Advances in Printed Electronics Driven by Sensor Technologies

The printed electronics industry has an unmatched ability to demonstrate "simple, doable" successes. Industry experts attribute this to the simplicity, ease of development, and low costs associated with printed electronic sensors.

Printing electronics is relatively straightforward. Materials are plentiful, structures are simple, and sensors do not necessarily require high resolution for strong functionality. Plus, by functionalizing the surface of a printed transistor, sensing functionalities can be enabled in a single step. "The barrier to commercialization is relatively low," Janos Veres, program manager for printed electronics at PARC, a Xerox Company, told IMT.

IDTechEx expects hybrid CMOS (complementary metal-oxide-semiconductor) image sensors to become the second largest printed electronics market, after biosensors. CMOS sensors are used in cameras, from high-end DSLR (digital single-lens reflex) cameras to smartphones. Traditionally, their light-sensitive layer is made of silicon. In hybrid CMOS sensors, the silicon can be replaced with printable photoelectric materials, including organic or quantum dot semiconductors, in applications where high dynamic range, high sensitivity, and infrared detection are necessary (consumer electronics, security cameras, etc.).

Piezoresistive sensors are already an established market; the two largest segments are consumer electronics and healthcare. IDTechEx expects growth in those segments to continue and predicts the piezoresistive sensor market will triple by 2018 with significant expansion in the automotive arena.

Dr. Guillaume Chansin, technology analyst for IDTechEx, said the automotive industry will be very interested in the thin and lightweight characteristics of printed sensors. "In some cases, printed sensors can be more reliable, as there are no moving parts," he said. Chansin also predicted flatter designs for controls and switches, as "printed piezoresistive sensors can be made thin and flat, and you can use them with your gloves on."

IDTechEx expects other sensors to develop as well and deliver better performance, new form factors, and ease of customization. This includes photodetectors made with a new generation of light-sensitive materials (the same materials used to make hybrid CMOS and x-ray sensors), temperature sensors, and gas sensors.

In addition to products entering the market from glucose test strip manufacturers (currently the largest printed electronics biosensor market) such as Lifescan and GSI Technologies, R&D continues in healthcare, electronics, intelligent packaging/security, and automotive.

In the healthcare market, the Korea Advanced Institute of Science and Technology (KAIST) recently published a paper on an exhaled breath sensor to detect diabetes and lung cancer in breath. Their research showed that platinum-coated tin dioxide (SnO2) fibers can identify acetone or toluene (markers for diabetes and lung cancer, respectively) at very low concentrations. The University of the West of England recently integrated a printed cholesterol sensor with a printed battery and a printed display based on organic and flexible technologies.

For the electronics market, FUJIFILM and Panasonic have cooperatively developed an organic CMOS sensor technology utilizing an organic photoelectric conversion layer with a photoelectric conversion property. The outcome is an organic CMOS sensor that prevents overexposure, even in bright light, and delivers bright video even with a dark subject. The companies see a wide range of applications including security cameras, in-vehicle cameras, mobile devices, and digital cameras.

NikkoIA is exploring depositing photodetection materials as a thin film layer onto electronic reading substrates. The signal is read by active or passive amorphous silicon thin-film transistor backplanes, CMOS substrates, or printed electronics flexible substrates. NikkoIA sees their sensing products applied to and product- and human-related security, including payment processing and border monitoring.

Smart packaging and brand protection is another area where printed electronics has a firm grip. "The premise of smart labels is that there is active intelligence in the label -- sensing, data storage, display, eventually RF communication," said Jennifer Ernst, executive vice president of sales and development for Thinfilm Electronics.

Thinfilm, the first company to commercialize printed rewritable memory (utilizing organic logic developed by PARC), recently announced that an international luxury goods company will begin using Thinfilm's Brand Protection Solution for product authentication and assistance tracking counterfeit activity. With a signal embedded in the memory, the solution, said to be the first into the market, will help secure products from counterfeiters. "Even the simplest of solutions," said Heidi Arnesen, Thinfilm Communication Manager, "will have a little bit of intelligence."

The Thinfilm Smart Sensor Label can track data for goods such as pharmaceuticals and perishable foods. The flexible sensor, the first printed electronic system powered solely by batteries, contains memory, logic, and the temperature sensor. It can be mass produced inexpensively, using roll-to-roll manufacturing. Commercial availability is expected by the end of 2014.

"We can produce millions at a time," said Arnesen, and "with such low cost we can bring intelligent labels to even disposable items. With Thinfilm technology the infrastructure is minimal, which makes a smart label a cost-efficient alternative to both RFID and silicon based chips."

Another example of temperature monitoring is offered by Insignia Technologies. Using a range of pigments and inks, its sensors change color when exposed to gases or UV light. The indicators contain an embedded timer printed on a plastic substrate, to show when a package has been opened or when food is past its use-by date. Their current focus is on product quality and freshness in food packaging.

In the automotive sector, senor manufacturer IEE's Occupant Classification system uses piezoresistive sensors to monitor car seat occupancy. The pressure sensitive matrix sensor uses pattern recognition and anthropometric parameters to determine passenger type -- adult, child, or empty child safety seat/vacant -- and deploy the airbag accordingly, if necessary.

T-Ink's Smart Surface 3D In-Mold Overhead Console, which features screen-printed capacitive switches, debuted in the 2013 Ford Fusion. The company's In-Mold "smart plastics" process allows its inks to conform to any shape and size substrate and be printed on the opposite side of a substrate.

Both IEE and T-Ink see additional applications for their products in the medical device industry.

Printed electronics is still in its infancy. Each day brings new ways to detect and measure a plethora of activities, from light, temperature, and gases to food freshness and physical pressure. The benefits to printing electronics are clear: lower cost, lower weight, smaller form factors, and more satisfied customers.

"Printed electronics will help enable not only the Internet of Things, but the Internet of Everything, where all items in the world are a bit smart, even disposable ones, making our everyday lives a little easier," said Arnesen.


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