Nature generates densely packed micro-and nanostructures to enable key functionalities in cells, tissues, and other materials. Current fabrication techniques, due to limitations in resolution and speed, are far less effective at creating microstructures. Yet, the development of extensive amounts of surface area per unit volume will enable applications and manufacturing strategies not possible today. Here, we introduce chaotic printing-the use of chaotic flows for the rapid generation of complex, high-resolution microstructures. A simple and deterministic chaotic flow is induced in a viscous liquid, and its repeated stretching and folding action deforms an ''ink'' (i.e., a drop of a miscible liquid, fluorescent beads, or cells) at an exponential rate to render a densely packed lamellar microstructure that is then preserved by curing or photocrosslinking.This exponentially fast creation of fine microstructures exceeds the limits of resolution and speed of the currently available 3D printing techniques. Moreover, we show that the architecture of the microstructure to be created with chaotic printing can be predicted by mathematical modelling. We envision diverse applications for this technology, including the development of densely packed catalytic surfaces and highly complex multi-lamellar and multi-component tissue-like structures for biomedical and electronics applications.
Conceptual insightsThis communication presents a simple, effective, and novel printing technique-one that is rooted in chaos theory and, more precisely, in the physics of chaotic mixing in a laminar regime. The main strength and differential attribute of this novel microfabrication strategy is its ability to create a densely packed microstructure at high resolution and speed in a predictable manner. Moreover, chaotic flows are deterministic, therefore, they are amenable to rigorous modeling and the microstructure resulting from them can be predicted using computational fluid dynamics platforms. In chaotic printing, a drop of ''ink'' (i.e., a drop of a miscible liquid, nanoparticles, or cells) is injected into a viscous and Newtonian soldifiable liquid. A chaotic flow is then applied to generate a very complex microstructure at an exponential rate, which is then preserved by a crosslinking or curing step. This exponentially fast creation of a linear structure (meters), and the accompanying rapid decrease in the length scales of the micro-and even nano-structure, is not currently achievable by any other 3D printing technique. We envision the use of this platform for many relevant applications such as the fabrication of complex tissues, catalytic surfaces, supercapacitors, and highly reinforced materials, among others.
