Abstract: A stirrer for a planetary mixer has an upper central hub with two outwardly extending horizontal arms and two helical stirring elements, one depending from each arm. According to the presently preferred embodiments, the cross sectional area of the stirring elements is large enough that no bottom crossbar is necessary. The pitch angle of each stirring element is preferably constant from top to bottom. The leading side of the stirring elements has a flat surface whereas the trailing side is curved. The flat surface increases in size moving toward the bottom of the stirring element.

Abstract: A rotor-stator assembly includes a rotor and a stator, each of which includes at least one surface having a plurality of grooves defining a plurality of ridges and valleys. The grooves are located so that material in the rotor grooves is caused to collide with material in the stator grooves or vice versa. Ideally, the grooves have a curved cross section so that material is caused to spin in the grooves. Material spinning in a stator groove is caused to collide with material spinning in a rotor groove and vice versa. The number of times that particles are caused to collide depends on the number and length of the grooves in relation to the depth of the grooves. Shear zones are located between the grooves on the stator and the grooves on the rotor.