Innovative applications based on force sensing inks

When the COVID-19 pandemic started, it demanded changes from several industries. With strict social distancing measures around the globe, simple day to day tasks such as shopping or going to the hairdresser became logistical challenges. Many companies soon realized that the influx of consumers was decreasing and the need for innovative solutions, across industries, became a requirement to improve the situation. Therefore, those solutions have become a differentiating factor. At Henkel we believe that challenging times are a spring for innovation and one example is the “smart mat”, a result from our partnership with InnovationLab and their use of our force sensing inks.

About the Smart Mat

The smart mat has an intelligent sensor matrix embedded consisting of more than 8,000 individual sensors. This array allows the mat to differentiate between human steps and, for example, the wheels of a shopping cart. The latter was possible thanks to InnovationLab's capacity to print high-accuracy, sheet-to-sheet, and roll-to-roll electronics. This smart mat was placed in a German retail store and connected to an indicator that resembles a traffic light with the intent to keep social distance while people are queuing up. Whenever the smart mat sensed a person standing on it, the traffic light indicator would turn red. When there was no one on the mat, the indicator's light remained green inviting the next customer to move forward.

With studies showing a relationship between the social distancing measures and the COVID-19 cases and death toll (Khataee, H., Scheuring, I., Czirok, A. et al, 2021), the smart mat becomes even more relevant. However, this technology can also be implemented, among others, in the healthcare sector to track movement of healthcare workers in critical situations or in industrial plants to monitor workflow.

Conductive inks enable flexible force sensitive resistors

The smart mat is based on force sensing technology, which can be divided into load cells and force sensitive resistors (FSRs). Load cells provide accurate measurements but are bulky and require proper mounting to avoid hysteresis and induced offset. Therefore, they are not suited for applications where space is a constraint or where the sensing needs to be done in a very precise and small area. On the other hand, FSR sensors are thin and flexible, have wide measure ranges and can be easily used over many materials allowing for innovative applications. And the smart mat is based on these FSR sensors.

Henkel's conductive ink (Loctite 1010) as well as the force sensing inks (Loctite 7004LR and Loctite 7004HR) enable the smart mat. With these two types of inks, it is possible to create membrane switches which can detect whenever a force is applied onto the FSR ink generating a decrease in the electrical resistance. The conductive ink is used to print the electric circuits while the FSR inks are used on the pressure sensing area. Each of our force sensing inks has a different resistance profile so blends of the two inks can be used to tailor the resistance of the material to the needs of the application. Once the blend has been established, the inks can be screen printed onto a wide range of substrates.

At Henkel, we have over 35 years of experience aiding in the development process of printed electronics. We also have a strong network of partners across the supply chain that will support from product conception to market launch. The smart mat will also be featured on Henkel's state-of-the-art Inspiration Center for Adhesive Technologies at Düsseldorf, a space for close collaboration and development of new technologies and applications across industries. Let's think together and bring new ideas from innovation to life!

Sources :

Khataee, H., Scheuring, I., Czirok, A. et al. Effects of social distancing on the spreading of COVID-19 inferred from mobile phone data. Sci Rep 11, 1661 (2021).

Trent, D. Strain Gauge Load Cell Basics. Load Cell Central (n.d.).