Microsystem locomotion is a key component for minimally invasive neurosurgical procedures such as Deep Brain Stimulation (DBS). However, the intra body fluids and tissues vary by location and time, which pose many challenges for the locomotion of medical micro-devices. We develop and experiment a piezoelectric vibrating bender as a propulsion method for micro-robots in the brain parenchyma or the Cerebro Spinal Fluid (CSF). The actuator is able to adjust itself to the dynamic tissue environment using a part of the beam as an actuator element and a part as a sensor element. The adjustment is made by using a system identification (SI) process of the Multi-Input-Multi-Output (MIMO) system to set the actuation inputs for maximal propulsion generation, according to a control criterion. This research includes the modeling of the system in air, Silicon (Si) oil of 500cP and 60,000cP, the SI method of the MIMO system, and the validation of the theory and the control method empirically. Moreover, a 20 mm long actuator prototype was able to achieve 3 μN propulsive force in 500cP Si oil, as a mimic to a soft tissue.