Measurement and evaluation of the adhesive force between particles by the direct separation method

We developed a new apparatus to measure the adhesive force between particles with a high resolution of approximately 2 nN. The force was measured directly by applying a pulling force to the particles with a contact needle. In addition, the separation process was observed with a 3CCD camera during the measurement. The adhesive force of six kinds of pharmaceutical particles and glass beads was measured, and the effects of moisture, shape, and triboelectrification of the particles on the force were investigated. In the case of moisture-adsorptive particles, the force of adhesion increased rapidly with moisture content under high relative humidity. In the case of moisture-nonadsorptive particles, the force was affected by the particle shape and triboelectrification. The adhesive force of particles having sharp corners was greatly affected by triboelectrification at the corners of the particles. (C) 2003 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 92:560-568, 2003.