biostudies-literatureUnknown8(1)Naik Parrikar VPolyelectrolyte multilayer (PEM) thin films, fabricated at nano-scale by Layer-by-Layer (LbL) self-assembly techniques, have diverse nanotechnology applications. Precise thickness measurement during layer buildup is crucial in controlling the thickness. In this work, we present a novel optical measurement technique for in-situ analysis of the PEM film build-up by utilizing Etched Fiber Bragg Gratings (EFBG)-based sensors to quantify the deposited thickness. PEM films were deposited over EFBG by alternative deposition of weak polyelectrolytes Poly(allylamine hydrochloride)(PAH) and Poly(acrylic acid)(PAA) with quantitative analysis of adsorption and desorption steps at varying pH conditions. Further, the desorption process was observed in detail at the sub-nanometer scale, with PAA exhibitiCommunications chemistry208https://www.ebi.ac.uk/biostudies/studies/S-EPMC12274471biostudies-literatureSub-nanometer scale investigation of polyelectrolyte adsorption and desorption processes using etched fiber Bragg grating technique.PMC12274471Gurusiddappa R PNaik Parrikar VBoranna RThondagere Nataraj CPahal SBannur Nanjunda SKogravalli Jagannath RPfalseSub-nanometer scale investigation of polyelectrolyte adsorption and desorption processes using etched fiber Bragg grating technique.Polyelectrolyte multilayer (PEM) thin films, fabricated at nano-scale by Layer-by-Layer (LbL) self-assembly techniques, have diverse nanotechnology applications. Precise thickness measurement during layer buildup is crucial in controlling the thickness. In this work, we present a novel optical measurement technique for in-situ analysis of the PEM film build-up by utilizing Etched Fiber Bragg Gratings (EFBG)-based sensors to quantify the deposited thickness. PEM films were deposited over EFBG by alternative deposition of weak polyelectrolytes Poly(allylamine hydrochloride)(PAH) and Poly(acrylic acid)(PAA) with quantitative analysis of adsorption and desorption steps at varying pH conditions. Further, the desorption process was observed in detail at the sub-nanometer scale, with PAA exhibiti2025-01-01T00:00:00Z2025 Jul2026-03-31T10:43:23.465Z2025-08-24T03:09:05.27ZS-EPMC122744714068166310.1038/s42004-025-01602-2