Fluorescence Miniature Microscope
The Miniature Microscope (MiMi) is a miniaturized microscope system with several observation modes (fluorescence, bright field and phase contrast) for the automatic observation of live biological samples over extended periods of time in space.
A prototype fluorescence miniature microscope (‘Fluor-MiMi’) has been developed that serves as a demonstration model of an eventual flight instrument for use on the ISS Biolab facility of ESA. The flight instrument is aimed to fit inside a so-called ‘Advanced Experiment Container’ (AEC; inner volume <168 x 118 x 140 mm³) and, as such, can be accommodated in duploon both the static (microgravity) and on the centrifuge (1xgreference) rotor of Biolab.
The Fluor-MiMi prototype instrument consists of three parts: (1) optical system, (2) sample holder on XY-scan and focus (Z) tables and (3) electronics. The optical system enables bright field or phase contrast microscopy (diffused white LED illumination, automated change of observation mode) and fluorescence microscopy.
The current implementation is based on use of GFP for study of live objects (473nm solid state laser input, >510 nm filtered detection). Off-line and/or automated change of objectives allows a 10x – 40x magnification range, and corresponding field of views. Microscope images in NTSC video format are generated by a built-in B&W CCD camera.
The sample holder allows accommodation and automated change of observed specimen and is designed such that (automated) liquid management can be added for the flight situation. For this, use can be made of the Biolab provisions or liquids can be stored and dispensed from within the AEC. For the prototype instrument the XYZ-table for the sample holder has been constructed from commercial elements, allowing a scan range of 5mm in all directions.
The electronic system, which will be housed inside the AEC in the flight model, is based on a micro-controller with embedded software and interface cards for control of, and power supply to, all motorised elements and light sources and for read-out of all sensors (temperatures, end switches, proximity). The prototype system is completed with a computer as ‘user interface’ and video equipment.
- Observation modes: Bright field (BF), Phase Contrast (PC) & Fluorescence (FL)
- Magnification: 10X & 40X
- Mechanisms: Phase Contrast, Objective magnification and sample position (5mm range) + Fluorescence
- Illumination: White Nichia LEDs for BF and PC mode, Nd:YVO4 Laser and filter set for FL mode
- Detector: Black & White CCD from Watec
- Pixel pitch: 12.5µm x 15µm
- Number of pixels: 811 x 508 pixels
- Resolution: 1µm at 40X
- Sensitivity: 0.3 mlux @f/1.4
- Dimensions: 155 x 137 x 101 mm³
- Mass: 1000g