title: Capillary-inertial colloidal catapults upon drop coalescence.
abstract: Surface energy released upon drop coalescence is known to power the self-propelled jumping of liquid droplets on superhydrophobic solid surfaces, and the jumping droplets can additionally carry colloidal payloads toward self-cleaning. Here, we show that drop coalescence on a spherical particle leads to self-propelled launching of the particle from virtually any solid surface. The main prerequisite is an intermediate wettability of the particle, such that the momentum from the capillary-inertial drop coalescence process can be transferred to the particle. By momentum conservation, the launching velocity of the particle-drop complex is proportional to the capillary-inertial velocity based on the drop radius and to the fraction of the liquid mass in the total mass. The capillary-inertial catapult is not only an alternative mechanism for removing colloidal contaminants, but also a useful model system for studying ballistospore launching.
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University , Durham, North Carolina 27708, USA.
authors.forename: Roger L
authors.identifier: 0000-0003-0946-5843
authors.initials: RL
authors.lastname: Chavez
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University , Durham, North Carolina 27708, USA.
authors.forename: Fangjie
authors.identifier: 0000-0001-7029-0312
authors.initials: F
authors.lastname: Liu
authors.forename: James J
authors.identifier: 0000-0002-7141-5823
authors.initials: JJ
authors.lastname: Feng
authors.affiliation: Department of Mechanical Engineering and Materials Science, Duke University , Durham, North Carolina 27708, USA.
authors.forename: Chuan-Hua
authors.initials: CH
authors.lastname: Chen