In this paper we report on the improvement of performance by minimizing scallop size through deep reactive-ion etching (DRIE) of rotors in micro-wind turbines based on micro-electro-mechanical systems (MEMS) technology. The surface profile of an MEMS rotor can be controlled by modifying the scallop size of the DRIE surface through changing the process recipe. The fabrication of a planar disk-type MEMS rotor through the MEMS fabrication process was carried out, and for the comparison of the improvements in the performance of each rotor, RPM testing and open circuit output voltage experiments of stators and permanent magnets were performed. We found that the smooth etching profile with a minimized scallop size formed using DRIE results in improved rotation properties in MEMS-based wind turbine rotors.

The electrolytic tilt sensor operates by measuring the change of conductance between detecting electrodes immersed in an electrolyte. Previously reported electrolytic tilt sensors detect an inclination only on one axis owing to the structural limit for symmetric formation of the detecting electrodes with a fiducial electrode as the reference on the same substrate. In this paper, we report the design and fabrication of a micro-electro-mechanical-system (MEMS)-based dual-axis electrolytic tilt sensor. The proposed tilt sensor has overcome its structural limit by placing the fiducial common electrode at the bottom of the electrolyte cavity for contact with the electrolyte through a via-hole. The proposed tilt sensor shows approximately 50 mV of change in the output voltage per degree of inclination angle in an operating angle range of ±70°.