ESCAPE21
Porto
Carras Resort, Chalkidiki –
“Nanoscale process systems engineering:
Design, fabrication, monitoring and control”
Thomas A. Adams II, Paul I.
Barton, and George Stephanopoulos
Massachusetts
Institute of Technology (MIT),
ABSTRACT:
Research
in nanoscale science and engineering1 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
devices (e.g. artificial tissues and sensorial systems, nanosystem biology for
health care and agricultural systems, scalable plasmonic devices,
chemico-mechanical processing, targeted cell therapy and nanodevices,
human-machine interfaces at the tissue and nervous system level) to become
reality.
Process
Systems Enginering (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. Thus, while novel deployments of fabrication
techniques (e.g. photolithographic pattern definition, etching, deposition,
diffusion) have been implemented for the construction of micro-processes, the
scope, theory and tools for “micro-scale process engineering” have remained
essentially unchanged.
Current
basic research though has pushed the scale of processing operations to
molecular and supramolecular levels of a few nanometers. Creative exploitation of hydrogen bonding, -stacking,
electrostatic and/or hydrophobic-hydrophilic interactions has led to deliberate
and purposeful molecular tectonics, yielding a fast growing repertory of
supramolecular structures with exquisite precision and functionalities, which
can and have been used as molecular
reactors, separators, molecular tubes, motors, shuttles or
pumps for the transport of materials,
molecular gates or channels for
the selective propagation of molecules,
etc.
With the
proposition of “nanoscale factories” as the next frontier of processing scales,
PSE must offer new theories and tools to handle the design, fabrication, simulation,
operation and control of active processing systems with the following
distinguishing features: (a) The “unit
operations” are self-assembled supramolecular 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.
Self-assembly
of molecules into supramolecular structures and their guided organization into
an integrated processing system are at the core of the needed new theories and
methodologies. Design issues arising
from the ensuing complexity and the looming threat of computational
irreducibility, must be addressed.
Information encoded into the judicious design of molecular structures
and networks is leading to a convergence of chemistry, biology and computer
science, with Systems Biology and the
recent emergence of Systems Chemistry being
the most visible manifestation. Molecular computers have opened the possibility
of preprogrammed operations at the local level of nanoscale unit operations and
the global scale of an integrated process.
What is the role of purposeful engineering, as exemplified by the
tradition of PSE, in shaping these developments?
In this
presentation we will discuss the foundational questions of nanoscale PSE that
need to be addressed with new theories and computational methodologies. In particular, we will discuss the following
scientific and technological questions: (1) How to synthesize the three
networks of chemical reactions (process topology; energy production and
dissipation system; monitoring and control), which compose the essential design
of any nanoscale process, using new views on self-replicating reaction
networks. (2) How to fabricate nanoscale
structures with desired geometries, using guided self-assembly processes. (3) How to engineer monitoring and control
systems, as integral parts of a processing topology, and how to deploy self-regulating
control architectures.