Inkjet Printing Controllable Polydopamine Nanoparticle Line Array for Transparent and Flexible Touch‐Sensing Application

A cost‐effective and environmentally benign inkjet‐printing technique is reported for fabrication of ultra‐fine polydopamine (PDA) nanoparticle line arrays (NPLAs) with controllable line‐to‐line spacing (pitch size). The narrowest single line width achieved is 4.7 μm, and tunable pitch size ranging from 77 to 380 μm is also achieved by exploitation of the evaporation‐driven convective particle self‐assembly mechanism. Controllable pitch size is accomplished by printing on hydrophobically recovered polyethylene terephthalate (PET) substrates after oxygen plasma treatment. A theoretical model is developed to investigate the NPLA growth mechanism, which shows good agreement with experimental measurements. Conversion of the NPLA to electrically conductive structure is achieved by a subsequent silver electroless metallization process. The fabrication of a transparent capacitive touch sensor as an application of this approach is also demonstrated. This technique offers manufacturing of conductive narrow lines by additive means with the advantages of low cost, low process temperature, and minimal environmental impact.