Freestanding Porous AI2O3 Substrates and Devices

As shown in the previous section, localized porous-type anodization and selective etching of A1 can be used for the fabrication of complex microstructures composed from freestanding porous AI2O3. As an example, Fig. 16a and b demonstrates SEM and optical images of microstructured porous AI2O3 substrates, which are utilized for sensor applications (Fig. 16c, d). The lateral dimensions of freestanding ceramic substrates were controlled by the mask design and process conditions. The thickness was controlled by the current density and duration of anodization (2 min anodization 

The presented examples show that the electrochemically micro-machined anodic alumina is advantageous for the fabrication of sensors and sensor arrays because of its thermal stability, controllable porosity, and a variety of options for the deposition of sensing materials. The fabricated and tested sensors have demonstrated high sensitivity and selectivity, long-term stability, low power consumption, as well as the reactivation fimction in the pulse mode. 

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