Inkjet Printing of Electrically Conducting Micron-Wide Lines and Transparent Conducting Films by Edge-Enhanced Twin-Depo
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Inkjet Printing of Electrically Conducting Micron-Wide Lines and Transparent Conducting Films by Edge-Enhanced Twin-Deposition Vadim Bromberg, Siyuan Ma, Timothy J. Singler Mechanical Engineering Department, SUNY Binghamton, Binghamton, NY 13902, U.S.A. ABSTRACT Roll-to-roll manufacturing holds the potential to rapidly and cheaply produce electronic devices in a flexible format as well as to effectively scale up production of emerging nanotechnologies. Developing scalable techniques for the efficient and effective use of solutionprocessed functional material is a significant factor in realizing the potential of roll-to-roll manufacturing. We present a novel inkjet deposition process developed to rapidly deposit arrays of micron-wide lines of silver nanoparticles for use as an optically transparent and electrically conducting film. The technique involves jetting a controlled number of space-overlapped drops of a dilute nanoparticle silver ink onto a substrate to form a long stable ink rivulet with two parallel and pinned edges. Subsequently, nanoparticles deposit preferentially at the two parallel rivulet edges due to edge-enhanced evaporation of the solvent. The final result is a twin-deposit of parallel continuous nanoparticle lines, each with a characteristic width less than 5μm and height less than 300 nm. The twin lines are separated by a predominantly particle-free region with the spacing between the lines ranging from 100 μm to 600 μm, where the spacing is a function of ink, substrate, and printing conditions. The effect of substrate surface and jetting parameters on nanoparticle line morphology is presented. Arrays of such lines have been printed and evaluated as potential transparent conducting films, showing an effective sheet resistance of ~5 Ω/□. This edge-enhanced twin-deposition technique has the potential for rapid, materialefficient, and lithography-free patterned deposition of functional material for use in roll-to-roll manufacturing. INTRODUCTION Coffee-ring”[1] deposition refers to the process by which a suspended/dissolved material in a volatile drop produces a characteristic ring-like deposit of solid material left on a flat surface after the liquid phase evaporates. Enhanced evaporation rates near the contact line region of an evaporating drop cause a replenishing bulk flow that deposits solid material in the contact line region. If the contact line is immobile (pinned), this deposition mechanism can proceed for the entirety of the evaporation resulting in the characteristic ring-like deposit of solid material. The coffee-ring deposition mechanism occurs in all solution-based material deposition processes that manifest contact lines. Since these material deposition processes usually seek thickness uniformity in the deposited material, the coffee-ring mechanism has been an impediment to patterned deposition. The pervasiveness of the coffee ring phenomenon has recently inspired research efforts to develop solution-based deposition processes that exploit the evaporatively driven accumulation of sol
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