All of these three states of a sub-electrode can be observed in the air, Figure 7B. Of course, in the tissue, the damping force of nearby tissues can influence the shape as well during the expanding process. Hence, the influence of biological tissue is still worth being investigated, Figure 7C (original photos in Figure 8). Due to the existence of tissue, the deflection of sub-electrode is weakened and results in relatively smaller magnitude of deflection angle in morphing state 1, Figure 7D. In state 2, the stylet is expanded out of the cannula and begin to contact with the tissue. As mentioned above, the deflected angle is almost unchanged and the radius of curved stylet also seldom changes. In state 3, not only the recovery of deflected cannula is damped by the tissue, but also the bevel tip of stylet is further affected by the tissue. Therefore, in this state, the deflected angle of cannula in tissue phantom is larger than that in air, and the bending radius of stylet in the tissue phantom is smaller than that in air.