The Impossible LED

This instructable is aimed to teach how to make an "impossible LED": the LED is switched on without any visible wiring. The LED itself is just supported by to pieces of glass, but despite this it can be switched on. The trick doesn't rely on any exotic electromagnetic field, zero point energy or dark matter annihilation generator... it is merely exploiting conductive glass.

Glass itself of course is not conductive, but is it possible to coat it with transparent thin (~100 nm) conductive layer of Indium tin oxide (ITO). ITO is a ternary composition of indium, tin and oxygen in varying proportions.

Indium tin oxide is one of the most widely used transparent conducting oxides because of its two main properties: its electrical conductivity and optical transparency, as well as the ease with which it can be deposited as a thin film. As with all transparent conducting films, a compromise must be made between conductivity and transparency.

• 2 x ITO glass substrates (mine are circular 50mm diameter. Thickness: 1.1mm. Resistance: 15 ohm/sq)
• multimeter (to check wich side of the glass is conductive)
• 1 x led
• 1 x eraser
• 1 x knife
• 1 x cyanoacrilate glue
• 2 x wires
• 1 x 9V battery

Note

1. to avoid fingerprints is better to handle the glass with gloves
2. the glass in the pictures is salvaged from a previous experiment, hence the grey spots. Anyway you can buy new and shiny ITO glass at reasonable price on ebay, or get it from an old phone touchscreen

• use the multi-meter to find which side of the glass is conductive (usually just one side is)
• cut 2 pieces of eraser to use them as spacers between the discs
• carefully put a little amount of glue on the spacers' edges
• glue the spacers to the glass on the conductive side
• wait for the glue to set
• carefully put a little amount of glue on the spacers' edges
• glue the second glass substrate on the spacers
• wait for the glue to set
• carefully insert the wires between the spacer and the glass
• carefully insert the led leads between the spacer and the glass (take note of the polarity!)
• power it up! and enjoy the magic!

Once you get this to work, you could unleash your fantasy and build something more exotic:

• use transparent rubber (in place of the white eraser) to enhance the magic
• you could use a dremel (or chemical etching maybe) to pattern the thin layer of ITO and create some tracks: now you have a transparent PCB! Use conductive glue to attach the components.
• build a crown of LEDs and sandwich it between two ITO glasses to create a futuristic bulb or a nerdy pendant
• build a 3D LED cube combining patterned ITO glass substrates and using conductive glue to position SMD LEDs
• ok, I admit it... my imagination stops here... :)