STTR Phase I: Ultra-Low-Cost Additive Manufacture of Transparent Conductive Electrodes

The broader/commercial impact of this Small Business Technology Transfer (STTR) Phase I project is to provide a fully additive method of manufacturing ultra-low-cost flexible transparent metal-mesh conductors. These transparent conductive electrodes offer superior performance at substantially lower cost than existing options based on indium tin oxide. Highly conductive and transparent conductor films enable applications such as current collectors for EMI shielding, flexible energy storage, capacitive touch screens, electrochromic window films, transparent light emitting diodes, solar cells, and more. This project will focus on large-scale production with high throughputs. Existing transparent conductive electrodes largely use indium tin oxide, but indium is a rare earth metal that has been steadily increasing in price as demand increases. Indium is also typically imported. Reducing the dependence on foreign inputs for optoelectronic manufacturing offers commercial and security advantages. While indium tin oxide has been used in some flexible devices, the material is ill-suited for these applications due to its brittleness imposing severe limitations on bend radius and bend cycles. Metal-mesh transparent conductive electrodes do not suffer from these limitations. Thus, a method of cheaply producing flexible transparent conductors will enable the development of smart windows, rollable transparent displays, portable solar panels, and other devices with new form factors. This Small Business Technology Transfer (STTR) Phase I project will (1) develop improved catalytic ink formulations that are compatible with high-speed micropatterning methods and (2) prototype an innovative system for roll-to-roll electroless plating of those catalytic traces with new methods of film conveyance and improved plating-bath control. Capital and operating expenses of existing methods used to make conductive metal micropatterns such as photolithography can be cost prohibitive for many applications and do not scale well. This project aims to eliminate these costly processes and instead use a fully additive process to make the micropatterns. These patterns will then be metalized using electroless plating to obtain conductive metal patterns. The challenge to be solved is that existing manufacturing equipment tends to be unsuitable for roll-to-roll electroless plating of flexible substrates. The modular plating equipment being designed as part of this STTR includes a novel conveyance system that is more compatible with electroless plating baths and new methods of process controls to achieve reliable plating of micro-scale fine metal lines. These new features will maximize flexibility and equipment uptimes. An additional goal is to develop a kit to retrofit existing off-the-shelf equipment to add roll-to-roll capabilities to further reduce equipment cost. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.