Understanding cracking dynamics across material classes: a Design of Experiments (DoE) approach

The development of low-cost, scalable transparent conductive electrodes is a critical goal for advanced optoelectronic applications. One promising strategy involves harnessing crack formation in thin films, traditionally viewed as a defect, as a functional design strategy for the fabrication of advanced electronic and optoelectronic devices; however, a systematic understanding of how different material classes respond to processing conditions is still lacking, limiting process control and reproducibility. This study presents a systematic investigation into the cracking behavior of solution-deposited thin films composed of four distinct materials, namely natural egg white, natural organic small-molecule (obtained from bovine bile) deoxycholic acid, synthetic block co-polymer Pluronic F-127, and inorganic TiO₂ anatase, selected for their diverse physicochemical properties and film-forming mechanisms. Using a full factorial design of experiments, we evaluated the influence of substrate temperature (4–50 °C), deposited volume (15–40 µL/cm²), and solution concentration (1–15% w/v) on crack morphology, quantified by crack width, spacing, and density. The results reveal material-specific sensitivities to processing conditions, with distinct trends observed for each material. Films exhibiting continuous and well-defined crack patterns were used as crack‑guided masks for silver deposition, enabling the formation of conductive meshes. Thermal evaporation in high vacuum of 50 nm Ag produced conductive meshes showing up to ~ 89% optical transmittance at 550 nm and sheet resistance of ~ 10 Ω/sq. This work provides insights into the mechanisms of crack formation and demonstrates a practical, low-cost, and scalable route for fabricating transparent conductive electrodes suitable for applications such as sensors, coatings, and biointerfaces.