Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion─Israel Institute of Technology, Technion City 3200000, Israel.
Department of Nanoengineering, University of California San Diego, La Jolla, California 92093, United States.
ACS Appl Mater Interfaces. 2022 Jul 6;14(26):30290-30298. doi: 10.1021/acsami.2c02605. Epub 2022 Jun 24.
To address and extend the finite lifetime of Mg-based micromotors due to the depletion of the engine (Mg-core), we examine electric fields, along with previously studied magnetic fields, to create a triple-engine hybrid micromotor for driving these micromotors. Electric fields are a facile energy source that is not limited in its operation time and can dynamically tune the micromotor mobility by simply changing the frequency and amplitude of the field. Moreover, the same electrical fields can be used for cell trapping and transport as well as drug delivery. However, the limitations of these propulsion mechanisms are the low pH (and high conductivity) environment required for Mg dissolution, while the electrical propulsion is quenched at these conditions as it requires low conductivity mediums. In order to translate the micromotor between these two extreme medium conditions, we use magnetic rolling as means of self-propulsion along with magnetic steering. Interestingly, electrical propulsion also necessitates at least the partial consumption of the Mg, resulting in a sufficient geometrical asymmetry of the micromotor. We have successfully demonstrated the rapid propulsion switching capability of the micromotor, from chemical to electrical motions, via magnetic rolling within a microfluidic device with the concentration gradient of the simulated gastric fluid. Such triple-engine micromotor propulsion holds considerable promise for in vitro studies mimicking gastric conditions and performing various bioassay tasks.
为了解决和延长由于发动机（Mg 核）耗尽而导致的基于 Mg 的微马达的有限寿命，我们研究了电场，以及之前研究过的磁场，以创建一种用于驱动这些微马达的三引擎混合微马达。电场是一种简便的能源，其操作时间不受限制，并且可以通过简单地改变电场的频率和幅度来动态调整微马达的移动性。此外，相同的电场可用于细胞捕获和运输以及药物输送。然而，这些推进机制的局限性在于 Mg 溶解所需的低 pH 值（和高电导率）环境，而电推进在这些条件下被抑制，因为它需要低电导率介质。为了在这两种极端介质条件之间转换微马达，我们使用磁滚动作为自推进的手段，同时进行磁导向。有趣的是，电推进也至少需要 Mg 的部分消耗，从而导致微马达具有足够的几何不对称性。我们已经成功地在具有模拟胃液浓度梯度的微流控装置内，通过磁滚动展示了微马达从化学运动到电运动的快速推进切换能力。这种三引擎微马达推进对于模拟胃条件并执行各种生物测定任务的体外研究具有很大的应用前景。
