A combined theoretical and experimental study is presented to investigate the interplay of forces in the spin-dewetting process in order to achieve enhanced control over droplet generation. In this regard, toluene–polystyrene (PS) film is spin dewetted on a solid substrate to generate an array of droplets. The underlying mechanisms of the spin dewetting of the films into the droplets are explained with the help of a theoretical model followed by a long-wave linear stability analysis (LWLSA). Stabilizing forces like solution viscosity and surface tension play essential roles. The study uncovers that the centripetal force stretches the film radially outward, before it becomes ultrathin and undergoes dewetting under the influence of van der Waals forces, while the surface tension force acts as a stabilizing influence. On the other hand, the viscous force kinetically stabilizes the system to expedite or delay drop formation on the substrate. An imbalance of these factors ultimately decides the droplet spacing, which leads to interesting morphologies such as singlet, doublet, triplet, and clusters of droplets at specific PS concentrations in the range 0.0001–0.0005%, with a ~10–14 nm average droplet height. The experimental data revealed that, at ~3000 rpm, PS (0.01–0.1%) results in critical droplet spacings of λ_max~98–172 μm, leading to immediate dewetting and uniform droplet formation. Our theoretical predictions are in close agreement with the experimental results, validating the present model. The insights gained in this work provide a foundation by presenting a robust framework for controlled droplet generation by optimizing process parameters to achieve the desired droplet size, distribution, and uniformity. The findings have broad applications in material science, biomedical engineering, and related disciplines.

Multiple particle tracking (MPT) is a powerful technique for microrheological characterization of biomaterials. In this study, we employ an in situ microfluidic platform to systematically investigate the effect of cross-linking density on the viscoelastic properties of a model biogel- “crosslinked hyaluronic acid (HA)-cryogel” modified with polyethylene glycol diglycidyl ether. MPT enables real-time extraction of microscale rheological parameters, providing localized insight into the mechanical behavior of the gels. To complement MPT, we utilize Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and confocal laser scanning microscopy to characterize the extent of cross-linking, morphological features, and porosity of the hydrogels. A major challenge in biological systems is the real-time quantification of localized microrheological properties, which we address using the proposed MPT methodology in a model HA-based biogel. Our results offer a detailed understanding of how varying cross-linking densities influence the local viscoelastic response of HA biogels. These findings can inform the rational design of HA-based hydrogels with tunable mechanical properties, supporting a wide range of biomedical applications, including tissue engineering, drug delivery, and viscosupplementation.

This research examines partial dewetting and labyrinthine morphologies in thin polystyrene (PS) films using a ternary solvent mixture of water, acetone, and methyl ethyl ketone (MEK) (15:3:7 by volume). The films are initially glassy but destabilize due to the solvent into mixed structures containing labyrinth-like patterns and holes, not droplets. Morphological changes result from solvent–nonsolvent interactions. MEK is a good solvent that swells the film, lowers the glass transition temperature, and increases chain mobility, while acetone, as a cosolvent, provides uniform solvent uptake, and water as a nonsolvent reduces film–substrate affinity and promotes spreading-driven dewetting. The opposing influence of these factors leads to viscosity gradients that drive heterogeneous nucleation of holes, their growth to large size, and partial coalescence. The process ends before equilibrium is reached as rapid evaporation of MEK balances driving forces with viscosity, and traps intermediate structures. The physics behind the existence or a mechanical pathway to intermediate structures is provided by studies of the spreading coefficient and hole growth. This work demonstrates engineering solvent mixtures for controlled non-equilibrium surface patterning in polymer thin films.