Conductive plastics, or polymers, have been a blip on the radar screen for decades. A lot of effort has gone into trying to synthesize, successfully, such materials. However, real success has been elusive. There have been some successes, but large-scale, commercial materials are not yet ready for prime time.
There are numerous challenges with conductive polymers. However, in the end, the problem lies in trying to combine two fundamentally incompatible materials. While that integration has been successful in areas such as semiconductors, combing the insulative properties of polymers with the electrical and optical properties of metals has not met with the same success.
However, that may change. New developments in additive manufacturing show promise. In fact, additive manufacturing researchers have devised a way to sense, remotely, motion via Wi-Fi backscatter. And, without any interconnecting wires or need for power at the sensor. That is big!
With the emergence of the Internet of Everything/Everyone (IoX), sensors are going to explode. Up until now, it was feasible, in most cases, and workable in the more extreme cases, to use either wired or wireless links. However, going forward, the applications for sensors are going to outstrip the traditional interconnect methodologies. That is why this is so exciting.
There is a new generation of sensors coming. These are very basic, with little intelligence, and for very simple applications. Such sensors are going to be prolific within the IoX, and require out-of-the-box thinking and technologies because of their environment. The challenge, here, is to find a way to connect these sensors, both inexpensively and overcoming their challenges.
In many IoX, as well as 5G, applications running even a small switch-closure wire between a sensor, its source point, and a local wireless node is often challenging. Particularly if that point is located, or positioned, on moving objects such as doors, warehouse items, bicycles and retail items – the list is endless – all items that are poised to be “things” on the IoX.
This is where advancements in conductive plastics will play a part, once (and it will, eventually) this technology become practical. The brain trust at the University of Washington has found a way to marry 3D printing and additive manufacturing. These objects, comprised of plastic with embedded conductive threads, can be made to function as sensors. They can be connected, wirelessly, to the local 2.4-GHz Wi-Fi node. The methodology is ingenious, using RF backscatter techniques, which allow the Wi-Fi system to note the change in physical appearance or location of the sensed object.
For a more detailed explanation of the concept, go to: 3D Printing Wireless Connected Objects, which explains the concept. It shows the many test widgets they built and discusses the range of tests they conducted. While not on the scale of a Mars rover, the proof of concept is, nevertheless, quite accomplished, especially in lieu of the difficulty of marrying plastic and RF.
In this case, the transceiver is capable of receiving fundamental actions from the objects: movement and contact closure, mainly. There are some other apps they are working on such as detecting the levels of liquid.
Now, let us elaborate on backscatter for a bit. Backscatter is a technique that uses a transmitted signal that bounces off an object – like Radar and X-rays. This technique works because the reflected signal varies from the referenced signal when there is change in the target object. The objects can be fitted with antennas of different types to enhance the signal properties.
Therefore, when an object changes state, the transceiver’s received signal reflects that change. States of the object can be analyzed and equated to certain signals. The reflected signal is a narrowband transmission that rides on the top of the ambient Wi-Fi signals, in this case the signal consists of the positional data of the object.
There are some challenges, however. One is noise. The backscattered signal is extremely low in power, and, therefore, difficult to detect. Successes have been limited to test environments with very short distances.
And, if low signal levels are not enough, at such levels, the omnipresent noise from any number of sources, along with adjacent signals, cause marginal signal-to-noise ratios (SNR). Even more challenging becomes the movement itself. This is because of the Wi-Fi system’s coverage area, which is affected by the object’s physical location and/or movement out of the coverage area (which might not be a problem for warehouse items but would be for retail or highly mobile objects such as bicycles).
The signal issues can be addressed, to some degree, by tuning signal paths and adding en/decoding to the data stream. They have been able to encode up to 12 bits of data that can be sent in a short stream. In this case, the data is sensed and decoded by a smartphone-based maglink receiver. Data rates are slow, around 10 bps, but one has to start somewhere. While this is not, exactly, the Indy 500 of data rates, there are a slew of emerging IoX applications where such low rate data streams are exactly what the doctor ordered.
In the end, I keep an ear to the ground with conductive polymers because I find it a technology with tremendous potential and applications, if the many challenges be overcome. So far, it has not shown to be viable, nor practical in the real world. However, as technologies evolve, new vehicles, such as 3D printing, devices, and new signal processing techniques begin to chip away at the challenges.