In the near future, bad environments could produce good results.
Whether it’s a bar code label or an RFID tag, the extreme temperature fluctuations, vibration, acceleration/deceleration, abrasion and overall rough handling containers can suffer in transit usually results in only one thing: damage to the label or tag. But in the future, rough handling might actually prove to be an asset to data collection technologies.
A new generation of nanotechnology designed for energy harvesting could turn all of these negative environmental factors into electricity to power sensors, data loggers, and boost the range of battery assisted passive tags.
There is considerable research under way in the nanomaterials community to find ways to develop energy harvesters using acoustic, vibrational, heat and mechanical energy. And just as thin film batteries have enabled the development of smaller yet more capable RFID tags, nanogenerators could usher in a generation of “perpetually recharged” devices.
The most common devices today that turn mechanical stress into electricity utilize piezoelectric materials.
The concept of using mechanical stress to generate electrical currents is far from new. The phenomenon was first observed in 1880 by the brothers Pierre Jacques Curie but didn’t find a practical application until World War I when it was used by the French to develop an early form of sonar.
The principle is simple: apply mechanical stress to these materials and they generate a burst of electrical current in proportion to the mechanical energy applied. Reverse the process and run a current through piezoelectric materials and they change shape in response to the level of the current. Everyone should be familiar with this since it’s what used for the microphone and ear piece of many telephones.
Conventional piezoelectric materials such as lead zirconate titanate (PZT) can transform upwards of 80% of the mechanical force applied to it into electricity. However, ceramic materials like this tend to be relatively thick and rigid which doesn’t make them ideal for use in the vast majority of RFID tags.
True, these materials could be embedded in the bottom of pallets so that they would absorb mechanical force every time the pallet’s moved and, more importantly, with every bump in the road. However, the efficiency and life expectancy of such a configuration is questionable. Skidding a pallet across a concrete floor could scrape off enough of the material to make it flush with the pallet itself and render it useless. Clever mounting could provide a “wear strip” that could easily be replaced to protect the piezoelectric material itself but, again, a single long skid across a floor could remove this material as well. In other words, maintenance would be an ongoing nightmare. However, equally important is that top pallets might be resting on a relatively pliable surface such as several layers of stretch wrap and might not receive sufficient mechanical stress to be effective.
|Photograph of a piece of silicone rubber with PZT ribbons covering the top surface. (Image: Dr. McAlpine, Princeton University)|
What’s needed, then, is a material that can withstand — and benefit from — the stresses of these environments but which would not require careful maintenance.
That’s where new nanomaterials come into play. New materials are being developed that can be embedded in flexible materials such as plastic and even fabric. At present, the most advanced devices are piezoelectric but that does not rule out the future development of acoustic or temperature-energized devices.
While an acoustic-powered device may seem a little far-fetched, consider that nearly every material handling and storage environment is literally “abuzz” with minute vibrations — from fluorescent lights to refrigeration/ventilation systems to road vibration. These are all acoustic phenomena that could potentially be harnessed to power electronic devices.
In the RFID world, data logging would clearly be one of the first uses.
A reusable data logger using flexible nano-piezoelectric material could be inserted between cartons on a pallet where it would be subjected to sufficient small vibrations that occur during transportation to record a real-time histogram of temperature, vibration, shock and so forth without being subjected to the danger of damage from lift trucks or other handling hazards.
Similarly, hard shell RFID tags on pallets could incorporate this material to record stresses induced by shock, temperature or pressure changes.
Single-use RFID labels with this type of material could contain a variety of sensors and have extended range, all powered by the nanomaterial.
In some instances, a battery or other type of energy storage device would be required, in addition to the piezoelectric material which only generate current with each instance of strain or force. Therefore, an object at rest in a quiet environment will not generate any power.
Of course, any potential use of nanomaterials versus existing and evolving thin film battery technology depends on the power requirements of the device(s), expected life of the device and cost of the new technology. These nanomaterials will likely be more expensive initially than thin film batteries so the decision criteria will, oddly enough, be very similar to today’s discussion of the benefits of bar codes versus RFID.
In other words, if these nanomaterials can do something thin film battery technology can’t do — or they can do it better or longer — then nanomaterials will be used. Otherwise, it’s more likely thin film batteries will continue to be used.
Still, nanotechnology — whether it’s used for energy generation, flexible displays or as a way to construct even smaller electronic devices — will likely transform RFID over the next ten years. And it’s well worth keeping it “under the microscope”.