A new technique using ultrathin silicon-based membranes has allowed scientists to perform high-resolution infrared spectroscopy of biomolecules in water, according to a study published in Analytical Chemistry. This method, called scattering-type scanning near-field optical microscopy (s-SNOM), enables researchers to examine biological samples in conditions that closely resemble their natural environments, with a resolution of just a few tens of nanometers. The research, led by Dr. Alexander Veber and Dr. Maria Eleonora Temperini, shows that infrared measurements taken in liquid environments match standard infrared reference data, opening the door to more accurate analysis of biomolecules in their native states. Biomolecules such as proteins and DNA naturally exist in water, but water's strong absorption of infrared light has made it difficult to study them using s-SNOM. In previous studies, scientists found that placing ultrathin silicon nitride or silicon carbide membranes between the sample and the atomic force microscope (AFM) tip could help overcome this challenge. These membranes act as a protective layer that allows infrared light to pass through while keeping the sample in a liquid environment. However, until now, there had been no thorough comparison between the near-field measurements obtained using these membranes and the established far-field infrared spectra used as references. To address this gap, the international research team tested various silicon-based membranes and analyzed biological samples both in dry and aqueous conditions. The samples included bovine serum albumin, DNA molecules, and α-synuclein protein fibrils, which are linked to Parkinson's disease. The researchers combined detailed experimental data with a theoretical model known as the finite dipole model. This model helped explain the interactions between the AFM tip, the membrane, and the liquid at the nanoscale. Their findings confirmed that the signals obtained from individual biomolecules closely match established infrared reference data, allowing for precise chemical mapping of biological structures. This method is especially useful for studying biological and chemical processes with high spatial resolution, such as how proteins move or how molecules interact in materials that facilitate chemical reactions. By enabling s-SNOM analysis in water, the technique brings researchers closer to observing biological systems in their natural, functional states. The study was published in Analytical Chemistry in 2026.