# Joule Heating

Understanding both Joule heating and electrothermal effects is critical for the proper design of microdevices. FLOW-3D provides a useful and robust flow simulation tool to model these physical processes.

## Simulation of a Cell Culture Chamber

A simulation of a cell culture chamber is shown below. On the left is the chamber geometry. The middle image shows temperature distribution due to Joule heating on the right, the electrical potential distribution in a plane 5 micrometers above the electrodes is shown.

## Simulate Resistance Heating in Bubble Jet Printheads

Thermal bubble-driven printheads require some method of vaporizing a small volume of ink. The resulting vapor bubble pushes ink through a nozzle creating a tiny droplet which, along with millions of other droplets, creates a printed image. A common method of heating the ink is to pass an electrical current through a thin layer of metal to generate resistance, i.e., Joule heating.

The duration and the magnitude of the electrical pulse must be chosen carefully so that the right amount of heat is generated. Too little heat will fail to vaporize the ink. Too much heat will cause the droplet to be too large and risks possible damage to the printhead. FLOW-3D provides all the tools necessary to simulate the many complex and intertwined physical processes in thermal bubblejet printheads.

FLOW-3D offers two methods to simulate resistance heating in bubble jet printheads. This modeling flexibility is convenient for users, allowing a greater range of scenarios to be simulated depending on the amount of information available.

### Method 1: Specify Heating Directly with a Power Pulse

The first method is to simply specify the heating directly. This allows the actual heater geometry and resistance heating within to be replaced by a power vs. time distribution.

### Method 2: Simulate Joule Heating with a Voltage Pulse

The second method is to specify the actual heater geometry and the applied voltage across the heater. The Joule Heating model is used to compute the resulting heat dissipation generated within the heater.