Electric-Field-Oriented Growth of Long Hair-Like Silica Microfibrils and Derived Functional Monolithic Solids

Controlled self-assembly using molecules/nanoparticles as building block materials represents an important approach for nanofabrication.

We present a "bottom-up" fabrication approach to first grow a new class of inorganic (silica) long hair-like microfibrils or microwires and then to form monolithic solid pellet that contains parallel arrays of bundled microfibrils with a controlled orientation. During the sol-gel solution processing, reactive precursor species are utilized as molecular "building blocks" for the field-directed assembly growth of microfibrils driven by an electric field of pulsed direct current (dc) with controlled frequency.

We have demonstrated a novel reactive electrofibrilation process that combines an external field with a solid-phase nucleation and growth process which in principle has no limitation on the type of reactions (such as the one here that involves sol-gel reaction chemistry) and on materials compositions (such as the example silica oxide), thus will enable bulk production of long microfibrils of wide variety of inorganic materials (other oxides or metals). Furthermore, we have fabricated uniquely architectured monolithic solid materials containing aligned microfibrils by "wet press" of the in-situ grown microfibril structure in the electric field. The consolidated monolithic slabs (1 cm × 1 cm × 3 mm) have shown anisotropic properties and desirable retention of DNA molecule fragments, thus, could serve as a platform stationary-phase materials for future development of capillary electrochromatography for biomolecule separations.

Electrical field-guided self-assembly is an effective approach in producing long (hair-like) ceramic microfibrils, which can be further used in consolidation fabrication of oriented structured ceramic monoliths with potential for capillary electrophoretic chromatography and other separations applications. This original work was recorded through a patent application to understand the fibril formation mechanism and its process.