A micron‐sized nanoporous multifunction sensing device

In this work, a capacitive sensor based on Anodic Aluminium Oxide (AAO) porous structures has been developed. In some cases, the pores have been also conformally coated with a high chemical pure SiO2 by means of Atomic Layer Deposition (ALD). Temperature measurements have been done in DI water obtaining a response of 5 nF/°C. pH measurements have been performed and the responses obtained are between 0.2 and 1 nF/pH. The reproducibility of the sensors has been found to be high and a larger hysteresis effect has been observed in the samples with alumina pores rather than in the SiO2 ones. The hysteresis seems to be related to the charging of the oxide upon application of a voltage.