Microfluidic Capillary Arrays for Pixelated Control of Multimaterial Flows.

We present a novel approach for the production of customizable microscale multimaterial flow cross-sections. Here, a 3D-printed array of microfluidic capillaries selectively maps numerous viscosity-matched fluids to control the cross-sectional geometry of a heterogeneous Poiseuille flow. Whereas previous work has demonstrated relatively simple axisymmetric flows, our approach is highly scalable to complex cross-sectional geometries and large numbers of fluid inputs, and enables tailored cross-sections without the limitation of radial symmetries, enabling the production of arbitrary fluidic 'images'. We further design and implement an automated algorithm that generates a 3D model of an integrated flow extruder manifold tailored to the desired cross-sectional geometry, which is then 3D printed. This design exploits laminar flow conditions to scale down cross-sectional features, permitting an effective resolution amplification of two orders of magnitude from the minimum feature size of the 3D-printed device. We demonstrate the spatial tuneability of the approach with a variety of periodic and asymmetric multimaterial flow geometries and for hydrogel microfibre production, in doing so utilizing up to 2347 individually defined fluidic pixels. With the ability to arbitrarily define flow cross-sections with microscale precision, this approach has the potential to enable emerging applications requiring highly customized flows across optofluidic, biofabrication and lab-on-a-chip devices.