A Simple Numerical Tool for the Evaluation of Acoustic Radiation Force on Helices

Helical microswimmers are prospective agents in biomedical applications such as targeted drug delivery. Most of the helical swimmers are actuated with external magnetic field due to its biocompatible nature. Acoustic actuation is another biocompatible mode of actuation that may be used alongside the magnetic fields to improve the propulsion and control of the swimmers. In order to design helical swimmers suited for acoustic actuation, it is vital to develop appropriate modelling tools to understand the effects of acoustic radiation forces on helical structures. Such complex structures do not have any analytical formulae available for use and finite-element based methods are computationally expensive. A simple numerical tool is presented here that approximates the helix as a chain of small spheres. The sum of the forces acting on the spheres is found to be close to the radiation force evaluated from the finite-element simulation for the helix. The sensitivity of the approach with respect to physical and geometric parameters such as material properties, swimmer geometry and number of spheres used for the approximation are demonstrated.