Chamolly Alexander, Lauga Eric
Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, CB3 0WA, Cambridge, UK.
Eur Phys J E Soft Matter. 2019 Jul 16;42(7):88. doi: 10.1140/epje/i2019-11854-3.
The design of artificial microswimmers has generated significant research interest in recent years, for promise in applications such as nanomotors and targeted drug-delivery. However, many current designs suffer from a common problem, namely the swimmers remain in the fluid indefinitely, posing risks of clogging and damage. Inspired by recently proposed experimental designs, we investigate mathematically the dynamics of degradable active particles. We develop and compare two distinct chemical models for the decay of a swimmer, taking into account the material composition and nature of the chemical or enzymatic reaction at its surface. These include a model for dissolution without a reaction, as well as models for a reacting swimmer studied in the limit of large and small Damköhler number. A new dimensionless parameter emerges that allows the classification of colloids into ballistic and diffusive type. Using this parameter, we perform an asymptotic analysis to derive expressions for colloid lifetimes and their total mean squared displacement from release and validate these by numerical Monte Carlo simulations of the associated Langevin dynamics. Supported by general scaling relationships, our theoretical results provide new insight into the experimental applicability of a wide range of designs for degradable active colloids.
近年来，人工微游动器的设计引起了广泛的研究兴趣，因为它在纳米马达和靶向药物递送等应用中具有潜力。然而，目前许多设计都存在一个共同问题，即游动器会无限期地停留在流体中，存在堵塞和损坏的风险。受最近提出的实验设计启发，我们对可降解活性粒子的动力学进行了数学研究。我们开发并比较了两种不同的化学模型来描述游动器的衰变，同时考虑了其表面化学反应或酶促反应的材料组成和性质。这些模型包括无反应溶解模型，以及在大达姆科勒数和小达姆科勒数极限下研究的反应性游动器模型。出现了一个新的无量纲参数，它可以将胶体分为弹道型和扩散型。利用这个参数，我们进行了渐近分析，以推导胶体寿命及其从释放开始的总均方位移的表达式，并通过相关朗之万动力学的数值蒙特卡罗模拟对这些表达式进行验证。在一般标度关系的支持下，我们的理论结果为可降解活性胶体的广泛设计的实验适用性提供了新的见解。
