Discussion Forum

Hello all,

I am currently trying to model a Joule-heating, electrothermal microgripper in COMSOL 5.5/5.6, and am basing the model on the existing COMSOL thermal actuator physics model with a novel actuator/gripper geometry. The real-world gripper prototype has already been created and tested in-lab up to a maximum applied voltage of 10 volts, and functions well.

The simulation material is polysilicon and the material properties are not temperature dependent.

As is done in the COMSOL thermal actuator model, convective heatflux is used with defined heat transfer coefficients which are based on the thermal conductivity of air, and the air gap between the actuator and the substrate. The surrounding air is set at a constant room temperature.

The voltage and ground boundary conditions are applied to the bottom of fixed anchors which hold the gripper in place. These anchors are also set at constant room temperature, which mimicks the substrate as an infinite heatsink.

The issue is that there is severe temperature buildup on the hot arms, often times exceeding the melting temperature of polysilicon. I am out of ideas as to why the temperature is really high in these regions as they should be hundreds of degrees lower, as is confirmed by the real-world prototype.

I am looking for any and all support or guidance on this issue as I have tried everything that I could to fix it, to no avail.

Thanks, Alex