Not the Sensors Your Father Used

Sensors Insights by Tom Kevan

Increasingly, the sensors empowering the smart devices of the Internet of Things will bear little resemblance to the sensors of the past. Advances in miniaturization, integration, and material science are pushing the limits of sensitivity, space, and cost that define where and how sensors can be used and what functions they can perform.

New Materials
One of the advances redefining sensors is the harnessing of carbon nanotubes. These atomic-scale materials have incredible electrical, mechanical, and physical properties. They conduct electricity better than copper, provide more strength than steel, and transfer heat better than any other material. Using nanotubes to create sensors raises the prospect of versatility and sensitivity previously impossible.

The New Electronics article "Nanotechnology Prepares to Hit the Mainstream" explains how nanotubes either naturally or as a result of functionalization react strongly to specific gases. To functionalize a nanotube, "you just choose a chemical group that would interact strongly with the molecule you want to sense and attach it to the outside of the carbon nanotube." This ability to customize nanotubes will allow sensor makers to tailor devices to sense specific substances as needed. In addition, these sensors will be able to measure very low concentrations of the substances. For some gases, their sensitivity will be in the very low parts-per-million range.

Packing More Punch into Smaller Packages
Other transformational advances will result from a combination of better materials and improved fabrication techniques. In the case of new timing and inertial measurement units (IMUs), University of Michigan engineering researchers have created a robust device that delivers multifaceted functionality in a tiny form factor.

The Nanowerk article "When GPS fails, this speck of an electronic device could step in" describes how the researchers built a 13 mm3 package containing a master clock and six sensors that detect movement in six different axes. To make their ultra-compact IMU, the researchers developed a fabrication process that allows them to stack and bond the seven different devices in layers. This reduces the form factor of the unit from the size of a baseball to an object smaller than a kernel of corn, opening a whole new range of applications that can be served. Then to increase the sensing modules' durability, the engineers used fused silica (high-quality glass) instead of the traditional silicon.

Overcoming the Bottom Line
While improving sensitivity, expanding versatility, and shrinking form factors will sweep aside major impediments to the evolution of sensors, cost still represents a key obstacle. If the Internet of Things is to incorporate 20 billion sensor-enabled devices within the next five years, as industry leaders predict, the price point of sensors must come down. This is where 3D printing comes into play.

The MIT Technology Review article "A Battery and a "Bionic" Ear: a Hint of 3-D Printing's Promise" tells how recent advances in 3D printing—using micro nozzles, inks containing metallic nanoparticles, and photocurable resins—are being used to print features as small as 1 micrometer, creating miniature battery components, antennas, and optical structures. Although the technology has yet to be refined enough to produce integrated electronics, the advances do hint at how 3D printing will change the way electronic devices are made. This additive technology is significant not only because it enables the production of miniature electronic components, but also because it promises to significantly reduce manufacturing costs.

Evolution, Not Revolution
All these technological advances will change sensors dramatically—but not overnight. Look for incremental advances among most sensor types. But the sensors required to fit into ever-shrinking spaces while performing increasingly complex functions are prime candidates for major makeovers in the near term.

Tom Kevan is a New Hampshire-based freelance writer specializing in technology.

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