NIST Tech Beat - September 26, 2003

Using laser light as tweezers and a scalpel, scientists from the National Institute of Standards and Technology (NIST) have demonstrated the use of artificial cells as nanovials for ultrasmall volume chemistry. The approach may be useful for faster, cheaper identification of new pharmaceuticals and for studying cellular-level processes. The researchers will report their results in the Sept. 30 edition of Langmuir.

Top: Fluorescent images show two liposomes, one filled with dye and another filled with calcium ions.

Bottom: After fusing, the contents of the liposomes mix and react producing an increase in the total fluorescence.

The artificial cells, called liposomes, are tiny spherical containers that self-assemble from natural fats (phospholipids and cholesterol). Measuring micrometers in diameter, the fluid-filled membranes are currently used in cosmetics and for drug delivery.

The NIST team developed an improved method for using liposomes as tiny test tubes for mixing chemicals with volumes measured in trillionths of liters. Their experimental setup allows simultaneous trapping of two liposomes without deforming or stressing their membranes, a problem with some other techniques. They used pairs of infrared lasers ("optical tweezers") to bring two liposomes into contact and a single ultra-violet laser pulse (the "optical scalpel") to fuse the two cells together. Once fused, the contents of the two cells mix and react. One liposome in each pair contained fluorescent dye, and the other contained calcium ions. After the cells merged, fluorescence increased as a result of the reaction between the dye and the ions.

The optical scalpel achieves cleaner fusion and less leakage of contents than the typical technique using pulsed electric fields. The liposomes fully enclose their reactant chemicals, minimizing evaporation. Consequently, the technique also may be useful for quantitative studies of chemical reactions involving samples in the quadrillionths of liters.

Rating the Performance of Residential Fuel Cells

Residential fuel cells sound almost too good to be true. Take a hydrocarbon fuel such as natural gas, use a catalyst to extract hydrogen from it, react the hydrogen with air and, presto, you have a home power plant!

As the hydrogen and the oxygen in the air combine, they produce electricity. The primary “waste products” of the whole process are water and heat. But that’s not all! The "waste" heat can be captured to provide space or water heating for the home.

Residential fuel cell systems can produce about five kilowatts of power or 120 kilowatt-hours of energy a day—more than enough to operate the average household. But a lack of performance data on how well fuel cells work under different conditions is one of several factors slowing marketplace acceptance of the new technology.

Researchers at the National Institute of Standards and Technology (NIST) have just launched an effort to supply the needed information. They are studying how changing electrical and heating demands, outside temperatures, humidity and power systems affect the efficiency of fuel cells made by different manufacturers.

NIST will submit its draft fuel cell test procedures and rating methodology to a standards committee composed of industry, independent standard organizations, government and academic representatives. With consensus procedures in place, fuel cell manufacturers should be able to evaluate and improve the electrical and thermal energy efficiency and output of their products. Ultimately, consumers will be able to use NIST-developed performance ratings to understand the financial costs and benefits of fuel cells operated in specific geographic and climate conditions, at different times of the year, and for different purposes such as heating or electricity generation.

Dual Microscopes Illuminate Electronic Switching Speeds

Designers of semiconductor devices are like downhill skiers—they thrive on speed. And achieving speed in the semiconductor business is all about the stuff you start with. While silicon is still the mainstay of the industry, circuit designers also would like to put materials like gallium nitride and silicon carbide into wider use. Such advanced semiconductor materials can operate at higher voltages and provide faster switching speeds, an important characteristic in determining how fast a semiconductor circuit can process information.

Reporting in the Sept. 22 issue of Applied Physics Letters, a National Institute of Standards and Technology (NIST) researcher and a Korean guest researcher describe a new method for scanning semiconductors for defects that may help accelerate the market for these newer materials. The duo combined an atomic force microscope with a scanning capacitance microscope and then added custom software and a simple on/off switch for the AFM’s positioning laser.

The result is an instrument that can measure how fast a material generates electrical charges and then map those speeds in sections (at least for gallium nitride) that are only about 100 nanometers square. Current methods for measuring switching speed (carrier lifetime) produce only bulk averages.

According to NIST co-developer Joseph Kopanski, the system allows quick scanning of semiconductor wafers for defects that otherwise may not be found until an expensive device has already been built on the material. Most defects in semiconductors (i.e. sections with missing atoms) are presumed to slow down the speed that charges move through a material. Kopanski says further research using the new technique should determine if this assumption is correct. A patent application is pending on the technique.

Metal Stamping Project Aims
At Cutting Manufacturing Costs

With new, one-of-a-kind test equipment, National Institute of Standards and Technology (NIST) researchers aim to stamp out costly, delay-causing errors in the design of dies used to make sheet-metal parts ranging from car hoods to airplane wings to pots, pans and cans.

The U.S. auto industry alone is estimated to spend more than $700 million a year on designing, testing, and correcting new dies for its latest models, each containing about 300 stamped parts shaped by dies and presses. About half of the total goes for remedying unanticipated errors—manifested as wrinkles, splits, excessive thinning or other defects.

