Integrating LEDs into the paper can be an effective method to built a paper-based prototype that mimicries an OLED printed surface. Also building a lowtech Display that uses a higher amount of LEDs can be realized easily with the Cirquid method.
One way to imitate a OLED surface on the paper is to use a SMD-LED that has two isolated cables connected to it’s annode and kathode. Simply ba printing two seperate Cirquids onto the papaer and pinning the cabel’s ends through them. For making sure that the position of the SMD-LED and it’s connection with the Cirquids is secured, the paper and the thin LED has been placed between a regular lamination foil and was laminated. Due to the maximal thickness of the lamination machine, this method only works with rather thin LEDs.
Also hiding a SMD-LED behind a printed Circuit can give the illusion of an upglowing paper-surface or OLED print on the paper’s surface.
For building a LED Matrix that serves as a Display, the LEDs can be pinned into the printed Cirquids directly. The layout of the printed PCB has to be considered carefully to avoid unwanted connections between connected electricity.
By using a two-layered PCB Layout and seperating unavoidable touch-points between these layers, transparent tape can be used. Also the layers have been laminated separately and have been laminated one more time after they have been put on top of each other. Here you can see the PCB Layout and the position of the LEDs without the lamination process.
And another picture of the laminated version of the Paper PCB’s front- and backside.
Because the paper has been laminated, the saltwater’s evaporation is slowed. Because of this the display stays active for more than one hour without applying any additional saltwater. The connection between the paper and the LED-Pins stays stable, even when the PCB gets deformed.
By unsing charlieplexing technique a Arduino Uno board can control current flow within the printed circuits to individually regulate the light of each LED within the matrix.
Integrating many SMD-LEDs into a 3 x 3 grid display is another interesting approach, but be aware that it can become a fiddly work and requires some patience. It can be helpful to pin only one cable of the SMD-LED into the paper and let the facing LED-Pin be placed directly on the paper’s surface.