We report here the successful development of a new instrument, the Centrifuge Polarizing Microscope (CPM). The CPM was developed to explore, by high-extinction polarized light microscopy, the dynamic alignment, linkage, and interaction of macromolecules, fine structure, and organelles in living cells and developing embryos being centrifugally stratified. It should also find applications in material sciences, e.g., for examining centrifugal stratification, compaction, and alignment of liquid crystals and emulsions; the CPM uniquely allows continuous observation and measurement of the weak birefringence exhibited by molecules and fine structures that are oriented, or become oriented, under centrifugal acceleration.

Centrifuge microscopes of various designs have been built since the 1930s but were not equipped for polarization optics. In the 8-cm-radius rotor of our prototype CPM, spinning between the objective and condenser lenses with numerical apertures of up to 0.55, the specimen chamber is illuminated stroboscopically by a 5- to 7-ns intense flash of 532-nm-wavelength light from a Nd- YAG laser, synchronized to fire exactly as the specimen intersects the axis of the objective lens (Fig. 1).