We introduce an innovative optical phase shifter that utilizes a microelectromechanical system (MEMS) tuning mechanism, providing low power consumption, fast tuning, small dimensions, and high performance. In this approach, a rotating MEMS actuator is presented, enabling bi-directional actuation, which allows for both an increase and decrease in the effective mode index and phase shift. This provides lower operating voltage and shorter response time compared with other existing MEMS actuators. The proposed device exhibits impressive functional characteristics, including an overall dimension of 1920 μm2, an effective phase shifting length of 30 μm, an insertion loss of 0.033 dB, an operating voltage of 10 V, a tuning time of 2.5 μs, and a phase shift of more than 3π at a wavelength of 1550 nm. With such advantages, this device is well-suited for use in large photonic integrated circuits, enabling complex applications such as artificial intelligence applications including machine learning, neural networks, and neuromorphic computing.