Battery-free smart homes

Researchers Dr. Christian Ortolf, Taimur Aftab and Sergio Gutierrez from the Department of Microsystems Engineering (IMTEK) at the University of Freiburg want to develop sensors based on the technology behind Surface Acoustic Waves (SAW) for the smart home sector. The wire- and battery-free sensors are intended to replace currently available battery-powered products and thus be more resource-efficient and environmentally friendly than current solutions. The team is supported in founding its start-up “SenSAWtious” by Prof. Dr. Leonhard Reindl, former head of the Department for Electrical Measurement and Test Methods at IMTEK, and by Prof. Dr. Stefan J. Rupitsch, the new head of the Laboratory for Electrical Instrumentation and Embedded Systems, also at IMTEK. The German Federal Ministry of Education and Research will fund the start-up project for one year starting in May 2021 with an EXIST business start-up grant worth 147,800 euros.

Surface acoustic waves are sound waves that propagate flat on a surface in two dimensions. The propagation speed of such waves depends on the mechanical deformation of the material, the temperature and on deposits on the surface. With the help of these various dependencies, SAW sensors can accurately measure chemical and physical quantities, so they can be used, for example, to determine temperature and pressure. To read out the data, the wireless sensors are in radio communication with a reader via an antenna.

„Up until now, SAW sensors have not been used in the smart home sector because the sensors did not have a strong enough range to be readable over the required distance and the readers were too expensive,“ says Christian Ortolf. However, due to the battery-free energy supply and their durability, SAW sensors are more environmentally friendly and more convenient to use than existing products, he adds. To make use of the sensors, the team will also develop lower-cost SAW readers that serve as a bridge to the regular smart-home system. In this way, the sensors can tell smart-home users via cellphone messages, for example, whether a window is still open when they leave the house and whether the heating system is unnecessarily heating the surroundings.

The team used DESMA physics simulation software to help develop the sensors. “The software allows us to reduce the design process of the SAW devices from many months to a few weeks, which is why we already have requests to co-design with other companies,” Ortolf says. At first, a sensor is to be developed that registers the opening of windows and doors. In the long term, however, the founding team would also like to position itself in the smart home market with other battery-free products.

For more information about the EXIST business start-up grant