Instabilities and Dewetting Dynamics in Thin Polymer Films

Thin polymer films deposited on solid substrates often exhibit a rich variety of morphological instabilities driven by the interplay of capillary forces, long‐range intermolecular attractions and viscous dissipation. As film thickness falls below a critical threshold, attractive van der Waals forces give rise to a negative disjoining pressure that destabilises a uniform layer, leading either to spontaneous spinodal dewetting or to nucleated hole formation. In spinodal dewetting, small thermal or thickness fluctuations are amplified continuously, producing a characteristic pattern wavelength. In contrast, nucleation dewetting proceeds via discrete hole initiation at surface defects or heterogeneities, followed by rim formation and coalescence. When films are cast by rapid rotation, the centrifugal force and solvent evaporation rates introduce an additional regime, spin dewetting, which controls droplet size and spacing. Surface energy gradients or thermal Marangoni stresses can further modulate flow and generate complex textures. Substrate surface chemistry, topography and polymer–substrate adhesion profoundly affect the kinetics of hole growth, rim instability and ultimate droplet morphology. Understanding these mechanisms is vital for optimising applications in organic electronics, optical coatings, biomedical patterning and microfluidic device fabrication.

Research from Nature Portfolio

Recent studies have demonstrated how solution concentration and substrate patterning govern dewetting morphologies in spin-coated liquid crystal films. In one investigation, films of a nematic liquid crystal were spin coated at varying solute concentration to reveal a transition from isolated droplets to continuous coverage, with periodicity and mean droplet diameter decreasing as concentration increased. The work also contrasted textures in the spinodal regime against those in the nematic continuous films, and showed that substrate topography can align dewetted droplets along predefined contours. Another effort examined polymer films suspended above elastic micro‐pillar arrays and measured the spatially perturbed dewetting force fields. Elastic restoring forces of deformed pillars locally balance capillary driving forces, breaking circular symmetry in expanding holes and imprinting the symmetry of the underlying pattern onto dewetted structures.

Research from all publishers

Investigations into bilayer systems of ferroelectric and semiconducting polymers have revealed a strong dependence of dewetting on substrate thickness and surface tension components. By measuring contact angles on underlying layers and modelling the disjoining pressure as a function of film thickness, researchers showed that the parameter window for stable coverage shifts with substrate composition, enabling controlled hole suppression for organic electronic devices. Complementary theoretical and experimental work on spin-dewetted polystyrene films has employed long‐wave linear stability analysis to elucidate the roles of van der Waals attraction, surface tension and viscous forces under high‐speed rotation. The studies quantitatively predict droplet spacing and height across a range of polymer concentrations and spin rates, providing a robust framework for tunable micro- and nano-scale droplet generation with applications in material templating and biomedical assay development.

Instabilities and Dewetting Dynamics in Thin Polymer Films publication trend

The graph below shows the total number of articles in instabilities and dewetting dynamics in thin polymer films across all publications each year (not limited to Nature Index journals).

Technical terms

Dewetting: The process by which a liquid film ruptures and retracts from a substrate, forming droplets or holes due to unfavourable surface interactions.

Spin dewetting: A dewetting regime in spin‐coated films where centrifugal forces, solvent evaporation and viscous forces jointly determine rupture and droplet patterning.

Disjoining pressure: The net pressure arising from long‐range molecular forces across a thin film, which can destabilise or stabilise a uniform layer depending on film thickness.

Capillary forces: Surface tension–driven forces at the liquid–air interface that seek to minimise surface area and influence flow near contact lines.

Marangoni effect: Flow induced by gradients in surface tension, which can be generated thermally or chemically and modify dewetting dynamics.

References

1. Dewetting Effects in Poly(vinylidene fluoride-trifluoroethylene) Thin Films on Poly(3-hexylthiophene) Substrates. ACS Applied Polymer Materials (2023).
2. Transition from Spin Dewetting to continuous film in spin coating of Liquid Crystal 5CB. Scientific Reports (2018).
3. Phase transition and dewetting of a 5CB liquid crystal thin film on a topographically patterned substrate. RSC Advances (2019).
4. Measurements of periodically perturbed dewetting force fields and their consequences on the symmetry of the resulting patterns. Scientific Reports (2021).
5. Controlled Micro–Nano-Scale Droplet Generation via Spin Dewetting. Processes (2024).