Open-loop control of directed self-assembly of colloidal particles in a microfluidic device

Directed self-assembly provides a practical route for the manufacture of structured materials. Future processes based on self-assembly will need to be equipped with suitable automated controllers for improved performance. Open-loop control is needed when real-time observation of a self-assembly system is difficult. An automated open-loop control method for directed self-assembly of microspheres in a microfluidic device with multiple electrodes is developed and characterised experimentally. The control objective is to create an elementary particle density distribution between two regions in the device. An empirical model is developed to describe the motion of the particles such that open-loop control becomes feasible. Experimental characterization shows the effectiveness of the approach. Finally, it is demonstrated how a first-principle model describing electroosmotic flow can also be used to predict the particle motion, which provides opportunities to develop open-loop control schemes for directed self-assembly systems for which no real-time observation is available in future work.