Self-organized electrodes using controlled coffee stain phenomena for high aspect ratio polymer effect transistors on 3D substrates
An important advantage of polymer electronics is the possibility of solution processed electronics and therefore the use of fluid mechanic concepts to achieve novel fabrication techniques. An interesting feature of a drying droplet of a nano-particle colloidal solution of is the coffee stain effect. If the contact angle of the droplet is less than 90deg, and the ambient conditions encourage droplet drying, the droplet has a maximum evaporation rate at the boundary. Due to temperature and hence surface tension gradients, there results an effective flow of nanoparticles to the boundary. When the droplet completely dries out, we are left with a ring like stain of nanoparticles which decreases in concentration from the periphery inwards. One can think of a scenario where this phenomenon could be used for electrode deposition using silver nano particle-water colloids.
Sambandan, S.; Arias, A.; Wong, W.; Street, R. A. Self-organized electrodes using controlled coffee stain phenomena for high aspect ratio polymer effect transistors on 3D substrates. Electronic Materials Conference (EMC 2009); 2009 June 24-26; University Park, PA.