Electrolytic tilt sensor fabricated by using electroplating process

This paper proposes new electrolytic tilt sensor fabricated by MEMS process especially using electroplating process to form vertical electrodes each of which is connected to planar electrode. Comparing with conventional electrolytic tilt sensors having difficulty in manufacturing in small size, the present tilt sensor can be manufactured in small size, particularly in very small height, having comparable performance, thus resulting in mass production possible, while still having a variety of manufacturing in higher height which is possible using electroplating process. In order to perform the electroplating process, an assembly of SU-8 polymer and PDMS was used as electroplating mold, former not being removed to form outer wall of sensor cavity but latter being removed to make a cavity in which electrolytic solution is contained. The nonzero null output voltage offset has minimum value in the range of 100-800 Hz of the frequency of alternating input voltage source. Analytically derived equation and experiments to examine how the sensor cavity size affects the performances confirmed that smaller the cavity diameter D, the smaller sensitivity but larger angle range. Compared to commercial electrolytic tilt sensor products, the fabricated tilt sensor has comparable performances such as angle range of about +/-40 degrees, especially linear range of about +/-10 degrees, sensitivity of 4.4V/degrees in case of V-in = 1 V (rms), and resolution of 0.5 arc min. (C) 2011 Elsevier B.V. All rights reserved.