Session: SYMP 2-1: Magneto-Responsive Materials Modeling, Optimization, and Performance

Paper Number: 140233

140233 - Swept Volume Performance Optimization of 3d-Printed Micrometer-Scale Magnetic Artificial Cilia 

Cilia plays a pivotal role in maintaining several biological systems, and analyzing its oscillatory dynamics in the realm of low Reynolds numbers becomes imperative. Moreover, the cilia typically range from sub-100  complicating the fluid-structure interaction between cilia and fluid. Recently, much interest has been shown in wirelessly actuating these implanted cilia for remote drug delivery, self-propulsion, and self-cleaning. One of the promising actuating systems is driven by oscillatory magnetic fields generating cilia motions. Magnetic Artificial Cilia (MACs) are actuated wirelessly by the magnetic field to produce oscillatory motions generating net fluid transport.

The MACs studied experimentally in this work are 3D printed using 2-photon crosslinking, which is a combination of two-photon lithography and C,H insertion cross-linking. A reactive anthraquinone group in a prepolymer is activated by a femtosecond laser (780 nm) via a two-photon transition, and a C,H insertion reaction subsequently leads to crosslinking in neighboring chains and covalent bonding to the surface. This allows high resolution down to the nanometer range because the square dependence of the 2-photon transition on the laser intensity means that the CHic reaction only takes place within a small volume element (voxel). Using prepolymers in combination with superparamagnetic nanoparticles, it is possible to print microactuators from a polymer-nanoparticle composite in a single step.

The sophisticated 2-PP method enables the fabrication of MACs with different head sizes and shapes to enhance the sweeping performance, eg the amount of volume displaced transverse to the cilia during an oscillatory cycle. The interaction between fluid and oscillating MACs in sub-100  is challenging to analyze as it requires highly sophisticated cameras and flow-sensing units on the micrometer scale. Therefore, COMSOL Multiphysics is employed to analyze the oscillatory dynamics of these MACs. This work uses Multiphysics simulation by combining magnetic field, solid mechanics and laminar flow with suitable magnetic, fluid, and solid boundary conditions. The swept volume performance, i.e., displacement of cilia and volume of fluid displaced, increases with the increase in the aspect ratio of the cilia. However, the swept volume performance reaches an optimized head size for each aspect ratio of the cilia, which is analyzed by Multiphysics simulation and validated by experimental results. Simulation results agree with experimental results when scaled by the nondimensionalized head size to the power 2, which suggests a parabolic (and thereby optimizable) dependence on geometry. The simulation results show similar trends of intermediate maxima, which are consistent with the experimental results. Multiphysics simulation provides a framework to analyze and further optimize the shape and size of MACs for user-specific applications.

Presenting Author: Ankan Dutta Pennsylvania State University

Presenting Author Biography: Ankan Dutta graduated in mechanical engineering from Jadavpur University, India, in 2020. He is currently a third-year Engineering Science and Mechanics graduate student at Penn State under Prof. Huanyu Cheng. Ankan is also an NIH T32 Fellow in the Center for Neural Engineering at Penn State. His research interest spans from stretchable ultrasound arrays and wearable sensors to multiphysics simulation of neural probes and magnetic cilia. He is also the entrepreneurial lead of a startup spun out of the lab, NeuroXR, which was selected as an NSF ICorps National Team.

Authors:

Ankan Dutta
Nicolas Geid
Bowen Li
Jurgen Ruhe
Huanyu Cheng
Paris Von Lockette