A disposable BOD microsensor using a polymer substrate

A disposable microbial sensor was designed, fabricated and tested for standard BOD (biochemical oxygen demand) measurements. A transparent cyclic olefin copolymer (COC) substrate was used for sensor fabrication. Standard lithographic procedures in addition to techniques like screen printing and electroplating were used to fabricate the sensor. A layer of a microbial strain of Trichosporon cutaneum was immobilized over one pair of sensor electrodes while the other was used as a reference. Depending on the respiratory activities of the microbial strain in different samples, the BOD values of the samples could be measured in terms of difference between the output signals. The sensor layer was enclosed by an injection-molded passive microfluidic channel on the top. The BOD sensor was calibrated and tested with standard BOD solutions and samples obtained from a wastewater reclamation facility. Good correlation with chemically determined BOD₅ values was obtained with fast response time. Advantages of the BOD microsensor include: (a) fast BOD measurement; (b) disposability from a low cost, chemically inert polymer substrate; (c) flow-through sample injection scheme; and (d) possible future integration of on-chip optics.