Looking over the history of hot end design there have been many iterations which have lead to overall improvements. However there is one element that as far as I can see that has not significantly changed even since the early days and that is a large heat sink used to actively heat the hot end. Commonly referred to as the heater block and in many different iterations between brands and span in history but always present. I was using a TS-80 soldering iron and amazed at the efficiency of the tight control loop linked with an 18w ceramic heater, the key difference being the heater being integrated into the tip with the temp probe very close to where the solder meets the tip (small thermal mass). It honestly outperformed older much more powerful large heat sink solutions I have used in the past. I'm wondering if the technology of a in tip heater right in the very tip would be a valuable addition to the wealth of 3D printer technologies. The advantages intended would be; Smaller heated area requiring less cooling on heatbreak Tight control loop (lower hysteresis) Smaller lighter hot end design Less retraction distances required Elimination of heater block Possible reasons why this approach has not been taken; Expensive construction of a consumable would be undesirable Difficulty in construction for metal/ceramic bonds and expansion causing issues Patents already prohibit application (have not searched this possibility yet) Advantages insignificant to justify Geometry difficult to work with having filament travel though middle of heater (even if sheathed by metal or other material) Looking for any insights, please let me know if my description is too vague.