Activating internal resonance in a microelectromechanical system by inducing impacts

As natural frequencies become commensurate, internal (autoparametric) resonances involving the corresponding modes may arise. This phenomenon has been recently increasingly reported in micro- and nanosystems. Due to the intrinsic nonlinearity, internal resonances may draw complex features, which can be desirable for developing novel devices with enhanced functionality based on energy transfer among the involved modes. Here, we examine the possibility of activating internal resonance by inducing impacts. Through a specially deposited dielectric layer to prevent short-circuiting, a microelectromechanical beam is deliberately operated to have impact with the substrate, which redirects the dynamics of the system. Driven by repetitive impacts, the device widens the frequency bandwidth around the first mode and activates a non-classical type of internal resonance, at a ratio of 7:2 between the first and third vibration modes. Interestingly, this internal resonance behavior is enabled in regions of the driving parameters space, where the branch would not have existed in the absence of impacts. The dynamical phenomena featured by the impacts are affected by the characteristics of the impacting surfaces, which may controllably tune the response. This study opens up research toward utilizing impacts for favoring internal resonance activations, including in cases where they are precluded in the smooth system, as well as engineering the associated modal energy exchange.