Bat­tery-free smart homes — researchers from Freiburg devel­op wire­less and bat­tery-free sensors

Three researchers from the Insti­tute of Microsys­tems Engi­neer­ing (IMTEK) at the Uni­ver­si­ty of Freiburg want to devel­op sen­sors based on Sur­face Acoustic Waves (SAW) tech­nol­o­gy for the smart home sec­tor. The wire-less and bat­tery-less sen­sors are intend­ed to replace pre­vi­ous­ly avail­able bat­tery-oper­at­ed prod­ucts and thus be more resource-sav­ing and envi­ron­men­tal­ly friend­ly than cur­rent solutions.

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, tem­per­a­ture and deposits on the sur­face. With the aid of these var­i­ous depen­den­cies, SAW sen­sors can accu­rate­ly mea­sure chem­i­cal and phys­i­cal vari­ables, so that 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.

“So far, SAW sen­sors have not been used in the smart home sec­tor because the sen­sors do not have a strong enough range to be read­able over the required dis­tance and the read­ers are too expen­sive,” says Chris­t­ian Ortolf. How­ev­er, due to their bat­tery-free pow­er sup­ply and their long ser­vice life, SAW sen­sors are more envi­ron­men­tal­ly friend­ly and more con­ve­nient to use than exist­ing prod­ucts. To make use of the sen­sors, the team will also devel­op cheap­er SAW read­ers that will serve as a bridge to the reg­u­lar smart home sys­tem. For exam­ple, the sen­sors can inform smart home users via mobile phone mes­sages whether a win­dow is still open when they leave the house and the heat­ing is there­fore heat­ing up unnecessarily.

The team is assist­ed in the devel­op­ment of the sen­sors by the physics sim­u­la­tion soft­ware DESMA. “The soft­ware allows us to reduce the design process of SAW com­po­nents from many months to a few weeks, which is why we already have requests to co-design with oth­er com­pa­nies,” Ortolf says. As a pre­lude, 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 and indus­try with oth­er bat­tery-free products.

The researchers Dr. Chris­t­ian Ortolf, Taimur Aftab and Ser­gio Gutier­rez from the Insti­tute of Microsys­tems Engi­neer­ing (IMTEK) at the Uni­ver­si­ty of Freiburg would like to devel­op sen­sors based on Sur­face Acoustic Waves (SAW) tech­nol­o­gy for the smart home sec­tor. The team is sup­port­ed in found­ing their start-up “Sen­SAW­tious” by Prof. Dr. Leon­hard Reindl, the for­mer hold­er of the pro­fes­sor­ship for Elec­tri­cal Mea­sure­ment and Test Meth­ods at the IMTEK and by Prof. Dr. Ste­fan J. Rupitsch, the new hold­er of the pro­fes­sor­ship for Elec­tri­cal Mea­sure­ment and Embed­ded Sys­tems, also at the IMTEK.