Yes that make it a lot easier.
So here's the answer to your question as to how "impulse welding" works.
Impulse Welding uses a thin resistant wire or band, usually called a heating element, that heats up in a few hundreds of a a second to operating temperature. Once it reaches the desired temperature it holds it for , once again a desired time, then the energy is removed from the element to allow the sealed components to cool to a state that give you your weld. This is different that a heated die type tool, since the advantage is very quick seal times, and the ability to cool the process down before taking the pressure away. This ability to hold pressure is very important when sealing hard to seal materials, since you need to insure the two parts are properly knitted together before removing the pressure. Constant heat dies tend to pull the seal apart prior to the knitting of the 2 parts.
Pressure is important, but too much can cause "extrusion" of the material, therebye reducing the strenght (cross section) of the seal. So the "black magic" part is balancing the amount of pressure with the correct profile of temperature.
Something in the 40um thickness could be sealed in about 1 to 2 seconds and if all goes well can end up to be stronger than the material around it.
Now the next question is shape. Straight seals are the easiest but many shapes are also very doable. We've made sealing elements as small as a 12mm dia. ring seal, with and element width of .8mm wide to 10mm wide bands 4 meters long.
Hope that helps.
Bob