A patent application US 3,766,094 (shown in detail in an accompanying document) gives the details of an interesting device. While it is only an application and not a full patent, the information implies strongly that Michael built and tested many of these devices.
While the power output is low, the design is of considerable interest. It is possible that the device works from picking up the output from many radio stations, although it does not have anything which is intended to be an aerial. It would be interesting to test the device, first, with a telescopic aerial added to it, and second, placed in an earthed metal box.
The device is constructed by casting a small block of a mixture of semiconductor materials such as Selenium with, from 4.85% to 5.5% Tellurium, from 3.95% to 4.2% Germanium, from 2.85% to 3.2% Neodymium, and from 2.0% to 2.5% Gallium. The resulting block is shaped with a dome on one face which is contacted by a short, pointed metal probe. When this arrangement is fed briefly with an oscillating signal, typically in the frequency range of 5.8 to 18 Mhz, it becomes self-powered and can supply electric current to external equipment. The construction is as shown here (click to enlarge):
The circuit used with this component is shown as (click to enlarge):
Presumably the output power would be increased by using full-wave rectification of the oscillations rather than the half-wave rectification shown. Michael says that increasing the dimensions of the unit increases the output power. The small unit shown in this example of his, has been shown to be able to provide flashing power for an incandescent lamp of up to 250 mA current requirement. While this is not a large power output, it is interesting that the output is obtained without any apparent input. Michael speculates that the very short connecting wires may act as radio reception aerials. If that is the case, then the output is impressive for such tiny aerials.
This excerpt is taken from here