3D printing was the result of a lot of researchers working on a lot of parts, and when the dust settled, none of them could build a really practical printer without paying off all the other patent holders, most of whom were playing dog-in-the-manger with their patents while trying to elbow out the competition.
You see that with a lot of inventions. They may go through several cycles of invention / related invention / non-conbination / wait / patent expiration until enough necessary parts of the technology are patent-expired that the remaining necessary inventions can be assembled in a single company's product and the technology finally deployed.
Thermoacoustics, for instance, just had its second round of patent expiration and is in its third round of innovation. The basic idea is to make a reasonably efficient heat-engine and/or refrigerator (or a machine that combines, for instance, one of each) with no moving parts except a gas. Mechanical power in the form of high-energy sound inside a pipe is extracted from, or used to create, temperature differences.
There are some really nice gadgets coming out of it, built mainly out of plumbing comparable to automotive exhaust systems and tuned manifolds, maybe with some industrial-grade loudspeakers built in, or their miniaturized or micro-minaturized equivalent. (Example: A hunk of pluming with a gas burner, about 12 feet high and maybe eight feet on a side. Oil fields often produce LOTS natural gas in regions, like big deserts, where it's uneconomic to ship it to market. It gets burned off and vented. (CO2 is weaker greenhouse gas than CH4, by a factor of several). Pipe the gas into the plumbing, light the burner, and it burns part of it to get the power to cool and liquify the rest. As a liquid it's economic to ship and sell it. Then you get to use much of the otherwise wasted energy, displacing other fuel supples and reducing overall carbon emssion.
I hope this is the cycle where things hit the market.