Flexible and printed sensors continue to find new applications. This, in turn, is spurring new markets to emerge in a wide range of fields.

NextFlex is working on numerous sensor projects, and Art Wall, director of fab operations at NextFlex, said that he is seeing opportunities for flexible and printed sensors in the military and consumer spaces.

“Both military and civilian-focused companies have looked at what we have done in the flexible microcontroller space and realized that if we could attach or build flexible sensors compatible with the flexible microcontroller architecture, you’ve taken something that’s interesting and really made it applicable – something that people really can make use of,” Wall said. “We’re taking tech demonstrations and adding sensor capabilities that can make them a true product.”

Tekscan has been producing printed sensors since 1983 and is probably best known for its work with Dr. Scholl’s and its Custom Fit Orthotics Kiosk, where a customer stands on a low-profile mat that is embedded with a custom pressure mapping matrix. The software walks the customer through a process and in less than two minutes, they receive an orthotic recommendation based on their foot pressure pattern, arch type, and foot length. Tekscan CTO Rob Podoloff said it’s hard to visit a technology conference or read a technology publication without the subject of printed and flexible sensors being front and center.

“A lot of this has to do with the demand for smart and sleek devices that pack many capabilities into a small, lightweight package,” Podoloff said. “At Tekscan, we manufacture printed piezoresistive force and pressure sensor technologies. When you factor the size you have to sacrifice to embed a load cell into the device, or the complex circuitry required to integrate a strain gage or MEMs device, those are some tall orders for the design engineer. Printed sensor technologies allow the engineer to incorporate force- or pressure-sensing capabilities, without needing to sacrifice space, weight and power within a design.”

Podoloff said while it may take some engineers by surprise, printed force- and pressure-sensing technologies are not a new development whatsoever.

“In fact, Tekscan has been manufacturing printed sensors since the mid-1980s, so we’ve seen first-hand how quickly demand has grown. We currently own 18 patents in printed force- and pressure-sensor technologies, the most recent of which was issued at the end of 2019,” Podoloff added.

SPEC Sensors, LLC just launched its SPARROW gas sensor system, which connects a carbon monoxide monitor to smartphones, allowing people to monitor the environment in real-time. SPEC Sensors, LLC GM Ed Stetter noted that there is great interest in measuring gases and other parameters transdermally.

“These could be medical devices that detect alcohol or ketones through the skin and monitor a number of conditions,” Stetter said. “Of course, flexible sensors could more easily become part of existing and new infrastructure like lights or automotive components. I think for gas sensors, in particular, some of these would be very new applications, and our challenges there are more performance right now than form factor, but the truly revolutionary high volume products will likely be for flexible sensors.”

Bonbouton has been developing graphene printed sensors designed to provide preventive medicine and enable better health and well-being for diabetes care. Laura Saracho, head of product marketing for Bonbouton, reported that printed and flexible sensors offer key advantages in healthcare.

“I definitely see a bright future for printed and flexible sensors, especially hybrid systems that can be applied to different substrates/materials,” Saracho said. “Our ability to use polymers for more breathability and enhanced human interface presents an exciting future for sensors that can be used for numerous human physiology applications.”

Nick Skelton, marketing manager, Brewer Science, observed that opportunities for flexible and printed sensors continue to grow every month/quarter for a few different reasons.

“There is a growing awareness of the benefits of printed and flexible technology,” Skelton said. “It is getting out there to people who aren’t just in the industry but are looking for new technology integration solutions that provide them with fast, highly efficient sensing. There is an urgency within several industries to implement faster, smarter sensing systems and arrays where conventional sensing options are not fully adequate to meet requirements.

“We are overcoming technical challenges – with any new technology or innovation there are challenges at the beginning that typically slow opportunities. Over the last three months, we have made significant improvements to reduce drift, while addressing other challenges within the industry,” Skelton added.

Among other projects, Ynvisible has been working with InviSense on thin, passive humidity sensors for the construction industry. Ynvisible CEO Jani-Mikael Kuusisto noted that printed flexible sensors offer several form factors and product integration advantages.

“Application fields where conformability is a major factor are areas with a great opportunity for printed sensors,” Kuusisto said. “It allows the introduction of sensors into places where it previously may not have been possible due to confined spaces, harsh conditions, or where conventional sensing systems were uneconomical to implement.”

Key End-Use Markets

In speaking with industry leaders, automotive, healthcare and gas sensors are already areas of interest. For example, Skelton said that automotive, healthcare and environmental sensing are very promising markets for flexible and printed electronics. 

“Automotive manufacturers continue to look at printed electronics for printed interconnects, in-mold electronics and touch sensors. The healthcare industry continues to be testing and evaluating the use cases for better wearable devices,” added Skelton. “Other promising markets right now are in water and environmental quality monitoring, where customizable form factor or cost of ownership needs are not met by existing technology.”

John Hannafin, global product manager for Sun Chemical, said that medical diagnostics and patient tracking appear to be leading the way.

