewire with 400 μm diameter, which can access 1 mm diameter vessels whose branching angle is larger than 90 degrees. The designed steering mechanism consists of a flexible eccentric tube with inner micro patterns, which can bend in two different curvatures when pressurized. Its distal sharp curve of the 2 mm segment allows access to small diameter vessels because it provides a large steering angle even in confinement inside the narrow vessels. Its proximal gradual curve of the 9 mm segment allows access to relatively large diameter vessels because of its large steering distance. Fabrication of the steering mechanism uses a template and does not use adhesion or division. A 3D printed cylindrical template is patterned by stamping and chemically removed after silicone coating. The performance of selective insertion of the proposed guidewire is evaluated in a blood circulatory system specially developed to mimic human arterial environment. It emulates viscosity, pressure, and flow velocity inside the blood vessels as well as bifurcation geometry. Experiment result shows that the proposed guidewire can access 1 mm diameter vessels with 128 degrees of bifurcation angle. The developed guidewire uses only biocompatible materials including driving fluid.