Molecular Diodes: Irreversible Motion in Nanofabricated Arrays
PRINCETON UNIV NJ
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The metamaterial design is summarized in Fig. 1. We were able to show 1 that it is possible to direct particles entrained in a fluid along trajectories much like rays of light in classical optics. A nanostructured, asymmetric post array forms the core hydrodynamic element and is used as a building block to construct nanofluidic metamaterials and to demonstrate refractive, focusing and dispersive pathways for flowing beads and cells. The core element is based on the concept of deterministic lateral displacement where particles choose different paths through the asymmetric array based on their size Particles larger than a critical size are displaced laterally at each row by a post and move along the asymmetric axis at an angle to the flow, while smaller, sub-critical particles move with the flow. We create compound elements with complex particle handling modes by tiling the core element using multiple transformation operations we show that particle trajectories can be bent at an interface between two elements and that particles can be focused into hydrodynamic jets using a single inlet port. Although particles propagate through these elements in a way that strongly resembles light rays propagating through optical elements, there are unique differences in the paths of our particles as compared to photons. The unusual aspects of these modular, nanofluidic metamaterials form a rich design toolkit for mixing, separating and analyzing cells and functional beads on-chip. As an example of the modular aspect of the metamaterial design, Fig. 2 shows the paths formed by particles in a series of focussing and defoccusing hydrodynamic lenses.