Self-assembly of artificially manufactured microcomponents using the entropic effect

- Applicability of excluded volume effect was examined for self-assembly of microfabricated components.
- Microcomponents fabricated by negative-phtoresist were found to form clusters in the solution containing dense macromolecules upon agitation.
- Shape complementarity of bond formation was investigated to understand design rules for assembly of specific patterns.

The excluded volume effect, or depletion attraction, is the phenomenon describing induced aggregation of colloidal particles suspended in a densely crowded macromolecule solution. In this work, we attempted to utilize this effect for the self-assembly of artificially manufactured microcomponents on a 10-100 μm scale. The bonding energy does not originate from the nature of the surfaces, but is generated by an increase of the translational entropy of macromolecules in solution. Thus, simple immersion of the microcomponents in the macromolecule solution allowed us to observe their assembly, based on shape complementarity, to minimize the free energy of the system. However, it became apparent that elaborate design is required for specific bonding between complementary shapes, in addition to merely increasing the contact surface area.