A nanochannel liquid cell was used to quantify the electron inelastic mean free path (λ_IMFP) in water. The experimental values show large offsets from the generally accepted models, and can be used to determine the liquid thickness in a liquid cell.

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By creating new designs of liquid phase transmission electron microscopy (TEM) systems we develop new capabilities for measurements of physical and chemical processes. A microfabricated chip with suspended nanochannels [1,2] provide high resolution imaging possibilities, direct TEM imaging of flow in nanochannels, and also makes electron holographic TEM possible [3]. Mapping the particle velocity profile gives a position dependence of flow velocity matching that of parabolic Poiseuille Flow in the observed nanochannel geometry. As the nanochannel system makes it possible to follow the detailed dynamics of nanoparticle motion and agglomeration in a confined system, the commercially available systems with clamped membrane chips also allow detailed studies of diffusion processes. Numerous papers have reported highly limited diffusion in liquid phase TEM of particles in close contact with the membrane, and we have made a detailed study of the Brownian motion of the sub-population of fast and freely moving particles, Fig 3. Their diffusion is Brownian with Gaussian step length distribution, and the diffusion coefficient can be matched with the Faxén correction to diffusion near surfaces, but is also influenced by the STEM beam current.The nanochannel system provides an interesting confined geometry for new types of experiments studying nanoscale fluidics and interactions, where also the potential mapping capabilities of holographic TEM is possible [5].