One of the hottest areas in the world of wireless sensors is automotive tire-pressure monitoring systems (TPMSs), with government mandates in the wings acting as a spurring agent. Present-day tire-pressure monitoring systems are indirect yet low in cost. but the more expensive direct tire-pressure monitoring method—where every tire has a sensor and transceiver—is favored by many sensor and automotive subsystem OEMs. Of course, such systems require batteries to operate. Battery-less direct systems have been developed, but they've yet to be proven in the field.
According to Dirk Leman, TPMS product manager for Melexis, the direct method will likely prevail, being phased in over the next few years. He notes that "battery-based technology is here to stay for some more years, and passive technologies are mature enough to penetrate niche applications in the near future. However, for a Tier 1 supplier implementing passive technologies, the road map, business model, and leveraging of existing competencies are at least as important as the individual product cost when selecting a single technology."
In the long run, he cautions that intelligent indirect technologies may generate a bigger growth potential for MEMS sensors than direct TPMSs. That's because they can offer increased safety and comfort in addition to pressure monitoring.
Medical applications are numerous. The potential for wireless sensing also extends to the medical field, where wearable electronics will make a huge impact on remote patient bio-monitoring and bio-chemical detection. For instance, wireless strain gauge sensors can be used to measure in-vivo total knee-replacement joint loads in humans. According to Steven Arms, president of Microstrain Inc. (www.microstrain.com), "We've shown that this can be done in a collaborative project with the Scripps Institute (www.scripps.edu) and Johnson & Johnson (www.jnj.com)."
In another development, Microstrain and the Department of Veterinary Medicine at the University of Wisconsin in Madison (www.wisconsin.edu) measured bone plate growth in-vivo in lambs. The company also performed in-vivo vertebral spine bone strains in humans in collaboration with the Department of Orthopedics at the University of Arizona (www.arizona.edu) and re-animated paralyzed human limbs in a cooperative project with the Bioengineering Deptartment of Case Western University (www.cwru.edu) using control systems based on strain gauges.
The plain magnet is still being used, in combination with a new sensing methodology, to hold together large broken bones more accurately and safely in humans. Present methods use X-rays and a surgeon's skill to do this, but it's more costly, less safe, and less accurate and takes a longer time. So in a joint project with Virginia Tech (www.vt.edu), the University of Virginia (www.virginia.edu), the Carilion Biomedical Institute (www.biomedicalinstitute.org), and Carilion Health Systems (www.carilion.com), Triad Semiconductor (www.triadsemi.com) developed intramed-ullary nails (IMNs) that allow orthopedic surgeons to safely, quickly, and accurately hold broken bones together. The group's prototype magnetic targeter system uses a target magnet on a wand within the IMN and an LED display (Fig. 2).
Sensors of all types will also find uses in many industrial applications for monitoring the health of rotating machines and motors and to track the health of our nation's infrastructure. Radatec (www.radatec.com) reports on a microwave-based proximity/displacement sensor that allows the monitoring of machinery in extremely harsh environments at high rotating speeds and very high temperatures.
The aforementioned medical applications from Microstrain are also being used to keep track of the structural integrity of bridges, tunnels, highway overpasses, buildings, and other civil structures. Their EmbedSense strain-gauge-based wireless-transmission modules provide low-power, battery-operated sensing nodes at high data-acquisition rates required by civil authorities. Scalable arrays of passive strain gauge sensors can be interrogated remotely. Switched-reactance methods eliminate many components such as the RF oscillator, crystals, and feed-through antennas.
USHERING IN NANO
Nanotechnology will no doubt play an important role in sensing. At last month's Sensors Expo, held in Detroit, Mich., Dean Aslam, associate director at Michigan State University (www.egr.msu.edu), presented "multi-walled carbon nanotubes" (CNTs), which were grown to form a preconcentrator section of a micro gas chromatograph for sensing chemicals. Featuring wall layers ranging from 5 to 30 µm and lengths up to 500 µm, the CNTs offer an ultra-high surface area and low energy consumption, as well as superior adsorption/desorption characteristics compared to other known materials. The work was supported by the Engineering Research Centers Program of the National Science Foundation (NSF) and is part of the research work being performed at the University of Michigan's Center for Wireless Integrated Microsystems (WIMS).
No matter what type of nano-device emerges, nanotechnology itself needs lots more research and must be mastered before it can be realized. Professor Ahmed Busnaina, a leading nanotechnology researcher at Northeastern University (www.northeastern.edu) and a keynote speaker at Sensors Expo, holds this opinion. He says the industry needs to develop nanotemplates as nanomanufacturing tools for nanodevices and sensors as a bare minimum before the technology can flourish.
