Etch-free addressable organic sensor arrays

- An organic capacitive sensor array was designed with an interlocking diamond structures.
- PEDOT:PSS electrodes were patterned through an etch-free UV exposure process.
- Spatial location of a conductive touch stylus could be accurately determined.
- Device transparency across the visible spectrum is >80%.
- Direct UV patterning process is suitable for roll-to-roll manufacturing.

Using a direct UV fabrication technique, an organic transparent 8 × 8 capacitive touch screen panel has been designed, fabricated and characterized. The active electrode material is poly(3,4-ethylenedioxythiophene): poly (styrenesulfonate) (PEDOT:PSS). The UV process provided spatial control over the PEDOT:PSS film conductivity, which was subsequently used to fabricate the touch screen panel. This process does not require external photoresists or secondary development and etch steps. The UV patterning of PEDOT:PSS provided a 3-order-of-magnitude reduction in material conductivity between exposed and unexposed regions. Spatial location of touch events can be accurately identified by monitoring relative changes in capacitance at each of the individual elements of the array. A typical touch event causes a measured capacitance reduction of ∼100 fF at the touched intersection. The tested devices exhibit high optical transmission exceeding 80% across the visible spectrum. This technology allowed the device to be realized in a single processing step that is amenable to large scale, high-throughput organic fabrication techniques such as roll-to-roll processing.