This grant provides funding for the investigation of capillary-driven self-assembly of asymmetric nanoparticles in inkjet printing of colloidal suspensions for scalable nanomanufacturing. Low-cost inkjet printing for the delivery of solution-processed functional materials onto flexible substrates has become a revolutionary technology for roll-to-roll processing of electronics and photovoltaics. However, the current technology is incapable of producing nanosized features and well-controlled patterns due to the well-known coffee-stain effect. Asymmetric nanoparticles can break the symmetry during capillary-driven self-assembly and may lead to improved feature resolution during printing. Janus nanoparticles (JNPs), which refer to colloidal particles with two regions of different surface chemical composition, will be used in this study to facilitate particle assembly due to the orientation-dependent interactions. The project that combines novel nanoparticle synthesis, multiscale modeling, in-situ observation, and advanced characterization will focus on the fundamental understanding of orientation-dependent interactions of JNPs with a moving contact line and a liquid-vapor interface away from equilibrium.
If successful, the results of this research will lead to several technology advancements. Using JNPs as solid surfactants, the deposition of JNPs can be better controlled to avoid coffee-ring patterns commonly encountered in inkjet-printed structures. Using JNPs as tunable building blocks will lead to a large class of dynamically switchable micro-devices and smart surfaces. The proposed work will help establish important correlations between the assembly and deposition of JNP-based inks from evaporating colloidal drops and thin films, as well as the JNP design, ink formulations, processing conditions, and substrate properties. Such knowledge will potentially enable environmentally-benign, large-area inkjet printing, spray deposition, and slot-die coating processes for high-throughput production of next generation flexible electronics. This project will build an exciting interdisciplinary collaboration, enable new course materials, and directly benefit undergraduate researchers and K-12 teachers via Drexel?s REU and RET sites, as well as women and under-represented minority students.
