Demirörs Ahmet F, Stauffer Alex, Lauener Carmen, Cossu Jacopo, Ramakrishna Shivaprakash N, de Graaf Joost, Alcantara Carlos C J, Pané Salvador, Spencer Nicholas, Studart André R
Complex Materials, Department of Materials, ETH Zurich, 8093 Zurich, Switzerland.
Soft Matter. 2021 Jan 28;17(4):1037-1047. doi: 10.1039/d0sm01449d. Epub 2020 Dec 8.
Precise control over the motion of magnetically responsive particles in fluidic chambers is important for probing and manipulating tasks in prospective microrobotic and bio-analytical platforms. We have previously exploited such colloids as shuttles for the microscale manipulation of objects. Here, we study the rolling motion of magnetically driven Janus colloids on solid substrates under the influence of an orthogonal external electric field. Electrically induced attractive interactions were used to tune the load on the Janus colloid and thereby the friction with the underlying substrate, leading to control over the forward velocity of the particle. Our experimental data suggest that the frictional coupling required to achieve translation, transitions from a hydrodynamic regime to one of mixed contact coupling with increasing load force. Based on this insight, we show that our colloidal microrobots can probe the local friction coefficient of various solid surfaces, which makes them potentially useful as tribological microsensors. Lastly, we precisely manipulate porous cargos using our colloidal rollers, a feat that holds promise for bio-analytical applications.
精确控制流体腔室中磁响应粒子的运动对于未来微机器人和生物分析平台中的探测和操纵任务至关重要。我们之前已将此类胶体用作微尺度物体操纵的穿梭器。在此，我们研究了在正交外部电场影响下，磁性驱动的Janus胶体在固体基板上的滚动运动。利用电诱导的吸引相互作用来调节Janus胶体上的负载，进而调节与下层基板的摩擦力，从而实现对粒子前进速度的控制。我们的实验数据表明，实现平移所需的摩擦耦合随着负载力的增加从流体动力学状态转变为混合接触耦合状态之一。基于这一见解，我们展示了我们的胶体微机器人可以探测各种固体表面的局部摩擦系数，这使其有可能用作摩擦学微传感器。最后，我们使用我们的胶体滚轮精确操纵多孔货物，这一成果有望用于生物分析应用。
