Nanoscale Process Systems Engineering Towards molecular factories, synthetic cells, and adaptive devices
Research in nanoscale science and engineering has been primarily directed towards the design and manufacturing of (a) materials with passive nanostructures (e.g. nanostructured coatings, dispersion of nanoparticles, and bulk nanostructured metals, polymers and ceramics), and (b) active devices with nanostructured materials (e.g. transistors, amplifiers, targeted drugs and delivery systems, actuators and adaptive structures). Research on the design, fabrication and operation of integrated “nanoscale factories”, i.e. processes with unit operations and materials movement among these units at the nanoscale, along with the requisite energy supply system and monitoring and control infrastructure, is lagging seriously behind. It is progress at this frontier that will enable the research visions of molecular factories, synthetic cells and adaptive devices1 (e.g. artificial tissues and sensorial systems, nano-system biology for health care and agricultural systems, scalable plasmonic devices, chemico-mechanical processing, targeted cell therapy and nano-devices, human-machine interfaces at the tissue and nervous system level) to become reality.
Process Systems Engineering (PSE) as an area of academic chemical engineering research, has effectively solved all the major technological problems associated with simulation, design, control, diagnosis, scheduling and planning of operations for large-scale continuous and batch chemical processes. As the focus of research moved in scale from cubic meters to cubic millimeters, the design, simulation, control and programmed operation of “plants or labs on a chip” benefited from the accumulated PSE technologies, since the underlying physico-chemical phenomena could still be handled under the same assumption of effective continuous media.
However, integration of functional nanoscale units into a coherent process with specific overall functionality and behavior has not yet started in earnest, and has only been mentioned in passing as a future goal and justification of current research. With the proposition of “nanoscale factories” as the next frontier of processing scales, PSE must offer new theories and tools to handle the design, simulation, operation and control of active processing systems with the following distinguishing features: (a) The “unit operations” are self-assembled supra-molecular structures at the scale of a few nanometers. (b) The spatial topology of the “process flowsheets” is guided by molecular scaffolds and the unit operations are positioned in space through directed self-organization mechanisms of independent units. (c) The operation of such “supramolecular factories” is driven by pre-programmed information encoded in the design of the system itself, and is robustly controllable through local feedback loops with no evidence of centralized coordination mechanisms.
In this presentation I will focus on two points: First, I will argue that the existing scope, theory and tools of PSE are insufficient for understanding the design principles and operational behavior of a nanoscale process, e.g. a eukaryotic cell or an artificial supramolecular factory. In order to set the background for this argument, we will briefly review (a) the structure and components of a nanoscale process, (b) the features that drastically differentiate them from processes at the macro- and microscale, and (c) the research trends in constructing nanoscale unit operations, material transport mechanisms, energy support systems, and molecular signaling networks for monitoring and control. Second, I will offer a series of research propositions that need to be addressed before Nanoscale PSE can tackle the deliberate engineering of living cells or the design of new classes of materials and devices based on active processing systems at the scale of a few nanometers.
