A team of researchers at TU Delft has further optimized the process of 3D printing graded microstructures. A lot of minds are working on this problem because graded densities make for an incredibly efficient use of mass. Bones are a great example: a bone’s density is higher where the bone endures more strain and lower where it bears less weight. As a result, the bone has a high strength-to-weight ratio and is rigid where it needs to be while also being more flexible at other points. That change in density is a microstructure gradient, and it’s found all throughout nature, but 3D printing those gradients has proven difficult.
The main obstacle to fabricating microstructure gradients is matching the compatibility of adjacent unit cells; the microstructures have to physically connect with each other, but with differing densities, their geometries don’t necessarily align well, meaning some unit cells won’t be touching the adjacent unit cells of a differing grade. This creates structural integrity issues that can cause problems during and after a 3D print. The solution is mostly computational and algorithmic because the best 3D printing hardware can produce pretty much any geometry. The trick is creating that geometry.