Measurement of friction force in a toothbrush tuft using Levitation Mass Method (LMM)

The friction force in a single toothbrush tuft (group of bristles) is measured using Levitation Mass Method (LMM). The experimental measurement is performed by sliding a rounded tip extension block over the surface of the tuft. This extension block is connected to one end of the moving part that is a slide of pneumatic linear bearing. Since the friction of the moving part is so small that it can be neglected, the inertial force of the moving part is equal to the dynamic surface friction force of the tuft opposite to the direction of motion. The tested toothbrush tuft used is made of nylon material with 25 bristles, has a length of 10 mm and a diameter of 0.2 mm. The velocity of the moving part is measured precisely from the beat frequency and the rest frequency using an optical interferometer. After getting the velocity, the other data like the acceleration, the inertial force, and the position of the mass is calculated numerically. The friction inside the bearing is determined using the same instrumentation with an average value of 2.05 mN.