Printed sensors with flexible electronics are very well suited to smart buildings for automated control systems, says a report from UK analyst IDTechEx that identifies the satew of commercial readiness.
Smart buildings need multiple sensors, and the low weight and thin-film form factor of printed sensors will allow installation in walls, floors and ceilings to detect water leaks, air quality, usage patterns, and more.
Given the large areas involved, low-cost manufacturing is essential for some building-integrated applications such as touch-sensitive walls. This functionality is achieved by printing carbon-based conductive inks with conventional graphics printers. By arranging multiple capacitive printed sensors underneath decorative graphics, people can interact with the ‘wall’ to produce light and sound (generally produced via conventional electronics at this stage). Currently, this application of printed electronics is used primarily for promotional purposes, such as marketing campaigns.
Touchless light switches using capacitive touch are another application that utilizes the ability of capacitive sensors to detect the proximity of conductive objects (such as hands) rather than pressure. Given the current COVID-19 situation, technology that enables contactless switching is also attracting increased interest.
Pressure sensors have long been manufactured using screen printing of both conductive inks and a force-sensitive resistive material, with car occupancy sensors the most common application. The low production costs mean that these sensors can be used to cover very large areas such as flooring. Potential applications include monitoring customers in a shop or patients in a hospital, without the privacy concerns associated with cameras. Pressure-sensitive floor pads have also been developed and deployed in shops to help enforce COVID-19 social distancing requirements.
An innovative and commercially available interior application is thin-film moisture sensors. These determine humidity using a printed antenna that is read remotely by an RFID reader, enabling non-destructive measurement. The basic principle is that a moisture sensitive layer changes the resonant frequency of the antenna. The thin-film format enables the sensor to be placed behind waterproof tiles to check the waterproofing efficacy.
Capacitive printed sensors can also be used to sense water. Using cheap carbon-based ink printed onto reels of plastic means a thin strip of leak detective material can be cost-effectively spread around the perimeter of a room. The sensors communicate wirelessly with the cloud whenever a change in capacitance is detected, with most of the processing performed in the cloud.