**B. Complete drying and curing process**

Since the highest working temperature of plastic material is normally lower than 200°C, the over 350°C curing temperature for SiO2 curing is not acceptable. This issue can be solved by replacing the plastic substrate by glass. Even though the glass substrate is fragile for shear stress, it can be made thin and thus flexible. Section 3.1 gave one example of how thin, how large, and how flexible can the thin glass be.

### **C. Doubled isolation layers**

Either the sputtered SiO2 or the completely cured SiO2 ink will not solve the profound impact of electrostatic adhesion between upper electrode layer and the isolation layer. As a result, the sputtered SiO2 or the completely cured SiO2 ink will still degrade owing to the detachment of electrode material from the upper substrate. To prevent the electrode material from detaching from its substrate, a good solution is to cover the electrode with the isolation material. When this device is ON, the combinational thickness matches the color design value in the second section and the output color is expected to be the same. However, as summarized in Table 8, the OFF state non interfered color needs to be specially designed. The thickness in this table was easily divided the isolation layers into equivalent two parts from its originally designed value. Compared to the data for single layer, the data for double layer will form a larger triangle which is a drawback explained in section 4.1.


Table 8. OFF color difference from single and double layer designs.
