Division of Chemistry and Biological Chemistry, School of Physical and Mathematical Sciences, Nanyang Technological University , Singapore 637371, Singapore.
Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR) , 2 Fusionopolis Way, Innovis, 08-03, Singapore 138634, Singapore.
ACS Appl Mater Interfaces. 2016 Sep 14;8(36):23941-6. doi: 10.1021/acsami.6b07766. Epub 2016 Aug 29.
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 microdroplets, 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's smallest centrifuge and (2) a miniature and localized viscometer. Our LM is responsive to an 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 ∼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 spinning LM as an ultrasensitive spin-to-viscosity transducer to quantify the viscosity of the external suspended liquid in the relative viscosity (η/ηwater) range of 1-70 using ≤1 mL liquid sample. Collectively, the ensemble of benefits offered by spinning LM creates enormous opportunities in 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.
液态大理石通过将疏水性颗粒自发涂覆在液体表面上形成非粘性包裹壳，从而提供了一种有吸引力的微滴操纵方法，将微滴隔离在该包裹壳中。虽然使用磁性纳米粒子制备的液态大理石能够实现对微滴的精确时空驱动，但这些操作通常仅限于微滴的简单和线性空间操纵。在此，我们展示了微升级液态大理石（LM）的独特的三维旋转及其随后的两种应用：（1）世界上最小的离心机，（2）微型局部粘度计。我们的 LM 对外加旋转磁场有响应，其旋转速度可在 0 到 1300 rpm 之间编程。这种旋转产生了前所未有的离心力，在半径约为 1mm 的 LM 中产生了>2g 的离心力。这种离心力在外围产生了向外的径向流体流动，使 LM 能够作为微离心机，用于具有>85%分离效率的纳米颗粒的沉降。此外，我们将旋转的 LM 用作超灵敏的自旋粘度传感器，使用≤1mL 的液体样品，在相对粘度（η/ηwater）为 1-70 的范围内定量测量外部悬浮液的粘度。总体而言，旋转 LM 提供的一系列优势为多功能磁机械装置的发展创造了巨大的机会，例如有前途的表面敏感微传感器、微型离心泵，甚至具有定向传热和传质机制的微反应器。
