Rapid diagnostic testing at the site of the patient is essential when a fully equipped laboratory is not accessible. To maximize the impact of this approach, low‐cost, disposable tests that require minimal user‐interference and external equipment are desired. Fluid transport by capillary wicking removes the need for bulky ancillary equipment to actuate and control fluid flow. Nevertheless, current microfluidic paper‐based analytical devices based on this principle struggle with the implementation of multistep diagnostic protocols because of fabrication‐related issues. Here, 3D‐printed microfluidic devices are demonstrated in a proof‐of‐concept enzyme‐linked immunosorbent assay in which a multistep assay timeline is completed by precisely engineering capillary wetting within printed porous bodies. 3D printing provides a scalable route to low‐cost microfluidic devices and obviates the assembly of discrete components. The resulting rapid and seamless transition between digital data and physical objects allows for rapid design iterations, and opens up perspectives on distributed manufacturing.

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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.

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