The Carnot efficiency of a heat engine is 1 - T_low/T_high. When operating between 305K and 300K (room temperature(ish)), for example, this is 1 - 300/305, or about 1.6%. In other words, the absolute most amount of energy a device operating over a 5 K temperature difference at room temperature is pretty dismal. Just because their band gap (for lack of a better term) is small does not make this device "useful."

For all stories about heat engines running between smaller temperature differences, the smaller the temperature difference, the less excited you should be. For example, I have a device that reaches the Carnot efficiency across temperature gaps of 0K! HINT: It's a rock. Or a paper clip. Or a wet tissue. Or...

Can anyone explain the importance of this to someone with no understanding of physics?

I didn't see in the article a T_low or T_high where this device was operational. Normally TEGs work well with high temperature differences (attached to the side of a hot wire pipe with a heat sink on the opposite side), and they work poorly at lower temps (room temp). Anyone know what temperature range this device is made for?

Misleading title:

> high-power density of 12 microwatts per 1cm2

The article says:

> shortened the silicon nanowires to 0.25nm

That's a very short wire. Isn't that about the diameter of a silicon atom? I thought the smallest wires we could make on silicon were about 20nm _wide_.

12 microwatts per 1 cm2

Could this make radioactive batteries more feasible?

By bringing the temperature differential down, we could use a fairly weak heat source to charge up a device.

Would we be able to use a tiny amount of shielded radioactive material to provide a constant heat source and use that heat for the temperature differential?

Wonder how useful this might be for space travel.

Spaceships are essentially thermos bottles (metal tube surrounded by vacuum).

So lots of surface with large temperature differences.

>> For instance, it may be possible to charge your smartwatch during your morning jog someday.

Already possible using 1970s mechanical tech. Or solar. Im sure there are uses, but dont go with wristwatches for your explanations.