Dust accumulation sensing system with a screen-printed interdigitated sensor

Regardless of the importance of air filtering, there are quite few technologies to observe the purity of a filter. Optimizing the filter replacement cycle is necessary from the cost efficiency and the ecological point of view, being a motive for sensor technology development. In this paper, we propose and demonstrate a concept for that purpose. A capacitive sensor element is screen-printed directly onto the filter surface and assembled in 3D printed frame to observe the particle accumulation while the filter is in use. An additional sensor element is printed to the back side of the filter to act as a reference. That reference sensor improves the sensitivity of the system by enabling the compensation of the temperature and humidity fluctuations. The sensor was placed inside a robot vacuum cleaner and its performance was demonstrated and evaluated by repeated cleaning cycles in a controlled environment. By measuring the difference between the two capacitances of the sensors, an increase of up to 1.55 pF was observed, which equals +9.3% of sensor’s initial capacitance value. After cleaning the sensor area, a permanent increase of 0.4 pF was measured, which equals +2.4% of the initial capacitance value.