A MEMS tilt sensor with expanded operating range and improved sensitivity

Abstract

In this paper, a simple and novel method of expanding the operating range of inclinations and of increasing the sensitivity of convection-based tilt sensors is shown. Even though the previously reported convective tilt sensors fabricated in our laboratory have their own merits in performing dual-axes inclination measurement with excellent linearity and symmetric sensitivity, they showed limited operating range from −90 to 90° because of their structural limitations. However, this proposed tilt sensor has overcome the structural limitations and it detects inclinations wider than the ±90° range on two axes with symmetric sensitivity. The improved performance could be achieved by removing the membrane at the bottom of the microheater and temperature sensors for unlimited gas movement in the cavity when it tilted over the ±90° range. The operating range of the newly proposed tilt sensor expands to ±180° compared with that of the previously reported convective tilt sensor. Moreover, various designs of cavities and cap substrates were adopted to improve the sensitivity of the proposed convective tilt sensor. The mass production of the proposed convection-based tilt sensor is still feasible because it can be fabricated at a low cost because of its simple fabrication step. Its sensitivity is high and it has a very wide-angle detection range.

Effect of heater geometry and cavity volume on the sensitivity of a thermal convection-based tilt sensor

“…Even under the same conditions, if there are changes in the heater's materials and physical shape, the thermal convection state in the sealed space also changes, and the sensor's sensitivity is consequently affected. 25,[27][28][29] In order to confirm changes in sensitivity according to the shape of the heater, sensors with three different shapes of the heater were fabricated. Figure 6(a) shows the heaters with straight line, zig-zag, and circle shapes with identical temperature sensors.…”

“…However, the expansion of the sealed space in the bottom wafer did not improve the output of the top wafer correspondingly with the expansion. 25,30) This is believed to be due to the low density of hot air which rises readily, and as a result, the expansion of the bottom wafer does not have a significant impact on the sensor's sensitivity.…”

“…In thermal convection-based tilt sensors, [22][23][24][25][26][27] the sensor detects the flow of thermal from a heat source in its sealed chamber and uses the changing temperature distribution to detect tilting. Therefore, these types of sensor have no solid mass and they are simple to process and manufacture.…”

Triboelectric Nanogenerator Based Self-Powered Tilt Sensor

“…Generally, TENG can be used in three modes: vertical contact mode [9], sliding mode [10] and single electrode mode [11].…”

“…Different approaches have been used to develop MEMS based tilt sensors like capacitive [9,12,13], electrolyte [21,14,15], resistive [10], thermal [11], optical [16,17] and inductive [18].…”