Miniaturized low temperature co-fired ceramics (LTCC) biosensor for amperometric gas sensing

The miniaturization of an amperometric biosensor device by multilayer technique using low temperature co-fired ceramics (LTCC) tapes as construction material was investigated. An internal Ag/AgCl reference electrode of the miniaturized device is prepared by partial chlorination of a screen-printed Ag layer. Different chlorination techniques were evaluated to gain stable electrodes, which obey the Nernst equation. Novel diffusion membranes, compatible with the LTCC process, were developed. Different strategies were evaluated to achieve the necessary degree of hydrophobicity of the ceramic membranes in order to keep buffer/enzyme solution inside the micro-device, and at the same time to conserve the necessary gas diffusion into the device. A well-known formaldehyde dehydrogenase-based system was inserted into the LTCC setup to demonstrate the advantages of the LTCC setup compared to the conventional macro-device. The LTCC micro-device shows a linear response curve in the range of 500 ppb to 10 ppm, a sensitivity of 0.5 μA/ppm (0.5–10 ppm), t 90-response times of 6–14 min and a detection limit of 76 ppb (S/N = 3). With this characteristic, the miniaturized enzyme gas sensor achieves the performance of the well-established macro-device while requiring just half of the enzyme and one tenth of the buffer solution.