I believe this is what you are trying to do.
If that is so,then make 2 objects. One rectangle with the thickness you want the piece of TPU to be and one text object.
The shortcut to add Text is ⇧ Shift + A > Text.
Make the text thickness you want from Properties > Object Data Properties (green letter icon) > Geometry > Extrude/Offset
Then move the text to overlap each other having a thicker text than the rectangle's thickness.
Make the Text a Mesh by selecting the text and from the top left of the viewport, Object > Convert > Mesh.
Have in mind that boolean modifier won't work if the text isn't a mesh. Choose the rectangle, make a boolean modifier from Properties > Modifier Properties and pick Boolean. Select the Text as the object and apply the modifier by hitting ⌃ Ctrl + A.
If you apply and move the text object you can see the see-through text.