This research was received in response to the Active Nanostructures and Nanosystems initiative, NSF 06-595, category NIRT. Manufacturing at the nanometer-scale has the traditional challenges associated with ensuring superior quality, cost, speed, and production flexibility, as well as added constraints on the precise molecular/atomic configuration of the product. This research seeks to develop the molecules, hardware, and software needed to meet the challenges of hierarchical nanomanufacturing. Precise control of solution processed inorganic materials will be achieved using inorganic synthesizing proteins (ISPs) that are identified via combinatorial biology. ISPs are growth 'seeds' that can nucleate the target inorganic materials when brought into contact with an engineered aqueous electrolyte. Hardware for ISP seed 'planting' will rely on the protein-compatible patterning techniques dip-pen nanolithography, micro-contact printing, and thermo-responsive protein adsorption. New software algorithms are being developed to compute the optimal locations for planting ISP seeds on a surface to produce the highest accuracy object with the fewest number of tool moves. The final step in the protein-aided manufacturing process is to immerse the seeded surface in the growth electrolyte to spontaneously grow the object. Several scientific issues will be addressed. Rapidly identifying ISPs with selective affinity for specific inorganic polymorphs is key to understanding and controlling the growth of materials with desired crystallinity. The impact of protein patterning method on the molecular orientation and synthesis activity of ISPs will be studied, as will the scale-dependence of patterning and growth. Robust geometric modeling and tool path planning software will be developed to ensure good build fidelity for both isotropic and anisotropic crystal growth over hierarchical geometries. This research addresses key societal challenges associated with alternative energy, sustainability, and the development of scientific and engineering human resources. The technology test bed for this research is the fabrication of ZnO solar cells, where new nanomanufacturing approaches offer the potential for significant improvements in performance and cost of solar energy conversion. Currently, solar cells and most electronic devices are made using high temperature, low pressure, and toxic reagents. The room temperature, water-based protein-aided manufacturing process proposed here demands modest energy inputs and uses low toxicity precursor reagents, thereby impacting the sustainability and efficiency of our economy. The graduate students working on this project will be integrated into nanotechnology-oriented programs aimed at improving the diversity of scientists and engineers, as well as a global partnership where they will have the opportunity to gain international experiences.
This ambitious project engaged an interdisciplinary team of scientists and engineers to bring the power of biology to nanomanufacturing. In nature, proteins orchestrate the growth of biological hard tissues such as bones, teeth, and shells made of inorganic materials, without the need for external tools. In contrast, manufacturing relies heavily on the use of tools to orchestrate how materials come together to create useful products like photovoltaic solar cells. Here we engineered proteins to serve the same function as proteins in nature---nucleation, growth and orchestration of inorganic materials---but we create them for materials with technological uses. We demonstrate the engineering proteins, and show they can nucleate and modify the formation of zinc sulfide and zinc oxide, two semiconductors that are useful in solar energy harvesting, as well as silver, a plasmonic metal with high conductivity, and calcium phosphate, a biological material. Through this work, we have helped establish the ground rules for extending the power of proteins into the manufacturing domain. At the same time, we have demonstrated a new method to accelerate the patterning of material "seeds"---the locations where materials nucleate and grow---so that tool-directed orchestration of thin film patterning is much more effecient than traditional tools used for nanomanufacturing. A mathematical model is developed to describe the growth of metals from seed sites, and it is used to optimize the use of tools for patterning. We call this process "orchestrated structure evolution" (OSE), and find that OSE can accelerate thin film patterning by 100X compared to conventional raster patterning used in nanomanufacturing.
