Design principles for transient sieves based on colloidal motors

• Applicant: Professor Dr. Benno Liebchen
• Subject Area: Statistical Physics, Nonlinear Dynamics, Complex Systems, Soft and Fluid Matter, Biological Physics
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 509491635

While conventional motors have a typical size ranging from millimeters to meters, recent years have led to the development of colloidal motors ("microswimmers") that do not require moving components and that can generate directed motion on the micro- and nanoscale. The central idea of this project, in collaboration with A2, is to use these novel motors for the first time to design, realize and optimize a transient sieve. Here we exploit the fact that the dynamics of the motors can be directed by external fields, such as spatiotemporally modulated light fields (laser). This allows a transient sieve for Janus particles to be created, based on light barriers which can be dynamically opened and closed in such a manner that the motors can pass the light barrier selectively, depending e.g. on their size, surface morphology or on the type of cargo particles attached to them. This sieve operates out of equilibrium and features a highly selective permeability that is controlled by the (nonadiabatically fast) switching dynamics of the light barrier, i.e. it is a transient sieve. The focus of project B1 is to develop a detailed understanding of the basic ingredients that are necessary to describe and systematically control such a sieve. In particular, this concerns the influence of rapidly time-varying external fields on colloidal motors, which has been little explored so far, but which is of central importance for the modeling and optimization of a transient sieve. To this end, in B1 we span the entire range from the development of a detailed model describing the coupled dynamics of colloidal motors, the ambient flow field and the temperature field to an effective model to describe the spatiotemporal dynamics of the motors and cargo particles. These developments make optimal use of the applicant's prior experience in modeling and simulating colloidal motors and invoke collaborations with projects B2, B3 and B4. In addition to its importance to conceptually demonstrate the usability of colloidal motors for creating a transient sieve and for the experiments in A2, this project will create generically new insights on controlling colloidal motors with external fields as well as a general method for determining reduced models that are relevant beyond TRANSIEVES.

• DFG Programme: Research Units
• Subproject of: FOR 5584: Transient Sieves