Despite the many merits that radio frequency identification (RFID) and Near Field Communication (NFC) technologies offer to modern logistics, there are numerous scenarios in which wireless tags have so far been unable to fully replace paper-based labels and bar codes. The main reason for this is that a paper label can have both a scannable bar code and information that is readable by individuals without the need for additional, specialized equipment.
To some extent, the fact that such NFC RFID tags are not instantly readable (or amendable) by people has held back their proliferation. However, adding an updatable display to the tag has traditionally proved impractical, because it would be too power-hungry. There will, nevertheless, be increasing demand for exactly this form of dual functionality in the future.
Vaccine Data at-a-Glance
Here is an example that illustrates this point. In the United States, changes to the directives relating to how vaccines are stored are set to have major implications. In many cases, a regularly updated visual indicator, detailing the temperature at which the vaccine containers have been kept throughout the previous 24-hour period, will be required. This will help to safeguard against damage to the vaccines that could be caused by interruptions in their refrigerator’s operation. Real-time monitoring systems of this kind will need a display on each vaccine container, but if the power consumed by the display is too high, such arrangements will not be feasible.
It is becoming ever more apparent that finding a way to merge the instant human-readability of a display with the updatability and internet connectivity of a wireless tag would be highly advantageous. This would enable operatives to view the status of a particular item at a glance, while also allowing them to transfer data to and from it via NFC RFID. To achieve this, however, requires that product designers completely re-evaluate their strategy when it comes to specifying displays.
Why TFT LCDs Are So Power-Hungry
There are two characteristics endemic to thin-film-transistor liquid-crystal displays (TFT LCDs) that mean even the most advanced versions still have sizeable power-consumption figures. First, they require a backlight to make the display’s contents visible. Second, these displays must constantly be refreshed (normally 50 or 60 times every second), which is another ongoing drain on power. The impact of these factors on the overall power budget make such optoelectronic components wholly unsuitable for applications for which there are limited battery reserves that must last for a long time.
Introducing E-paper Displays
Through the emergence of e-paper displays (EPDs), a more power-efficient and convenient alternative is now seeing commercial uptake. Widespread proliferation seems destined to follow. EPDs have the major operational advantage over TFTs of not requiring a backlight. Furthermore, they do not need to be constantly refreshed—power is only needed to update the contents of the display. The rest of the time, an EPD continues to render the same information without any refreshes.
Both these attributes result in displays that are significantly more energy-efficient than TFT LCDs. An EPD can run off a single coin cell for several years without draining even half of its energy. A TFT of comparable size would use hundreds of cells within that span of time. In many cases, EPDs enable designers to completely eliminate a local power source, and to run solely from scavenged RF energy. As a result, designers and engineers can explore applications for displays that would have been impossible to achieve using TFT-based solutions.
By using e-paper, a human operative no longer needs to carry a specialized scanner to read data from a tag. Instead, this information is visible at any time, and does not consume energy in remaining so.
Basic Principles of EPD Technology
An EPD incorporates two electrodes, with the upper one being transparent. Between the two electrodes are tiny micro-capsules, which are the “pixels” that make up the display. These capsules are just 0.2 millimeters (0.008 inch) in diameter, thus offering relatively high resolutions. Inside each capsule are electrically charged spherical pigment particles, which are normally white (positively charged) and black (negatively charged).
Applying a negative charge to the electrode above a capsule allows the positively charged white particles to rise into view. Apply a positive charge, and the black ones will become visible to the eye. In this way, it’s possible to display text and images that deliver the same degrees of readability we associate with printed media. Different shades of gray or monochrome gradients can also be displayed.
Since the content displayed on EPDs is reflective, it is not affected by external lighting conditions in the way that TFT LCDs are. As a result, you can read an e-paper display even in bright sunlight. Furthermore, because EPD-based assemblies do not require a backlight or certain other components that are essential for TFTs, they are typically more streamlined, lightweight and cost-effective. Flexible EPDs are also available.
Using EPDs in Health Care
Incorporating both EPDs and wireless location-tracking technology into hospital beds can help medical staff to identify a patient, know where he or she needs to be taken and what treatment that individual is to be given. The same technology could be used to tag organs and other items that need to be moved around the hospital. This location information can be used to inform medical personnel of a patient’s or item’s current location, so they can be fully prepared when the individual or item arrives. When they do, the EPD can confirm that they have the right person or object, as well as provide the critical data they require to proceed.
In situations for which the cost of what you’re tracking is high—as is the case with vaccines or donated organs—it’s relatively straightforward to justify the investment in technology that helps protect against the loss or spoilage of these items. The same is true in a hospital environment, when you consider the risk of legal action if a patient is incorrectly identified and accidentally given the wrong treatment.
This technology is equally well-suited to other asset-management contexts, such as the storing of laboratory equipment or test instrumentation. Here, the wireless tagging element provides each item’s exact location at any given time, while the EPD enables warehouse workers to view data such as when it was last serviced or calibrated. There is even the option here to restrict the updating of the EPD to certain authorized personnel, to minimize the prospect of erroneous information being recorded.
An Ideal Complement for NFC RFID Tags
The need to use a specialized scanner with wireless tag technology has resulted in far slower market uptake than was originally envisaged. As this article explains, there is a great deal of scope for e-paper to help make up the shortfall. It presents engineers with a highly effective complementary technology for NFC RFID technology, thanks to its ability to provide human-readable information without the need for additional equipment. Moreover, it has very little impact on the tag’s power budget, unlike a TFT LCD would.
EPD specialist Pervasive Displays is collaborating with recognized leaders in NFC RFID technology to position itself at the forefront of such deployments—supplying integrated solutions that add the extra dimension to wireless tags, which will drive this sector forward.
Scott Soong is the CEO of Pervasive Displays and has more than a decade of experience in software, in addition to 12 years working in displays businesses. During his career, Scott has been a founding partner at four startup companies, including Pervasive Displays. Scott sits on the board of several other technology businesses as a consulting partner. He was a board member of One Laptop Per Child (OLPC), which looks to provide children in developing countries with a rugged, low-cost, low-power, connected laptop. Scott has an MBA degree from the Haas School of Business at the University of California, Berkeley, as well as a BA degree from the University of Michigan at Ann Arbor.