Tardigrades, carrot carotenoids and the DIY Raman spectrometer (IV)
Fig. 1: The DIY Raman microscope spectrometer might help with many analytical tasks. As already illustrated you can use it for the investigation of tardigrade 'tuns' (i.e. tardigrades in the dry state). But you might make use of it as well in order to identify synthetic resins and pain reliver pills, check jewelry or to study minerals like the ones shown in the image above.
Agreed, at first glance it sounds crazy to build this kind of analytical equipment at home. Raman spectroscopy appears to be terribly complicated and chained to expensive instrumention. But the DIY has become feasible because we can take profit from a combination of three modern technical innovations: the solid state laser, interference filters and CCD imaging chips.
Fig. 2: For our DIY Raman we can use a green 532 nm laser which is merely thumb-sized. Our laser is passively cooled, just by air. It came with its own current supply which delivers 5 volts and 0,5 A. The output power is 50 mW. Be warned that this is the 50fold light intensity of a common laser pointer. So please take care that it is not accessible to children, that it is bearing a warning sign at that you do not direct its beam towards your eyes!
The microscope type which is most suitable for our experiment
was already discussed in the previous issue of our magazine (cf. our discussion
of potential Raman microscopes).
Fig. 3: A Nikon Optiphot microscope, built about 1986, in incident light configuration, with LED illumination and trinocular camera head.
The laser can simply be placed in the position of the LED light. As it has to be focused sharply on the sample under investigation any obstruction, in particular the matte filter, has to be removed. In order to fit the laser into the lamp thread we simply built a mechanical adapter with a thread and some fittings from Ebay - plus some glue:
Fig. 4: This self-built mechanical adapter keeps the laser in a fixed position. The laser just slides neatly into the fitting.
From this point onward you are working at your own risk. High energy lasers are dangerous and can harm your eyesight. Furthermore you should know that many lasers send infrared radiation (invisible radiation) as well which might be even more dangerous. So proceed slowly and carefully!
Fig. 5: The laser is wired and the laser power supply in place, ready for use ...
The eye-pieces should be turned away from the operator, e.g. towards a wall, or be fully closed. In the next issue we will provide some practical hints concerning laser power use, filter choice and the consequences for spectrum quality.
© Text, images and video clips by
Martin Mach (firstname.lastname@example.org).