title: Capillary Drop Penetration Method to Characterize the Liquid Wetting of Powders.
abstract: We present a method to characterize the wettability of powders, based on the penetration dynamics of a sessile drop deposited on a slightly compressed powder bed. First, we show that a direct comparison of the wetting properties of different liquids is possible without having to solve the three-dimensional liquid penetration problem, by considering the appropriate dimensionless variables. We show that the contact area between the sessile drop and the powder bed remains constant during most of the penetration process and demonstrate that as a result, the evolution of the dimensionless penetration volume is given by a universal function of the dimensionless time, with no dimensionless parameters. Then, using a reference liquid that completely wets the powder, it is possible to obtain an effective contact angle for a test liquid of interest, independent of other properties of the powder bed, such as permeability and a characteristic pore size. We apply the proposed method to estimate the contact angle of water with different powder blends, by using silicone oil as the reference liquid. Finally, to highlight the potential of the proposed method to characterize pharmaceutical powders, we consider a blend of lactose, acetaminophen, and a small amount of lubricant (magnesium stearate). The proposed method adequately captures a significant decrease in hydrophilicity that results from exposing the blend to excessive mixing, a well-known effect in the pharmaceutical industry.
authors.affiliation: Chemical and Biological Engineering Rutgers and ‡Mechanical and Aerospace Engineering Rutgers, The State University of New Jersey , Piscataway, New Jersey 08854, United States !--Q1: Please confirm the postal code in the affiliation, as we have inserted the required information.-->.
authors.forename: Zhanjie
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Chemical and Biological Engineering Rutgers and ‡Mechanical and Aerospace Engineering Rutgers, The State University of New Jersey , Piscataway, New Jersey 08854, United States !--Q1: Please confirm the postal code in the affiliation, as we have inserted the required information.-->.
authors.forename: Yifan
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Chemical and Biological Engineering Rutgers and ‡Mechanical and Aerospace Engineering Rutgers, The State University of New Jersey , Piscataway, New Jersey 08854, United States !--Q1: Please confirm the postal code in the affiliation, as we have inserted the required information.-->.
authors.forename: Fernando J
authors.initials: FJ
authors.lastname: Muzzio
authors.affiliation: Chemical and Biological Engineering Rutgers and ‡Mechanical and Aerospace Engineering Rutgers, The State University of New Jersey , Piscataway, New Jersey 08854, United States !--Q1: Please confirm the postal code in the affiliation, as we have inserted the required information.-->.
authors.forename: Gerardo
authors.initials: G
authors.lastname: Callegari
authors.affiliation: Chemical and Biological Engineering Rutgers and ‡Mechanical and Aerospace Engineering Rutgers, The State University of New Jersey , Piscataway, New Jersey 08854, United States !--Q1: Please confirm the postal code in the affiliation, as we have inserted the required information.-->.
authors.forename: German
authors.identifier: 0000-0003-3860-7329
authors.initials: G
authors.lastname: Drazer