(266b) Engineering Tunable Hydrogel Beacon Arrays for Extended-Range Colloidal Transport

The short range of conventional, equilibrium-based interactions in aqueous suspensions—typically well under a micron—often poses a significant challenge when manipulating colloidal systems over larger distances. Anirudha et al. recently introduced an alternative mechanism, termed “soluto-inertial” (SI) interactions, whereby hydrogel beacons charged with solute establish and maintain chemical potential gradients. These gradients can drive diffusiophoretic migration of colloidal particles across millimeter-length scales, with each particle type responding according to its specific surface–solute interactions. Previous efforts largely focused on single, homogenous beacons, limiting the complexity of particle trajectories.

Here, we present a versatile extension of the SI approach by deploying arrays of hydrogel beacons with distinctly varied compositions and solute loading profiles. Within a microfluidic environment, these compositionally diverse beacons create overlapping chemical fields that selectively attract or repel specific colloids, enabling parallel sorting and patterning without external pumps or complex geometries. We systematically characterize how differences in beacon properties—such as partition coefficients, swelling behavior, and spatial placement—alter the solute gradients and long-range particle migration.

These findings demonstrate a straightforward method for engineering large-scale colloidal organization using only passive chemical gradients. By combining multiple beacon types into a single platform, we greatly expand the palette of achievable SI interactions, setting the stage for advanced applications in separations, sensing, and tailored soft-material assembly.