The effect of the anodization voltage changes on the electric resistance of porous anodic alumina barrier layer and its thickness used in strain sensing devices

To investigate the influence of aluminum anodization voltage on the barrier layer thickness of porous anodic alumina (PAA) and its electric resistance used in different technologies such as strain-sensing technology, samples in different voltages and variety condition of mild and hard anodization were fabricated. In different researches, different anodic alumina thicknesses have been tested and their effect on protection against humidity is studied by monitoring sensor resistance. Measurement of electrical resistant of barrier layer during the voltage changing shows that there is a transition region in which electric resistance of samples is located between hard and mild anodized region. The SEM investigation reveals that the barrier layer thickness is linearly proportional to the anodization voltage. But the barrier layer resistance in hard anodization is lower than that one in mild anodization. The observed paradox can be related to higher ionic mobility of ions in barrier layer which is formed in hard anodization.