One of the hottest areas in the world of wireless sensors is automotive tire-pressure monitoring systems (TPMSs), with government mandates in the wings acting as a spurring agent. Present-day tire-pressure monitoring systems are indirect yet low in cost. but the more expensive direct tire-pressure monitoring method—where every tire has a sensor and transceiver—is favored by many sensor and automotive subsystem OEMs. Of course, such systems require batteries to operate. Battery-less direct systems have been developed, but they've yet to be proven in the field.
According to Dirk Leman, TPMS product manager for Melexis, the direct method will likely prevail, being phased in over the next few years. He notes that "battery-based technology is here to stay for some more years, and passive technologies are mature enough to penetrate niche applications in the near future. However, for a Tier 1 supplier implementing passive technologies, the road map, business model, and leveraging of existing competencies are at least as important as the individual product cost when selecting a single technology."
In the long run, he cautions that intelligent indirect technologies may generate a bigger growth potential for MEMS sensors than direct TPMSs. That's because they can offer increased safety and comfort in addition to pressure monitoring.
Medical applications are numerous. The potential for wireless sensing also extends to the medical field, where wearable electronics will make a huge impact on remote patient bio-monitoring and bio-chemical detection. For instance, wireless strain gauge sensors can be used to measure in-vivo total knee-replacement joint loads in humans. According to Steven Arms, president of Microstrain Inc. (www.microstrain.com), "We've shown that this can be done in a collaborative project with the Scripps Institute (www.scripps.edu) and Johnson & Johnson (www.jnj.com)."
In another development, Microstrain and the Department of Veterinary Medicine at the University of Wisconsin in Madison (www.wisconsin.edu) measured bone plate growth in-vivo in lambs. The company also performed in-vivo vertebral spine bone strains in humans in collaboration with the Department of Orthopedics at the University of Arizona (www.arizona.edu) and re-animated paralyzed human limbs in a cooperative project with the Bioengineering Deptartment of Case Western University (www.cwru.edu) using control systems based on strain gauges.
The plain magnet is still being used, in combination with a new sensing methodology, to hold together large broken bones more accurately and safely in humans. Present methods use X-rays and a surgeon's skill to do this, but it's more costly, less safe, and less accurate and takes a longer time. So in a joint project with Virginia Tech (www.vt.edu), the University of Virginia (www.virginia.edu), the Carilion Biomedical Institute (www.biomedicalinstitute.org), and Carilion Health Systems (www.carilion.com), Triad Semiconductor (www.triadsemi.com) developed intramed-ullary nails (IMNs) that allow orthopedic surgeons to safely, quickly, and accurately hold broken bones together. The group's prototype magnetic targeter system uses a target magnet on a wand within the IMN and an LED display (Fig. 2).
Sensors of all types will also find uses in many industrial applications for monitoring the health of rotating machines and motors and to track the health of our nation's infrastructure. Radatec (www.radatec.com) reports on a microwave-based proximity/displacement sensor that allows the monitoring of machinery in extremely harsh environments at high rotating speeds and very high temperatures.
The aforementioned medical applications from Microstrain are also being used to keep track of the structural integrity of bridges, tunnels, highway overpasses, buildings, and other civil structures. Their EmbedSense strain-gauge-based wireless-transmission modules provide low-power, battery-operated sensing nodes at high data-acquisition rates required by civil authorities. Scalable arrays of passive strain gauge sensors can be interrogated remotely. Switched-reactance methods eliminate many components such as the RF oscillator, crystals, and feed-through antennas.
USHERING IN NANO
Nanotechnology will no doubt play an important role in sensing. At last month's Sensors Expo, held in Detroit, Mich., Dean Aslam, associate director at Michigan State University (www.egr.msu.edu), presented "multi-walled carbon nanotubes" (CNTs), which were grown to form a preconcentrator section of a micro gas chromatograph for sensing chemicals. Featuring wall layers ranging from 5 to 30 µm and lengths up to 500 µm, the CNTs offer an ultra-high surface area and low energy consumption, as well as superior adsorption/desorption characteristics compared to other known materials. The work was supported by the Engineering Research Centers Program of the National Science Foundation (NSF) and is part of the research work being performed at the University of Michigan's Center for Wireless Integrated Microsystems (WIMS).
No matter what type of nano-device emerges, nanotechnology itself needs lots more research and must be mastered before it can be realized. Professor Ahmed Busnaina, a leading nanotechnology researcher at Northeastern University (www.northeastern.edu) and a keynote speaker at Sensors Expo, holds this opinion. He says the industry needs to develop nanotemplates as nanomanufacturing tools for nanodevices and sensors as a bare minimum before the technology can flourish.