Describing neutron spin echo data from undulating lipid vesicles: recent advances

For almost 30 years, the Zilman-Granek stretched exponential [Zilman & Granek (1996). Phys. Rev. Lett. 77, 4788-4791] has been used to obtain bending rigidities of membranes in lipid and surfactant vesicles from neutron spin echo data. However, with the advent of improved spectrometers that can easily measure Fourier times up to some 100 ns and even 1 µs, more subtle effects become visible in the data, which requires a refined theory. Recently, we published a framework for analysing such neutron spin echo data [Granek et al. (2024). Eur. Phys. J. E 47, 12]. Here, we apply this framework to different model membranes. The purpose of this paper is twofold. We intend to elucidate some often overlooked parameters, such as vesicle diffusion, size, lamellarity and membrane tension, that limit the quantitative interpretation of bending modulus values from NSE data. We also present some future opportunities to better understand the membrane dynamics and major sources of dissipation at the nanoscale uniquely probed with NSE.