The concept of 'displays everywhere', which may be extended to wearable sensors, signal tags or energy devices, implies ubiquity of electronic devices not only in walls or appliances but integrated in all kind of domestic objects, such as clothes, bags or wrappings, and is expected to preside over our daily lives in the near future. For this expectation to succeed, Electronics industry must face compatibility with three new paradigms: flexible substrates -to be adapted to different surfaces and geometries-, large areas (eventually up to square meters), and lightness. In any case, this revolution can only take place from a drastic reduction of the production costs. As it is well known, these paradigms are difficult to access solely for conventional microelectronics technology based on silicon or other crystalline materials, and many alternatives based in new materials and procedures have been proposed. Thus, a manufacturing facility based in the roll-to-roll (R2R) technology is considered a suitable candidate to achieve high yield over large areas in a cost effective way. In consequence, those patterning techniques compatible with R2R production lines are receiving enhanced attention.
In this contribution, we exploit the possibilities of a dry and subtractive lithography based on electrical microdischarges to pattern both electrodes, cathode and anode, of organic devices, particularly displays based in organic light emitting diodes (Fig. 1). Using a homemade prototype rated at technology readiness level 4, we demonstrate that electrical discharge lithography may overcome many obstacles such as tilt correction and relocation after processing, avoiding the use of masks and many of the photolithographic steps. This is thanks to the electrical monitoring during operation as well as a precise electronic control of the position, with 1 µm reproducibility. Since sparks are very fast processes (range of few µs or less) features may be performed at speeds of tens mm/s, ensuring scalability to large areas (cms), and hence compatibility with high throughput manufacturing lines. Of particular interest results patterning of graphene as electrode, due to the practical absence of residues under electrical discharges. Other advantages and drawbacks will be discussed, as well as physical aspects involved.