Electron tomography in soft materials

• Recent advancements in electron tomography and its application to polymer nano-structures are summarized.
• Truly quantitative tomography has been achieved by “full-rotation-tomography” with needle-shaped specimens.
• Scanning electron tomography is useful to observe polymer hierarchical structures.
• Perspective and challenge for further development and application of electron tomography to soft materials are assessed.

This review summarizes the recent advances in electron tomography (ET) and its application to polymer nanostructures. Truly quantitative three-dimensional (3D) images of polymer nanostructures can now be obtained by reducing or eliminating the missing tilt range in ET experiments. The reduction of the resulting missing wedge provides sub-nanometer resolution, which is sufficiently small for soft materials. Because soft materials often exhibit hierarchical structures, observation of a large volume with edges several micrometers in length is important to capture the structural elements on a scale larger than tens of nanometers. The introduction of scanning optics to ET has made it possible to obtain 3D data from micrometer-thick polymer specimens by using conventional electron microscopes at a relatively low accelerating voltage of 200 kV. We present some examples of the structural analysis of soft materials, such as nanostructures of self-assembled block copolymers and fuel cell electrodes.

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