The Cryo-SECOM Workflow is currently one of the three products that cover the majority of steps of the conventional cryo-lamella preparation process in a single workstation. While the competitive systems are strongly focused on the SEM/FIB coexistence being supported by a simple FLM add-on, the MIMAS system has been designed with a high-end FLM/FIB configuration utilising our state-of-the-art METEOR optical microscope. In our system, the FLM microscope plays a key role in localising molecular specimens of interest within the sample volume, as the longitudinal image resolution goes beyond the diffraction limit reaching ~50 nm, even at low signal-to-noise ratios. This directly translates into a higher success rate of the lamella milling process, as the system is much more precise in localising the targeted molecular interactions, ensuring that the lamella is being milled around and not through them. Additionally, we use a special optical interferometric mode to measure a lamella thickness with a ±5 nm precision, thus eliminating the need for an expensive SEM column.
The introduced concept of the sample transfer overcomes the cons of an automated transfer autoloader. Manually operated actively-cooled high-vacuum transfer of a multiple sample batch is now loaded directly on the microscope sample stage. This eliminates moving samples one by one within different microscope modules, reduces the processing time, and improves the sample quality and success rate by ensuring the same milling angle for each grid. Most importantly, our preparation station and cryo shielding prevent parasitic ice growth, thus all the samples remain contamination-free 24/7 until the automatically performed lamella preparation process is completed for the whole batch. With the new approach, the end user gains a system, where a batch of samples is manually placed in the microscope, which is similarly done in the competitive systems, however, we do not use a complicated and expensive autoloader.
The updated Cryo-SECOM concept has several key advantages: (i) state-of-the-art FLM with super-resolution and lamella thickness control capability, making the SEM obsolete, (ii) automated lamella milling process of a whole batch without the need for an expensive autoloader, yet with a high milling angle repeatability (iii) low contamination rates, and >90% success rate for a significantly lower offering price.
