Hierarchical assembly of protein microspheres

•Hierarchical self-assembly of functionalized protein microspheres.•Static self-assembly produces protein scaffolds with controllable properties.•Directed-assembly of magnetic functionalized microspheres produces flexible fibers.•Promising for tissue scaffold and micro-mixing applications.

We demonstrate two techniques for the hierarchical assembly of protein microspheres into larger structures. In the first, static self-assembly driven by the buoyancy force of low-density protein microspheres creates a close-packed ensemble, which is freeze dried to form a protein scaffold. The internal pore size and surface area can be controlled through the protein microsphere diameter. In the second technique, directed-assembly of magnetic nanoparticle functionalized protein microspheres is demonstrated. An applied magnetic field directs the assembly into flexible fibers with lengths controlled by the microsphere number density. Taken together, these techniques provide a starting point to explore the design and assembly of complex functional materials.

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