4. Biomimetic assembly of functional nanoscale materials.

Assembly of functional inorganic nanomaterials is a fundamental challenge. Nature adopts a superior approach in biomineralization, where “matrix” macromolecules induce nucleation of inorganic crystals at specific locations with controlled size and morphology, and sometimes even with defined growth orientation. We apply the biomimetic principles derived from biomineralization processes to the assembly of nanoscale functional materials into nanoscale systems. We carefully control surface organic molecules to promote heterogeneous nucleation at designated regions while completely suppress homogeneous nucleation elsewhere, therefore enable the controlled bottom-up assembly of inorganic nanomaterials directly from solution. Following this principle, arrays of crystalline ZnO nanorods and CdS semiconductor materials were nucleated and assembled directly from solution onto flexible polymer substrates at the desired precise locations and then fabricated into arrays of photodetector devices for large-area macroelectronic applications.

Figure 5. ZnO and CdS nanomaterials assembled on flexible polymer substrates following the biomimetic approach and their applications for macroelectronics.

This biomimetic approach is general to many semiconducting, magnetic, and other functional nanomaterials and many polymer substrates of arbitrary shape. In collaboration with Prof. Paul Nealey’s group from ChemE department at UW-Madison, We have expanded this approach to truly nanoscalebottom-up assembly using self-assembled nano-structured block copolymers as templates. Furthermore, in collaboration with Prof. Ron Rianes’ group and Prof. Sam Gellman’s group, we are exploiting synthetic collagen protein and b–peptide fibrils to specifically nucleate and assemble nanocrystals in a programmable fashion.