News in small-tech research and development

System maps nanomechanical properties

The National Institute of Standards and Technology (NIST) has developed an imaging system that quickly maps the mechanical properties of materials—how stiff or stretchy they are, for example—at scales on the order of billionths of a meter. The new tool can be a cost-effective way to design and characterize mixed nanoscale materials such as composites or thin-film structures.

The NIST nanomechanical mapper uses custom software and electronics to process data acquired by a conventional atomic force microscope (AFM), transforming the microscope’s normal topographical maps of surfaces into precise two-dimensional representations of mechanical properties near the surface. The images enable scientists to see variations in elasticity, adhesion, or friction, which may vary in different materials even after they are mixed together.

An AFM normally reveals a material’s topography (left). NIST’s new apparatus maps nanomechanical properties (right).
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The system can make an image in minutes whereas competing systems might take an entire day.

The images are based on measurements and interpretations of changes in frequency as a vibrating AFM tip scans a surface. Such measurements have commonly been made at stationary positions, but until now 2D imaging at many points across a sample has been too slow to be practical.

The DSP-RTS (digital signal processor-based resonance tracking system) can lock onto and track changes in frequency as the tip moves over a surface. It can produce a 256 × 256 pixel image with micro-meter-scale dimensions in 20 to 25 minutes. Adding capability to map additional materials properties can be as simple as updating the software.

CNT-based sources to improve electron microscopes

Xidex Corp. has won a contract from the US Department of Energy (DOE) for scalable manufacturing of carbon nanotube (CNT)-based field emission sources for use in scanning electron beam instruments such as scanning electron microscopes (SEMs) and transmission electron microscopes (TEMs). The project is aimed at significant improvement in the imaging resolution, signal-to-noise ratio, and processing speed of SEMs and TEMs used in materials science, biotechnology, forensics, medical research, the semiconductor industry, and the emerging nanotechnology industry.

A carbon nanotube AFM tip.
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“We plan to manufacture CNT field emitters on metal substrates that can be integrated into SEM and TEM electron guns,” says Vladimir Mancevski, Xidex’s CTO. “The company plans to demonstrate a scalable production processes for making the CNT emitters.”

CNT emitters directly address a longstanding problem in electron microscopy, says Paul McClure, Xidex’s president and CEO. “Electron optical columns have improved significantly in the last 15 years, but the field emission source itself has basically not changed. Our carbon nanotube-based source represents a new possibility for a breakthrough. This project will have a huge impact on all areas of electron microscopy.”

Partners to design “revolutionary” MEMS superheat control

Freescale Semiconductor and Microstaq are developing an intelligent refrigerant superheat control system that combines Freescale’s MEMS pressure sensing, processing, and control technology with Microstaq’s MEMS silicon expansion valve (SEV). These compatible high-pressure, high-flow solutions are designed to improve HVAC and refrigeration system energy efficiency and reliability, while also enabling predictive system maintenance, according to the companies’ claims.

Freescale’s advanced superheat control module is engineered to operate with HCFC and HFC refrigerants, including R410A, R407C, and R22. Microstaq’s high-pressure, high-flow silicon MEMS valve technology is capable of working with any refrigerant in an extremely compact package. The module is compatible with virtually all air conditioning, heat pump, and refrigeration applications.

“Microstaq’s silicon valves measure only 6 x 10mm and consume a fraction of the power of conventional solenoid or stepper motor designs while providing closed-loop control and higher accuracy,” says Sandeep Kumar, Microstaq’s president and CEO. “Our intelligent MEMS silicon expansion valves will revolutionize the flow control industry in the same way digital light processing [DLP] MEMS changed the display world.”

First reference materials for bionanotech

The National Institute of Standards and Technology (NIST) has issued its first reference standards for nanoscale particles targeted for the biomedical research community—literally “gold standards” for labs studying the biological effects of nanoparticles. The three new materials—gold spheres nominally 10, 30, and 60 nanometers in diameter—were developed in cooperation with the National Cancer Institute’s Nanotechnology Characterization Laboratory (NCL).

Nanosized particles are the subject of a great deal of biological research, in part because of concerns that in addition to having unique physical properties due to their size, they also may have unique biological properties. Research in the field has suffered from a lack of reliable nanoscale measurement standards, both to ensure consistency of data from one lab to the next and to verify the performance of measurement instruments and analytic techniques.

These gold nanoparticles serve as reference standards.
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The new NIST reference materials are citrate-stabilized nanosized gold particles in a colloidal suspension in water. They have been extensively analyzed by NIST scientists to assess particle size and size distribution by multiple techniques for dry-deposited, aerosol, and liquid-borne forms of the material. Dimensions were measured using six independent methods.

In addition, the materials have been chemically analyzed for the concentrations of gold, chloride ion, sodium, and citrate, as well as pH, electrical conductivity, and zeta potential. They have further been sterilized and tested for sterility and endo-toxins. Details of the measurement procedures and data are included in a report of investigation accompanying each sample.

Explosives-on-a-chip improve detonators

Tiny copper structures with pores at both the nanometer and micron size scales could play a key role in the next generation of detonators used to improve the reliability, reduce the size, and lower the cost of certain military munitions.

Developed by a team of scientists from the Georgia Tech Research Institute (GTRI) and the Indian Head Division of the Naval Surface Warfare Center, the highly uniform copper structures will be incorporated into integrated circuits, then chemically converted to millimeter-diameter explosives. Because they can be integrated into standard microelectronics fabrication processes, the copper materials will enable MEMS fuzes for military munitions to be mass-produced like computer chips.

“An ability to tailor the porosity and structural integrity of the explosive precursor material is a combination we’ve never had before,” says Jason Nadler, a GTRI research engineer. “We can start with the Navy’s requirements for the material and design structures that are able to meet those requirements.”

