Piezoelectric Beam for Intrabody Propulsion Controlled by Embedded Sensing

The body is a very challenging environment for locomotion. The mechanical properties of intrabody fluids and tissues vary by location and time. In order to move an embedded biomedical device such as a deep brain stimulation electrode, one has to identify the properties of the environment and set the propulsive actuator's input accordingly. We developed a piezoelectric actuator for propelling a microrobot in cerebro spinal fluid or burrowing in the brain tissue parenchyma. The propulsion is created by the vibration of the beam at the resonance frequencies. The driving of the actuators is controlled by in situ multi-input multi-output system identification (SI) using part of the beam as sensor and part as actuator. In this study, we model the sensing of the device, present the SI method, the calculation of the input signals to achieve maximal propulsion, and we test the driving method experimentally. The microactuator is examined in 500-cP silicon oil and a 20-mm-long actuator can achieve 3-μN propulsive force.