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# Strain Calculation by Image Processing

## Steps (cont'd...)

(vii) The figure below shows the processed image of different pre-strained condition. The final actuation area is calculated by counting the number of pixels having zero intensity value as the area represented by black colour is the actuation area. The same procedure is followed for every image of the sample and the number of pixels in the actuation area are counted i.e. the number of black pixels in the binary image is counted. The strain value at certain voltage is given by the following equation :
Strain = $(A_v - A_0) / A_0$
Where $A_v$ is number of black pixels at V voltage and $A_0$ number of black pixels at 0 voltage.

(viii) From the count of black pixels the areal strain can be obtained. But for finding the actual area of the DE sample the pixel area must be known. The pixel area can be found from the initial un-cropped image by counting the number of pixels in the 1 cm length on the scale. The pixel length is given by cm. From this the area of the pixel is known and hence the actual area can be found.

(ix) From the count of black pixels the area strain can be obtained. But for finding the actual area of the DE sample the pixel area must be known. The pixel area can be found from the initial un-cropped image by counting the number of pixels in the 1 cm length on the scale. The pixel length is given by 1/(no of pixel in 1 cm length) cm. From this length area of the pixel can be found.

Figure: Electrode image after application of high voltage