Cora Rotary Pump for Implantable Left Ventricular Assist Device: Biomaterial Aspects

Abstract

Our group is developing a left ventricular assist device based on the principle of the Maillard-Wankel rotative compressor: it is a rotary, not centrifugal, pump that produces a pulsatile flow. Stringent requirements have been defined for construction materials. They must be light, yet sufficiently hard and rigid, and able to be machined with high precision. The friction coefficient must be low and the wear resistance high. The materials must be chemically inert and not deformable. Also, the materials must be biocompatible, and the blood contacting surface must be hemocompatible. We assessed the materials in terms of physiochemistry, mechanics, and tribology to select the best for hemocompatibility (determined by studies of protein adsorption; platelet, leukocyte, and red cell retention; and hemolysis, among other measurements) and biocompatibility (determined by measurement of complement activation and toxicity, among other criteria). Of the materials tested, for short- and middle-term assistance, we chose titanium alloy (Ti6Al4V) and alumina ceramic (Al2O3) and for long-term and permanent use, composite materials (TiN coating on graphite). We saw that the polishing process of the substrate must be improved. For the future, the best coating material would be diamond-like carbon (DLC) or crystalline diamond coating.

Material-specific thrombin generation following contact between metal surfaces and whole blood

“…Titanium alloys have also been commonly used because of their high corrosion resistance [5]. In recent years, titanium and surfaces coated with titanium nitride have also been used in contact with whole blood (e.g., in heart valves, heart aid devices and heart pumps) [6][7][8].…”

Protein adsorption and platelet attachment and activation, on TiN, TiC, and DLC coatings on titanium for cardiovascular applications

“…Favorable results have been reported for applications such as surgical needles for corneal surgery, 8 materials for total joint replacement, 3,9 orthopedic pins and screws, 10 dental prostheses, 11 medical guidewires, 12 heart valve replacements, 13 and rotary pumps for left ventricular assistance. 14 The use of TiN for dental prostheses [15][16][17][18] and for hip joint and heart valve replacements 19,20 has also been reported.…”

Hemolysis Resulting From Surface Roughness Under Shear Flow Conditions Using a Rotational Shear Stressor

“…Minimizing the hemolysis level is a key development task to avoid thrombus formation. The causes of hemolysis include various factors (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19), with surface roughness as one of the most important. Surface roughness is an important parameter in the manufacture of centrifugal blood pumps.…”