“Sensor-Filter”–Intelligent Micro Filter System in Foil Technology

A novel micro filter system (sensor filter) enables standalone detection of its own loading status as well as monitoring the filtrate for the first time. This sensor filter consists of two micro-perforated sensor-foils containing interdigital capacitors (IDC) and a filter membrane placed in between. 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” IDC. The “lower” IDC downstream the filter serves to compensate temperature and/or conductivity variations of the fluid itself. The calculation of the sensor filter behavior using an elementary IDC model and an estimation of the filtrates permittivity applying different continuum models explains the sensor's response qualitatively. This theoretical model was confirmed by measurements with particles and yeast cells.