Powder-Based 3D Printing of Autonomous Concentration Gradient Generators

Concentration gradients feature widely in many biomedical processes (e.g., cell evolution, chemotaxis, personalized healthcare, and drug screening). The concentration gradient generators (CGGs) developed previously have used either static gradients or gradients maintained by a continuous co-flow. This article describes a platform for the manufacture of autonomous CGGs through inkjet 3D printing on a powder bed. The intrinsic microporosity of the 3D-printed devices produces efficient flow-independent gradient profiles. Computational fluid dynamics modeling of the porous devices reveals that mechanical dispersion, rather than diffusion or flow velocity, dominates the gradient formation. The gradients remain stable for up to 120 h with no need for external pumping systems and with minimal user intervention because on-device evaporation and capillary forces are the sole drivers. The ease of transitioning between a computer model of an object and its fabrication allows the rapid development of custom concentration gradients.