High Performance Low Cost Impedance Spectrometer for Biosensing

Cell culture assays have become a routine testing method in the medical and pharmaceutical research. Real-time monitoring of cells on a substrate using electrical impedance is a convenient and non-invasive method of analysis. Cell proliferation and apoptosis can be quantified and characterized by electrical impedance in a time-dependent manner. Unfortunately monitoring several cell cultures at the same time is challenging because of the prohibitive costs of impedance analysis equipment or rather slow response if multiplexing the front-end of an impedance analyzer. We propose a low cost high performance impedance analyzer based on a two channel delta-sigma 16-bit ADC. The device can handle frequencies between 30 Hz and 10 kHz with input impedances ranging: 100mOhms - 10Mohms. The Automatic Level Control (ALC) algorithm allows for steady non-invasive voltage levels on the measured impedance independent of measuring frequency and impedance value. The device prototype performance is compared to commercial analyzers used for monitoring cell growth and related cell based e.g. biosensing applications. Low production cost and robustness to component tolerances owed to special digital processing inside the Digital Signal Controller (DSC) make this device very suitable to mass production, the first step in becoming a readily available tool.