Nanosensors for machines
Back to Basics: Lower-cost nano sensing technologies are making their way into pressure, position, and motion sensors, transmitters, and power supplies.
Mark T. Hoske
Nanosensing technologies are helping make the machine sensing portion of the control loop (sense, measure, actuate, and repeat) smaller and more reliable to make manufacturing more efficient and effective. Nanotechnologies continue to be discovered and applied to a wide range of applications, and ever smaller sensing elements have found a place in industrial machines—among these, silicon-based pressure sensors, position and motion sensors, even valves and transmitters. [Note: Some liberties are taken with the term “nano.” A nano PLC (programmable logic controller), while small compared to a traditional PLC, would be cumbersome to measure in nano scale: 1 nanometer = 1 billionth of a meter; there are 24.4 million nanometers/in.]
One manufacturer, Baolab, announced availability of evaluation kits by the end of February 2012 for its “NanoEMS” technology, promising to improve and shrink future sensors and communications technologies. Baolab Microsystems 3D NanoCompass is an electronic 3-axis micro electromechanical system (MEMS), incorporating nanoscale structures within the standard metal structure of a high-volume manufactured complementary metal-oxide semiconductor (CMOS) wafer.
Dave Doyle, Baolab CEO, said in a Jan. 12 announcement that the move from lab to fab shows the company’s technology is “reliable, scalable, and repeatable. This was the critical stage that our customers have been waiting for.” The NanoEMS process “makes it much easier and more cost effective to integrate MEMS sensors with microcontrollers and associated electronics all on the same chip in the same CMOS production line. This is the breakthrough that will enable high-volume, consumer electronics products to have intelligent sensors, meeting the increasing demand for smarter, more aware devices," Doyle said, advancing nanosensors. And industrial products, which are rapidly taking advantage of consumer electronics trends, will benefit with development of nanosensor technologies. Specifically, MEMS motion sensors will benefit, and Baolab NanoEMS structures also easily may be incorporated into ASICs for RF antennas, RF switches, and near field communication applications, including, the company said:
- Vibrating antennas to overcome limitations of classic (static) antennas such as compact superdirective/superesolution antennas/lenses that require phase shifters and gains with an accuracy not currently realistic. Vibrating antennas make these feasible along with spatial multiplexing communications for mobile telecoms and Internet.
- Thermo-magnetic RF switches and antennas: By exploiting the low value of the Curie temperature of nickel, it is possible to build RF switches, filters, and reconfigurable antennas. This creates a novel category of reconfigurable, reliable RF MEMS components, since there are no moving parts, achieving compelling RF specs, low power consumption, and low cost thanks to CMOS processing.
- Modal switches: This topology enables compelling specifications for RF switches with low-capacitance ratio and high isolation, using low-cost, low-resistivity CMOS substrates. The principle is based on transferring power from the different transmission modes in a transmission line, using reconfigurable MEMS loads to balance and unbalance the line.
- Integrated passives, including inductors, transformers, capacitors: Integrated inductors with a helicoidal shape typical of off-chip inductors offer reduced losses (higher Q) and smaller parasitic capacitance (higher resonant frequency). It is also possible to create transformers with any winding ratio.
- Integrated capacitors for low-frequency applications, especially power, where the tangent capacitance is used instead of the traditional approach using secant capacitance. When capacitors are used in voltage regulators, only a small fraction of the charge stored in the capacitor is typically used to regulate the voltage. This kind of capacitor allows a higher percentage of the stored charge to be used to regulate the voltage, which makes it possible to implement smaller, integrated filters and regulators, with superior performance.
- RF filters: The small feature size of CMOS processing makes it possible to implement RF MEMS filters up to the GHz band required for cell phone communications and significantly increase the electromechanical coupling. Current MEMS RF mechanical filters have a problem with very low electromechanical coupling, which means low sensitivity; they try to offset this by using a very high voltage but with limited success.
- Power converters: Integrated charge pumps and power supplies will drop in cost and be more compact and efficient.
- Mark T. Hoske, content manager for Control Engineering, CFE Media, can be reached at mhoske(at)cfemedia.com.
www.nano.gov says fingernails grow about 1 nm/sec.
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