Binary Zero-Power Sensors: an alternative solution for power-free energy-autonomous sensor systems

Energy-autarkic sensor systems use energy from their environment for operation and data transfer. This needs both an efficient energy harvesting strategy and an appropriate energy storage management but also ultra-low-power technologies for sensors, signal processing, and wireless signal transfer. Binary Zero-Power Sensors are threshold switches which take the switching energy directly from the quantity to be measured. For this purpose stimuli-responsive polymers—in particular hydrogels—are used which swell upon the influence of particular quantities like humidity, temperature or pH value. The swelling causes the deflection of a flexure element closing or opening the contacts of a switch. In this manner they deliver the switching states “ON” and “OFF” without any additional electrical energy.