Thermodynamics and rheology of the Hughes press

Among the methods used for the rupture of cells by means of solid shear, the Hughes press is best known. It operates by forcing an aqueous suspension of cells previously frozen at −27°C under pressure through a narrow circumferential gap. The mode of action requires a knowledge of the isentropic compression of the solid phase and its possible involvement with a phase change from ice I to ice III. It is shown that the mechanical properties of the solid mixture are relevant. A model is proposed of the plastic flow for the geometry of the press and it is shown that cell breakage is proportional to the velocity of the plunger and inversely proportional to gap width.