Computational Investigation of Tissue and Blood Vessel Growth Trade-Offs in Hierarchical Lattices

Computational design is growing in necessity for advancing biomedical technologies, particularly when considering complex systems with numerous trade-offs among design decisions and resulting biomechanical behavior. In tissue engineering applications, porous bone scaffold structures enabled by 3D printing can have intricate lattice structures and hierarchical features that mimic the biological hierarchy of natural bone. However, these hierarchies create challenges in predicting the tissue regeneration process and how different scales of the hierarchy drive varied biological behaviors. Smaller pores facilitate tissue growth while larger pores are necessary for blood vessel growth, however, identifying favorable trade-offs to maximize growth of both tissue and blood vessels remains a challenge, especially for complex 3D printed structures. Here, we adapt tissue and blood vessel growth models for predicting biological growth in scaffolds with varied combinations of beam diameter size, unit cell topology, and hierarchical pore size/distribution. Findings demonstrate that on a normalized scale lattices with no large voids provide greater tissue growth but less blood vessel growth in comparison to lattice layouts with large void areas. A lattice with large void channels provided the greatest blood vessel growth but poorer tissue growth, while a lattice with evenly distributed large voids provided a better compromise between the two types of growth. Overall, these findings demonstrate the merit in computational investigations for design trade-off comparisons in tissue scaffolds, and provide a foundation for future explorations of biological design decisions for regenerative medicine and 3D printed systems.

W. LaJean Chaffin, Ph.D.

It is with deep sadness that we report the death of W. LaJean Chaffin, PhD. Dr. Chaffin died at her home in Lubbock, Texas on April 20, 2021. LaJean was an exceptional individual, both personally and professionally, and she will be greatly missed. Her passing leaves a large void in our field of medical mycology.…

Non-stackable molecules assemble into porous crystals displaying concerted cavity-changing motions

With small molecules, it is not easy to create large void spaces. Flat aromatics stack tightly, while flexible chains fold to fill the cavities. As an intuitive design to make...

Influence of Heat Reflective Coating on the Cooling and Pavement Performance of Large Void Asphalt Pavement

To reduce the temperature of asphalt pavement in summer, and alleviate the urban heat island effect, a comprehensive method of combining a heat reflective coating and large void asphalt pavement was proposed. Using the developed coating cooling test equipment, the cooling effect of the coating on a large void asphalt mixture was studied in six different proportions, four different colors, and four different dosages, and the durability of the coating was verified by abrasion tests. Finally, the best dosage of the coating was recommended through an adhesion test of the coating, and a water permeability and anti-skid performance test of the pavement. The results show that the reflectivity of the coating can be improved by adding functional fillers, of titanium dioxide and floating beads, into the coating. The order by reflectivity and cooling effect of the four color coatings was green > red > gray > blue, and the maximum cooling value of the green coating reached 9.7 ℃. The cooling performance of the coating decreased with the increase of wear time, and the rate of decrease was fast, then slow, and finally tended to be stable after 20,000 times wear. The coating reduced the anti-skid performance and the water permeability coefficient of large void asphalt pavement, but still maintained a high level. The green coating with 15% titanium dioxide and 10% floating beads is recommended as the cooling coating for large void asphalt pavement, and its dosage should be controlled at about 0.4–0.8 kg/m2.

Particulate Scale Multiparticle Finite Element Method Modeling on the 2D Compaction and Release of Copper Powder

Herein, two-dimensional (2D) single-action die compaction process of copper (Cu) powder was simulated by the multiparticle finite element method (MPFEM) at particulate scale. The initial packing structure, generated by the discrete element method (DEM), was used as an input for the FEM model, where the mesh division of each particle was discretized. The evolution of macro- and microscopic properties, such as relative density, stress distribution, particle deformation, void filling behavior, and force transmission, during compaction and pressure release processes have been systematically studied. The results revealed that the force is mainly concentrated on largely deformed regions of the particles during compaction and formed a contact force network, which hindered the densification process. In the compact, the shorter side of the large void edges rendered higher stress than the longer side. On the other hand, the stress distribution of small void edges remained uniform. After pressure release, large residual stress was observed at the contact area of the adjacent particles and the maximum stress was observed at the particles’ edges. Moreover, the residual stress did not proceed to the interior of the particles. Meanwhile, the stress of large void edges has been completely released but exhibited a nonuniform distribution. The smaller fraction of void filling resulted in a larger reduction of the released stress after pressure removal. Also, the particles closer to the upper die exhibited higher average equivalent von Mises stress inside the particles during compaction and pressure release processes.