Direct observation of the inner structure of unstained atmospheric cells by low-energy electrons

Imaging at nanometre-scale resolution is indispensable for many scientific fields, such as biology, physics, chemistry, materials science and nanotechnology. Electron microscopy is an important technique to produce high-resolution images of biological samples. Inner structure inspection of cell samples of a few micrometre thickness is enabled using a high-voltage electron beam (EB) of around 1000 kV. However, large and complex equipment is required for such systems. Therefore, a more convenient and simple measurement system is desired. Here, we show clear observations of the inner structure of unstained atmospheric cells using a low-voltage EB of less than 10 kV. Experiments suggest that whole cell imaging by a low-voltage EB is enabled by the transmission electrons (TEs), and TEs are of very low energy of less than 20 eV. Therefore, the damage to the biological samples is very low. Our microscope system can easily be applied for diverse samples, such as cells, bacteria, viruses and other organic samples.