Flexible and Printed Sensors – Five Applications for FMs

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18 February 2021 | Updated 25 February 2021

Research shows that innovative printed and flexible sensors can offer several benefits over their more established rigid counterparts.

Technology market research company IDTechEx profiled over 50 companies to gather an overview of the diverse underlying technologies and applications of printed and flexible sensors. 

Sensors of this type constitute the largest printed electronics market, and IDTechEx forecasts that the market for fully printed sensors will reach $4.5 billion by 2030. 

These lower-weight sensors can offer potentially lower manufacturing costs since printing facilitates high-throughput continuous production methods. Printed and flexible sensors can measure a wide range of parameters and can be employed in emerging applications, including industrial IoT, wearables, automotive interiors, and smart buildings.

What are Flexible and Printed Sensors?

Rigid sensors usually consist of bulky materials such as glass or ceramics, but flexible sensors are printed on flexible substrates such as plastic, textiles or paper. This has the added advantages in terms of mechanical flexibility, thinness and weight reduction.

Some may consist of a very simple structure with only a few electrodes, others are much more complex and require the deposition of multiple layers. 

Five Innovative Printed and Flexible Sensor Technologies for Facilities Management

1. Hybrid Piezoresistive and Capacitive Sensors for Touch Screens – Capacitive touch sensors can be found, for example, on top of smartphone and tablet displays. Piezoresistive sensors are used to detect changes in pressure. Both these functionalities can be combined within the same multilayer printed film to form hybrid sensors. Such sensors can detect both proximity and pressure, enabling buttons that illuminate prior to contact but only actuate with a firm press. They can also be utilized in robot grippers to detect when the “fingers” are close to objects and measure the pressure distribution.
2. Thin-Film Organic Image Sensors for Fingerprint Recognition –  Most image sensors are made from small rigid pieces of silicon. However, many other semiconductors can also be used to detect light, including printable organic semiconductors. These have the advantage of being very thin since the light-absorbing layer is only a few hundred nanometers and are cost-effective to manufacture over large areas, making them applicable to biometric sensing such as fingerprint recognition. Furthermore, unlike silicon, the absorption spectrum of organic semiconductors can be adjusted, including into the NIR region.
3. Printed pH Sensors for Temperature Monitoring – Currently, most methods of measuring pH are either inaccurate/subjective (universal indicator paper) or relatively costly (electronic probes with a reference electrode). German firm Accensors have recently developed a method for printing pH sensors, in which an affordable and simple sensor can be created by printing just one nanoliter of a proprietary material. A printed temperature sensor usually accompanies these pH sensors to ensure accurate readings (since pH is a function of temperature). Arrays of printed pH and temperature sensors have been incorporated within prototype wound monitoring patches.
4. Moisture Sensing via RFID for Leak Detection – Swedish company InviSense have developed a printable thin-film sensor that can detect moisture. A printed RFID antenna coil is coated with a moisture absorbing material. As moisture is absorbed, the capacitance associated with the coil also changes, changing its resonant frequency. This can then be detected remotely by an RFID reader. The key advantage of this approach is that the thin film format of the sensor enables it to be placed behind bathroom tiles and that testing can be performed in a non-destructive manner.
5. Electronic Noses for Gas Leak Detection – Relative to sound, sight, and touch, smell is one of the human senses that has yet to be effectively digitized. One of the challenges is that odours are made up of multiple gas molecules in different concentration ratios. The “electronic nose” approach to gas sensing aims to resolve this challenge by using an array of semiconductors, such as carbon nanotubes, that are functionalized slightly differently. By algorithmically comparing the conductivity changes across the different sensor regions with reference data, the gas composition can be determined.

The full IDTechEx report “Printed and Flexible Sensors 2020-2030: Technologies, Players, Forecasts”, can be accessed here. 

Picture: a picture of a modern office corridor

Article written by Ella Tansley | Published 18 February 2021

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