So I have had the idea of trying to make a transparent circuit. I thought it would make for some cool looking projects, LEDs floating around. When I first had the idea I did a little googling to see what others had tried and found some nice examples. Some were made on glass, copper foil was glued to the glass then etched, or a nice flexible circuit using bare conductive paint.

The glass circuit looked lovely and was really the effect I am hoping for (lost the link) but a thing a lot of these circuits had in common was wide ugly tracks. So my goal it to create an easy method to print transparent circuits with thin minimalist tracks…

So here is my first attempt.

 

It is a small piece of laser cut acrylic. Very simple, just four tracks and three leds. I initially cut the holes and outline then etched the tracks, however the etch only left very shallow grooves. So I then cut the tracks into the acrylic, ensuring it did not cut all the way through. I then back filled the grooves with bare conductive paint. I then used a little more paint to stick on the LEDs. I left it over night to properly dry and this morning applied some power.

This is with a 5v supply and no resistor…

    

 

Yes, it is lit. Very dimly. It is more visible on the right when I shaded the light. So, I measured the track resistance (probably should have done this first) and its a whopping 12 kΩ! Yeah this isn’t gonna do. Below is a pic of the LED lit directly for comparison.

I had a look at the bare spec sheet and it offers a resistance of 55 Ω/sq (55um thickness), this is pretty darned high if I’m going to use narrow tracks. Another quick google and silver conductive paint, often used for car window heater repairs, has a resistance of 0.04 Ω/sq (10um thickness). This is more like it. Small syringe of silver paint on its way…