**4.1. Nanoporous Si characterization**

The morphology of the synthesized porous Si film is characterized by SEM microscopy (**Figure 7**). When the anodization process is tested for 60 mA/cm2 , some multiple pores are crowded inside a single larger pore rather with a crater shape. When the anodization process is tested for 300 mA/cm2 , some huge pores reached 7 μm size. However, the current density of 50 mA/cm2 offered the optimum porosity for the enzyme entrapping [22].

**Figure 8** presents the designed mask for the nanoporous Si region configuration.

Then, **Figure 9** presents the next mask used for the metal deposition on nanoporous Si material.