“Non-invasive monitoring of glucose and some cardiac functions are creating a lot of demand,” Hannafin reported. “Of course, the Internet of Things and the commensurate infrastructure is already being built to support the anticipated demand. This infrastructure will also enable the consumer brand groups to support item level tagging and smart surfaces which drive the consumer experience in the retail space.”

Stetter also pointed to environmental sensing for cities and vehicles, as well as healthcare.

“For gases, we see smart cities as one of the most promising markets, monitoring for pollution and other gases in urban environments (some call this IoT or Industrial IoT),” Stetter said. “Auto manufacturers are also interested in indoor and outdoor air quality monitoring and some see the car or bus as the best platform on which to monitor outdoor pollution. As sensors improve and costs go down I think individuals will also see value in this information and seek out wearable or fixed home air quality monitors. Healthcare is also ripe for growth with sensor applications. In the gas space, breath and transdermal monitoring and diagnosis of conditions or chronic diseases are definitely promising.”

Saracho noted that Bonbouton is heavily invested in the healthcare market, especially preventive care.

“In order to see promise with this end-use, we need to focus on 1) comfort; 2) the precision/accuracy of the sensor readings; and 3) scalability/ease for manufacturing partners to adopt the sensing technology,” Saracho added.

Ultimately, Podoloff can see sensors being used in many different fields.

“I don’t think there is a market or industry where printed sensors are not, or should not be, in high demand,” Podoloff said.

“Certainly, we’ve worked with a lot of different industries including medical devices, manufacturing systems, vehicle/tire design, consumer goods, athletics – you name it. That’s really one of the most exciting parts of being in the printed sensor business; new applications and uses come our way every day.

“I do think that medical devices are generally a hot market for this type of technology,” Podoloff added. “There seems to be a clear trend toward medical devices that put the patient experience at the forefront of the design. Devices like infusion pumps need to function with little-to-no direct human interaction, and thin printed sensor technologies go a long way in helping make these concepts possible.”

Kuusisto noted that printed sensors can impact all the end markets Ynvisible is directly or indirectly dealing with.

“Health and wellness is the sector that most strongly comes to mind,” he added. “But also, logistics, retail, environmental sensing and construction are particularly promising fields. Conformable sensors are allowing a wide range of end applications: anything from monitoring humidity in built infrastructure to novel consumer experience-enhancing features to e-commerce, and new types of solutions for healthcare to minimizing waste. We need to stop staring solely at the price of sensors and rather look at the benefits and efficiencies their use brings to end products. Ultimately the spread of printed sensors will have huge positive impacts on sustainability and eco-efficiency.”

Wall said that there are so many potential end-use markets, it’s hard to know which one will take off sooner than the rest.
“I think of two promising end-use markets, one military and one civilian,” Wall said. “On the military side, there are many applications, but if I were to pick one, the safety of the warfighter is an area that has real importance, whether they’re engaged in conflict or not. Even with things like maintenance on aircraft, safety could be enhanced by the right flexible or wearable
electronic devices.

“On the civilian side, I’d say a compelling use case is asset monitoring,” added Wall. “It’s a broad topic, but in some cases, it could be something as simple as locating objects and knowing where they are, answering the question of ‘where did I put my tools, my assets?’ You could think of it as an extension of the Internet of Things.”

Kuusisto said hybrid sensor systems in the form of smart labels are already available in the market.

“We recently announced a collaboration with Identiv,” Kuusisto said. “Identiv’s uTrust Sense Temperature Tracker is a compact datalogging NFC smart sensor that tracks and stores temperature readings. The temperature sensing and logging chip are grain-sized, and the label is flexible. Through our collaboration, Identiv is introducing Ynvisible’s EC displays as the visual indicator into the system. This makes it possible to instantly visually identify the NFC smart sensors (or labels) that have experienced temperatures outside the allowed temperature range and require immediate attention.”

“A recent brand new application for our sensors is in shutoffs for CO for portable generators. Every year a few hundred people are killed when they start their portable generators indoors or in places with poor ventilation. We co-designed a sensor-based shutoff for portable generators that will turn the generator off if it’s started indoors,” Stetter reported.

“We are also in the Array of Things project in Chicago with hundreds of pollution sensing nodes deployed throughout the city,” Stetter added. “We are still crunching the results but you can see some of them on our website. We have many other customers with projects in air quality. We recently also built and ran human trials on a transdermal alcohol monitor. This work was funded by NIH and we pretty conclusively demonstrated a high-performance monitor for alcohol that you can wear on your wrist and is BLE enabled with an app.”

“There’s a lot of printed sensors in the market right now, especially in sports,” said Saracho. “You’ll find various products that mostly use pressure sensors to measure things like running form and skiing orientation. However, we have yet to see pressure sensing adding large value in other industries. For preventive health, we’ll be looking at temperature, humidity and other physiology sensing elements.”

“You can go down any list of things that can be sensed: we can see applications for temperature monitoring, humidity, volatile organics, even in the area of MEMS or in areas like motion sensing and location,” Wall observed. “As another example, optical sensing is something we’re doing now for medical applications. It’s almost harder to find a form of flexible sensing that wouldn’t be of interest to someone.”