The Future is Thin, Flat and Flexible

What’s ahead for antennas, heaters and inks.
by Michael LeFebvre

In the 39 years I’ve been in the printed electronics industry, I’ve had the privilege of witnessing, influencing and playing a part in life-changing innovations such as the SonoCine ultrasonic breast imaging device and printed wearable therapeutics. As brilliant as these breakthroughs were back in the day, however, they don’t hold a candle to today’s conductive transparent thin films that are enabling limitless design and engineering possibilities.

The following is a synopsis of some of the leading-edge technologies and their applications. After reading about the following examples based on my current experience, I think you’ll agree that the future of our industry is exciting indeed!

Aesthetic and Green

Transparent, flexible antennas. Today’s 5G frequencies don’t penetrate buildings well, and the need for more antennas to facilitate 5G speed is growing exponentially. The problem is that consumers don’t want unsightly features (read: antennas) attached to their products or visible anywhere within their environments.

A new class of antenna is emerging to solve that problem. Transparent antennas, made with flexible, conductive hybrid films offering performance equivalents to leading low-loss, ceramic-based PCB laminates, work as well as traditional nontransparent printed antennas. They can be leveraged for automotive, cellular, NFC, Wi-Fi/Bluetooth, LPWAN and GNSS/satellite use, to name a few.

Chasm Advanced Materials believes high-performance transparent antennas have the potential to overcome connectivity challenges in a variety of fields, including automotive, enterprise IoT and smart cities. These antennas can be easily integrated with glass or windows, providing a level of freedom that is hard to match. With peel-and-stick options, users can upgrade their connectivity setups without drilling holes or risk of damage to their assets. Furthermore, this technology can be integrated using various methods, such as optical clear adhesive (OCA) lamination and film insert molding processes.

Transparent heaters. Our industry has long leveraged IME to carry electronic signals for heaters. At DuraTech, for example, we manufacture resistive heating elements to de-ice polycarbonate snowplow headlights. This is done by inserting a functional thin-film printed with conductive silver ink into an injection molding tool so it bonds with the resin of the molded lens. As a result, snowplow headlights illuminated with low heat-producing LEDs stay free of snow and ice.

Companies like Chasm are taking that technology further. For example, optical cameras, LiDAR and radar sensors in advanced driving assistance systems (ADAS) don’t perform well in fog, rain, snow and cold conditions. Yet solutions like embedded microwires or indium tin oxide films can result in energy loss or distortion, thermal gradient issues or are easily cracked. Chasm’s AgeNT heaters are compatible with camera, lidar and radar sensors, delivering rapid and uniform heating over the entire camera lens, lidome or radome surfaces (Figure 2). The heaters are transparent, with no visible wires, and are stable during temperature, humidity and UV aging tests. Moreover, they are compatible with standard automotive voltage (12V), making them easily integrated into existing vehicle systems. In comparison, other emerging technologies struggle to provide enough power density at 12V. AgeNT heaters can be mass produced at low cost, making them an attractive solution for automotive manufacturers and suppliers.

The next step in transparent heater technology extends to road management systems. An example in development includes printed spherical heaters inserted into the compound curves of a toll system’s glass fisheye lenses. Sensors within these lenses must be able to operate in all weather conditions to identify vehicle size – from motorbikes to semi-trailers – to determine what toll rate applies to each vehicle. Another example is heaters for solar-powered cameras placed at fixed road junctions to help municipalities and snow removal companies gauge road conditions. Armed with accurate information supplied by snow-, ice- and fog-free cameras, they can then determine how to mix the appropriate brine solutions and where to put them to keep roads safe for driving.

Cavitated inks. For most users, cavitation implies powerfully destructive liquid microjets and shock waves that will pit the hardest metals or ceramics. These are caused by significant pressure changes that form vacuum bubbles, which collapse when the pressure is greater on the outside of the bubbles. One example is when a propeller turns in the water to decrease pressure, thus forming the vacuum bubbles that ultimately collapse and pit the metal propeller. Today, however, cavitation is being leveraged in an entirely different way that’s rocking our industry.

ACI Materials has developed a controlled cavitation process that produces functional inks with nanoparticle dispersion to less than 0.1μm. Essentially, the process forms vacuum bubbles within the material and then fractures the bubbles to release the energy.  This energy is released in the form of liquid microjets and shock waves, creating the ultimate dispersion of the product mix and achieving near primary particle size (elimination of large agglomerates). Cavitation does not alter the morphology of malleable particles, although layered structures like graphite and nanoclays will exfoliate, forming high aspect ratio particles. The cavitation process creates ink with superior conductivity and mechanical performance, permitting printers with a squeegee and a flood bar to be used where we could never have imagined; markets like power management, for example, that were were formerly off limits due to ink limitations.

