Exploring confinement effects on lipid diffusion across length scales with a scalable platform

Confinement effects are one of the main drivers of the heterogeneity observed in membrane dynamics, yet many open questions remain regarding their physical origins and manifestations across various experimental techniques. We have developed a simple platform that enables us to systematically probe the effect of confinement size and geometry over many different length scales in supported lipid bilayer systems. Here, we form fixed obstacles on a SiO₂ chip and then investigate how the two-dimensional diffusion of DLPC lipids is affected by the presence of these structures. Using optical microscopy techniques-- namely Fluorescence Correlation Spectroscopy (FCS) and Fluorescence Recovery After Photobleaching (FRAP)-- we observe that FCS and FRAP reveal different trends in diffusion as a function of confinement size; these variations ultimately originate from the different length scales probed by each technique. Our platform enables us to generate arbitrary patterns, which we use to experimentally test several previously published models, finding substantial discrepancies between simple analytical descriptions of confined diffusion and our experimental data.

A key advantage of our platform is its scalability and adaptability; we are not restricted to forming patterns on SiO₂, and the size of these patterns can be adjusted. This flexibility will allow for further exploration of confinement effects on nanoscale dynamics using new techniques, such as color centers in diamonds. By investigating how confinement influences diffusion at the nanoscale, we aim to construct a comprehensive understanding of how local behaviors contribute to the global dynamics observed by FCS and FRAP.