AIM: Sensors incorporated in lab-on-a-chip (LOC) platforms permit in situ measurements of analytes over time [1]. LOC approach with integrated impedimetric sensor has been used in this study aiming to develop a sensor for biomass estimation during cell cultivation in the novel, cost-effective microbioreactor (MBR). Interaction between cells and electromagnetic radiation in different frequency ranges enables detection and characterization of various cellular parameters. In the radio-frequency (RF) range, viable cells are polarizable and act as dipoles, hence the number of cells directly influences the dielectric permittivity of measured impedance [2]. In that sense, an impedimetric approach allows sensing the cell concentration and therefore biomass. Additionally, the LOC approach enables good control and collection of data relevant for the cultivation process [3]. METHODS: Cost-effective technologies of MBR and sensor fabrication are presented, as well as their integration and testing results obtained with MRC-5 cells used as model adherent cells. RESULTS: Developed impedimetric sensor in MBR has been able to detect number of cells i.e. biomass, as well as all the phases in batch cell cultivation over 96 h - lag, exponential, stationary, and death phase. CONCLUSION: By combining biocompatible and transparent materials, the LOC system provides a basis that allows additional integration of electrodes, sensors, or optical components, and has a potential for the rapid production of low-cost and reliable MBRs that can be used in cultured meat research. Impedance-based sensing is a good approach for biomass monitoring in MBRs.