ACI Materials has developed and currently produces the world’s only cavitated functional inks. These specially formulated inks enable the solderability of silver-based additively manufactured printed circuits, permitting high-throughput, low-cost component attach in FHE applications. When this process is combined with a substrate such as PET, which is very low-cost, printers can work toward a cost-comparative way to additively manufacture circuits – a benefit for them and the environment.

Cavitation also makes the ultra-fine dispersion of carbon nanomaterials possible (Figure 3). This matters in the manufacturing of stretchable fixed-resistance heaters, for instance. Functional fillers, including carbon, must be fully dispersed to consistently print a trace with a target resistance. If not fully dispersed, the shearing forces of screen printing can continue to disperse the carbon fillers during the print run. This changes the resistance of each print throughout the print run. Achieving full dispersion of carbon fillers is extremely difficult. Through cavitation, carbon is fully dispersed before it ever goes on the screen, resulting in consistently even output temperatures from fixed-resistance heaters, even in print runs of thousands of heaters.

Ultimately, cavitated inks could make a tremendous difference to our personal carbon footprint. Cavitated ink, for example, can be used on stretchable material, enabling the creation of wearable heaters that conform to the human body – and withstand wash cycling and drying. So, if we can make a four-foot scarf with a printed heater that measures just 18″ for the part of the scarf that wraps around your neck, how likely are you to turn up the heat in your home? Not very. It’s thin, flat, flexible, convenient and extremely power-efficient in more ways than one.

Finally, cavitation itself is a green manufacturing process. Because it takes place in a closed stainless-steel environment, no VOCs are released (which also results in yields of nearly 100%).

More and more, OEMs are mandating designers prove we’re not contributing to the waste stream. If we can’t bring two or three environmentally sustainable options to the table that our customers can take to their boards of directors, we’ll lose the business. Medical manufacturing is a prime example, and this is where cavitation can also be a game-changer.

Take glucose monitoring systems; millions of which are used daily. With cavitation, we can print those monitors using a tenth of a gram less silver per sheet to achieve the same signal strength. Not only does less silver end up in landfills when those monitors are discarded, the monitors themselves cost providers less. When you’re quoting the printing of 300 million glucose monitors in a year, we’re talking about significant cost savings and substantially less silver ending up in the waste stream.

Photobiomodulation. Wearable photobiomodulation (PBM) therapy is another new frontier for printed functional electronics. Previously known as low-level laser therapy, PBM is a medical treatment that applies low-level lasers or LEDs to the surface of a person’s body to relieve pain and accelerate the healing process. It’s a proven alternative to traditional treatments, such as opioids, for pain and inflammation. New applications promise benefits beyond tissue healing and pain reduction and include cosmetic applications for acne treatment and wrinkle reduction.

Not only do PBM wearable patches offer convenient, effective treatment for numerous medical conditions, they are also non-invasive, making them safer for the patient than other medical treatments (Figure 4). They also don’t use harsh chemicals that can irritate skin like many acne treatments, and they come with very little packaging – no bottles, caps or boxes that go directly into the waste stream.

Carewear’s Light Therapy system is a wireless, wearable, over-the-counter, FDA-cleared, CE MDD class IIa medical device for the management of pain and treatment of soft tissue injury, wrinkles and acne. It is paired with a digital health infrastructure, allowing clinicians to select treatment parameters and outcome indicators, monitor utilization and report in real time through the cloud.

Future Needs

The examples we’ve looked at here are indicative of the central role functional printed electronics will have not only in the development of exciting new products that will improve our living standards, but also by eliminating waste and scrap and allowing resource-efficient material choices.

To sustain our momentum, it is imperative that the industry actively promotes science, technology, engineering and mathematics (STEM) education at every level and at every opportunity. The printed electronics industry isn’t alone in the search for skilled workers, and competition continues to increase as technology permeates a growing number of employment sectors. In fact, the International Monetary Fund reports that by 2030, there will be a global shortage of more than 85 million tech workers, representing $8.5 trillion in lost annual revenue.

We are up to the challenge, though. The future of our industry is so exciting that it’s easy to share our enthusiasm. On a personal level, many of us are involved in local programs to promote STEM. Let’s keep that going; who knows where it can lead us next?

Ed: This article was originally published in TechBlick and is reprinted here with permission of the publisher and author.

Michael LeFebvre is director of innovation at DuraTech Industries (duratech.com); michael.lefebvre@duratech.com.