Three-dimensional self-assembly of structures using the pressure due to a ferrofluid in a magnetic field gradient

We developed an inexpensive and simple system for three-dimensional self-assembly of micron-sized nonmagnetic particles into millimeter-scale structures using the differential pressure exerted by ferrofluids in the presence of magnetic field gradients. We demonstrate it by assembling separate individual 5, 10, and 21μm diam polystyrene beads into millimeter-sized spherical and ellipsoidal structures. The system can also self-organize its smaller components by volume and provide compressive forces of hundreds of piconewtons on millimeter-scale structures. Extensions of this method have assembled multicellular systems.

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