Analysis of flow field around magnetic-responsive soft materials using tomographic particle image velocimetry

The hydrodynamics induced by deformation of magnetic-responsive soft materials are investigated and the resultant flow field is analyzed using tomographic particle image velocimetry (tomo-PIV). Magnetic-responsive composite arms incorporated with a multifunctional joint design are actuated by an external magnetic oscillating field with a period of roughly 1 sec. The tomo-PIV system quantifies the surrounding aqueous flow at 250 frames per second. The effects of asymmetric multimodal actuation (i.e., folding versus bending) on the flow field are compared with the single actuation mode, by creating an asymmetric joint at the mid-point of the magnetic material. In addition, the effect of non-symmetric time interval of positive/negative magnetic field generation is investigated on the flow field around the magnetic material. Analysis of the kinematics of the soft material, as well as the velocity, vorticity and pressure of the flow field surrounding the magnetic material indicate that the kinematics of the non-symmetric time interval of magnetic field provides sufficient time for the flow to become steady between each upward and downward stroke motions. Thus, the peak values of vorticity and pressure decrease to smaller magnitudes compared to the symmetric case. In addition, the asymmetric joint at the mid-point of the magnetic material arm affects the flow in a way that the peak values of both vorticity and pressure are larger in the downward motion (rigid body motion, i.e. folding) compared to the upward motion (elastic deformation, i.e. bending).