squaresand

Squaresand is a synthetic granular medium consisting of uniformly sized, square-shaped particles. Designed for experiments in granular physics and for testing industrial handling of non-spherical grains, squaresand provides a controlled alternative to conventional sand, which is typically irregular in shape.

Particles are fabricated from glass, ceramic, or polymer by microfabrication or precision 3D printing to produce square cross-sections with flat faces. Typical particle sizes range from 0.5 to 5 millimeters, with tolerances kept within a few hundred micrometers. The material's surface roughness is controlled to adjust interparticle friction.

Squaresand exhibits distinct packing and flow behavior compared to spherical or rounded grains. The presence of sharp edges promotes interlocking, increasing the angle of repose and reducing flowability in hopper experiments. Packing fraction depends strongly on surface roughness and particle aspect, with researchers reporting higher jamming thresholds for square particles than for spheres of similar size.

Applications include fundamental studies of jamming transitions, granular segregation, and hopper discharge; teaching demonstrations of how particle shape affects bulk properties; and calibration material for granular flow simulators. Production remains specialized and is typically limited to research laboratories, though small-scale consumer experiments may use square-shaped beads produced by laser-cutting or 3D printing.

Variations include squares with beveled edges, hollow square shells to reduce density, and composites with coatings to modify friction. The term squaresand is sometimes used generically to refer to any square-particle granular material, rather than a specific product.