# Modeling and Design Enhancement of Electothermal Actuators for Microgripping Applications
## 4 Discussion  
In this work, we investigated the impact of perforations on the operation and performance of electrothermally actuated microgrippers. To do so, we first conducted finite element simulations in order to generate the temperature distribution and displacement of electrothermal actuators when subjected to different voltages and verify them against previously published experimental results. The present simulation results showed good agreement with their experimental counterparts. Then, we introduced and analyzed a novel design of microgrippers, including perforated electrothermal actuators. Different perforation configurations were tested. The simulation results revealed that adding perforations to the hot arm of the electrothermal actuators resulted in a larger displacement and lower temperature of the gripping arm without affecting the mechanical strength of the microgripper. The maximum operating voltage of the microgripper was set equal to 8 V. At this voltage, the gap opening was observed to reach an increase of 13% when adding perforations. Moreover, the tip temperature of the perforated microgripper was reduced \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Total Tip** & **Upper Tip** & **Lower Tip** & **Von-Mises Stresses** \\  & **Displacement (\(\mu\)m)** & **Temperature (\({}^{\circ}\)C)** & **Temperature (\({}^{\circ}\)C)** & **(GPa)** \\ \hline No perforation & 9.885 & 978.29 & 978.29 & 2.25 \\ Single row square & 10.707 & 867.01 & 867.02 & 2.23 \\ Single row circular & 10.685 & 871.22 & 871.25 & 2.26 \\ Double row square & 11.240 & 731.30 & 731.30 & 2.01 \\ Double row circular & 11.176 & 739.71 & 739.72 & 1.89 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Performance characteristics of the different microgrippers when operating at 8 V.  
Figure 19: von-Mises stress distributions obtained for the different microgrippers subjected to an applied voltage of 8 V.  
to 731.30 \({}^{\circ}\)C in comparison to the 978.29 \({}^{\circ}\)C obtained in absence of perforations. A stress analysis of the perforated microgripper showed that the highest von-Mises stresses are achieved at the hinges connecting the hot/cold arm to the anchors. The values of these stresses were found in the range of 1.89 GPa to 2.26 GPa, which is smaller than the yield strength of the core material of the microgripper (polysilicon). This indicates the safe operation of the perforated microgripper while simultaneously gaining a larger gap opening and lower operating temperature when compared to its non-perforated counterpart actuated with the same voltage. The present study provides a baseline for the implementation of an unconventional design of microgrippers which exploits the impact of perforations on their operation with lower power requirements and temperatures. A potential extension of the present work is to implement and experimentally test the performance of perforated microgrippers, proposed for the first time in this study. Their capability to achieve sufficient movement of the arms in order to handle small objects, while operating at lower temperatures and consuming less power, will be assessed. Different perforation configurations in terms of shape, number, and distribution can be considered. The experimental results can also be used to further validate the present FEM-based computational model to simulate the response of electrothermally-actuated microgrippers. Fatigue is also an important aspect to consider in order to ensure the appropriate operation of the microgripper over many cycles, which involve the heating/cooling process along with recurring deformation of the arms. A fatigue analysis can be considered as a future direction of the present study. Conceptualization, P.D.P. and M.G. ; methodology, M.G. ; software, P.D.P. ; validation, P.D.P., M.G. and A.A.; formal analysis, M.G. and A.A.; investigation, A.A.; resources, P.D.P. ; data curation, P.D.P. ; writing--original draft preparation, P.D.P. ; writing--review and editing, M.G. and A.A.; visualization, P.D.P., M.G.