In this report, the origin of micronuclei responsible for the onset of decompression sickness is investigated, The formation of cavities by tribonucleation between hydrophobic and hydrophilic surfaces has been studied using a new force measuring device, LLIFE (Light Lever Instrument for Force Evaluation). Using this instrument, the interaction force between silica surfaces in equilibrium with the cationic surfactant cetylpyridinium chloride has been measured above and below the critical micelle concentration. A long range hydrophobic attraction is evident between adsorbed monolayers and a DLVO repulsion is apparent between adsorbed bilayers. It is shown that the formation of cavities on separation occurs not only between hydrophobic monolayers but between hydrophilic bilayers, should the bilayers be squeezed sufficiently to cause rupture. The demonstration that cavities may arise upon separation between bilayers is new and leads to the postulate that cavities are formed in vivo by the rupture of cell membrane bilayers, thereby providing the nucleation sites for bubble formation should sufficient gas supersaturation occur.