Open-Loop, Barrier-Free, Continuous Langmuir-Blodgett-Based Multipass Multilayer Deposition

Langmuir-Blodgett (LB) assembly enables controlled film transfer, yet thick multilayers remain slow and difficult to scale because conventional fabrication requires many discrete deposition cycles. Here, we report an open-loop, barrier-free, continuous-feed LB-based platform that recirculates a flexible polyethylene terephthalate (PET) substrate through the air-water interface to build particulate multilayers within a single uninterrupted run. Surface pressure is monitored in situ with a Wilhelmy plate without barrier compression or feedback control and serves as an operational descriptor of an evolving interfacial state. Using a methanol-based SiO₂ dispersion, we map how substrate speed v and injection rate Q govern surface-pressure dynamics, initiation-stage deposition behavior, and final multilayer outcomes. Early cycle interruption experiments show that deposition begins as spatially localized streaks and patches associated with repeated entry and exit meniscus interactions, consistent with meniscus-mediated pinning and intermittent entrainment rather than uniform layer transfer on each pass. The resulting films form robust micrometer-scale porous multilayers whose loading depends on operating conditions. These results establish a parameter-based framework linking substrate speed and injection rate to interfacial evolution and multipass buildup in a recirculating geometry, providing a basis for scalable interfacial deposition strategies that retain LB-like process visibility.