Nowadays the need to study cells and tissues in environments more similar to physiological ones turns out to be one of the greatest tools for the development of new bioreactors, and to better understand most of the physiological phenomena at cell and tissue level. Soluble species spatial gradients are known for their morphogenic action during cell development, and they take place in a three-dimensional (3D) environment. In addition, the 3D gradient of mechanical properties of each tissue influences cell migration, differentiation and activities. In this work we describe the design and realization of a bioreactor able to generate three-dimensional concentration gradients, and the realization of a gel matrix with a 3D gradient of mechanical properties. The topology of this device was initially designed and modelled using Computational Fluid Dynamics (CFD), and subsequently realized through rapid prototyping techniques. A hydrogel matrix was then polymerized in the main chamber in order to “froze” the gradient. The matrix had an inner gradient of mechanical properties, because a 3D gradient of cross-linker was established in the main chamber before  polymerization was started.