Fundamentals of Self-Aligned Capillary-Assisted Processes for Flexible Electronics

The goal of flexible electronics is to combine electronic functionality with mechanical flexibility to enable applications such as flexible displays, wearable electronics and flexible lighting products. High performance electronic devices require fine dimensions and precisely aligned layers of multiple electronic materials; hence, a key challenge in the field is developing a manufacturing platform capable of economically producing these architectures on flexible substrates. This award supports fundamental research on a new, liquid ink-based manufacturing process known as Self-Aligned Capillarity-Assisted Lithography for Electronics (or SCALE). SCALE has the potential to be a disruptive technology in the field of printed flexible electronics, because it removes a significant technological barrier, the need to precisely align printed layers of functional ink, reduces cost, and makes possible flexible electronics-based new products that will improve our quality of life. The fundamental studies will impact many scientific and engineering fields, including printed electronics, electronic ink development, fluid mechanics and interfacial phenomena. The efforts also include research experiences designed to retain freshmen in engineering, development of manufacturing educational materials and outreach to industry.

SCALE involves imprinting a multilevel, recessed open network of reservoirs, capillaries and device structures on a flexible substrate, delivering electronically functional inks into the reservoirs by inkjet printing and using capillarity to selectively and sequentially fill features to create electronic components, devices and circuits. SCALE has many advantages: it is additive, self-aligned, highly parallel, amenable to roll-to-roll (R2R) processing, and scalable in terms of manufacturability and substrate area. SCALE-based conductive networks, capacitors, resistors and thin film transistors have features sizes in range of ~5 µm and below, but the target reservoirs for ink delivery, on the other hand, are an order of magnitude larger, which enables the R2R approach. This research uses a combined approach of fluid mechanics modeling, fundamental processing experiments, including high speed visualization, and electronic ink development to uncover the science and engineering of R2R SCALE. The team will use a unique Multifunctional R2R Coating and Printing Apparatus in the Coating Process and Visualization Lab, as well as a R2R nanoimprinting apparatus to demonstrate an all R2R approach.