*3.5. Boundary Condition*

In the solid mechanics interface, the glass substrate is selected in the fixed constraint condition, as shown in Figure 5a. The piezo ceramic layers in the bi-morph actuator have an anti-parallel polarization configuration. To adapt for the polarization direction in the simulation, an additional base vector system is created with the base vector 'x3' set to −1 instead of default 1. The default base vector system is selected as the coordinate system for the piezo 1, and the additional base vector system is selected as the coordinate system for the piezo 2 (Figure 5b). In the heat transfer interface, all the boundaries are selected in the temperature constraint, to set the entire domain to the required temperature (Figure 5c). In the laminar flow interface, the walls of the fluid chamber are selected with a no-slip boundary condition (Figure 5d). Since the fluid chamber is a closed domain, there is no inlet, outlet, or open boundary conditions.

**Figure 5.** Domains with fixed boundary condition in solid mechanics physics module (**a**), piezo 1 with default base vector system and piezo 2 with modified base vector system (**b**), domains with temperature boundary condition in heat transfer in solids and fluids physics modules (**c**), and domains with wall boundary condition in laminar flow physics module (**d**).
