Nonlinear Models for Optimal Placement of Magnetically-Actuated Cilium

Artificial cilia systems are used for microfluidic manipulation. By analogy to the biological cilia, such systems seek to mix, separate, or propel fluids, particularly in the low-Reynolds-number regime, without damaging sensitive samples. An important category of artificial cilia systems is magnetically-actuated artificial cilia, since the driving magnetic field does not interact with many samples of interest. Simulation results are presented to show that linear modeling fails to adequately predict the optimal location due to strong nonlinear effects; using the linear result to select magnet placement results in amplitudes 84% lower than the amplitude with the optimal placement found using the nonlinear model. This represents a substantial loss in efficacy. Since large amplitudes are desirable to enhance flow manipulation, the results illustrate the importance of nonlinear dynamics models in the design of magnet-cilia devices.