## 3 Results
### Impact of Insertion Speed to Electrode Insertion Forces  
To investigate the dependence between electrode insertion force and electrode friction, insertion forces at different insertion speeds (0.1, 0.5, 1.0, 1.5, 2.0 mm/s) were recorded. Data was acquired from a distance of 30 mm, inside the scala tympani model lumen.  
As shown in Figure 3a, electrode insertion forces between \(-\)0.0008 N and 0.018 N were recorded, depending on insertion depth. Minima forces were detected within the first 10 mm of insertion, approaching force maxima towards the end of the feed and subsequently with a force decrease. All recorded force maxima were found to be similar. However, the highest insertion force maximum were detected at a speed of 1.5 mm/s (0.018 N), followed by 0.1 mm/s (0.17 N) and 2.0 mm/s (0.16 N). Complementary, insertion force maxima recorded at the speeds of 0.5 mm/s and 1.0 mm/s were 0.14 N and 0.13 N. Interestingly, we observed three force peaks at each insertion speed as distance increased. The insertion force reaches the first peak between insertion distances of 3 and 4 mm/s, the second peak between 13-15 mm, while the third peak is reached between 25-28 mm. Notably, the steepest insertion force progression and the highest second peak were recorded  
Figure 2: Cochlear electrode friction force and friction coefficient at five different pulling speeds. (**a**) Friction forces of the cochlear electrode recorded during pulling along a friction partner. Mean friction force curves over 30 mm pulling track (distance) are shown. Pulling speeds were set to 0.1 mm/s (black), 0.5 mm/s (blue), 1.0 mm/s (orange), 1.5 mm/s (green), 2.0 mm/s (violet). n = 7 repetitions with 0.5 mm/s, n = 10 repetitions with 0.1 mm/s and 1.0 mm/s, n = 12 repetitions with 1.5 mm/s and n = 14 repetitions with 2.0 mm/s pulling speed were performed. Lines represent the standard deviation. (**b**) Cochlear electrode friction coefficient calculated from mean friction force. Pulling track was 30 mm and pulling speeds are 0.1, 0.5, 1.0, 1.5, and 2.0 mm/s. n = 7 repetitions with 0.5 mm/s, n = 10 repetitions with 0.1 mm/s and 1.0 mm/s, n = 12 repetitions with 1.5 mm/s and n = 14 repetitions with 2.0 mm/s pulling speed were performed. Data are presented as mean with positive standard deviation (lines). \(p\)-values were calculated by one-way ANOVA followed by [PERSON]’s Multiple Comparison post hoc test. *** \(p\) < 0.01, *** \(p\) < 0.0001 and n. s. = not significant compared to mean friction coefficient at 0.1 mm/s.  
at a speed of 1.5 mm/s (26.7 mm/0.082 N) followed by 0.1 mm/s (26.7 mm/0.067 N), 2.0 mm/s (26.3 mm/0.050 N) and 1.0 mm/s (26.25 mm/0.049 N). In contrast, the flattest force progression and the lowest second peak are detected at an insertion speed of 0.5 mm/s (26.74 mm/0.034 N). Moreover, while most recorded insertion forces are characterized by smooth pattern, the insertion speed of 0.1 mm/s induced a more variable course of the insertion force, indicated by a fluctuated graph pattern.  
For quantitative evaluation of insertion forces, we calculated mean insertion forces at different insertion speeds (Figure 3b). As expected, a speed of 1.5 mm/s leads to the highest mean insertion force (0.25 N \(\pm\) 0.007 N), followed by 0.1 mm/s (0.02 N \(\pm\) 0.008 N), 2.0 mm/s (0.019 N \(\pm\) 0.003 N) and 1.0 mm/s (0.016 N \(\pm\) 0.001 N). The lowest mean insertion force was detected at a speed of 0.5 mm/s (0.014 N \(\pm\) 0.003 N). Statistical analysis revealed that the mean insertion forces recorded at 0.1 and 1.5 mm/s are significantly increased, while the insertion speeds of 2.0 and 1.0 mm/s showed no significant difference if compared to 0.5 mm/s.  
In conclusion, the attained data demonstrates a profound impact of the electrode array insertion speed on the insertion force. Notably, insertion speeds of 0.5 and 1.0 mm/s result in significantly lower insertion forces, while an insertion speed of 1.5 mm/s leads to the significantly highest insertion force, followed by 0.1 and 2.0 mm/s.