New self-supporting polymer thin film for nanoparticle analysis in STEM/TEM

• Self-supporting polymer film allows high-contrast nanoparticle imaging. • Improves nanoparticle dispersion and interfacial stability. • Achieves 29 % better resolution than Formvar, 32 % better than graphene oxide. • Film thickness of 3.5–22.9 nm ensures high electron beam transparency. • Scalable, low-cost casting produces 8 million grids from 20 g of polymer. The demand for high-resolution imaging of nanomaterials continues to grow across disciplines. However, conventional support films for transmission and scanning transmission electron microscopy (TEM/STEM) are often limited by low beam resistance, suboptimal resolution, toxicity concerns, and high production costs. This study introduces a new application of a self-supporting, biocompatible thin film composed of hydrophilic, crosslinked poly[N-(2-hydroxypropyl)methacrylamide] (p(HPMA)) as an alternative to traditional carbon or organic polymer supports. The film forms a stable, continuous interfacial layer that promotes homogeneous nanoparticle dispersion and minimizes aggregation, critical factors for accurate analysis of nanoscale interfacial interactions. By embedding nanoparticles within the hydrated polymer matrix, the film provides a consistent and reproducible interface, enabling detailed observation of particle behavior, stability, and interactions at both solid-liquid and solid-vacuum boundaries. Resolution measurements show improvements of up to 29% over Formvar and 32% over graphene oxide. Film thicknesses range from 3.5 to 22.9 nm, spanning the holes in Lacey and Quantifoil grids. The film is produced using a rapid, scalable casting method using standard laboratory materials. TEM and STEM imaging confirm its structural and beam stability under accelerating voltages up to 200 kV. Nanoparticle dispersion and film integrity are preserved for at least six months. These findings highlight the potential of this polymer-based support film as a cost-effective and sustainable platform for high-resolution electron microscopy, with broad relevance to colloid and interface science, nanomedicine, and environmental nanotechnology.