The step-out frequency of untethered magnetic millirobots depends on a lot of factors, and simulations in viscoelastic media are not yet available. Therefore, a universal empirical model has been created to predict the step-out frequency of untethered magnetic millirobots in various media based on the Buckingham Pi theorem.
The model provides a method to evaluate the viability of new millirobot designs in soft tissue using a single measurement in a tissue phantom.
Finally, the model is applied to determine the complex modulus of an ovine brain using ex vivo experiments.