Spinning Liquid Marble and Its Dual Applications as Microcentrifuge and Miniature Localized Viscometer

Liquid marble offers an attractive droplet manipulation approach by isolating microdroplet in a nonstick encapsulating shell formed via the spontaneous-Coating of hydrophobic particles onto the liquid surface. While liquid marble prepared using magnetic nanoparticles enables precise spatiotemporal actuation of micro-droplets, these manipulations are generally limited to simple and linear spatial maneuver of microdroplets. Herein, we demonstrate the unique and three-dimensional spinning of microliter-sized liquid marble (LM) and its subsequent dual applications as (1) :the world smallest centrifuge and.(2) a miniature and localized viscometer. Our LM is responsive. to applied rotating magnetic field, with its spinning speed programmable between 0 and 1300, rpm. This spinning generates an unprecedented centrifugal force of >2g in a LM of similar to 1 mm radius. Such centrifugal force facilitates an outward and radial hydrodynamic flow in the enclosed microdroplet enabling, LM to serve as a microcentrifuge for the sedimentation of nanoparticles with >85% separation efficiency. Furthermore, we apply ultrasensitive spin-to-viscosity transducer to quantify the viscosity of the external suspended liquid in the relative viscosity (eta/eta(water)) range of 1-70 using <= 1 mL liquid sample. Collectively, the ensemble of benefits offered by spinning LM creates enormous opportunities hi the development of multifunctional micromagneto-mechanical, devices, as :promising surface-sensitive microsensor, miniature centrifugal pump, and even microreactor with directed heat and mass transfer mechanism.