The DOE Office of Basic Energy Sciences (BES) comprises four divisions:
- Material Sciences ($302 million)
- Chemical Sciences ($156 million)
- Energy Biosciences ($25 million)
- Engineering and Geosciences ($16 million and $20 million, respectively)
The numbers in parentheses are the total operating expenses for each division in Fiscal Year 97, for a grand total of $519 million for BES. It is apparent that energy engineering research is only 3% of BES expenditures. Moreover, the other divisions have traditionally conducted a large part of their research on basic processes involving individual atoms, ions, and molecules in free flight or distributed on a surface; in many cases, these processes are nanometer-scale events. In contrast, engineering research has only recently been involved in sizes small enough that their relevant properties cannot be defined as a statistical average; hence, phenomenological laws are still a dominant feature of engineering research. For these two reasons, the current DOE effort to understand nanostructures is largely conducted in the first three science divisions listed above.
The history of technological advances is based on the need to produce devices that can perform a certain function in an optimum way in the context of some unavoidable constraints. Cost is often paramount; so are weight and dimensions. In some instances, large sizes are beneficial (e.g., economy of size in boilers, gas turbines, etc.), but in a number of cases, the trend towards smaller (and thus lighter) devices has accelerated. In particular, electronic chips have been steadily downsized to reduce the electron flight times and thus improve the speed of computer calculations. This has given birth to very efficient lithographic technologies; these, in turn, have led to microscale devices (cantilever beams, motors, burners) in the range between 1 mm and 1 micron. It has also made possible the design of sensors that can measure a range of microsize features inaccessible until recently (atomic force microscopy), and hopefully to control them. The engineering community is very involved with this upsurge of microelectricalmechanical systems (MEMS) technologies (there were 19 sessions on the subject at the Winter 96 ASME annual meeting!).
Another, newer thrust is the growing interest in quantum effects that appear at the next lower scale of events, from 1 micron to 1 nm, the so-called "nanophase." As mentioned above, these have been studied extensively in pure science-oriented research, that is, often in idealized conditions. In engineering applications, additional concerns are emphasized:
- the ability to represent phenomena that are likely to play a necessary part in an engineering device
- the ability to include a range of properties likely to be found in a realistic environment (ambient temperatures, complex geometries)
- the potential for manufacturing in quantity and at low cost
As mentioned earlier, the BES Engineering Division has a commitment to elucidate phenomena that are likely to become a factor in the operation of future technological devices. As a typical example, the study of multiphase flows has led to a thorough examination of boiling processes, with their variety of interfaces and associated dynamics (bubbles, droplets, slugs, etc.). This decade-long pursuit has led to increasingly lower scales: bubble generation in microcavities (Oregon State University), microsized pipes in heat transmission (Purdue University), and micron range phenomena near condensing surfaces. Similarly, research in suspensions has led to the study of diagnostics of microsized particulates (University of Minnesota). Very short time signals are also investigated in connection with fluxes through ultrathin materials (University of California, Berkeley). In the nano range itself, laser sources and two-dimensional electron waveguides are being explored (University of Texas, Austin).
Microengineering and nanoengineering research at BES has evolved out of other programs, and is not the result of the sudden creation of a large nanostructures program. This trend towards the phenomenology of smaller scales is likely to amplify in coming years. In addition, it should be kept in mind that a large amount of new nanoscale knowledge keeps being produced in the "pure sciences" divisions of BES, especially in the materials division.
An example of the extensive involvement of the materials division in nanostructure research is the multilaboratory project titled "Nanoscale Materials for Energy Applications," funded at over $7 million in FY 95. The project is one of the focuses of the DOE Center of Excellence for the Synthesis and Processing of Advanced Materials; its activities are discussed throughout the annual report Materials Sciences Programs FY 95 (DOE/ER-0682, May 1996), and its goals are summarized on p. 95: