"Sensor-filter" - intelligent micro filter system in foil technology
A novel micro filter system (sensor filter) has been developed that automatically detects its current loading status by an online measuring technique. This enables automated filter, samples and process monitoring. The sensor filter is based on the combination of a sensor system and a filter technology into one foil layer system (foil-MEMS). This is realized using two sensor foils with capacitive electrode structures (interdigital capacitors) and a filter membrane which is placed between the sensor foils. The capacitive detection of the filtrate (cells or particles) is possible via the alteration of the permittivity of the fluid upstream the filter at the "upper" interdigital capacitor. The "lower" interdigital capacitor downstream the filter serves to compensate temperature and/or conductivity variations of the fluid itself. The functionality of the sensor filter was examined using a special designed measurement chamber with solutions of polystyrene beads and yeast (Sac charomyces cerevisiae). In doing so the sensor filter system was characterized and the loading process was measured capacitively. Finally the results were confirmed qualitatively using different theoretical calculation models.