Improvement of Polystyrene Nano-Spheres Density and Uniformity of Mechanical Organization on PDMS Substrates Lotem Kitaroo and Sharon Luzky

This project involves the study of polystyrene nanospheres deposited on PDMS (Polydimethylsiloxane) samples. The PDMS samples have undergone a mechanical rubbing process for various durations to create surface patterns. Following this, the samples were subjected to a sputtering process in a clean room environment to coat them with polyspherene nanospheres.

The primary objective of the project is to achieve a dense and uniform mechanically organized layer of polystyrene nanospheres on the PDMS substrates. This dense coating is crucial for the intended applications of these nanospheres in fields such as nanoelectronics, biomedical devices, and surface coatings. 

A key application for the mechanical organization of the nanospheres is in optical solutions. The organized coating of nanospheres creates an uneven surface at the nanometer level, imparting special optical properties. This uneven surface causes some of the light rays to be absorbed by the surface rather than being reflected, which can be utilized in various advanced optical applications.

Despite the systematic approach, and despite the expectations from a thermodynamic point of view and the desire for low energy, the SEM (Scanning Electron Microscope) images reveal that the polystyrene nanospheres are not achieving the desired dense packing. Instead, the nanospheres appear to be sparsely distributed, with noticeable gaps between them, which undermines the effectiveness and uniformity required for their applications.

The problem occurs during the image processing and analysis of the SEM images. It has been observed in every image and type of sample, regardless of the duration of the rubbing process.

Images of the samples were taken using SEM and processed and analyzed in Python. The analysis consistently reveals that the polystyrene nanospheres are not achieving the desired dense packing. Instead, the nanospheres appear to be sparsely distributed, with noticeable gaps between them. This consistent pattern across all samples and durations suggests a systemic issue with the process.

During a group discussion held in the presence of the project leader, SEM images were shown to study the dispersion of the layer on top of the substrate. It was discovered that the dispersion was not uniform and the digits had shrunk. As a solution, the group suggested choosing a different deposition method instead of sputtering, believing that sputtering was the cause of the shrinkage.