The MiniTEM instrument is a desktop-top low-voltage easy to use TEM that was introduced last year. It has a high degree of automation in the microscope alignment, image acquisition, and analysis process.
The microscope runs at 25 keV, which enables imaging of biological (negative stain and tissue sections) as well as inorganic samples prepared with standard methods. It is small, robust, requires only one standard wall socket, and can be hosted in any lab or office. The GUI is developed for Windows 8, and designed for a touch screen, allowing convenient search through the sample with pinch-zooming (changing magnification). The instrument has an integrated image processing and analysis library, which allows the user to design and apply analysis scripts. A graph based interface is used to create scripts which can be saved for future use and applied to multiple images, either acquired on the fly or manually acquired and stored in a folder.
Here, we show how the MiniTEM instrument can be used to extract a user independent size distribution of particles in a sample in a highly automated manner. We designed analysis scripts for automatic image acquisition followed by segmentation and extraction of characteristic measures of individual particles. As a final step, obvious false-positives are manually removed which simultaneously updates the extracted measures. In the first example we image (at 1.46 nm/pixel) and analyze influenza viral vectors kindly provided by Max Planck Institute for Dynamics of Complex Technical Systems. The resulting size distribution was compared to and does agree with the distribution derived from corresponding analysis in high-voltage images (Tecnai G2 Spirit, 1.85 nm/pixel, 100 keV), see fig. 1. In the second example, we investigate the size distribution of mixtures of two differently sized polystyrene spheres (at 1.46 nm/pixel). The measured distribution (fig. 2) again coincides with the expected