By fitting NIST's metal-stamping test station with an X-ray stress measurement system, the Institute’s materials scientists now can make detailed maps of stresses and strains as sheets of steel and other metals are punched, stretched or otherwise shaped to achieve the desired part geometry. According to project leader Tim Foecke, the system can measure stress and strain behavior in many different directions while the sheet is being stretched in two directions simultaneously, a condition most commonly seen in forming operations. Current methods extrapolate from strain measurements taken from tests that stretch the sheet in only one direction. As a consequence, newly designed dies often must undergo successive rounds of refinement to correct for these simplifications in computer models.

U.S. automakers and producers of steel, aluminum and other metals, including developmental ones, are supplying Foecke’s team with samples for testing and evaluation. The project will result in a novel database of materials’ properties that designers can feed into computer models for predicting whether would-be dies can form particular metals into specified shapes, within tolerances. Project findings might point the way to new metal-forming methods.

Cases Protect Cherished Documents From Hurricane Isabel

Only a day after their debut at the National Archives, new high-tech encasements for the nation’s most cherished documents—the Declaration of Independence, Constitution and Bill of Rights—were locked in a “battle of the bulge” with Hurricane Isabel. Designed and built by researchers at the National Institute of Standards and Technology (NIST), the hermetically sealed, titanium-framed encasements were commissioned by the National Archives to preserve the nation’s “Charters of Freedom” for future generations.

The significant drop in atmospheric pressure (about 23 millibars) due to Hurrican Isabel, caused the glass covers of the precision-machined encasements to deflect outward by an estimated 2.4 millimeters. No problem. The bulge was well within the limits set by the NIST team, who factored in the potential for the most severe hurricane-caused pressure drops conceivable into their design. The encasements were unveiled on Constitution Day, Sept. 17. For more on the encasements, go to: www.nist.gov/public_affairs/Charter/charters_of_freedom_project.htm.

Free CD Demystifies Complex Standards System

A new CD from the National Institute of Standards and Technology (NIST) can help steer engineers, novice trade-association representatives and new government staffers through the thicket of organizations, activities, policies and laws related to standards and measurement in the United States.

With an easily digested helping of technical detail, the free electronic primer* provides an integrated view of major public and private-sector components of the nation’s measurement and standards system. These elements are sized up from several key perspectives, including global trade and regulatory affairs.

Capsulized descriptions are supplemented by pointers to copies of trade agreements, federal laws and other background documents. Links to relevant Internet resources, such as Web sites of standards development organizations and regional measurement alliances, are found throughout. For example, the section on conformity assessment (the umbrella term for testing and other means of assessing whether a product meets regulatory and customer requirements) contains pointers to copies of international agreements and other efforts to harmonize such formal requirements. It also features links to multinational organizations working to eliminate duplication or needless variation in the standards and regulations of trading partners.

Five major sections survey relevant topics and activities in the areas of measurements, standards, conformity assessment, regulations and global activities. An additional section describes NIST, its programs, and its supporting technical roles and services.

To get a copy of the compendium-like CD, contact the editor, Elisabeth Parker, at
(301) 975-3089; or elisabeth.parker@nist.gov. Note: (added 3/31/04) Current supplies of the CD are exhausted. Additional copies are expected in a few months.

*An Overview of the U.S. Approach to Standards, Conformity Assessment, and Metrology (NISTIR 6978)

World Trade Center Information Needed—The National Institute of Standards and Technology (NIST) recently detailed its plans to collect first-person data to study occupant behavior and evacuation, and emergency response as part of the federal building and fire safety investigation of the World Trade Center (WTC) disaster following the terrorist attacks of Sept. 11, 2001. Survivors, first responders (including retirees) and family members who communicated with victims after the aircraft impacts also are being asked to contact NIST toll-free at (877) 221-7828 to learn if and how they can volunteer to participate. For more information, go to http://wtc.nist.gov/media/provide_info.htm.

Ionizing Radiation—The 12th annual meeting of the Council on Ionizing Radiation Measurement and Standards will be held at the National Institute of Standards and Technology (NIST) in Gaithersburg, Md., on Oct. 27-29, 2003. Topics covered will include: traceability in measurement standards for medical applications; homeland security; occupational, public and environmental radiation protection; and industrial applications and materials effects. For further information, see: www.nist.gov/public_affairs/confpage/new031027.htm.

Tiny "Test Tubes" May Aid Pharmaceutical R&D

Rating the Performance of Residential Fuel Cells

Dual Microscopes Illuminate Electronic Switching Speeds

Metal Stamping Project Aims At Cutting Manufacturing Costs

Cases Protect Cherished Documents From Hurricane Isabel

Free CD Demystifies Complex Standards System

Tiny "Test Tubes" May Aid
Pharmaceutical R&D

Metal Stamping Project Aims
At Cutting Manufacturing Costs