Abstract
Constructing micro-sized machines always involves the problem of how to bring the energy (electric, magnetic, light, electro wetting, vibrational, etc.) source to the device to produce mechanical movements. The paper presents a rotational micro-sized motor (the diameter of the rotor is 350 µm) driven by low frequency (200–700 Hz) circular vibrations, made by two piezoelectric actuators, through the medium of a water droplet with diameter of 1 mm (volume 3.6 µL). The theoretical model presents how to produce the circular streaming (rotation) of the liquid around an infinitely long pillar with micro-sized diameter. The practical application has been focused to make a time-stable circular stream of the medium around the finite long vibrated pillar with diameter of 80 µm in the presence of disturbances produced by the vibrated plate where the pillar is placed. Only the time-stable circular stream in the water droplet around the pillar produces enough energy to rotate the micro-sized rotor. The rotational speed of the rotor is controlled in both directions from −20 rad/s to +26 rad/s. 3D printed mechanical amplifiers of vibrations, driven by piezoelectric actuators, amplify the amplitude of the piezoelectric actuator up to 20 µm in the frequency region of 200 to 700 Hz.
Highlights
The miniaturization of mechatronic devices, especially miniaturization of rotational micro-sized motors, has been at the forefront of the research efforts of scientists and engineers who have been developing microelectromechanical systems (MEMS) tirelessly for more than three decades.The first micro-sized rotational motors based on electrostatic energy supply to the rotor, were designed and tested in the laboratory environments in the years around 1990 [1,2]
The review paper reported the development of electromagnetic micro motors in the last two and a half decades [4], while review paper presented the methods for measurements of wear for micro electrostatic motors and some method for lubrication of their bearings [5]
The focus of our paper is to present a novel and unique microfluidic vibrational driven rotational micro motor, which produces the rotation of the rotor from the energy induced by the circular vibration in the water droplet
Summary
The miniaturization of mechatronic devices, especially miniaturization of rotational micro-sized motors, has been at the forefront of the research efforts of scientists and engineers who have been developing microelectromechanical systems (MEMS) tirelessly for more than three decades. Shilton et al and Yeo et al used two oppositely directed surface acoustic waves (frequency 20 MHz) driven fluid-coupled disk (diameter 5 mm) controlled in both directions at rotational velocities of 235 rad/s and at a max torque of 60 nNm [14,15,16] They reported two versions: the first one needed liquid fluid between the disk and the substrate, and the other worked without the liquid. The focus of our paper is to present a novel and unique microfluidic vibrational driven rotational micro motor, which produces the rotation of the rotor from the energy induced by the circular vibration in the water droplet. The comparator switched the Peltier element’s reference temperatures from below to above the dew point temperature plus the hysteresis of 3 ◦C
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