Georgia Tech researcher Jason Nadler poses with materials used to form copper structures that are precursors to explosive compounds.
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The research will lead to a detonator with enhanced capabilities. “The long-term goal of the MEMS Fuze program is to produce a low-cost, highly reliable detonator with built-in safe and arm capabilities in an extremely small package that would allow the smallest weapons in the Navy to be as safe and reliable as the largest,” says Michael Beggans, a scientist in the Energetics Technology Department of the Indian Head Division of the Naval Surface Warfare Center.

Reducing the size of the fuze is part of a long-term strategy toward smarter weapons intended to reduce the risk of collateral damage. That will be possible, in part, because hundreds of fuzes, each about a centimeter square, can be fabricated simultaneously using techniques developed by the microelectronics industry. The next step will be for Indian Head to integrate all the components of the fuze into the smallest possible package—and then begin producing the device in large quantities.

A specialist in metallic and ceramic cellular materials, Nadler says the challenge of the project was creating structures porous enough to be chemically converted in a consistent way—while retaining sufficient mechanical strength to withstand processing and remain stable in finished devices. “Designing materials on the nano-scale, micron-scale, and even the millimeter-scale simultaneously as a system is very powerful and challenging,” he says. “When these different length scales are available, a whole new world of capabilities opens up.”

Tiny gas sensor is quick, energy efficient

Engineers at MIT are developing a tiny sensor that could be used to detect minute quantities of hazardous gases much more quickly than current devices. The researchers have enabled the common techniques of gas chromatography and mass spectrometry (GC-MS) in a device the size of a computer mouse. They plan to complete the device within two years and eventually, to build a detector about the size of a matchbox.

Current versions of portable GC-MS machines, which identify gas molecules in approximately 15 minutes, are about the size of a full paper grocery bag and use 10,000 joules of energy. The researchers’ version consumes about 4 joules and produces results in 4 seconds.

Scaling down gas detectors makes them much easier to use in real-world environments, reduces the amount of power they consume, and enhances their sensitivity to trace amounts of gases, according to MIT professor Akintunde Ibitayo Akinwande. Also, smaller systems can be precisely and inexpensively built using microfabrication and batch-fabrication.

The analyzer works by breaking gas molecules into ionized fragments, which can be detected by their specific charge (ratio of charge to molecular weight). Gas molecules are broken apart by stripping electrons off the molecules, or by bombarding them with electrons stripped from carbon nanotubes. The fragments are then sent through a long, narrow electric field. At the end of the field, the ions’ charges are converted to voltage and measured by an electrometer.

Microfluidics device forms tumor for drug discovery

Researchers at the University of California, Berkeley, have developed a microfluidics device that can form tumor spheroids in a large-scale, reproducible manner amenable to high-throughput drug screening protocols.

Over the past few years, researchers have found that small, spherical conglomerations of tumor cells are superior to individual cells for predicting the response of malignant cells to a variety of anticancer treatments. To trap a reproducible number of cells in an environment that causes the cells to adhere to one another in discrete structures (the tumor spheroid), Luke Lee and colleagues designed a microfluidics device that uses the properties of fluid flow at the nanoscale to capture cells within a U-shaped structure.

MIT research scientist Luis Velasquez-Garcia, left, and professor Akintunde Ibitayo Akinwande, say their tiny sensor can detect biochemical warfare agents. Photo: Donna Coveney
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Once trapped, the cells continue receiving nutrients and oxygen—or added drug molecules—as the fluid passes through a tiny perfusion channel sounding the larger U-shaped structure, in much the same way that small tumors receive nutrients as they leak from surrounding blood vessels.

The researchers are able to create as many as 7,500 traps per square centimeter, each of which can hold between nine and eleven cells. Research by other investigators has shown that tumor spheroids of this size, though difficult to make, have higher resistance to drugs than do monolayers of cells.

Once trapped, the cells begin to adhere to one another, forming what resembles a small mass of cells, rather than a collection of discrete cells. These small masses may accurately represent tumors early in their development. The researchers note that they can alter the size of the U-shaped traps to produce larger spheroids.

nCoat collaborates with solar energy companies

Sunvention USA and BSR Solar Technologies GmbH are using nCoat’s nanotechnology coatings in a concentrated solar thermal power system, which concentrates solar radiation and creates highly efficient heat absorption and retention in the heat collection element. The two companies are also using nCoat coatings to protect solar “Green Energy” systems.

“Thermal absorption and transfer coatings used in solar energy production is a new market segment for nCoat,” says Paul Clayson, nCoat’s CEO. “Combining our nanotechnology coatings products and experience with commercialization of solar energy systems positions nCoat to capture revenue at the leading edge of the projected exponential market expansion.”

“Single nanotechnology” reduces precious metal requirement

Mazda Motor Corp. has developed what it is calling “the world’s first” catalyst for cars that uses “single nanotechnology” to substantially reduce the amount of precious metals required. Single nanotechnology, the company says, can control smaller-than-nanoscale particles.

The new development enables Mazda to reduce the amount of platinum and palladium used in automotive catalysts by 70% to 90%. And, the company says, it does not result in any changes in the performance of purifying gas emissions and maintains the high durability of conventional catalysts.

In automotive catalysts, precious metals promote chemical reactions that purify exhaust gases on their surfaces. In conventional catalysts, the precious metals are adhered to a base material. Exposure to exhaust gas heat causes the precious metal to agglomerate into larger particles. This reduces the catalyst’s effective surface area and catalytic activity, which requires the use of a significant amount of precious metals to counter and maintain an efficient purification performance.

To increase the precious metal surface area, the new catalyst uses particles less than 5nm in diameter. As a result, according to company claims, there is no agglomeration of the precious metal particles.