This experiment shows my first dielectric coated EHD thruster, which is basically my low profile lifter, coated in a thin layer of insulating material. This lifter has its foils sprayed with 3 layers of PTFE coatings, whilst its anode wire is coated with a plastic coat, the same used for PCB insulation coating. These materials were chosen for their low dielectric constant in the range 1 to 3. The surrounding dielectric still flows through the asymmetric electric field generated by the device at the same E-field gradient, but is not in contact with the active parts of the device. This is somewhat different from what one expects as a sealed device, as it is not 'enclosed' as a whole unit. But this structure enables the surrounding dielectric (air) to 'flow' within it, and thus let the accelerating ions transfer their momentum to the neutral air molecules. For momentum exchange, the dielectric must be a 'particulate' dielectric, the heavier the better. All fluid dielectrics with the exception of vacuum will undergo EHD forces. Smooth take-off and landing are controlled by the variable HV power supply. The unsealed version of this lifter weighs 19g and has a lifting capacity of 20g. In this movie, 4 nuts weighing 5g each can be seen, one on each upper corner. Viewing this lifter in total darkness shows no corona light, only total darkness. The actual sound is much more smooth than the one you hear, it changed to a more rough sound during sampling and compression of the movie file.
You may need to install the 'Video Email Player' in order to view the video clips shown below. To install this player, simply click on the link below, and then execute the downloaded file. This brief, one-time installation automatically copies file 'mmvem.exe' to your Windows installation directory, and associate all *.vem files with it.
This experiment shows that the foil coating effectively smooths out small surface defects which would normally result in a high electric field gradient and thus minimises unwanted negative ionisation/corona at the foil whilst increasing thrust. Electrical energy previously lost in negative corona generation, reverse thrust generation and hissing sounds are now eliminated. Most of all, negative ions previously generated at the foil, which result in reverse thrust on their path to the corona wire, have now been eliminated. Current consumption when compared to the unsealed version decreased for the same reasons, and with the same 80 Watt power supply, the lifter can now handle payloads of up to 25g, an increase of 5g lifting capacity over the unsealed version. This experiment shows that the conductive elements of EHD thrusters need not be directly exposed to the surrounding air or flowing dielectric, and a thin dielectric coating of low K over the collector helps to eliminate reverse thrust.
