Bifurcation-based mechanical sensing of microchannels using microrobots

We present a minimally invasive method for probing the mechanical properties of soft-walled microchannels by analyzing the bifurcations in the periodic motion of a magnetically actuated microrobot. Under oscillatory magnetic excitation, the microrobot undergoes transitions, including grazing and fold bifurcations, during wall interactions that are highly sensitive to local stiffness and damping. Experiments and numerical continuation reveal consistent bifurcation shifts across channels of varying compliance, enabling mechanical characterization through frequency-dependent response. A piecewise-smooth dynamical model incorporating fluid damping and compliant boundaries captures the observed behaviors. This bifurcation-based approach leverages dynamic signatures to provide a sensitive method for mechanical sensing in simplified confined environments. It lays the groundwork for future extensions towards applications in tissue diagnostics, vascular health monitoring, and soft material characterization.