• Intrinsically nanoscale: Nanoscale dimensions enable new capabilities in magnetometry, including determinations of spatial variations in magnetic fields using parallel measurements.
  
  
• Temperature resilience: The technology is insensitive to temperature from -173 °C to room temperature, making it suitable to a wide range of operating conditions.
  
  
• Sensitive: The nanotube’s one-dimensional structure lends itself to superior sensitivity to strain compared to conventional electromechanical materials such as silicon.
  
  
• Small power and footprint: The technology provides reductions in power consumption, mass, and size compared to conventional magnetometers.
  
  
• Economical: The low mass and required operating power of the sensor enables redundancy across spaceflight applications without adding to the propulsion cost.
  
  
• Adaptable: The sensor technology is very agile, adapting to zero-gravity environments and large, dynamic measurement ranges.
  
  
• Reliable: The relatively simple sensor design provides device reliability, helping to ensure uninterrupted operation and continued device integrity.

The subject technology’s intended use is as a magnetometer, an instrument used for measuring magnetic forces and fields, particularly the magnetism of Earth and other planets. The NanoCompass has important spaceflight applications as a strain-based magnetometer:

• In situ magnetic field measurements in space
• Attitude control of spacecraft in Earth’s orbit
• Study of the magnetosphere of Earth and other planets in orbit
• Study of the geomagnetism of planetary bodies on a lander or aerial vehicle

While magnetometry is its intended use, the sensor design itself is exceptionally straightforward.  Modifications of sensor dimensions or materials used in the fabrication may allow adaptation to other magnetic field and strain-based sensing applications:

• Military and homeland security
  • Sometimes called “smart dust,” myriad small magnetometers can be dropped or scattered to form a sensing network for perimeter or border security
  • Small, portable personal detection devices for individual soldiers
  • Airport security
    • Identifying potentially dangerous articles
    • Verifying package shipment compliance with FAA regulations
• Small personal compasses and GPS devices
• RFID tags – Magnetometer technology could be used to extend the range of radio frequency identification tags
• Energy: Oil, gas, and nuclear industries
  • Pipeline monitoring for rust
  • Pipeline mapping
  • Down-hole magnetometer measurements
• Replace SQUIDs in health care diagnostics:
  • MRI
  • Magnetoencephalography
  • Magnetogastrography
• Small current sensors/probes for use in electronic circuitry
• Magnetic ink recognition (MICR) readers
• Magnetic stripe readers (for public transportation fare cards, airline boarding passes, etc.)
• Navigation systems
• Calibrating laboratory field sources such as solenoids or Helmholtz coils
• Ore analysis (e.g., measuring weak fields in rocks)
• Evaluating effectiveness of magnetic shielding materials

What it is

Figure 1 Schematic of SWCNT magnetometer design. The functional components consist of a mechanically suspended SWCNT basis, a magnetically responsive Fe bar, and electrodes to record an electromechanical response as the Fe needle experiences torque in magnetic field.

Figure 2

Figure 3 These scanning electron micrographs depict two recent prototypes of the NanoCompass technology.

NASA Goddard’s NanoCompass is a nanoelectromechanical systems (NEMS)-enabled magnetometer technology that addresses the limited payload allowance expected in next-generation spaceflight missions. The sensor design takes advantage of the sensitivity of SWCNT electrical properties to strain, making very detailed measurements possible. An array of several of these nanoscale magnetometers can be used for high-spatial resolution magnetometry, a capability not possible with most conventional magnetometers.

The magnetometer design is illustrated by the schematic in Figure 1. It consists of a free-standing network of SWCNTs suspended between electrodes and mechanically coupled to a magnetically responsive, high aspect-ratio ferromagnetic component, analogous to a compass needle. Whereas a conventional compass typically employs an optical readout, torque on the Fe needle during operation of the NanoCompass transduces ambient magnetic field strength into an electronic signal. The straightforward design helps to drive high device reliability and robustness, and compatibility with integrated circuit manufacturing suggests easy incorporation into a portable package. Operation of the magnetometer requires additional components, including a voltage supply, current amplifier, and digital data acquisition. Current laboratory testing employs rack-mounted electronic instrumentation and PC-based LabView automated data acquisition, but low-power operation can potentially be supported by a simple battery. 

Key findings in the use of SWCNTs for magnetometry

The viability of using SWCNTs in a strain-based magnetometer has been shown by the fact that their electrical resistance shows no observed magnetic field dependence up to 0.36 T. This suggests that a large dynamic measurement range is possible, with minimal need for data manipulation and interpretation. In addition, cryogenic studies show that SWCNTs exhibit strong resistance to low temperatures, but relative insensitivity to thermal fluctuations at temperatures above -173°C. This suggests that a wide range of operating conditions will be possible.  Most spaceflight and Earth-based applications fall into this temperature range, eliminating the need for sophisticated thermal control systems.

Why It Is Better

Compared to Goddard’s NanoCompass design, existing fluxgate-type sensors (which utilize electrical current induction in large coils of wire to sense the intensity and spatial direction of magnetic fields) are bulky and inefficient instruments that utilize aging technologies and materials that are suffering a shortage within commercial markets. By contrast, Goddard’s design offers orders-of-magnitude reductions in sensor weight and sensor power, enabling redundancy in spaceflight applications without additional propulsion cost. What’s more, Goddard’s design offers nanoscale measurements, whereas fluxgate designs provide only cm-scale resolution.

In addition, carbon nanotubes exhibit an electromechanical response that is orders-of-magnitude higher in electrical conductance than the response seen in more conventional electromechanical materials, such as silicon. This exceptional sensitivity to strain is partly due to the nanotube’s one-dimensional nature and makes the carbon nanotube material ideal as a structural and electronic foundation for a strain-based magnetometer. While taking advantage of their sensitivity to strain, Goddard’s magnetometer design also overcomes the difficulties inherent in using SWCNTs, such as avoiding inhomogeneities in electronic properties (SWCNTs can vary from semiconducting to metallic) and precisely placing individual tubes. Finally, Goddard’s use of an as-grown chemical vapor deposited network requires minimal processing of the SWCNTs used in the sensor, hence minimizing defects and impurities common to solution-processed nanotubes.

This technology is part of NASA's Innovative Partnerships Program, which seeks to transfer technology into and out of NASA to benefit the space program and U.S. industry. NASA invites companies to consider licensing the Design of a Lightweight, Low-power Magnetometer based on a Single-Walled Carbon Nanotube Network technology (GSC-15060-1) for commercial applications.

For information and forms related to the technology licensing and partnering process, please visit the Licensing and Partnering page. (link opens a new browser window)

If you are interested in more information or want to pursue transfer of this technology, please contact:

Innovative Partnerships Program Office
NASA Goddard Space Flight Center
E-mail: techtransfer@gsfc.nasa.gov