Patient-Specific Compliant Vessel Manufacturing Using Dip-Spin Coating of Rapid Prototyped Molds

Abstract

A procedure for manufacturing cardiovascular system models using patient-specific data, rapid prototyping, and a multistep dip-spin coating process is presented here. Improvements to a previously developed process permitted the fabrication of flexible complex vascular replicas. The primary improvement included the development of a two-axis rotation mechanism that enabled a pseudorandom rotation of the coated mold in space, providing uniform coats. Other improvements included the use of a low viscosity (1500–2000cP) silicone solution that allowed for complete coverage of the mold, and developing a procedure for fixing defects. The dip-spin coating procedure was shown to be effective for the manufacture of compliant cardiovascular membranes, such as an arterial bypass graft with an internal flow passage and an abdominal aorta with nonuniform radial geometry, tapered diameters, bifurcations, and small branches. Results from a design of experiments comparing two dipping setups demonstrated that horizontally dipping the model produced coatings with more uniform thicknesses along the length of the model when compared to vertical dipping. For a 250-mm-long model, the difference in thickness between the top and bottom of the membrane was 0.42±0.069mm and 0.09±0.077mm for vertical and horizontal dippings, respectively. Mold diameter also affected the thickness of the membrane, with membrane thickness increasing as mold diameter decreased. Thickness data comparing locations at approximately the same height of the mold but with different diameters showed thicknesses of 2.54±0.198mm and 1.95±0.140mm for 7.85mm and 15.20mm diameters, respectively. Moreover, the differences in thickness between these locations were 0.60±0.128mm and 0.58±0.231mm for vertical and horizontal dippings, respectively; thus, membrane thickness variations occurred with mold diameter irrespective of the dipping setup. Depending on the prescribed tolerance for membrane thickness, the vertical dipping setup may be recommended for use because (1) it was easier to use since only the mold was immersed in the coating solution and no special protection of the dipping mechanism was required and (2) it produced fewer defects in the coatings since the solution always dripped from downfacing surfaces of the mold. Using this dip-spin coating procedure, patient-specific cardiovascular membranes can be manufactured and used in the development of medical devices, research requiring accurate anatomical models, and education and training.

An In Vitro Assessment of the Cerebral Hemodynamics Through Three Patient Specific Circle of Willis Geometries

“…4(a). Horizontal dipping provides a greater uniform wall thickness when compared with vertical dipping, as demonstrated by Arcaute and Wicker [54], who replicated large-sized arterial vessels. The ABS inner core was attached to a fixture and slowly lowered into the silicone for one minute intervals, as shown in Fig.…”

“…This study describes the simulation of cerebral blood flow conditions through three thin walled CoW models manufactured from medical images. The application of the horizontal dipping procedure similar to that described by Arcaute and Wicker [54] for replicating large-sized vessels was key to creating uniform CoW models, with inner diameters ranging from 6.2 mm for the right ICA down to 0.7 mm for the AcoA. The CNC machined molds, as described by others for manufacturing the aorta [6,10,12,25] and carotid vessels [57] can replicate accurate arterial vessels, but these machined molds are not capable of creating complex cerebral networks which are quite torturous in multiple planes.…”

“…The inner core was slowly withdrawn using a DC rnotor/controller, which allowed the excess silicone to run off the model. A uniform wall thickness was achieved by removing the inner core at a slower rate at which the silicone mixture ñows down the core model [54]. To prevent webbing at branching points and damage to small diameter vessels (< 1 mm) a thin wall thickness of 0.1 mm was applied per dip and the inner core was horizontally rotated at 20 rpm (see Fig.…”

Multi-material stereolithography

“…Since their introduction more than 20 years ago, AM systems have been used in a variety of applications. These applications have ranged from the more conventional prototyping and rapid tooling (Radstok, 1999) to more advanced applications such as fabricating flexible cardiovascular models (Arcaute and Wicker, 2008), medical implants and tissue engineered constructs (Dhariwala et al, 2004;Arcaute et al, 2006;Lee et al, 2007;Choi et al, 2009b), 3D electronic devices (DeNava et al, 2008), micro-channels (Wicker et al, 2005b;Choi et al, in press) and various micro-systems (Mizukami et al, 2002;Palmer et al, 2006;Neumeister et al, 2006). There are numerous AM technologies available in the market.…”

Development of a mobile fused deposition modeling system with enhanced manufacturing flexibility

“…The heated extrusion process of a thermoplastic filament offered by FDM enables the use of virtually any thermoplastic material including several standard commercial thermoplastics such as ABS and polycarbonate (Stratasys, Inc., Eden Prairie, MN (http://www.stratasys.com)), a unique watersoluble material (Wicker et al, 2001;Medina, 2002, 2003;Cortez et al, 2007;Arcaute and Wicker, 2008), biocompatible materials (Espalin et al, 2010), heterogeneous materials (Qiu and Langrana, 2002), and many other material possibilities. These materials can be used in FDM to make arbitrary freeform shapes including movable mechanical parts that do not require assembly, and because many of these materials are similar to production materials, FDM offers the potential for incorporation, in some way, in finished part production and/or part repair.…”