Aerosol-based technologies in nanoscale manufacturing: from functional materials to devices through core chemical engineering

Manufacturing of nanoscale materials and devices offers a number of exciting opportunities for chemical engineers to contribute substantially in product development, process scale-up, and environmental compliance. Current research in nanoscale science and engineering has been directed primarily toward the design and synthesis of (a) materials with passive nanostructures (e.g., nanostructured coatings, dispersion of nanoparticles, as well as bulk nanostructured metals, polymers and ceramics), and (b) active devices with nanostructured materials (e.g., transistors, amplifiers, targeted drugs and delivery systems, sensors, actuators and adaptive structures). Such materials are usually produced through self-assembly of nanoparticles in gasor liquid-phase processes or through compaction of nanopowders. Even though nanoparticles have been in use for a long time (e.g., carbon black, photographic films, fumed silica), the knowledge base for their synthesis and characterization has increased dramatically in the last 30 years with the development of a number of sophisticated scientific instruments, new synthetic processes at the nanoscale, and computational advances. This progress has contributed decisively to the development of effective and quantitative understanding of (a) nanomaterial properties and their dependence on their constituent parts, and (b) synthesis methods on which their fabrication is based, resulting in the discovery of new materials with an array of new functionalities and potential applications with promises of more to come in the future. To date, however, rather little of the aforementioned has been translated into actual industrial products. Most of these exciting discoveries have been made in basic science laboratories with little motivation or capacity to investigate and invent processes for the economic manufacturing of these nanotechnology products; the ‘‘bread and butter’’ of chemical engineers. In fact, little is known about how well these new properties are reproduced during large-scale manufacturing of such nanomaterials. More importantly, there is little understanding on how such manufacturing processes can be designed and operated, while issues arise regarding the controllability of such process operations and sustainability of the product quality, safety and potential hazards for personnel, environment and consumers. The associated risks constitute key issues in developing manufacturing technologies by major industries, a drive that has been part of what is recently referred to as ‘‘green’’ manufacturing. Two of the major challenges are: first, low-cost manufacturing of sophisticated nanostructured materials, and second, the economical and reliable assembly of such materials into functional devices. To meet these challenges a quantitative advancement of the current understanding of the corresponding manufacturing technologies is needed for the synthesis of mixed, functionalized and/or layered nanomaterials, significantly beyond the simple ones in the market today, with close attention to product handling, safety and health effects. Furthermore, assembling of devices with such materials (e.g., synthesis, deposition and processing of multilayers of functional nanoparticles) is needed to meet today’s engineering challenges in energy, mobility, health and life sciences (e.g., nonintrusive medical diagnostics and even cures for chronic and serious illnesses). While most of the current research in nanotechnology is driven by the imperative of scientific questions on the synthesis and characterization of passive nanoscale materials and/or active devices, with minimal attention paid to the Correspondence concerning this article should be addressed to S. E. Pratsinis at sotoris.pratsinis@ptl.mavt.ethz.ch.