Bioprinting is a new way to build living tissues in a lab, and it offers great hope for modern medicine. A Bioprinting CFD simulation is a key tool that helps scientists understand and improve this process. In this method, special cone-shaped needles are used to print a special gel called a bioink, which contains living cells. The shape of the conical needle is very important. However, pushing the bioink through the tiny needle tip can create strong forces that damage or kill the cells. A Bioprinting With Conical Needle Fluent simulation lets us see these invisible forces and understand the mechanical cell damage. By studying the bioink flow, we can design better needles that protect the cells. This helps improve cell viability and makes the final printed tissue healthier and stronger. This CFD study is based on the methods in a trusted research paper [1].

• Reference [1]: Li, Minggan, et al. “Modeling mechanical cell damage in the bioprinting process employing a conical needle.” Journal of Mechanics in Medicine and Biology05 (2015): 1550073.

Figure 1: A diagram of the bioprinting process showing the conical needle, the focus of this Tissue Engineering CFD study [1].

Simulation Process: Fluent Setup, Meshing the Conical Needle Geometry

For this Conical Needle CFD analysis, we first created a 2D model of the tapered needle geometry based on the exact sizes given in the reference paper [1]. Then, using ANSYS Meshing, we created a perfect, structured grid with 100,000 cells. A structured grid gives very accurate results for this kind of simple, straight geometry. In ANSYS Fluent, we defined the bioink as a cell-alginate mixture. This careful setup allows us to accurately calculate the forces that act on the cells as they are pushed through the needle.

Post-processing: CFD Analysis, Visualizing Bioink Velocity and Damaging Wall Shear Stress

The velocity contour provides a clear, professional visual of the bioink flow. The professional visual shows that as the bioink is squeezed from the wide entrance to the narrow tip, it speeds up very quickly. The speed increases from almost 0 m/s to a maximum of 367.2 m/s at the exit. This rapid change in speed creates stretching forces. Cells in the center of the needle move much faster than cells near the wall. This difference in speed can stretch the cells and damage their delicate outer membranes. This first step of the analysis shows us where the flow becomes dangerously fast.

Figure 2: Velocity distribution from the Bioprinting With Conical Needle CFD analysis, showing the rapid acceleration of the bioink.

The wall shear stress contour shows us the direct result of this high speed and is the most important factor for cell damage. This professional visual pinpoints the exact danger zone for the cells. The stress on the cells rises to an extremely high level right at the narrowest part of the needle. Our analysis measured the peak wall shear stress at an incredible 4,100,000 Pascals. This force is thousands of times higher than what a living cell can survive. The contour also shows that this dangerous stress happens in a very small area, creating a sudden, sharp spike that is very harmful. The most important achievement of this simulation is the precise identification of the location and magnitude of this deadly shear stress spike, giving engineers the exact information they need to redesign the needle’s shape to reduce these forces and dramatically improve cell survival in future bioprinting applications.

Figure 3: Wall Shear Stress distribution from the Conical Needle Fluent analysis, highlighting the peak stress location that causes mechanical cell damage.